Communications in Electromyography

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M O01~HE ORBICULARIS OCULI REFLEX DURING THE EARLY AND THE LATE STAGE OF FACIAL NERVE LESIONS. M.St~hr and F.Petruch~ (T~bingen, W.Germany). During the early stage of a traumatic or idop~hic facial nerve lesion there is a reduction in amplitude, or an absence of t~orbicularis oculi reflex depending on the degree of paresis. In patients with an incomplete facial paresis, it is sometimes difficult to distinguish between a peripheral and a central origin. By recording the reflex response on both sides, it is found that only patients with ~dpheral paresis will show unilateral reduction in the reflex response. During the la~e stage after a facial nerve lesion the reflex responses are normal when only a neurapraxia had occurred in the acute stage. After lesions with an axonotmesis or neurotmesis of the facial nerve and ensuing reinnervation the following results are typically obtained: I. As a result of the slowing in the impulse conduction in the nerve fibres which have sprou~d the latencies of the early and late reflex response are prolonged. 2. The amplitudes of the reflex responses are decreased proportionately to the degree of paresi~ due to incomplete motor recovery. 3. As a result of faulty reinnervation with a misdirection of fibres which originally innervated the orbicularis oculi muscle, the reflex response occurs in all reinnervated muscles on that side of the face.

M002.HALF MAXIMAL VOLUNTARY CONTRACTION OF EIGHT DIFFERENT MUSCLES FOR 60 SECONDS IN NORMAL SUBJECTS. S.L.Visser and W.de Rijke. (Amsterdam, The Netherlands). In 20 normal test subjects the following functims were examined: flexion and extension of the elbow, abduction of thumb and little finger, flexion and extension of the knee, and dorsal and plantar flexion of the foot. Half maximal voluntary contractions were executed for 60 seconds. The EMG was recorded with surface electrodes. Integrated amplitude, peak-to-peak amplitude and number of peaks were determined over 60 seconds The trend was calculated. Normal values are presented and compared with data from the literature. There were marked intermuscular differences. Half maximal contractions can be very constant during 60 seconds(SD<5%; trend ¢I0%). The integrated amplitude was also fairly constant (SD 10-20% in relation to regression line) but in the course of 60 seconds showed an increase (trend up to +70%). The number of peaks was likewise fairly constant (SD 5-15% in relation to regression line) and showed a decrease over the course of 60 s~conds (trend up to-60%). Probably as a result mainly of volume conduction,

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15-30% of the integrated amplitude of the agonist was found in the area of the antagonist. There were few significant differences between the dominant and the non-dominant side. With the exception of a difference in tension (ratio 2-2.5:1), there were few significant EMG differences between men and women.

M003.THE EMG AS A PROGNOSTIC AID IN "A FRIGORE" FACIAL PARALYSIS~ FOLLOW-UP OF 129 PATIENTS. P.Negrin and P.Fardin. (Padova, Italy). 129 patients affected by "a frigore"~facial paralysis were subjected to systematic EMG examinations, in the first days after the onset of the paralysis, at the end of the third week, at the third month and so on until the reinnervation was complete. On the basis of the clinical evolution the patients were divided in two groups: the first (78 patients) showed a complete or near complete recovery within 3-4 weeks, the second (51 patients) showed only a partial recovery, beginning after the third month. The most interesting findings were the large amount of EMG activity during voluntary effort in the first days and the excitability of the nerve trunk at the end of the third week. The presence of the EMG activity during voluntary effort is a mark of benign prognosis, whereas its absence signifies a late, incomplete reinnervation, beginning after the third month. Nevertheless, in patients showing no signs of improvement during the first 3 weeks, the persistence of nerve trunk excitability often corresponds to an almost complete reinnervation, without severe associated movements dues to misdirection of the regenerated fibers.

M004.EMG OF THE ANAL SPHINCTER MUSCLE IN AMYOTROPHIC LATERAL SCLEROSIS AND SHY-DRAGER SYNDROME. M.Sakuta, T.Nakanishi, Y.Toyokura and Y.Shimada. (Tokyo, Japan). In amyotrophic lateral sclerosis (ALS), urinary and rectal control is not impaired until the later stage of the illness. In the case of the Shy-Drager syndrome, on the other hand, urinary and rectal dysfunction appears in almost all patients. The purpose of this report is to present EMG findings of the external sphincter muscle of the anus (ESA) which were in a striking contrast between ALS and Shy-Drager syndrome. In 10 normal subjects, tonic discharges with frequencies of 3 to 6 Hz were obtained at rest. Increased voluntary contraction showed interference pattern. The motor unit potentials had wave forms of 2.7*0.9 phases, duration of 3.6±1.2 ms and amplitude of 480±100 pV.

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In 30 patients with ALS,EMG of the ESA revealed essentially the same pattern as the normal controls, indicating no signs of denervation of the ESA. In 8 cases of clinically definite Shy-Drager syndrome, tonic discharges at rest markedly decreased. The motor unit potentials on voluntary contraction were diminished in number, and had highly polyphasic forms with mean duration of 10.9-17.8 ms. and mean amplitude of 320-1900~V. These findings suggest that, in the Shy-Drager syndrome there is specific damage of lower motor neurons which innervate the ESA.

M005.SENSORY CONDUCTION IN POLYNEUROPATHIES. F. Schumm and M. St~hr.

IN THE SAPHENOUS NERVE (T~bingen, W.Gern,any).

Measurements of the sensory conduction in the saphenous nerve are suitable for the early diagnosis of polyneuropathies for several reasons: I. The length of the nerve segment examined as compared with all other nerves of the legs guarantees greater accuracy. 2. The nerve does not pass any physiological entrapments. 3. The evoked nerve action potential is relatively high making it possible to calculate exactly latencies, duration, amplitude and number of phases. 4. The upper and lower segment of the nerve can be investigated separatel~ in a relatively short time, by simply displacing the stimulating electrode. Measurements were made with a DISA 2-channelelectromyograph (DISA 14 A 21) and a Digital-A~rager (DISA 14 G 01). Sensory action potentials were recorded using steel needles. The saphenous nerve was stimulated on the medial aspect of the knee and above the medial malleous with surface electrodes. Sensory response potentials were recorded using an averaging technique. Significant and easily detectable changes in patients with polyneuropathies and deviation from the normal values obtained in 70 normals were assessed for the following parameters: I. nerve conduction velocity in the proximal and distal segments of the saphenous nerve. 2. Amplitude, duration and number of phases of the evoked nerve action potentials. Measurements in the saphenous nerve have proved successful in the early diagnosis of polyneuropathies, even in minor cases where there was no clinical indication of a periphery neurogenic lesion. Furthermore, they are suitable for distinguishing between lesions of the femoral and of the saphenous nerve and in differentiating them from lesions of the 3rd. and 4th. lumbar nerve roots.

M006.SENSORY AND MOTOR CONDUCTION VELOCITY IN HEPATIC NEUROPATHY. C.Vasilescu, A.Florescu and N.Balta.(Bucharest, Romania).

The electroneurographic study of peripheral nerves in 18 patients with chronic postviral hepatitis showed slight (p~.05) slowing of motor conduction velocity (CV) with slight increase of terminal latency, and significant slowing (p~0.001) of sensory CV in the digit II and IV-wrist portions of the median and ulnar nerves (34.7-1.2 and 32.8~1.5 m/s) and in their palm-elbow segments (38.2±1.4 and 39.7±0.8 m/s) with a sTgnificant fall (p¢0.05) in the amplitude of sensory EPs. Also significant (pO.001) was the CV decrease in the mixed, sensorimotor potentials in the wrist-elbow segments of the median and ulnar nerves: 40.9±1.3 and 40.9±0.7m/s There were no significant differences between the distal and the proximal segments of one and the same nerve fibre. In some cases, a correlation was found between the severity of chronic liver disease and the degree of sensory slowing. A mixed process of segmental demyelination and axonal degeneration is presumed to underline the CV slowing, particularly the sensory one. Such complex measurements permit an early diagnosis of hepatic polyneuropathy while regenerative capacity is still preserved.

M007.POSTSYNAPTIC POTENTIALS MOTONEURONS IN MAN. P.Ashby. (Toronto, Canada).

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The post stimulus time histogram (PSTH) of the firing of individual soleus motor units following stimulation of the popliteal or peroneal nerve have been used to explore the effects of extensor and flexor group I afferent volleys on the excitability of single soleus motoneurons in man. The action potentials of 30 voluntarily activated motor units of soleus were recorded with concentric needle electrodes in 7 subjects. Individual action potentials were selected using a window discriminator and a delay line. A laboratory computer was used to extract the action potential by repeated averaging and to generate interval data including the PSTH. Extensor group I volleys resulted in an early peak of increased impulse density in the PSTH of 75% of soleus mo toneurons. The latency suggest an analogy with la EPSP. The mean duration of the peak of increased impulse density, equivalent to the rise time of the EPSP, was 3.6 msec. Flexor group I volleys resulted in a transient reduction in the excltability of soleus motoneurons. The latency suggests an analogy with the la IPSP. It is suggested that this method could be used to derive some of the characteristics of postsynaptic potentials in single motoneurones in man.

M008. EFFECT OF LOCAL COOLING ON NEUROMUSCULAR TRANSMISSION IN MYASTHENIA GRAVIS. K.Ricker and G.Hertel. (W~rzburg,W.Germnay) Borenstein and Desmedt, 1975, showed that in myasthenia gravis local cooling increases the voltage of the MAP and the twitch force. They

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suggested that cooling might improve neuromuscular transmission in myasthenia. We studied the effect of local cooling on maximum tetanic force in 27 patients with myasthenia. The MAP and the isometric force of the adductor pollicis were registered. The ulnar nerve was stimulated at 50/s for 1.5 s. The hand and lower arm were placed in a tank which cauld be filled with hot or cold water. After cooling from normal intramuscular temperature(34-36oc) to 26-3D°c a definite increase in maximum tetanic force was registered in 10 patients with severe generalized myasthenia. However, at the same time the degree of neuromuscular failure increased during the stimulation.After about 0.8 to I s of stimulation a sharp decline in tension occurred. At the end of the stimulation the tetanic force was lower as compared to the values at normal temperatures. In severe myasthenia local cooling may cause an improvement of neuromuscular transmission with increase of the maximum tetanic force. This effect is very short because the decrement of force is much higher at lower temperature as compared to the decrement at normal temperature.

M009.1NCREASED VOLTAGE OF THE MUSCLE ACTION POTENTIAL AFTER LOCAL COOLING IN NORMAL SUBJECTS. K.Ricker and G.Hertel. (W~rzburg, W.Germany). The effect of local cooling has been studied in 25 normal subjects. The ulnar nerve was stimulated and the compound muscle action potential (MAP) and the isometric twitch force of the adductor pollicis muscle were recorded. Intramusuclar temperature ranged from 36,6 to 18,0 ° C. The unexpected result was that after cooling the amplitude of the MAP increased. At the same time the twitch force decreased. These findings cannot be explained as a result of an altered neuromuscular transmission in normal subjects. Possibly, the increase of the MAP reflects an effect of temperature on the muscle cell m e m b r a n e : It seems that an increased potential amplitude can also be foundat the nerve and at the end-plate. The decrease in twitch force possibly is caused by an effect of low temperature on the contractile apparatus.

M010.ELECTRONEUROGRAPHY AND CLINICAL SIGNS OF PERIPHERAL NERVE DYSFUNCTION IN DIABETES. G.Rabending, W. Fischer and G.Reichel.(Greifswald,

D.D.R.) Motor and sensory nerve conduction studies have been carried out in 789 patients with diabetes (79 of them with clinical evidence of polyneuropathy, 72 with clinically suspected pnp). Sensory nerve conduction more often was found to be involved than motor nerve conduction but in some cases slowing of motor nerve conduction was the only electroneurographic sign wi~in pathological ranges. The clinical conditions (no signs of pnp, suspected pnp, clinical evidence of pnp) were paralleled by different electroneurographic findings. To distinguish between the three clini-

587 cal categories, distal latency of sensory fibers in thel median nerve, sensory conduction of the median nerve and motor conduction of the tibial nerve were found to be of significant diagnostic value (discriminant analysis, test o ~ indispensability). Considering the relationships between age, clinical, and electroneurographic findings we may distinguish between 3 groups of diabetics in respect to peripheral nerve dysfunction. I. Below 20 years: peripheral nerve impairment in I/3, predominantly involving motor fibers of the median nerve without relation to known duration of diabetes; pnp occurs very seldom, 2. Between 20 and 40 years: impairment of motor nerve conduction in median and tibial nerve, and of sensory nerve conduction in median nerve; statistical relation between duration of diabetes, signs of microangiopathy and peripheral nerve dysfunction; clinical evidence of pnp in 20%. 3. 40 years and beyond: electroneurographic signs of peripheral nerve dysfunction in about 2/3 with slight predominance of motor nerve conduction in the tibial nerve; no relation between nerve dysfunction and known duration of diabetes; if there are signs of micro-and macroangiopathy, 90% of these patients showed peripheral nerve dysfunctio~ clinical signs of pnp in 50%.

M011.PROGNOSTIC VALUE OF THE AMPLITUDE OF THE EVOKED ACTION POTENTIAL DURING REINNERVATION IN BELL'S PALSY. P. Ucl~s. (Zaragoza, Spain). A survey of twelve recent cases of facial Bell's palsy has enabled us to assess the prognostic value of the amplitude of the muscle action potential obtained by stimulating the facial nerve by needle electrode and recording with surface electrodes. We compared the amplitude on the affected side with that on the normal side, as previously reported by Zander Olsen (1975). Our patients were all referred for examination three weeks to three months after the onset of the palsy, i.e. during reinnervation by collateral sprouting. Thus, the absolute criterie based on the amplitude of the muscle potential cannot fit the outcome and time course of recovery. Reexploration was performed on the calculated date of final recovery; all the pat lents reached force 3-4. In ten out of twelve patients (83%) force was graded as 0. In the remaining two patients (17%) as 3. All the patients had electrical activity on the paretic side on the time of the first exploration. Nine had a mixed pattern, and discrete activity. In nine patients we found fibrillations at more than two points in the same muscle. Mean duration and poliphasics were increased in all but two patients. Latency was above 4 ms in all patients. The evoked potential was poliphasic in all but one. Amplitude was above 10% of the normal side in all cases. On considering our results, it is clear that clinical signs are of limited value in predicting final recovery. All the EMG data indicated rein-

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neTvation. The amplitude of the evoked was of great value in this situation, shown by the second test, but it must to: I. Time from the onset, 2. EMG's parameters, and 3. rate of increase of the amplitude follow up.

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potenti~al as was be related

in a monthly

M012.SOME CHARACTERISTICS OF SPINAL EVOKED POTENTIALS RECORDED FROM BODY SURFACE IN MAN. M.Ebe, l.Homma and Y. Ishiyama. (Tokyo, Japan). Recording electrodes were placed on the-skin surface over the spine in humans and the triphasic and small responses (positive-negative-positive) were elicited by electrical stimu~tlon to peripheral nerves in the limbs. In seven subjects of 172±4.7 cm in height the peak latency of cervical response to the stimulation of the median ~ e at the wrist were 9.8~ 0.9 -12.5~0.8 - 17.4~1.1 msec, respectively. The peripheral nerve potential interfered frequently with the spinal potential through volume conduction. However, the spinal potentials were differentiated from the peripheral nerve potentials by the peak latency and the configuration. The responses were recorded from eletrodes located from the lumbar to cervical spine for the stimulation of tibial nerve at the popliteal fossa. In this case, the amplitude was maximum in the vicinity of Th 12 or L I and it was sharply decreased at the cranial part of spine. The peak latency delayed gradually from lumbal to cervical area. If the delay is dependent on the conduction of excitation in spinal cord, the velocity of conduction is 68~13 m/sec. The amplitude recovery curve of the spinal potential obtained by paired stimuli to the ipsilateral median nerve was compamd with that of peripheral nerve potentials and also compared with that of the spinal potential obtained by twin stimulation of bilateral median nerves (one stimulus to the right & the~her one to the left). The recovery of peripheral nerve potentials was the faster than the others, but there was no clear difference in the recoveries of spinal potentials between ipsilateral and bilateral stimulation.

the second one in amplitude, and the first one was reduced by vibration and the second one usually remained in initial amplitude. (2) Flaccid palsy: The first one was higher than the second one in amplitude. The second one was augmented by vibration. (3) Spasticity: Both were higher in amplitude. The first one was augmented marke01y by vibration and the second one was reduced. (4) Rigidity: Although the first one was higher than the second one, both ones were very much reduced by vibration, The influences of TVR not only at the spinal cord level b ~ also in the upper center could be observed in the H-responses. Although further more detailed analysis should be performed in this study some interesting inferences can be made.

M014.SINGLE-FIBER ELECTROMYOGRAPHY IN MYASTHENIA GRAVIS. D.B.Sanders, J.F.Howard and T.R.Johns. (Charlottesville, Virginia, USA). Single-fiber EMG studies were performed 106 times in the extensor digitorum communis muscles of 68 patients with myasthenia gravis. The patients were in various stages of treatment, ususally with high doses of corticosteroids. In each study the overall mean jitter, the proportion of fibers with normal neuromuscular transmission, and the proportion of fibersshowing blocking were determined. Abnormalities in each of these parameters correlated with the severity of clinical weakness. Five studies were normal by all criteria; two of these were in patients clinically in remission, and three were in patients having purely ocular myasthenia. Serial studies in 22 patients frequently correlated well with changes in clinical weakness, especially when the intervals between consecutive studies were longer than one month. We have found single-fiber EMG techniques to be of great value in confirming and quantitating the defect of neuromuscular transmission in myasthenia gravis, and in providing objective evidence of changes in neuromuscular blockade that may be too subtle to be demonstrated by other means.

MD13.ELECTROMYOGRAPHICAL ANALYSIS OF MUSCLE TONE ABNORMALITY USING TONIC VIBRATION REFLEX (TVR). M. Ioku. (Osaka, Japan).

M015.EFFECTS OF THE BRAIN CORTEX GANGLIOSIDES ON MOTOR UNIT REGENERATION IN RATS. ELECTROPHYSIOLOGICAL AND HISTOCHEMICAL STUDY. F.Aporti, M.R.Caccia, M.Finesso, G,. Meola and G.Scarlato. (Bergamo, Italy).

Electromyographical analysis of various muscle tone abnormalities was performed using the tonic vibration reflex (TVR). Short interval double volleys of the order of 2-15 ms. were given to the tibial nerve, and two successive H-reflexes to these stimuli were recorded. 90 Hz. frequency vibration was applied to the leg, hand and arm muscles. The influence of vibration was observed in'the H-reflexes in various muscle tone abnormalities. 40 patients were examined in this study. (I) Normal: The first H-reflex was higher than

In 60 Female wistar albino rats, transection and freezing of the nerve of the e~tensor digitorum longus (EDL) muscle were performed to study in vivo and in vitro physiological changes of the electrical and mechanical isometric responses during 40 days of nerve regeneration before and after administration of brain cortex gangiiosides. Histological and histochemical patterns of the EDL were also studied investigating the effects of brain gangliosides on the muscle fiber typology changes during the recovery. Correlation be-

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tween physiological and histochemical was also suggested.

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MOI6.THE USE OF "LATE" RESPONSES IN THE EVALUATION OF BACK PAIN: A CLINICAL-PHYSIOLOGICAL APPRAISAL. A.J.Shivde, C.Teixelraand M.A.Fisher.(Chicago, I l l i n o i s , USA). 60 consecutive patients with back pain with or without other evidence for a radiculopathy were examined. In none of these patients was there evidence to suggest other central or peripheral nervous system dysfunction. Evaluation of these patients included needle EMG examination of relevant limb and paraspinal muscles as well as studiesof "late" responses. These included F responses (57) and H reflexes (52) recorded from the soleus muscles. F response latencies were calculated as an average of 10 responses. Significant electrodiagnostic abnormalities were found in 49 of these patients. This included abnormalities of soleus H reflexes (20) and/or F responses (33) in 38 patients. In 12 patients, these were the only significant eiectrodiagnostic findings. The "late" response abnormalities included absence of H reflexes, asymmetrical prolongation (2 msec or greater) of H reflex or F response latencies, and bilaterally prolonged F response latencies. Myelograms were performed in 21 of the 60 patients, and an association (p<0.001) was present between abnormal soleus "late" responses and radiographic defects at the L5-$I in contr~t to the L4-L5 level. There was also an associtation between abnormal H reflex studies and decreased or absent ankle jerks (p~O.001) as well as clinical sensory signs (p<;[}.001), but no significant association between abnormalities of soleus "late" responses and a history of pain radiation into a limb or limitation of straight leg raising on physical examination. This study thus demonstrates the clinical usefulness of F responses (as well as H reflexes) in the evaluationof back pain and raises questioBs about the physiological basis of common "radicular" symptoms and signs.

H017.CLINICAL VALUE OF CAUDA-EQUINA-NEUROGRAPHY. J.J6rg. (DUsseldorf, W.Germany). The measurement of sensory or motor nerve conduction velocity is a good method for localisation of peripheral nerve lesions. Our results with cauda equina neurography demonstrate this too is of value for differentiation of lumbosacral disorders. The following procedure was used: a lumbar-puncture -needle, teflon-isolated except for the tip, was placed between the 2nd and 3tf lumbarvertebra near the cauda equina. After puncture the fibular-and tibial nerves on both sides were stimulated with rectangular impulses near the popliteal fossa and 224 mixed-action potentials of the lumbosacral roots were averaged. The mixed action potentials of normal adults are

biphasic, have the same configuration on both sides and their height is between 0.3 and 20 ~V depending needle's tip position. The conduction velocity is about 60 m/s and decreases with age. In cases of lumbosacral disorders with isolated or general nerve root affections, the cauda quina potentials are delayed, reduced, polyphasic or absent; the mixed conduction velocity is isolated or generaly slowed, these results were obtained from patients with protrusions compressing the lumbosaoral roots, cauda equina tumors, radiculitis or sciatic nerve lesions. The clinical, electromyographic, myelographic and operative results correspond with the neurographic investigations and in some cases this method has helped to localize the nerve lesion and so to establish the diagnosis.

M018.NEY WAYS OF STIMULATION OF BABINSKI'S REFLEX -EMG STUDY. M.Drobny. (Martin, Czechoslovakia). The effect of hammer stroke and passive plantar flexion of the great toe or myotatic stimulation, during the elicitation of Babinski's reflex were studied. An electromyographic method was used. Both stimuli were effective in all 19 patients studied and they showed EMG activity of leg flexors involved in Babinski's reflex or complex triflexion. The hammer stroke evoked polysynaptic response of both flexor and extensor muscles. Myotatic stimulation produced a monosegmental res. ponse of these muscles with shorter latency and a shorter period of activity. In cases with clear positive Babinski's reflex, the plantar reflex was found in latent form. The hammer stroke can be considered a new way of stimulation suitable for clinical purposes, whereas myotatic stimulation can be used in clinical experiments as a test of different drug effects on mono- and polysegmental reflex activity.

MO19.HABITUATION OF THE BLINK REFLEX IN DEMENTIA AND DYSKINETIC STATES. I . T . F e r g u s o n , B.B.Johnston and J.A.R.Lenman. (Dundee, England). Assessment of the ability of the blink reflex to habituate to a series of taps on the forehead is a recognised clinical test in Parkinson's disease Failure to habit,ate has also been recorded clinically in association with presenile dementia associated with cortical atrophy. A quantitative measure of this phenomenon may be obtained by assessing the ability of the blink reflex to adapt to a series of electrical stimuli applied to the skin over the supra-orbital nerve and this can be expressed as the habituation index (Penders and Delwaide, 1971). Using a modification of this technique we have studied habituation in patients with idiopathic and drug induced Parkinson's disease, states of dementia, and in addition dyskinesias, such as Huntington's disease, senile and drug induced chorea. Where dementia has been found to be asso-

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ciated with communicating hydrocephalus~ar intracranial tumour, habituation of the blink reflex has been studied before and after surgery. Significant differences have been found between the different clinical groups, patients with Huntington's disease showing a marked tendency for the reflex to habituate, in contrast to patients with other forms of dementia or Parkinson's disease. The implications of the findings is discussed in relation to the physiological mechanism underlying the blink reflex.

M020.NERVE CONDUCTION IN GUILLAIN-BARRE SYNDROME. I.HausmanowaPetrusewicz, B.Emeryk-Szajewska, K.Rowinsak-Marcinska and H.Jedrzejowska. (Warsaw, Poland). The investigations were concerned with the diagnostic value of the changes in various conduction parameters in the Guillain-Barr~ syndrome. They involved 20 patients (Group A) in the acute stage including four relapsing cases, and 30 healthy subjects, who had the syndrome over ten years earlier (Group B). Conduction was investigated in the facial, axillary, musculocutaneous, peroneal, sural and ulnar nerves(motor maximal and minimal and sensory velocity). In some cases the sural nerve was examined morphologically by light and electron microscopy. In the early acute stage of the disease all the electrophysiological parameters were abnormal in a statistically significant manner for the group as a whole. At the beginning of clinical improvement all parameters of conduction, were still abnorma|, sometimes even deteriorated, especially in the axillary musculocutaneous nerves Only at the stage of ~l] clinical recovery did conduction really improve, but rarely reached normal values. The relapsing cases were characterized histopathologically by ~nion bulb ~' structures and electrophysiologically by a significant slowing of con~ction, persisting in remission. Sensory conduction was changed almost equally with motor conduction in spite of the absence of clinical sensory symptoms. The conduction defect was more persistent in the u l n ~ than in the peroneal nerve / despite the more severe paresis of the legs/. The permanence of this defect was confirmed in group B. In all members of group B, conduction in the ulnar nerve was the only significantly altered parameter irrespective of whether their past disease had been severe or mild.

MO21SEGMENTAL SENSORY INNERVATION STUDIED BY THE RECORDING OF POTENTIALS FROM CERVICAL SPINAL NERVES. Y. Inouye and F. Buchtha]. (Copenhagen, Denmark). Spinal nerve potentials were recorded at the level of the fifth to the eighth cervical roots and evoked by stimulation of digits I to V, of the radial nerve at wrist, the musculocutaneous nerve at the elbow and the axillary nerve in the del~id region. The electrodes were placed at the correct level near the spinal nerve by X-raycontrol, and

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the optimum depth of insertion was determinded from the highest amplitude and the shortest rise time of the potential evoked by stimulation of mixed nerve. The spinal nerve or nerves at which stimulation of a given cutaneous area evoked potentials of highest amplitude were considered to receive most of the sensory fibres from that area. Potentials led-off from the adjacent spinal nerve may be conducted in volume from the nerve of maximum response, the decline in amplitude by volume conduction being 70-80 %. The connection of fibres from the cutaneous a r e ~ examined by this method was similar to the dermatopes obtained by the method of '~remaining sensibi|i~" by Foerster. However, there was considerable individual variation, and e.g. cutaneous fibres of digit V seemed to connect as often to the eighth as to both the seventh and the eighth spinal nerves. The cutaneous areas of digits I and II connected as often to C 7 as to C 6. In one of three patients with a cervical rib, the potential at the eighth spinal nerve evoked by stimulation of digit V was diminished in amplitude, split-up in shape and slowed in conduction.

M022.ELECTRONEUROPHYSIOLOGICAL STUDIES IN FAMILIAR AMYLOID NEUROPATHY-PORTUGUESE TYPE (F.A.N.). M.L. Sales-Luis. (Lisboa, Portugal). Electroneurophysiological studies were performed in 15 patients (ages 29 to 67) and in symptomfree -members of affected families (ages 9to64). These studies included: needle EMG; motor conduction velocities of deep peroneal and median nerves; sensory conduction velocities, sensory potentials and nerve potentials of the sural and median nerves. For the sensory studies Buchthal's needle-electrode teobnique and Gilliatt's superficial electrode technique were used. A. Patients - The most constant alterations are: absence of sensory potentials in the distal segment of sural nerve (100%); decrease of amplitude and polyphasy of the muscle response to stimulation of the deep peroneal nerve (93%); abnormalities of the sensory potentials (low amplitude and spreading) of the distal segment of the median nerve (93.7%). Proximal sensory (nerve) potential in sural nerve is absent in 73.3% and has a low voltage in 3.3%. The nerve potential of proximal segment of median nerve has a low voltage in 81.8%. The maximum motor and sensory conduction velocities are borderline or slightly decreased. B. Members of Families with F.A.N. - In 50% of the cases, abnormalities (low voltage, spread potentials) are detected in the distal segment of sural nerve, alone (31.3%) or together with alterations of the sensory potentials of the median nerve distal segment (18.7 %). Results suggest that F.A.N. is a peripheral neuropathy with predominant axonal damage of the distal segments of sensory fibers, compatible with a distal degenerative type of lesion. The results also suggest that it is possible to

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detect the disease before it becomes clinically evident.

M023.EFFECTS OF TOOTH PULP STIMULATION ON HUMAN JAW MUSCULATURE. M. Bratzlavsky and H. vander Eecken. (Ghent, Belgium). The investigation was carried out with eigth normal adult subjects in whom the pulps of healthy teeth had to be destroyed for therapeutic reasons. Canine, premolar and molar teeth have been investigated. In each subject, single electrical stimuli were delivered to the tested tooth thrcugh a monopolar electrode. Both sensory and reflex effects were analysed at different stimulation intensities. As reported previously (Arch. oral Biol., 21, 491-493, 1976) in several subjects the only sensation elicitable by pulp stimulation was a more or less intense painful prick. In contrast to what occurs in cats, pulp stimulation in man had no excitatory action on the digastric muscle and induced no clear jaw opening movement. Canine, premolar and molar tooth pulp stimulation elicited in all the subjects a bilateral short-latency, transient suppression of the voluntary masseter electromyogram,with a concomitant inhibition of the monosynaptic masseter reflex. In some subjects, an additional long-latency inhibition of masseter EMG and jaw jerk were evoked. The results suggest that the pulpar reflexes are due to true postsynaptic inhibition of jaw closing motorneurons. The existence of short-latency pulpal reflexes indicates that besides low threshold oro~acial input (Brain Res.1976, 124127, 1975), afferents conveying pain sensation and probably belonging to the A~lelta group have oligosynaptic connections with jaw closing motorneurons.

M024. EXTEROCEPTIVE INPUT AND MASTICATION. M.Bratzlavsky and H.vander Eecken. (Ghent,Belgium) In man, stimulationof lowthreshold intra- and perioral afferents, mediating tactile and light pressure sensation, induces short-latency inhibitory effects on the jaw jerk and on the voluntary jaw closing muscle EMG (Exp. Neurol.,36, 160÷65, 1972). These inhibitory effects vary considerably in intensity according to the state of activation of the jaw elevating muscles, being of much shorter duration during voluntary jaw closure than during relaxation of the jaw musculature. The results suggest that two separate internuncial circuits are involved in these short- and long-lasting effects. Although it has been clearly established that the pattern of masticationis mainly elaborated centrally, many investigators consider that exteroceptive input is involved in some way in the control of normal masticatory movements. The present observations support the latter view, by suggesting the existence of a modulated exteroceptive action on the jaw closing musculature.

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The functional significane of exteroceptive inhibitory inflow to jaw closing motoneurons might be to provide a positive feedback to central motor commands involved in voluntary relaxation of jaw closing musculature (Brain Res., 1976, 124-127, 1975). Apart from postsynaptic motoneuronal inhibition, a selective afferent inhibitbn of la input to jaw closing motoneurons could be quite purposeful in preventing autogenic reflex activation of the jaw elevating muscles, during the jaw opening phase of mastication.

M025.EXCITABILITY CHANGES OF QUADRICEPS AND BICEPS FEMORIS MYOTATIC REFLEXES FOLLOWING STIMULATION OF CUTANEOUS NERVES IN MAN. M.Gadea-Ciria and P.J. Delwaide. (Liege,Belgium). Excitability changes of motor nuclei have previously been studied in man following electrical stimulation of sensory nerves. However, a systematic comparison of nocioceptive and non nocioceptive stimulation on nuclei with antagonistic functions has not been achieved. In this study, we have analyzed the excitability curves of two antagonistic myotatic reflexes (quadriceps and biceps femoris) after stimulation of the sural (Su), saphenous (Sa) and lateral femorocutaneous (LFC) nerves. 26 normal adult volunteers were investigated. With non painful stimulation, thcre is a striking similarity between the results. In the quadriceps muscle, after a moderate phase of inhibition, a very marked facilitation appea which peaks at a 125 ms interval. The facilitation brought about by Su is the highest. Facilitation of the biceps femoris appears at the same interval but is less marked. With painful stimuli, the initial phase of inhibition in the quadriceps reaches the same degree as with non-painFul stimulation. A facilitation also appears around 125 ms but is clearly more marked; the LFC stimulation is the most efficient. In the biceps femoris, there is no initial inhibition. LFC stimulation produces between 80-125 ms a very marked facilitation. On the contrary, Sa and Su stimulations give only a slight facilitation. After 200 ms, the results differ: Su stimulation brings about an inhibition lasting more than 1000 ms. while Sa and LFC stimuli do not clearly modify the excitability. The pattern of facilitation and inhibition is discussed in the light of the current concepts of reciprocal inhibition.

M026. DISTAL CHRONIC SPINAL MUSCULAR ATROPHY INVOLVING THE HANDS. D.J.O'Sullivan and J.G.McLeod.(Sydney,Australia) Six patients with a 10-30 year histcry of slowly progressive wasting and weakness of the small muscles of the hand were studied electrophysiologically. In all patients the abnormal neurological signs were confined to the hamds and there was no clinical or radiological evidence of peripheral nerve, nerve root or central nervous system disease.

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Detailed electrophysiological studies established that the muscle wasting was due to chronic partial denervation; motor and sensory conduction studies were normal. These patients represent a form of chronic spinal muscular atrophy localised to the small muscles of the hand, the course of which is benign.

M027. LIMB ISCHAEMIA AND ACUTE NERVE COMPRESSION. I.R.~lil]iams, R.W.Gilliatt and D.Jefferson. (London, England). In six baboons an acute compression block was p r o duced by a weighted nylon cord placed over the anterior tibial nerve just above the ankle, as described by Rudge et al (J.Neurol.Sci.23,403,1974) Compression was maintained for one hour on each side under a single anaesthetic. On one side ischaemia of the hind limb was produced by a pneumatic cuff round the knee, inflated to 250-300mm~. The cuff was inflated two hours (2 animals) or three hours (4 animals) beforemechanical compression of the anterior tibial nerve was started, and continued during the one-hour period of compression. Nerve conduction studies commencing after 24 hours were used to assess the severity of the local block in the anterior tibial nerve and the time-course of recovery. Histo]ogical studies were used to assess the amount of Wallerian degeneration ]he completeness and duration of the local conduction block at the ankle and the amount of Wallerian degeneration produced by the nylon cord varied in different animals, but no consistent increase in the severity of the lesion could be demonstrated on the ischaemic side, although the ischaemia itself was sometimes sufficient to produce transient muscle and skin oedema underneath and distal to the cuff at the knee. These experiments provide no evidence that ischaemia contributes to the nerve damage found in acute compression syndromes.

M028. NERVE CONDUCTION VELOCITY AND ELECTROMYOGRAPHIC FINDINGS IN 5 PATIENTS WITH DIPHTHERITIC POLYNEUROPATHY. K.Fasshauer, W.F.Haupt, G.Huffmann and B.Leven. (Cologne, W.Germany). Foll@Jing the absence of diphtheria for many years we had the opportunity in 1976 to record the electrodiagnostic changes in 5 pmtients suffering from diphtheritic polyneuropathy. All our patients suffered from severe clinical courses with cardiac involvement, marked paresis and sensory changes. Besid~ elevations of motor chronaxie we registered marked spontaneous activity and a reduced neuropathic pattern of voluntary activity. Also we found the number of polyphasic potentials of low amplitude increased as in myopathies and differing from reinnervation potentials. They indicated a possible myopathic component. The motor and sensory nerve conduction velocities were diminished approximately 20% below the mean normal values,the sensory nerve po-

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tentia~ were often polyphasic, showed late components and diminished amplitudes. The diminished nerve conduction velocities corresponded to the previously described discontinuous myelin sheath destruction of diphtheritic polyneuropathy. These findings and the generalized denervation process indicate a similarity to idiopathic polyneuropathy (GUILLAN-BARRE-STROHL). The probable myopathic components of the voluntary activity pattern however are similar to electromyographic findings that we have seen in metabolic and toxic polyneuropathies. Diphtheric polyreuropathy therefore seems to be situated between inflammatory and toxic polyneuropathies.

M029RAPID IMPROVEMENT IN NERVE CONDUCTION AFTER RENAL TRANSPLANTATION. S.J.Oh, R.S.Clements,Jr., Y.W.Lee and A.G. Diethelm, (Birmingham, Alabama, USA). The acute changes in median sensory, median motor: peroneal motor and sural sensory nerve conduction velocity (NCV) were studied in 12 patients following the transplantation of either a live-related donor (6) or a cadaveric kidney (6). NCVs were determined pre-operatively and on postoperative days 1,2,4, 11 and 18 and were corrected to a skin temperature of 35 ° C. We have made the following obserw~tions: I. After transplantation, significant negative linear correlations were found between the median sensory NCV and the serum creatinine (P<0.001) and the serum urea nitrogen(P<0.01). 2. Improved NCV was observed on postoperative days 2,4 in all four conduction velocities, ranging from 2 m/sec in sural sensory to 5m/~c in median motor nerve conduction. 3. Improvement of NCVs was noted in both "liverelated donor group" and "cadaveric kidney group". 4. In patients who had subnormal NCV preoperative ly, the improvement of NCV was more pronounced and the improvement in median sensory NCV was significant (P<0.025). We conclude that rapid improvement in nerve conduction occurs after renal transplantation and that median sensory NCV rapidly reflects the acute metabolic alterations which follow renal transplantation.

M030.CORRELATION BETWEEN ADJACENT MOTOR UNIT INTERVALS. A.Rosenfalck and S.Andreassen. (Copenhagen,Denmark). Single motor unit potentials were identified over periods of 20 s. of isometric contraction of the anterior tibial muscle during constant effort (I-60% of maximal). The potentials were sorted automatically according to their shape and their relatively constant intervals thereby the error in their identification was diminished to less than I%. In normal subjects short and long intervals between motor unit potentials alternate and the

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correlation coefficient (RHO) of consecutive intervals was negative (RHO=-0.17, SD 0.16; mean value from 102 motor units from 4 subjects). In 10 patients with spasticity consecutive intervals were more similar than in normal subjects and the correlation coefficcient was positive or less negative than normal. In four of these patients the spasticity was secondary to cerebral or cerebellar haemorrhage and RHO was -0.3. In two in whom clinical findings suggested cerebeIlar involvement RHO was 0.11 and 0.26 and in four patients with multiple sclerosis RHO was less negative than normal. The negative correlation found in normal subjects requires a regulation system which acts within the typical interval length (50-100 ms) possibly operated via the "f-loop. The absence of this fast regulation causes the stereotyped interval pattern which corresponds to the positive correlation.

M031.RECORDING FROM A SINGLE MOTOR UNIT DURING STRONG EFFORT. S.Andreassen and Annelise Rosenfalck.(Copenhagen, Denmark). In large limb muscles the most selective recordings are obtained with small bipolar electrodes. To elucidate thisexperimental finding we calculated the extracellular field around a single muscle fibre from an intrace}lular muscle action potential. This model shows that a bipolar electrode is highly selective provided:l) the diameter of the recording surfaces are about half the diameter of the muscle fibres and 2) the distance between the electrode surfaces is of the same order or smaller (25-50 bm) than the diameter of the muscle fibres and that 3) the recording surfaces are oriented perpendicular to the muscle fibres, The field from distant muscle fibres is then attenuated and only 2 to 7 fibres close to the electrode contribute to the recording. Calculations of the power spectra of the action potentials shows that action potentials recorded bipolarly have larger contents of high frequencies than action potentials recorded monopolarly. The model also shows that the selectivity can be improved by high-pass filtering. Action potentials were recorded from the anterior tibial muscle of normal subjects with a bifilar electrode with holes burned into the wires. The electrode was passed through skin and muscle and the recording surfaces were positioned close to active muscle fibres. The amplitudes and the power spectra of action potentials recorded were in accordance with the model and no more than I-3 motor units appeared in the recording up to 60 ~ of maximal effort.

MO32.NEUROPHYSIOLOGICAL STUDIES NEURITIS. A . K u r d i . (Amman, J o r d a n ) .

IN DIPHTHERITIC

Although experimental diphtheritic neuritis has been widely used in the study of demyelination

and i t s e f f e c t on c o n d u c t i o n , o n l y f r a g m e n t a r y e v i d e n c e is a v a i l a b l e a b o u t n e r v e c o n d u c t i o n in the p a r a l y t i c phase o f the human d i s e a s e . F o l l o w ing a r e c e n t o u t b r e a k in J o r d a n , we have c a r r i e d o u t n e r v e c o n d u c t i o n s t u d i e s in 11 p a t i e n t s w i t h diphtheritic po]yneuritis aged 4-16 y e a r s . Using standard techniques, conduction velocity (CV) and d i s t a l m o t o r l a t e n c y (DML) were measured in the median and l a t e r a l p o p l i t e a l nerves. Electromyogram and s e n s o r y a c t i o n p o t e n t i a l s (SAP) were r e c o r d e d in o l d e r p a t i e n t s . 4 p a t i e n t ~ examined once o n l y d u r i n g the f i r s [ f i v e weeks a f t e r the o n s e t o f weakness had normal v e l o c i t i e s . The r e m a i n i n g 7 p a t i e n t s d e v e l o p e d s l o w i , , q ,of CV (minimum 18m/s) and i n c r e a s e d DML (nlaAilaJm 17.3ms) w i t h i n 3 t o 14 weeks a f t e r the o n s e t o f n e u r o l o g i c a ] s y m t o m s . l n 4 p a t i e n t s examined s e r i a l l y , reduced CV was f i r s t observed during zlinical r e c o v e r y . Evi dence o f d e n e r v a t i o n was found in each o f 3 p a t i e n t s examined w i t h c o n c e n t r i c n e ~ l e electrodes. SAPs were a b s e n t in one o f 3 p a t i e n t s s t u d i e d . The d e l a y e d o n s e t o f p e r i p h e r a l e l e c t r i cal a b n o r m a l i t i e s a c c o r d s w i t h the known time c o u r s e and d i s t r i b u t i o n of pathological changes ( V e i t h , B e i t r . P a t h o l . A n a t . 110: 5 6 7 , 1 9 4 9 ; F i s h e r & Adams, J . N e u r o p a t h . E x p e r . N e u r o l . 1 5 : 2 4 3 , 1 9 5 6 ) and emphasises the need f o r s e r i a l n e r v e conduct i o n s t u d i e s in p a t i e n t s s u s p e c t e d o f i l a v i n g diphtheritic po]yneuritis.

M 033.MONITORING UREMIC NEUROPATHY REFLEX RESPONSE LATENCY. O. K n o l l . ( M ~ n s t e r , W. Germany).

BY MEANS OF

Peripheral uremic neuropathy is an usual effect of uremic intoxication. In patients cn regular dialysis treatment signs of uremic neuropathy are therefore reliable indicators of inadequate therapy. Motor nerve conduction velocity commonly tested in uremic patients is not sensitive enough for detecting early stages of peripheral neuropathy. However, the latency of monosynaptic refl~ response proved to be a much more sersitive parameter of even subclinical neuropathy than motor nerve conduction velocity. A proprioceptive Hreflex was elicited by electrical stimulation of the tibial nerve. In 172 healthy subjects the interval in time between the direct response and the reflex response in the EMG depencied only on the body height. In 64 non-dialyzed patients with chronic renal failure the reflex response latency was delayed usually, when serum creatinine level was above 4-5 mg/100 ml. Motor nerve conduction velocity was slowed only in those patients, whose creatinine levels were above I0 mg/100 ml. Reflex response latency allows regular cheeks for uremic neuropathy even in non-dialyzed patients, when motor nerve conduction velocity is still normal. The test is for instance suitable for neurophysiological monitoring of patients under dietary therapy. The test takes less time and is no more disagreable for the patient than measurement of motor nerve conduction velocity; moreover the reproducability of results is better than that of nerve conduction velocity.

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M034. AN ELECTROMYOGRAPHIC STUDY OF TRAINING TECHNIQUE IN WELDING. I.Peters~n and R.Kadefors. (GSteborg,Sweden). In model tests in a workshop environment, a comparion was made between ten experienced welders (more than five years' experience) and ten inexperienced ones (less than one year's experience. All of them welded four electrodes by low vertical welding, high vertical welding and overhead welding respectively. Five muscles were examined: a) the deltoid, anterior portion,b) biceps brachii, c) the rhomboid, d) the trapezius, middle and upper protions, and e) the supraspinatus. The examination showed that with inexperienced welders fatigue changes appear in the EMG activity of the deltoid and supraspinatus muscles, and in the upper portion of the trapezius. Such ~hanges appear in the supraspinatus muscles of experienced welders, too, in spite of their long training and good working technique (Kadefors, Peters~n & Herherts, 1976). The fatigue reactions were thus more widespread in the inexperienced welders, in whom symptoms could appear even with high vertical welding, while they were conspicuous with overhead welding. Differences between experienced and inexperienced welders were noted also in respect of subjective local fatigue and feeling of discomfort. The results are of interest from two aspects. The more widespread and more pronounced fatigue reactions of inexperienced welders, we consider, give valuable information from the point of view of learning the welder's job. The constant strain on the supraspinatus muscle, also shown in other investigations by us, is of the greatest interest in the discussion of the mechanism which gives rise to shoulder pains, particularly in older welders (Herberts & Kadefors, 1976).

INTERNATIONAL FEDERATION - 9TH CONGRESS in RPO0 patients (4.5~0.7 ms) was longer than that in the control subjects (3.9~0.2 m s . P ~ . 0 1 ) It appears that in RPO0 patients not only the vasomotor system but also the nerve fibers themselves may be impaired.

M035. ELECTROPHYSIOLOGICAL STUDIES OF TIBIAL NERVE BY SIMULTANEOUS STIMULATION OF TOES I,ll and Ill. H.Ishibashi, T.Muneyuki, H.Yanagisawa and T. Yoshida. (Maebashi city, Japan). Sensory nerve conduction velocities (SCV) and sensory nerve action potential (NAP) and the duration of NAP (DAP) in tibial nerves were studied in 40 patients with polyneuritis and in 24 normal subjects, by the application of simultaneous stimulation to toes i, II and Ill which were able to make the amplitude larger than that reported previously. In healthy subjects, SCV from toe to ankle was 39.2~4.9 m/s (mean * SD) and that from ankle to knee was 58.4±3.8 m/s. NAP and DAP, were 10.1± 3.9 ~V & 3.31±0.72 ms at the ankle, and 2.1"0.7~V & 4.69±1.17 ms at the knees, respectively. 2 patients with ethambutol neuropathy and 3 patients with subacute myelo-optico-neuropathy showed the prolongation of DAP and normal NAP and SCV. In 21 patients with diabetic neuropathy,SCV, NAP and DAP were disturbed to thc~ same extent. Similarly, these parameters were disturbed in 14 patients with acute idiopathic polyneuritis. However, some patients with acute idiopathic polyneuritis showed prolongation of DAP and normal NAP and SCV. This study indicates that measurement of NAP and DAP by our method give additional and valuable information, and that abnormalities of DAP have more specific and characteristic value than those of SCV and NAP, in the diagnosis of peripheral neuropathy.

M035. ELECTROPHYSIOLOGICAL STUDIES ON RAYNAUD'S PHENOMENON OF OCCUPATIONAL ORIGIN. T.Tanabe, T.Watanabe, J.Sugano and T.Yoshida. (Maebashi city, Japan).

M03~. FIRING RATES OF HUMAN MOTOR UNITS IN PARTIALLY DEVERVATED MUSCLE. R.G.Miller and M.Sherratt.(Portland, Oregon,USA).

Raynaud's phenomenon of occupatioBl origin(RPOO) is also designated as traumatic vasospastic disease of the hand or vibration disease. In this study, sensory nerve conduction velocities(SCV), sensory nerve action potentials (NAP), motor nerve conduction velocities (MCV), and terminal latencies(TL) in the median nerves were measured in 15 RPO0 patients and in healthy subjects. The neural responses were recorded before, during, and after exposuring the skin of the upper extremity to high or lowtemperatures. The thermal b a ~ employed were 40 ° C and 10 ° C. With the load of 40°C, the SCV from finger to wrist and that from wrist to elbow were 53.6±6.38 m/s (mean~SD) and 61.2~5.43 m/s respectively in RPOO patients, while those in healthy subjects were 59.7±5.40 and 67.2~4.61 m/s respectively. Although the MCV from elbow to wrist was not significantly affected in RPOO patients, the TL from wrist to thener

Single motor unit firing rates were measured from the first dorsal interosseous muscle (FDI) of normal subjects and patients with weakness and clinical evidence of partial denervation of that muscle. Motor unit discharges were recorded at various levels of voluntary, stationary, isometr~ contraction of FDI. Minimum firing rates, where motor units began to fire steadily, were slightly lower in moderately weak muscle (8.6 impulses/sec,SD 2.4) compared to normal muscle (9.1 impulses/sec, SD 2.3). Significantly higher minimum firing rates were seen in severely weak muscle (11.5 i/sec, SD 2.5) compared to normal (p <01). Twelve motor units from severely weak muscle were recorded during sustained maximum voluntary contraction. Mean maximum firing rates for these units was 19.9i~c (SD 5.8), with the highest value of 29.7 i/sec in a patient with peroneal muscular atrophy. The mean increase in firing rate associated with

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an increased muscle tension of 100 gm was significantly greater in severely weak muscle (7.4 impulses/sec/100gm, SD 13.7) compared to normal muscle (2.9 impulses/sec/100gm, SD 2.6)(p<.01). Incremental increases in firing rates, corresponding to an increased force of co~traction of I% of maximum voluntary contraction,were found to correlate with increasi~ weakness.

M038.CONTROLLED INTRAMUSCULAR MICROSTIMULATION: A NEWTECHNIQUE FOR STUDYING THE MECHANICAL PROPERTIES OF HUMAN MOTOR UNITS. A.Taylor, M.J.O'Donovan, J.A.Stephens and R.A. Garnett. (London, England). A variety of electrophysiological techniques have been developed for detecting abnormalities of motor unit function such as neuromuscular transmission, muscle fibre propagation velocity and muscle fibre density. We now report a method for investigating attendant abnormalities in motor unit mechanical properties. While spike triggered averaging can be used for measuring motor unit twitch amplitude and contra~ tion time, it cannot be used for studying tetanic contractions. Single units have been excited in isolation by finely graded percutaneous stimulation of a nerve trunk but the selection of units by this method is inevitably restricted and problems of stability of stimulation make the study of unit tetani very difficult. A much more advantageous situation is to stimulate through a conventional bipolar needle electrode inserted a short distance from the motor point where the final branches of the motor axons are more widely dispersed. The position of the stimulating electrode and stimulus strength (50-100As, 0"30V) are adjusted until an all or nothing EMG response is detected. Provided reliable stimulation is possible without activating another unit EMG the mechanical responses of the unit can be recorded. Using this technique successful recordings have been made in normal muscles and in muscles affected by ischaemic vascular disease. Identification of the muscle fibres of single units by glycogen depletion has shown that fast twitch units are hi~tochemically Type II. In disease these units are abnormally weak, consistent with the observed atrophy of their constituent fibres.

M039.THE SYNAPTIC CONNECTIONS OF SINGLE MOTONEURONES IN MAN. J.A.Stephens and R.A.Garnett.(London,England). Abnormalities in any of the major peripheral components of motor units can now be detected by established techniques. The present report describes a method for studying their central connections. During voluntary contractions the p a t t ~ n o f discharge of a given motor unit is determined by the summed effects of a variety of segmental and supraspinal inputs. The synaptic effect of any particular input can be determined simply by

595 constructing a histogram of the time of occurrence of motor unit spikes followi~repeated suitably controlled stimuli. Using this approach the reflex responses of motor units in the first dorsal interosseous have been studied following stimulation of cutaneous and muscle afferents. Subjects maintained a contraction such that the unit under study fired steadily at about 10 pps. Concurrently ~imuli were repeated at 3/sec and a post stimulus time histogram of the occurrence of motor unit spikes accumulated. Light taps to the skin or modest clectrical stimulation of the digital nerves (2-3x sensory threshold) produced marked changes in the probability of motor unit firing (range±90%)%ypically the responses showed a rise in probability (mean latency 37 msec) followed by a decrease (mean latency 47 msec) followed by a large increase (mean latency 58 msec). Stimulation of muscle afferents by light taps over the muscle belly resulted in a large essentially monophasic increase in probability (mean latency 37 ms). Differences in the relative magnitude of these responses in neurological patients may reveal defects in specific segmental and/or supraspinal inputs to their motoneurones.

M040.REFRACTORINESS OF HUMAN NERVE AND MUSCLE FIBRES. S.J.Kopec, J.Delbeke and A.J.McComas.(Hamilton, Canada). A computer-aided subtraction technique has been used to study refractoriness in the terminal branches of median nerve fibres and in the thenar muscles In healthy control subjects aged 18-29 years the absolutely refractory periods ARPs) of most muscle fibres were 2.5-3.0 ms and were distributed unimodally; the ARPs of the fine motor nerve branches appear to be similar.The relatively refractory periods (RRPs) of the motor nerve fibres were approximately 7 ms. Cooling the thenar muscles to 20 °C produced a 3 -" 4 x increase in refractoriness of the nerve and muscle fibres. In muscles at normal or reduced temperatures it was often possible to record non-propagated muscle responses from the end-plate region at relatively short conditioning-test stimulus intervals. There was a slight increase in nerve refractoriness in older subjects. No difference in muscle fibre refractoriness could be found between young and old controls, or between patients with myotonic dystrophy, motor neuropathy and renal failure.

M041.QUANTITATIVE EVALUATION OF THE STRETCH REFLEX IN NORMAL HUMAN SUBJECTS. G.L.Gottlieb and G.C.Agarwal.(Chicago,lllinois,

USA). Measurements of reflex electromyogram responses in the human soleus muscle to torque disturbances of the foot were made. Pulse and step type torque disturbances of different magnitudes were applied during various levels of steady voluntary contra~

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596 t i o n s o f the muscles a c t i n g a t the a n k l e j o i n t and d u r i n g v o l u n t a r y p l a n t a r f l e x i o n s and d o r s i f l e x i o n s . The s p i n a l s t r e t c h r e f l e x component w i t h 50 msec l a t e n c y is shown t o be a l i n e a r f u n c t i o n o f t h e v e l o c i t y o f s t r e t c h . The s ] o p e o f this functional relationship depends on the l e v e l o f muscle c o n t r a c t i o n . The second component in the r e f l e x r e s p o n s e w i t h 120 msec l a t e n c y is q u i t e v a r i a b l e and s t r o n g l y dependent on the i n s t r u c t i o n s g i v e n t o the s u b j e c t . T h i s second component p r o b a b l y c o r r e s p o n d s t o what is c a l l e d in the literature the F u n c t i o n a l S t r e t c h R e f l e x . T h i s r e s p o n s e may i n v o l v e c o r t i c a l pathways

MF142.RAPID ELBOW MOVEMENTS IN PATIENTS WITH AMYOTROPHIC LATERAL SCLEROSIS. M.Hallett. (Boston, Mass., USA). The e l e c t r o m y o g r a p h i c p a t t e r n u n d e r l y i n g r a p i d (bal]istic) mow~ments is c h a r a c t e r i s t i c a l l y triphasic with sequential bursts of activity in the a g o n i s t (Ag 1 ) , a n t a g o n i s t (An1) and the a g o n i s t a g a i n (Ag2). E x p e r i m e n t s were d e s i g n e d to see how t h i s p a t t e r n m i g h t be a l t e r e d in p a t i e n t s w i t h a m y o t r o p h i c l a tera] sclerosis (ALS). P a t i e n t s and c o n t r o l s made s t e r e o t y p e d 20 ° elbow f l e x i o n s as r a p i d l y as p o s s i b l e w h i l e s u r f a c e EMG was r e c o r d e d from b i c e p s and t r i c e p s . The ALS p a t i e n t s were d i v i d e d i n t o the f o l l o w i n g g r o u p s : n o r m a l , w i t h normal e x a m i n a t i o n s o f the upper e x t r e m i t y ; spastic, with inc r e a s e d t e n s o n r e f l e x e s and t o n e , b u t w i ~ o u t a t r o phy; a t r o p h i c , w i t h a t r o p h y , but w i t h o u t increased tendon r e f l e x e s ; and m i x e d , w i t h i n c r e a s e d r e f l e xes and a t r o p h y . The c o n t r o l s u b j e c t s and norn~l p a t i e n t s had component d u r a t i o B s s i m i l a r to the v a l u e s p r e v i o u s l y r e p o r t e d f o r a s t e r e o t y p e d l0 ° movement (HalleG et al., J.Neurol.Neurosurg. Psychiat. 38:1154,1975) The s p a s t i c g r o u p showed a s l i g h t , but d e f i n i t e i n c r e a s e in the d u r a t i o n o f Ag 1, w i t h o u t change o f the o t h e r components. The mixed g r o u p showed a m o d e r a t e i n c r e a s e in the d u r a t i o n o f Agl as the only significant change. P a t i e n t s in the a t r o p h i c g r o u p , a l l o f whom were s e v e r e l y a f f e c t e d , showed a marked i n c r e a s e in the d u r a t i o n o f Ag I and a m i l d i n c r e a s e in the d u r a t i o n o f An 1. A f f e c t i o n o f upper m o t o r n e u r o n s leads t o a sma]l i n c r e a s e in the d u r a t i o n o f Ag ] and a f f e c t i o n o f l o w e r m o t o r neurons leads t o a l a r g e r i n c r e a s e . To g e n e r a t e s u f f i c i e n t accelerative f o r c e t o make a movement, the b r a i n compensates f o r m o t o r n e u r o n d e f i c i t by p r o ] o n g i n g the d u r a t i o n o f Ag 1.

M043.EFFECT OF PERTURBATIONS ON THE EMG PATTERN OF BALLISTIC MOVEMENTS IN MAN. M.Hallett and C.D.Marsden. (Boston, Mass.,USA). Flexion movements of the top joint of the thumb when performed smoo~ly (ramp movement) are under strong influence of a peripheral servo-loop a c t i ~ at "long-latency" (Marsden, Merton and Morton, J.Physiol. 257:1-44, 1976). Experiments were u n ~ m taken to see whether the electromyographic activity in rapid (ballistic) flexion movements could

be s i m i l a r l y i n f l u e n c e d . The EMG p a t t e r n o f b a l listic movements is t r i p h a s i c w i t h s e q u e n t i a l bursts of activity in the a g o n i s t (Ag 1 ) , a n t a g o n i s t (An 1) and the a g o n i s t a g a i n (Ag 2 ) . S u b j e c t s made s t e r e o t y p e d b a l l i s t i c f l e x i o n movemerits o f t h e thumb a g a i n s t the s p i n d l e o f a DCmot or w h i l e EMG was r e c o r d e d w i t h p a i r s o f w i r e electrodes inserted into flexor pollicis longus and e x t e n s o r p o l ] i c i s l o n g u s . At p r e - s e t times the t o r q u e o f the m o t o r was a l t e r e d in o r d e r t o d r i v e the thumb back ( s t r e t c h ) , a l l o w i t t o acc e l e r a t e ( r e l e a s e ) o r h a l t i t in i t s p o s i t i o n . The amount o f e l e c t r i c a l activity in A9 ] i n c r e a sed w i t h s t r e t c h and d e c r e a s e d w i t h r e l e a s e . Similarly, the amount of electrical activity in An I was decreased with stretch (release of the extensor) and increased with rele~,se (stretch of the extensor). A suitably timed h~It could decrease the activity in An I, but cid not increase agonist activity until the time of Ag 2. The conclusion is that the muscle activity remaim under some control of the peripheral servo-loop during ballistic movements and theft the amount of activity at any time is a result of the interaction ofthe supraspina] patterned signal and the i n p u t from the p e r i p h e r a l s e r v o - l o o p .

M044.PROGNOSTIC VALUE OF ELECTRODIAGNOSTIC METHO~ IN PERIPHERAL FACIAL NERVE PALSY. G.Huffmann, K . F a s s h a u e r and~.V.F.~upt..(K61n,W.Germa -

ny).

The f u n c t i o n o f the f a c i a l n e r v e can be examined by 4 e l e c t r o d i a g n o s t i c methods. It, the n e r v e e x c i tability t e s t and e l e c t r o n e u r o g r a p h y w i t h d e t e r m i n a t i o n o f the d i s t a l l a t e n c y the f a c i a l n e r v e is s t i m u ] a t e d o v e r the s t y l o m a s t o i d f o r a m e n . Chr o n a x i m e t r y and e l e c t r o m y o g r a p h y a r e p e r f o r m e d in the m u s c l e s . Cosmetic d i s f i g u r e m e n t due t o p e r i p h e r a l f a c i a l n e r v e p a l s y i m m e d i a t e l y poses the q u e s t i o n o f p r o g n o s i s . U s u a l l y , t h i s q u e s t i o n can be answered by c l i n i c a l e x a m i n a t i o n a l o n e . As soon as p a r a l y s i s o f f a c i a l muscles is p r e s e n t , p r o g n o s t i c s t a tements can be made by e l e c t r o d i a g n o s t i c methods a l o n e . Because o f the p o s s i b i l i t y of operative t r e a t m e n t i t is n e c e s s a r y to i d e n t i f y the i n f a v o r a b l e cases e a r l y . Whereas c h r o n a x i m e t r y r e n d e r s an i m p r e s s i o n o f the s e v e r i t y o f the n e u r a l l e s i o n , e l e c t r o m y o g r a phy can a l s o d e t e r m i n e the o n s e t o f r e i n n e r v a t i o n activity. E a r l y p r o g n o s i s w i t i ~ i n 6 days o f o n s e t can be d e t e r m i n e d o n l y by n e r v e e x c i t a b i l i t y tests and e ] e c t r o n e u r o g r a p h y , p r e f e r r e d by us, which a s s e s s the muscle p o t e n t i a l . I f the p o t e n t i a l amp l i t u d e d e c r e a s e s more than 35~ w i t h i n two days and the musc]e p o t e n t i a l d i s a p p e a r s between the f o u r t h and s i x t h d a y s , t o t a l d e g e n e r a t i o n o f the n e r v e w i t h p o o r p r o g n o s i s is i n d i c a t e d . Such d a t a can be o b t a i n e d by a t l e a s t two e l e c t r o d i a g n o s t i cal i n v e s t i g a t i o n s p r e f e r a b l y on the t h i r d day a f t e r o n s e t and one t o t h r e e days l a t e r .

M045.EMG AND FLUCTUATION POSTURE IN MAN.

OF CENTER OF GRAVITY WITH

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A. Miyake, S.Watanabe, H.Jijiwa, K.Yamaji and K.Komachi. (Gifu, Japan). Relationships between the fluctuation of center of gravity and muscle activity of the lower extremities was investigated in normal male volunteers adapting various postures; upright standing, easy bending, hard bending, forward leaning and backward leaning. The center of gravity was measured by the rectangular equilateral triangle force plate mounted on three differential transformer ceils sensing forward-backward and rightleft movements and vertical supportive force. By power spectrum analysis of fluctuation of the centre of gravity, all five postures were found to be characterized by large power in the low frequency range. During forward leaning and hard bending, a high frequency component and an in ~ crease of lower extremity muscle activity were observed. Furthermore, in forward leaning this component was seen at a slightly lower frequency than in hard bending. This high component coincides with gastrocnemius soleus muscle discharge and plays an important role in the righting refle~

M046.RESTING TREMOR IN ALCOHOLIC BRAIN DISEASE. S.Bajada and A.Fisher. (Perth, Australia). Upper" limb tremor is a relatively uncommon feature in severe alcoholic encephalopathy. Only 12% of the 245 patients reported by Victor,Adams and Collins manifested this feature, even though ataxia in some degree was presentin 87% of patients in whom examination was possible. This observation of disabling tremor in two patients in whom there were previously documented neurological complications of alcoholism appeared to justify further evaluation. Preliminary e]ectrophysiologica] studies in these two patients have shown the presence of resting or attitudinal tremor distally, coupled with a basic 3 to 4 Hz. tremor of upper limb girdles in one patient. In the other individual the tremor appeared to affect the axial musculature primarily,with again, a slow tremor of the upper limb girdles. The tremor patterns will be illustrated and a suggested mechanism advanced.

M047.NEURALGIA AND HYOERALGESIA FROM LOCAL NERVE LESIONS: PATHOPHYSIOLOGY. J.Ochoa. (Hanover, New Hampshire, USA). To c h a r a c t e r i z e the a n a t o m i c a l s u b s t r a t e of t r a u m a t i c nerve l e s i o n s c a u s i n g pain in the l i m b s , quantitative electronmicroscopy has been performed on surgical specimens obtained from selected patients studied clinically and by routine electrophysiology. Analysis of the morphological findings has revealed: a) Outpouring of nerve fibres through incontinent perineurium towards interfascicular spaces with formationof minute fascicles limited by dissident perineurial cells. b) Pathological changesin myelinated fibres, including axonal degeneration and regeneration and

592 focal demyelination and remyelinatior, of various severities. c) Pathological changes in unmyelinat:ed fibres indicative of axona] degeneration and sprouting. d) Numerical changes in fibre populations, at and dista] to the lesion: focal decrease or increase in total number of axons, focal decrease in mean fibre diameter and in myelin thickness. In terms of current theories for neuralgic pain, these findings would entail the following significance: Consistent finding of immature nerve sprouts, possible abnormal impulse generators, is in keeping with their putative role in spontaneous pain. Fibres with focally disrupted myelin sheaths might be ephaptically cross-excited: pain and hypera]gesia could result from excitation of certain small diameter afferents. Selective degeneration of large diameter fibres, presumed to release small afferents, is not a necessary f e a t u r e in these ( n o n - h e r p e t i c ) p a t i ~

M048. MEASUREMENTS OF THE INNERVATION RATIO IN THE HUMAN BRACHIAL BICEPS. E. St~lberg and L.Gath. (Uppsala, Sweden and Haifa, Israel). The radial decline of the extracellular action potential was calculated in steps of 25 ~Im up to a distance of 300 lJm from the muscle fibre, simulating the low-pass filter characteristics of the muscle tissue by one time constant and an attenuation factor (Gath and St~lberg, EEG.CIin. Neuro-physiol., in press). The average pick-up radius of the 25pm diameter electrode, used in the investigation, defined as the distance at which the peak to peak amplitude of the action potential declines to 200pv, was calculated from the data on the radial decline of 14 single muscJe fibre action potentials. Assuming a homogenous and linear spread of the fibres in the motor unit territory, the average number cf fibres in the motor unit of the biceps brachii was derived from the average fibre density in this muscle, the electrode pick-up radius, and the motor unit territory. For a pick-up radius of 283 pm found in the present investigation, a fibre density of 1.37 (St~Iberg et al., J.Neurol. Sci.27:291, 1976), and a motor unit territory of 5.1 mm in diameter (Buchthal et al., Acta Physioi.Scand., 45:72, 1959), the average number of fibres in the motor unit was found to be 225.

M04~-EMG QUANTITATIVE ANALYSIS IN INDUSTRIAL TOXIC NEUROPATHIES. A.Arrigo, A.Moglia, G.Sandrini, G.C:nquini and F. Tanzi. (Pavia,ltaly). T o x i c n e u r o p a t h i e s due to i n d u s t r i a l agents are not r e c o g n i z e d r e a d i l y enough to p r e v e n t the onset of clinical s¥~iptoms. The aim of our research has been to apply methods of EMG quantitative analysis in a group of 6 workers exposed to Dimethilfornamide (DMF) and to compare the findings with those in a contro] group of 6 norn~l subjects in the same age range. Tibialis anterior

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muscles of both sides were taken into consideration. EMGraphic studieswere carried out on one side by applying a M.U.A.Ps' automatic analysis method, previously described by Arrigo et al. (1975). On the controlateral side EMG tracings analysis was performed according to the methods described by Pinelli and Leifer (1976). Motor as well as sensitive conduction velocity of the lateral peroneal nerve were furthermore determined. We used a MEDELEC apparatuss for EMG examinations; analog signals were recorded on a magnetic Hewlett-Packard FM tape recorder and processed with a minicomputer DIGITAL PDP.8/L off-line. Data on the airbone concentration of DMF and time of exposure as well as clinical examination and laboratory analysis were of c o u r s e ~ s o taken into account. EMG data were then submitted to statistical analysis and assessed not only from the standpoint of compadng the control group and the workers exposed to the risk of poisoning but also to evaluate the reliability of the applied methods of analysis.

M05Q.THE EFFECT OF TEMPERATURE ON THE COMPOUND ACTION POTENTIAL IN NEUROMUSCULAR DISEASE AND NORMAL CONTROLS. E.H.Denys. (San Francisco, Calif., USA). The compound action potential amplitude of a muscle, elicited by indirect stimulation, is considered a function of the total number of activated muscle fibers; ~t is therefore decreased in neurogenic and myopathic diseases; in myasthenia gravis the amplitude is on the average also lower than normal. Because of the wide range of normal amplitudes, normality is difficult to assess on an individual basis. In the present study it is found that local cooling of the muscle may increase the amplitude, or more consistently, the total surface area of the negative potential; this increase is present to some degree in normal control~ but is much more prominent in patientswith amyothrophic lateral sclerosis; there is no relation between the amount of increase and the presence of a decremental response to repetitive stimulatio0 The increase is present when recording with surface as well as subcutaneous electrodes and reaches a maximum with increased cooling. Further data are being collected for presentation.

M051. ELECTROPHYSIOLOGICAL STUDIES IN CEPHALIC TETANUS. M.T.Shahani,D.H.Dastoor, E.P.Bharucha,G.H.Kashyap, F.D.Dastur, F.N.Kohiyar,V.P.Mondkar and KG.Nair (Bombay, India). 15 cases of Cephalic Tetanus representing 1.5% of all the tetanus cases seen during 18 months were studied in detail electrophysiologically. Three types of spontaneous activities were picI~=d up from the muscles of the face in different patients at rest. The spontaneous activity resen~)l~ fast firing of motor units producing mixed or interference patterns, denervation potentials

INTERNATIONAL FEDERATION - 9TH CONGRESS ~iphasic and positive sharp waves), high frequency discharge(like pseudomyotonia); these three different types of activities were not always present in the same patient at the same time. Study of patterns of activity were also made at minimum and maximum voluntary efforts. On maximal stimulation of the facial nerve "M" responds were picked up from the muscle Frontalis and muscle Orbicularis Oris. End plate studies were carried out by giving supramximal stimuli at I/s, 10/s and 50/sec.; change, if any, in the amplitude was noted. In some patients it was possible to study changes in electrophysiological parame ~ ters after producing a nerve block using injection of 2% procaine. The pathophysiology underlying all the electrophysiological changes is discussed. There is a strong suggestion of a tee lower motor neurone involving facial muscles in some of the patients.

M052.ELECTRICAL AND MECHANICAL RESPONSES OF E~OW FLEXORS IN MYASTHENIA GRAVIS, MYOPATHIES, AND IN CONTROLS; A NEW REGIONAL CURARE TEST. S.Horowitz and Ch. Krarup. (New. York, New York, USA and Copenhagen, Denmark). Electrical and mechanical responses of the elbow Flexors were studied in myasthenia gravls (29 patients) and in various myopathies, and were applied via wire-electrodes to the musculocutaneous nerve in the axilla. The decrement to repetitive stimuli was more pronounced in the elbow flexors than in the adductor pollicis~muscle (ADP), and in two patien~ only present in proximal muscles. After regional application of d-tubocurarine to proximal arm muscles, a decrement was elicited in 12 myasthenics who did not have a decrement before curare. Four of five myasthenics showed half the decrement after compared with that before thymectomy. The abnormalities in staircase potentiation in the elbow flexors were due to disturbances in neuromuscular transmission and not to additional defects in contractility. In contrast in the ADP. 37%ofmyasthenics had evidence of a defect in the excitation-contraction coupling. In five of eight patients with myopathy the staircase was negative, a decrement in the action potential was absent. In normals repeated trains of stimuli (I and 2/sec) produced progressive increase in potentiation and shortening of contraction and relaxation times. When tetanic stimuli were given during the trains the tetanic force and the post-tetanic potentiation of the twitch were diminished. These findings may reflect an altered time course and intensity of active state.

M053.TONIC GRASP REFLEX EVOKED BY VIBRATORY STIMULATION OF DIGITAL MECHANORECEPTORS. K.E.Hagbarth, E.Torebj~rk and G. Eklund. (Uppsala, Sweden). It is an old observation that grasping of a vibrating object may cause a "magnet reaction": the fingers tend to adhere to the object and difFiculties may be experienced in attemp~ to loosen

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the grip. This motor phenomenon has been studied in healthy adults by measuring finger flexion or grasp force developing in response to vibration (100 Hz, I mm) applied to the volar skin of the thumb or index finger. The motor response was abolished or greatly reduced by blocking of the digital nerves or by chlorethyl anaestesia of the skin underlying the vibrator. Evidence is presented suggesting that the end-organs responsible for the reflex are the rapidly adapting (RA) receptors in the glabrous skin which in normal exploratory movements contribute to the sensory discrimination of textures and which by feedback regulation may help to adjust the pressure excert~ ed by the moving finger to the mechanical characteristics of the object being explored.

M054.SINGLE FIBRE EMG IN MUSCULAR DYSTROPHIES. E.Stalberg and P.Hilton-Brown. (Uppsala. Sweden). Single Fibre EMG has been performed in patients w i ~ different muscular dystrophies. The fibre density within the motor unit is locally increased, particularly in Duchenne's dystrophy.This could be explained by fibre splitting, byinnervation of sequestered fibre segments after focal degeneration or by innervation of regenerating muscle fibres. In other parts of the motor unit degenerative processes may dominate. The impulse transmission in termiml nerve branches, motor endl~lates and/or muscle fibres is disturbed with increased jitter in about 20% of the recordings and with impulse blockings in another 5-10%. The propagation velocity in single muscle fibres is decreased mainly in parallel to fibre atrophy. The repolarisation process is often significantly changed with an abnormally strong supernormal phase. This seems to indicate a membrane defect perhaps localisedto t ~ t u b u l a r system. Single Fibre EMG results thus indicates; morphological changes in the dystrophic motor unit, impaired nerve-muscle impulse transmission and changed physiological characteristics of the muscle membrane.

M055. MANIFESTATION OF MOTOR CONTROL IN THE ELECTRICAL ACTIVITY OF MOTOR CORTEX AND OF MUSCLE. T.Nagypal, Sz.Toth and T.Frey.(Budapest.Hum~3ary). In our previous study and report on the International Seminarium of Biomechanics we pointed out how to evaluate the rest -contraction-rest periods of muscle by mathematical and computationalmethods. In this present study we show the manifestation of different type control mechanisms during the following situations: The patient controls the intensity of muscle contraction by means of a continuous numerical visual display of the power of ~econtraction. The patient was instructed to hold 1.5,5, 10 kp. power intensities during sustaEined contraction periods. In this case mevisual-motor servosystem continuously corrects the intensity of contraction above and below the fixed values. We

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analysed the correlations between the alternations of muscle power intensities on the one hand, and the electrical activities appearing in different cortical and subcortical structures of the brain and in the contracted muscle on the other. The electrical signals were transformed into series of n dimensional vectors. We employed some new mathematical /linear and nonlinear/ data reduction methods to qualify continuously the structure of this vector series. The changes in correlations between electrical events and muscle contraction power intensity as function of time were examined in healthy subjects and patients with spinal lesions. The characteristics of open and closed eyes control processes in muscle and EEG activities were established. It was found that the specific changes in electrical activity preceded by some milliseconds the changes in muscle contraction intensity.

M056. PNEUMATIC TOURNIQUET PARALYSIS IN MAN. C.F.Bolton and R.M.McFarlane. (London,Canada) A pneumatic tourniquet was applied to the upper arm of a 47 year old woman during surgical correction of a Dupuytren's contracture. Severe motor and sensory loss in median, ulnar and radial nerves resulted. Serial clinical and electrophysiological studies documented the features of this rare paralysis during the six month period of recovery. By stimulating at 1.0 cm.intervals, a severe conduction block in motor and sensory fibers of median and ulnar nerves was demonstrated over a 3.0 cm. segment of each nerve at the same level in the upper arm, presumably at the lower margin of the previously applied tourniquet. Conduction was normal distally and needle electrode study of muscle suggested only mild axonal damage had occurred. A complete reversal of the block resulted during the next six months, coincident with clinical improvement. These observations correlate closely with reports by Gilliatt and colleagues of experimental pneumatic: tourniquet paralysis in baboons in which intussusception of nodes of Ranvier and subsequent clemyelination were localized to 3.0 cm. segments at upper and lower margins of the tourniquet. Serial tests of sweating (ninhydrin fingerprint method) showed an absence of sweating in the first four weeks. When sweating returned, it was excessive and accompanied by a severe causalgic syndrome. This syndrome disappeared only after the conduction block in motor and sensory fibers had resolved. A possible mechanism ~=or the causalgia in this patient will be discussed.

M057. AMPLITUDES OF SENSORY NERVE ACTION POTENTIALS IN THE HAND RECORDED WITH SURFACE ELECTRODES. C.F.Bolton and K.E.Carter. (London, England).

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In a study of control subjects it was noted that in 27 males (mean age 34, range 17 to 58 years) and 27 females (mean age 37, range) 6 to 58 ~ars) mean values were essentially the same in both sexes For motor conduction velocity, distal latency and amplitude of muscle compound action potentials from stimulation of median, ulnar and peroneal nerves. However, statistically significant differences were noted for antidromic sensory nerve action potential amplitudes (negative phase) recorded with ring electrodes at index and little fingers on stimulation at the wrist of median and ulnar nerves: median - 25.7 and 34.6 ~V, ulnar - 2 ~5 and 36.4 ~V, males and females, res~ To inwzstigate Further the reasons for this difference, the skin circumferences at index and little fingers and wrist of 10 healthy males and 10 healthy females of similar age were measured. These values were related to sensory nerve action potential amplitudes recorded with ring electrodes at index and little fingers and d~sc electrodes at wrist on antidromic stimu]ation of median, ulnar and radial nerves,resp., and with disc electrodes at wrist on orthodromic stimulation of medi:an and ulnar nerves. Even in this relatively small series, almost the same mean values occurred for antidromic sensory nerve action potential amplitude as in the larger series noted above. However, a statistically significant, inverse relationship was found between skin circumferenc(, and both orthodromic and antidromic nerve action potential amplitude. The skin c i r c u m f e r ~ is, therefore, a measure of the remoteness of both disc and ring electrodes from nerve trunks, an important factor in sensory nerve action potential amplitude (Buchthal and Rosenfalk,1966~ Differences in skin circumference at the wrist and Fingers explain the sex differences noted above and, if taken into account, would increase the accuracy of control and patient data.

M 058. PROBLEMS IN THE CLINICAL ELECTROMYOGRAPHY OF EXTRAOCULAR MUSCLES W.E.Haupt, K.Fasshauer, G.Huffmann and H.Kruse. ( K ~ l n , W.Germany). The c l i n i c a l p r o b l e m s , the d i a g n o s t i c and t e c h n i ' cal problems in e l e c t r o m y o g r a p h y o f e x t r a o c u l a r muscles are d i s c u s s e d on the b a s i s o f F i n d i n g s in more than 100 p a t i e n t s . On o p h t h a l m o l o g i c a l and n e u r o l o g i c a l e x a m i n a t i o n , a l l p a t i e n t s showed p a r e s i s o f e x t r a o c u l a r musclL% With consideration to all clinica] data and e s p e c i a l l y to the h i s t o r y , d i a g n o s i s by e l e c t r o myography was p o s s i b l e in the m a j o r i t y o f cases, in less than one t h i r d , w a s o n l y a p r e s ~ p t i v e d i ~ s i s p o s s i b l e . Most common were m y o p a t h i e s which o f t e n were to be d i f f e r e n t i a t e d from e n d o c r i n e o r b i t o p a t h y . Among the p a t i e n t s w i t h i n f a n t i l e ptosis or n e u r o p a t h i c eye musc]e p a r e s i s we found seve r al cases o f p a r a d o x i c a l i n n e r v a t i o n (Duane syndrl~ me). U s u a l l y q u e s t i o n s c o n c e r n i n g e t i o l o g y and p r o g n o s i s o f t r a u m a t i c or spontaneous p a r e s i s o f

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e x t r a o c u l a r muscles co u ld be answered. The s i z e and anatomy o f e x t r a o c u l a r muscles pose many t e c h n i c a l and d i a g n o s t i c p r o b l e m s . E x t r a o c u l a r muscles can be examined o n l y in a small p e r i p h e ra l f i e l d in which even s l i g h t needle movements cause marked changes o f the i n n e r v a t i o n p a t t e r n . The normal a c t i o n p o t e n t i a l s a re so s h o r t t h a t the p o t e n t i a l d u r a t i o n cannot be considered a diagnostic criterium. Indirect stim u l a t i o n o f e x t r a o c u l a r muscles is not p o s s i b l e , t h e r e f o r e l e s i o n s i t e s in p e r i p h e r a l o c u l a r muslce p a r e s i s cannot be d e t e r m i n e d . There are p s y c h o l o g i c a l problems f o r the p a t i e n t s and the danger o f i n j u r y should not be d i s r e g a r d e d .

M 059. DOUBLE DISCHARGE OF MOTOR NEURONS IN NEUROPATHY AND MYOPATHY. V . S . J . Partanenand A.H. L a n g . ( T u r k u , F i n l a n d ) . By d e f i n i t i o n , the double d i s c h a r g e (DD) o f a voluntarily a c t i v a t e d m o t o r neuron comprises two motor u n i t p o t e n t i a l s o f a l m o s t the same a m p l i t u de and shape, o c c u r r i n g , a t an i n t e r v a l o f 2.5 t o 20 ms. The o c c u r r e n c e o f DDs was s y s t e m a t i c a l l y a n a l y z e d in 46 p a t i e n t s s u f f e r i n g from m y e l o p a t h y o r p r o x i m a l r a d i c u l o p a t h y , in 38 p a t i e n t s s u f f e r ing from p e r i p h e r a l n e u r o p a t h y and in 26 p a t i e n t s w i t h v a r i o u s m y o p a t h i e s . The c o n t r : ) l group c o n s i ~ ted o f 33 h e a l t h y p e r s o n s . At l e a s t 10 m o t o r units were s t u d i e d in e v e r y m u s c l e . B e f o r e being accept e d , t h e DD had t o o ccu r a t l e a s t t h r e e times d u r i n g an EMG run o f 0,5 - 1 m i n u t e s . In my e l o p a t h i e s and p r o x i m a l r a d i c u l o p a t h i e s , DDs were found in 22 p a t i e n t s , more F r e q u e n t l y in m . t i b i a l i s a n t e r i o r (60~) than in m. b ice p s b r a c h i i ~0%) In the c o n t r o l s no DDs were o b s e r v e d . DDs were i n f r e q u e n t in the d i s t a l n e u r o p a t h i e s and myopat h i e s , e x c e p t in two cases o f d y s t r o p h i a m y o t o n i ca where the i n c i d e n c e o f DDs co rre sp o n d e d t o the figures for myelopathies. Motor neurons u s u a l l y showed a t r a n s i e n t f a l l in firing f r e q u e n c y a f t e r DD. The f i r s t interval f o l l o w i n g the DD u s u a l l y i n c r e a s e s by 40 - 50~ and a l a t e n t e f f e c t o f i n h i b i t i o n seems to remain a f t e r a s i n g l e DD.Thus the i n h i b i t o r y e f f e c t o f DD upon the m o t o r u n i t f i r i n g r a t e seems t o be s p i n a l in o r i g i n . This is so c h a r a c t e r i s t i c of DDs t h a t i t can be used, f o r example, f o r d i f f e r e n t i a t i n g DD and other- types o f t i m e - l o c k e d activity in the EMG.

M 060. AUTOMATED MEASUREMENT OF MOTOR NERVE CONDUCTION VELOCITY. H . K r a f t . ( S e a t t l e , Washington,USA). A p r o t o t y p e d e v i c e which a u t o m a t i c a l l y measures the c o n d u c t i o n w ~ l o e i t y o f human m o t o r nerves has been designed and b u i l t . This nerve c o n d u c t i o n v e l o c i t y m e t e r (NCV m e t e r ) can measure m o t o r n e r ~ l a t e n c i e s w i t h o u t the use o f an o s c i l l o s c o p e ; it does t h i s by d e t e r m i n i n g the time i n t e r v a l between the b e g i n n i n g o f the nerve s t i m u l u s and the p o i n t a t which the p o t e n t i a l d i f f e r e n c e between the a c t i v e and r e f e r e n c e e l e c t r o d e s exceeds a p r e s e t v o l t a g e . This v o ] t a g e can be s e t a t 100,

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200, 300, 400 or 500 microvolts The stimulation pulse which is delivered is a square-wave with a duration of 200 microseconds and an amplitude of 150,200 or 250 volts. The main components of the NCV meter are an amplifier and pre-amplifier, two nerve stimulators, a detector which determines when m ~cle contraction has occurred, a time interval counter, a position encoder for determining the distance between the nerve stimulators, a computation unit which calculates conduction velocity, a sequence controller and a power transformer. Preliminary clinical tests on 17 median nerves indicate that conduction velocities determined consecutively by this device are more consistent (mean S.D. = 0.7 m/sec) than those in which nerve latencies are determined consecutively by conventional methods (mean S.D. = 1.6 m/sec). In addition, the NCV meter eliminates the need for measuring distance and calculating conduction velocity, thus reducing the time required to determine motor nerve conduction velocity.

M 061. THE SIGNIFICANCE OF SEVERAL EMG PARAMETERS AND ESCPECIALLY OF THE H REFLEX IN EARLY DETECTION OF POLYNEUROPATHY IN DIABETIC PATIENTS. H.M.Vingerhoets, S.L.H.Notermans, M.Spiertz and E.de Nobel. (Nijmegen, The Netherlands). The study concerns 40 patients with diabetes mellitus, chosen at random from a medical out-patient clinic. In a standardized questionaire special attention was paid to minor complaints, that might point toward a polyneuropathy. The patients were physically examined by two of us and also in this investigation special attention was paid to minor symptoms. These findings were correlated with the outcome from an extensive EMG investigation. D i s t u r b e d m o t o r c o n d u c t i o n v e l o c i t y o f the p e r o heal and the t i b i a ] nerve, a disturbed sensory conduction velocity o f the s u r a l n e r v e and d i s t u r b e d Hoffmann r e f l e x o v e r the s o ] e u s mu~6cle t u r n e d o u t to be v e r y s e n s i t i v e EMG s i g n s in e a r l y n e u r o p a t h y . Of t h e s e a p r o l o n g e d i n t e r v a l ] a t e n c y ( t i m e between the b e g i n n i n g o f the m a x i mal M r e s p o n s e t o the b e g i n n i n g o f t h e maximal H r e s p o n s e (Notermans and V i n g e r h o e t s : T h e i m p o r t ance of the Hoffmann reflex in the diagnosis of lumber root lesions; Clinical Neurology and Neurosurgery, 1974, vol.], p.54-65) was present in 77~ and thus turned out to be the most sensitive EMG sign. Several times pathologic EMG signs were found in advance of clinical abnormalities. In several cases (60%) the lifts complaints appeared to be autonomic disorders as for instance impotence, intermittent diarrhoea, symptoms of postural hypotension and very often skin disturbances on the soles of the feet. Also Achilles tendon refl~es were usually a b s e n t o r v e ~ a k in relation to the easily obtainable patellar reflexes. The p o s s i b i l i t y of treating and/or preventing d i a b e t i c n e u r o p a t h y by means o f a more e x a c t t r e a t m e n t and r e g u l a t i o n o f the d i a b e t e s is the s u b j e c t o f a c u r r e n t EMG i n v e s t i g a t i o n ,

M 062.ELECTRODIAGNOSTIC STUDY OF FACIAL NERVE AFTER CEREBELLOPONTINE ANGLE TUMOR OPERATION. Y.Tsukamoto. (Tokyo, Japan). The facia] palsy after operation for acoustic neurinoma is a difficult problem. Recently the number of cases whose nerves are spared during tumor surgery has increased. Nevertheless some of them never regain facial function clinically and electromyographical]y. However, nerve grafting using hypog}ossal, accessory or sartorial nerve is of little use, if applied more than 2 months after the nerve injury. To identify these unfortunate cases at an early stage and to apply anastomosis in time, successive eiectrodiagnostic studies were undertaken. The findings were divided into 3 groups. I) Even though the action potential on facial nerve stimulation may be diminished, it recovers within the forthnight and fu]] clinical r e c o v e r y f o l l o w s , - s u s p e c t e d neur a p r a x i a . 2) The p o t e n t i a l r e c o v e r s between 4-6 months but c l i n i c a l r e c o v e r y is u n s a t i s f a c t o r y with electromyographic evidence of misdirection and a d e c r e a s e d number o f N M U , - a x o n o t o m e s i s . 3) Normal potential is evoked for 2-3 days but it suddenly disappears and never re;overs, followed by permanent disabilities, -n~urotomesis. Consequently we should reconstruct the nerve by graftin~ when no action potential has been evoked by 2 months, even though the nerve appeared to be spared during the tumor surgery.

M 063. MOTOR NERVE CONDUCTION VELOCITIES IN MEDIAN, ULNAR AND LATERAL POPLITEAL NERVES IN NORMAL NIGERIANS. A . B . A r a b a and J . B . A p a n t a k u . ( L a g o s , N i g e r i a ) . Conduction Velocity Studies were carried out in fifty healthy Nigerians without neurological deficits. Conduction velocity was determined in the Median, ulnar, and the latera] popliteal nervesusing The Medelec MS6 Machine:. The results obtained for the Median nerve were Axilla-Elbow (6855.6 m/see) Elbow wrist (60.2~5.3 m/sec.). U]nar nerve Axilla-Elbow (62.5~7.0). Elbow wrist (56.655.3 m/sec), and lateral popliteal (Kneeankle segment 48.9~3~5). The pertinent literature will be reviewed.

M 064. CONDUCTION VELOCITY OF THE FACIAL NERVE IN "A FRIGORE" PALSY. C . I . S t a m a t o i u and C . V a s i l e s c u . ( B u c h a r e s t , Romania). Conduction velocity (CV) and distal latency (DL) in the facial nerve were measured in 20 patients with " a frigore 'L facial palsy. Stimulation with bipolar surface electrodes was used. The muscle potentials evoked in the upper-lip orbicular, lower-lip orbicular and frontal muscles were recorded by "Disa ~ coaxial needle electrodes. The stimulation electrodes were applied through the skin to the facial nerve preauricularly

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(proximal point), 2-3 cm laterally to the buccal commissure (inferior distal) and 2-3 cm superolaterally to the eye-ball commissure (superior distal). The CV and DL, measured 3-4 weeks after o n ~ of disease, were 18.552.1 m/s -4.850.9 ms. (recordings from #the lower~ip orbicular) and + . 20.5_2.8 m/s -4.2_0.7 ms (recordings from the upper-lip orbicular) in the lower branch of the facial nerve, while 25.552.8 ms - 4.1±0.5 ms. (recordings from the frontal muscle) in its upper branch. The CV slowi~ and DL increase, statistically significant as compared to the control group (p<0.001), were more marked in the lower than in the upper branch of the facial nerve.

brachii and the soleus, respectively. Inertial loads attached to the end of these moving extremities cause the tremor frequency to decrease for the index finger, to increase for the hand and the leg, and to remain nea~ly constant for the forearm, but the changes are rather small except in the index finger. The Laplace transform of an equation of motion including the stretch reflex provides the condition of a sustained oscillation in terms of the phase angle from which the oscillation frequency can be determined. Physiological parameters available seem to sup~rt the present model.

M 065. PHARMACOLOGICAL EFFECTS ON THE PELVIC SPHINCTER MUSCLES RECORDED BY EMG. E.Pedersen.(Aarhus, Denmark).

M 067. CONDUCTION BLOCK LOCALIZED TO THE BRACHIAL PLEXUS. W.Trojaborg. (Copenhagen, Denmark).

The pelvic sphincters are reflexly connected both with the urinary bladder and the legs, and vice versa. The effect of pharmacological age,s on the external urethral and anal sphincters was investigated by EMG from the sphincters, expecially in the hyperactive neurogenic bladder, with intravenous administration of the drugs. A variety of drugs can depress the sphincter activity some centrally acting (meladrazine, diazepam and the GABA derivative baclofen) and the peripherally acting dantrolene sodium, which exerts its action within the striated muscle cell beyond the neuromuscular junction, and in some cases the smooth-muscle relaxant flavoxate. Investigations with adrenergic blocking agents are also mentioned. The possible mechanisms of the depression of the EMG is discussed also on the basis of cystometric and urethral studiesas is the effect of anaesthetic agents on the vesical mucosa and the interrelations between flexor musclcs reflexes of the leg and the pelvic floor. The clinical use of these compounds as "bladder drugs" is not directly related to their ability to depress sphincter activity, or to their effectiveness as "antispastic drugs".

Compression palsies of the brachial plexus postoperatively and after carrying a heavy shoulder pack awe well known clinically. The pathogenesis, however, has not yet been established and electra physiological data are not available. The purpose of the present study was to determine the site and possible nature of the lesion in two patients, one with post-operative brachial plexus paralysis and another with a pack palsy. The characteristic electrophysiological findings in the acute stage were: I) discrete activity of low voltage at full effort, 2) widespread fibrillation potentials, 3) severe reduction in amplitude of muscle and sensory responses evoked or recorded above the site of nerve injury compared to those evoked or recorded below, 4) slowing of motor and sensory conduction across the damaged area (fossa supraclavicularisaxilla) using the musculocutaneous or radial nerves as indicators, Both patients made a full recovery clinically, the patient with postoperative palsy also electrophysiologically. The patient with pack palsy had electrophysiological evidence of Wallerian degeneration. Thus, the findings are consistent with a conduction block localized to the trunci of the brachial plexus, in one patient with and in another without axonal damage.

M 066. ANALYSIS OF PHYSIOLOGICAL TREMOR OF HUMAN EXTREMITIES DURING STROKE MOVEMENT. A.Watanabe, I.Fukumoto,K. Ikeda and M.Saito. (Tokyo, Japan).

M 068. CROSS-INNERVATION AFTER FACIAL PALSY. FACT OR FALLACY? W.Trojaborg. (Copenhagen, Denmark).

Tremor frequencies are usually measured by holding extremities in a position against gravity, which requires elaborate frequency spectrum analysis. In this study clearly observable tremor having a line spectrum is induced by relaxing the antigravity muscles during stroke movement. A small semiconductor accelerometer is used to detect the tremor. Extremities exhibiting the observabletremor include the index finger, the hand, the forearm and the shank in a sitting posture, and involved muscles identified by EMG are the interosseus dorsalis, the extensor carpi radialis, the biceps

Although re-innervation of perioral muscles from the contralateral facial nerve has been reported, its basis is not established with certainty. The purpose of the resent study was to determine whether the activity on the paralytic side evoked by stimulation of the non-affected nerve in patients with facial palsy was due to conduction along nerve fibre sprouts or due to muscle fibres crossing the midline. The mean latency of potentials recorded from the orbicularis oris muscle contralateral to the stimulated facial nerve was the same ~n patients and normal subjects. Moreover, in patients reexamined 2-31 months after the onset of facial

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nerve palsy there was no shortening of this latency. When perioral muscle fibres were stimulated at one side of t ~ m i d l i n e an action potential could be recorded the other side both in patients and normal subjects. The potential was similar in shape and amplitude whether evoked by nerve or muscle stimulation, and it was conducted at the same rate (5 m/s) in patients and in normal subjects. Thus, the contralateral responses are suggested to be due to conduction along muscle fibres crossing the midline rather than to crossinnervation.

M 069. ELECTROPHYSIOLOGICAL STUDY OF BRACHIAL PLEXUS: TRUNKS AND CORDS. N.Duarte, E.Lovelace and N.Singh.(New York, New York, USA). The value of conduction velocity in the lower trunk and medial cord of brachial ple~s in localization of plexus lesions has been established. Conduction velocity in the nerve fibres supplying hypothenar and thenar muscles in the supraclavicular fossa to elbow segment was studied. Thirthyeight males and 63 females aged 6 months to 87 years without plexus pathology or neuropathy constitute the control group. From a conduction velocity of 37 meters per second in this proximal segment at the age of 6 weeks, values increased to the normal adult range of 60-70 meters per second after thefirst decade of life. There was no statistical difference between conduction velocities in these median and ulnar nerve fibres. In 18 controls, mean velocities for median and ulnar fibres were 58.55±9.44 and + . . + 58.65-4.39 us,n~ cal,per as compared to 63.810.07 and 64.49-5.97 using tape for measuring the supraclavicular to elbow segment. Thirty~hree patients with plexus trauma or thoracic outlet syndrome were investigated. In patients with isolated lower trunk or medial cord lesions, the conduction was slower in ulnar than median fibres. Four patients had additional involvement of middle trunk or lateral cord (cervical 7 segment) and of these, 3 had predominant median slowing. In contrast, upper trunk or lateral cord lesions (5 patients) have normal conduction velocities in this segment, and in 7 with diffuse lesions, values were slowor borderline for both median and ulnar fibres. This technique differentiates involvement of lower from upper segmentally innervated portions of the brachial plexus.

M 070. DETERMINATION OF SYMPHATHETIC REFLEX LATENCIES IN MUSCLE NERVE FASCICLES FOR EVALUATION OF C FIBRE CONDUCTION VELOCITY IN MAN. B.G.Wallin. (Uppsala, Sweden). Measurements of C. fibre conduction velocity in man have so far only been made in a few ceses mainly for research purposes and information on C fibre conduction in different clinical disorders is sparse. The present report describes~ method for determination of sympathetic

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reflex latencies in muscle nerves which may give such information. Micro-electrode recordings of multiunit muscle nerve sympathetic activity (MSA) in man sho~ed that the sympathetic impulses occurred in pulse-synchronous bursts during transient blood pressure reductions. The pattern suggested potent baroreflex modulation of the sympathetic outflowand in agreement with this ac individually constant reflex latency was foun~ between blood pressure and neural events. In 60 subjects latency measurements were made by recording ECG and MSA in median or peroneal nerve and feeding the neural activity into an averager, triggered by the ECG. In peroneal nerves the latencies ranged between 1.16-1.57 s and in median nerves between 0.90-10.3 s. Although the latency dep~ds on conduction in the whole baroreflex arch the main determinant is probably propagation i n m e efferent post-ganglionic sympathetic: C fibres. This is supported by the differences in latency between median and peroneal recordings and by the finding that there was a positive correlation between reflex latency and subject height. Since reductions in C fibre conduction velocity probably would be detected as an increased reflex latency, it is suggested that the method can be used clinically for studying C fibre engagement in neurological diaseases.

M 071. AUTOMATIC NERVE CONDUCTION DETERMINATION. I:TECHNIQUE AND DATA PROCESSING. E.Thorup, B.Stigsby and P.Olsen. (HeIlerup, Denmark). A method of automatic determination of nerve conduction was developed using a general purpose computer (IBM 1800/HP 2100). After automation the results of the single measurements are achieved immediately which is of advantage for the further direction of the examipation. The communication to the centralized computer took place via a keyboard and a datascreen. The computer sampled 20 ms. triggered by the stimulus (sampling frequency 10 KHz, upper frequency limit of amplifier 3 KHz). The stimulating current was measured by a peak detector as the duration of the impulse was only 0.2 ms. The sensory latency was the time from stimulation to the first positive peak of the nerve potential. A significant peak was detected by the computer when the differential coefficient r f the possitive to negative change was equal to or more than four in each of two consecutive periods of 0.1 ms or had a mean value equal to or more than eight. The motor latency was the time from stimulation to the initial deflection of the muscle potential. The mean of a I ms period with the differential coefficient closest to zero was used as baseline. A significant deflection was detected by three consecutive samples outside the range of 3 SD. By reverse scanning the initial deflection was found. The potentials were shown on the datascreen together with the current, latency and amplitude befo~ storing for subsequent plotting and

604 print out.

M 072. AUTOMATIC NERVE CONDUCTION DETERMINATION; If:METHODOLOGY AND CLINICAL APPLICATIO~ B.Stigsby, P.Z.Olsen and E.Thorup. (Hellerup, Denmark). Technique and data processing of automatic determination of nerve conduction were described in the previous paper. To fulfil tkerequirements of the complex nerve conductionexamination five ~ p r o g r a m s handle I) motor threshold, 2) sensory threshold, 3) supramaximal sensory stimulation, 4) supramaximal motor stimulation and 5) administration of keyed-in parameters, lataneies and distances for subsequent calculation of condu~icn velocities along the nerve segments. The examiner controlled the measurement procedure. During sensory stimulation the computer presented the average potential of 10,20,40 or more sweeps together with ca]culated latency and amplitude. During motor stimulation the computer calculates latency and amplitude from one sweep at a time. A preanalysis delay up to 20 ms could be applied. The accuracy of the determination was tested by the measuring of simulated potentia]s of known latency and amplitude. The reproducibility was tested by serial sensory and motor stimulation of the same nerve. The greatest variability was found for motor latency determination (range:~ 0.1 ms). To compare the automatic determination with our conventional method of measuring on photographic paper simultaneous registration from 25 consecutive examinations of the median nerve were performed. The differences in latency, motor as we]] as sensory, were 1 to 2%.

M 073. OCULAR ELECTROMYOGRAPHY.BLINK REFLEX IN LEVATOR PALPEBRAE AND RECTUS SUPERIOR MUSCLES. A.Esteban and E.Salinero. (Madrid, Spain). Levator palpebrae (LP) and rectus superior(RS) are functionally sinergistic in vertical ocular movement and antagonistic in eyeclosure. However recording their EMG can be made difficult by artefact in forceful palpebral closure or impossible when there is any oculomotor disorder. Observations were made on 18 patients, 4 presenting facial paresis with normal ocular movements and 14 with definite disorders of oculopalpebral movement as of upward gaze, abolition of Bell's phenomenonand blepharospasm. Concentric needle electrodes were inserted successively into orbicularis oculi (00) and the ipsilateral LP and RS muscles. In pursuit vertica] movement, records were practically similar in both LP and RS muscl.es. In RS it was found a phasic synchronized discharge superimposed on basic activity In forceful eyeclosure, LP activity is almost completely inhibited whereas RS exhibited an increase in activity related to that in the orbicularis (Bell's phenomenon). Spontaneous blinking produces an abrupt and com-

INTERNATIONAL FEDERATION - 9TH CONGRESS plete inhibition o f LP t h a t was n o t always r e l a ted w i t h r e c i p r o c a l c o n t r a c t i o n o f the o r b i c u l a ris, activity o f RS b e i n g u n m o d i f i e d . Supraorbital stimulation elicits in the i p s i l a t e ra] O0 the w e l l - k n o w n R1 and R2 r e f l e x r e s p o n s e s . LP, e x h i b i t s a sudden i n h i b i t i o n o f the same l a t e n c y as R2, i n c r e a s i n g w i t h stimulus intensity. This inhibition a l w a y s p r e c e d e s the s y n c h r o n o u s burst of orbicularis R2. A s h o r t l a t e n t c y i n h i b i t i o n is s u b s e q u e n t l y f ound c o r r e s p o n d i n g t o R1. RS has n e v e r shown a decrement in i t s a c t i v i t y but o f t e n r e i n f o r c e m e n t r e l a t e d t o R2. The g l a b e l l a r r e f l e x g r o s s l y r e p r o d u c e s the p r e ceding findings. O c u l o p a l p e b r a l movement d i s o r d e r s qave p r e v e n t e d clear distinction between LP and RS muscles by means o f the t h r e e f i r s t m a n e o u v r e s . B l i n k and g]abellar r e f ] e x e s may be c o n s i d e r e d , in e v e r y c i r c u m s t a n c e as an e a s y , c l e a r c u t , differentiat i o n method.

M 074.AN ANALYSIS

OF PHASE-LOCKED MOTOR UNIT SPIKES TO FM VIBRATION OF A MUSCLE IN THE CAT. S.Homma and M.Mizote. (Chiba, Japan).

A spike of the primary ending can be divided into categories which correspond to the three types of intrafusal muscle fibres by Constant-Frequency (CF) or FM vibration. The vibration of 0.5 sec duration was applied repetitively 10 times or more every 2.0 sec to the tendon of the gastrocnemiums or soleus musc]e which was dissected free of surrounding tissue in the cat. The initial muscle length was determined by the single shock stimulus of ventral root. The threshold of a primary ending to vibratory stimulation was considered to be the smallest amplitude of vibration which elicited only a single la spike. The frequency-threshold relations ~ere investigated with stimulation from 10 to 100 Hz. The classification of these relations is changeable when several spikes are elicited under the larger amplitude or the larger initial length, but the cross-correlograms between FM vibrations and spikes of a primary ending have two kinds of steep peaks under the condition eliciting a few spikes for each vibratory stimulus. And, the similar pattern appears also between FM vibrations and spikes of a single motor unit. Each spike which belongs to the two peaks of the correlograms is a phase-locked one. It can be separated from other phase-unlocked ones. Under t h e e conditions, phase-locked spikes of a motor unit correspond to the category of primary endings.

M 075. MOTOR UNIT POTENTIAL FORM IN PARASPINAL MUSCLES. S.Devi, N.Singh and R.E.Lovelace.(New York, New York,USA). Electromyography of paraspinal muscles may be a valuable study in root disease. Classical measurements of duration and percentage of polyphasic motor unit potentials in disease compared with normal have therefore been made.

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Fourteen normal s u b j e c t s had p a r a s p i n a l muscles i n v e s t i g a t e d w i t h u n i p o ] a r T e f l o n coated needle e l e c t r o d e s (exposed t i p less than I mm). 20 to 97 motor u n i t p o t e n t i a l s from each p a t i e n t recorded on f i b e r o p t i c paper were measured f ~ d u r a t i o n and number of phases. In normals, a t o t a l of 418 motor u n i t p o t e n t i a l s , and in abnorma]s,471 pot e n t i a l s were measured. According to i n t e r n a t i o n al classification in excess of four phases was necessary for classifying potentials as polyphasic. The mean duration of the motor unit potential in normal subjects was 7.6~0.83 msec, and individuals with evidence of root compression,it was 8.34~1.26 nlsec. In normals, 7.2% of the motor unit potentials were found to be polyphasic, ~he-eas in patients with root disease, 15.7~ were polyphasic. Thus, the duration of motor unit potentials from paraspinal muscles appeared not significantly different in health and with denervation,nor differed significantly from normal muscles. The number of polyphasic potentials was significantly increased, by double, in denervation due to root disease. The short length of motor nerves may be related to the normal duration of motor unit potentials in denervation.

M 076. SPECIFIC ABNORMALITIES OF SINGLE MOTOR UNIT DISCHARGE PATTERNS IN TREMOR. B.T.Shahani andR.R.Young.(Boston,Mass.,USA). One of the several cardinal abnormalities of motor unit behavior long known to underly certain types of tremor is the tendency for single motor units (SMU) to be recruited during slow"tonic" ramp movements in brief bursts where the InstantaneousFiring Frequency (IFF) may reach 40-50Hza pattern normally seen only with quick "phasic" ballistic movements.SMU activity was recorded from theforearm using special electrodes;surface EMG and accelerometric records were also made. Physiological tremor was studied in 11 normal subjects, essential tremor in 6 patients and tremor in an attitude of repose in 6 patients with Parkinson's Disease (PD). With physiological tremor, the recruitment pattern was normal (progressing generally from smaller to larger amplitude SMU) and the IFF never exceeded the tremor frequency. In the patients with PD, 2 distinct groups of SMU were recognized. The Ist had smaller amplitude and lower tension thresholds and their IFF was 50-20 Hz -one SMU might be active 2 or 3 times in each 4-5Hz tremor burst. The 2nd had larger amplitude higher threshold SMU where the IFF never exceeded thetremor frequency. In contrast, the SMU activated duringessential tremor ~rmed a homogeneous group in which SMU did ~talways ~pear to follow the usual ~ n k order drecruitment. Such clearly definable abnormalities of SMU behavior permit a categorization which suggest fundamental differences in certain of the physiological mechanisms underlying these 3 di~erent t~mors.

M 077. SPINAL SHOCK

IN MAN: A STUDY OF TBE

H-

REFLEX, M.Georgesco, France).

H.Duday and J.Cadilhac.iMontpellier,

The H-reflex of the soleus, reflecting motoneurone excitability, was studied in 24 patients with complete spinal sections and spinal shock. During the first 24 hours, the H reflex was abolished in 5 out of 7 patients and only the direct response (M) was obtained. In the r-emaining 2 patients seen at the 18th and 24th houEs, the H reflex was present. From the second to the 11th day, the H reflex was present in all cases, but the recruitement curves were abnormal as well as the recovery cycles (lack of the phase II of ~rimary facilitation" and reduction of the amplitude of the phase IV, of "secondary facilitation'~ On successive examinations (8 patients), the H reflex reappeared before the deep tendon reflex. The recruitement curves and the excitability cycles progressively returned to normal. These results are compared with those of Weawer et al (1963), Diamantopoulos and Olsen (1967) and Ashby et al. (1974). They show the importance of the d e p ~ i o n of the motoneurone excitability during the initial stage of the spinal shock and make it possible to complete the classical picture of spinal shock in man, the evolution of wich is schematically: I) stage of complcte spinal shock (before the 24th hour), with total disappearance of the spinal activity either clinical or electrophysiological; 2) stage ot clinical s p i n a l shock w i t h a b o l i t i o n of the deep tendon r e f l e x e s but w i t h reappearence of the e l e c t r o p h y s i o l o g i c a ] r e f ] e x e s ; 3) regression of c l i n i cal s p i n a l shock.

M 078.ACTIVATION PATTERNS IN SPASTIC MUSCLES STRETCHED BY PASSIVE AND ACTIVE MOVEMENTS. E.Knutsson and A.M~rtensson. (Stockholm,Sweden). To study how spastic reflexes are changed during voluntary movements, the activation of the m u ~ l ~ stretched during passive and active knee extensions and flexions was determined in 24 patients with spastic hemiplegia or paraplegia. The speed of themovements was kept constant throughout the movements at 15,30,90 and 180 degrees/s by means of a modified ser~o-controlled isokinetic dynamometer (Lumex, Cybex II). The passive resistame to movements and the strength of the active movements were determined with strain gauge transducers. Muscle activation in extensor and flexor muscle groups was indicated by surface emg. The resistance to passive movements, excluding the weight of the limb, varied between 0 and 60 Nm in the 42 paretic limbs examined. The spastic restraint in active movements was equal to the passive resistance as judged from emg activity in 9 muscle groups. Reciprocal inhibition of the spastic reflexes during voluntary movement was seen in 6 muscle groups. In 47 muscle groups, the activation was larger when the muscle were co-activated as antagonists in active movements than when activated by an identical passive movement. Thus, co-activation of antago-

606 nists exceeding motion, seem to paresis. It may spastic stretch or by errors in activation.

INTERNATIONAL the reflex activation at passive be a common feature in spastic be caused by facilitation of reflexes during volunta~ effort the descending command for muscle

M 079. SELECTIVE MODIFICATION OF HUMAN SPINAL AND LONG£OOP REFLEXES BY VIBRATION. R.G.Lee and A.Hendrie. (Calgary, Canada). Previous studieshave shown that the reflex EMG response following sudden displacements of the human wrist includes a short latency spinal component (MI) and two later components (M2 and M3) which are believed to represent long-loop reflexes mediated via supraspinal pathways. It is well known that vibration, a potent activator of IA afferents, suppresses monosynaptic spinal reflexes. The present study was carried out to investigate the effects of vibration on the later components of the stretch reflex. Recordings were obtained from ten normal human subjects using a computer controlled torque motor to initiate stretchesof the wrist flexor muscles. A 120 Hz. commercial vibrator was applied over the distal part ofthe fore arrm. Subjects were instructed to actively oppose the applied torques and averaged EMG responses with and without vibration were plotted. In all subjects vibration caused a marked suppression of EMG activity during the MI period (30-55 msec.following the stimulus), the area of MI being reduced to values between 8-40% of the area during control trials. No significant suppression occurrred over the M2~M3 interval (55 90 msec.) as a result of vibration. In fact vibrati~ caused a slight increase in the ~ize of M2 in some subjects. These observations suggest the possibility that the later components of the stretch reflex may be mediated peripherally by pathways other than the IA afferents. An alternative explanation, suggested from recent work by Bawa and Tatton (Canada Physiology 8:27,1977) is that the individual components of the EMG response are generated by separate sub1~opulations of the mononeuron pool. Synaptic inputs for M2 and M3 motoneurons may be such that vibration does not affect them in the same manner as it does MI motoneurons. (Supported by the Medical Research Council of Canada).

M 080. A NEUROPHYSIOLOGICAL HYPOTHESIS CRAMPS. S.E.Bj~rkqvist. (Turku, Finland).

OF MUSCLE

During therehabilitation of patients with confirmed (operated) or suspected ischiadic syndromes,its was found that painful muscle cramps are very common in the musculaturesupplied by N.tibialis about 3-10 months after the nerve lesion. The muscle cramps are especially provoked by muscle movements that are not opposed by any

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external force. Stretching the muscle forcifully ends the cramp. This implies that regulatory reflexes are involved. The routi~ EMG w i ~ c o n c e n t r i c needle electrodes in forty such muscles, mainly plantar muscles, which according to the patients often had painful cramps, showed enlarged muscular action potentials and often very marked fasciculations. Fasciculations were seen in almost all muscles, while the contralateral muscle, if without symptoms , generally had none. During muscle cramps, the enlarged action potentials could be seen to repeat with a frequency of 30-50 Hz, but otherwise nothing special could be idertified in the EMG. Fasciculations have been thought to arise in sprouting, immature alfamotoneurone collaterals. The fasciculations in cramping muscles thus are an indication of active sprouting and reparation Hypothesis: After neurogenic lesions sprouting alfamotoneurone collaterals may accidentally innemate some denervated muscle spindles. This makes the stretch reflex a positive feedback system, and causes a muscle cramp when the involved alfamotoneurone is activated. Cooling m e skin over the muscle, which reduces gammamotoneurone activity and the stretch reflex in spasticity, has no effect on the muscle cramps The muscle cramps disappear later together with the fasciculations, which is taken as an indication of noramlization of the sprouts and the reparative process with time.

M 081. EMG FEEDBACK IN REHABILITATION. S.E.Bj6rkgvist. (Turku, Finland). The use of visual and auditory feedback of amplified but unrectified EMG activity has been used in the rehabilitation of neurological patients at the Rehabilitation Examinations Centre of the Social Insurance Institution in Turku,Finland. Rectified or otherwise modified EMG activity seems to give no advantage over plain EMG activity from dermal electrodes. Feedback through a loudspeaker seems more effective than feedback through an oscilloscope, but co~bTned feedback is best. Feedback from two muscles, i.e.protagonist and antagonist, is more effective than single channel feedback from the protagonist only. In lower motor neurone lesions EMG feedba~khas only slight or no effect. In pyramidal tract lesions with even very minimal remaining activity as little as a daily 20-30 minute training session for two weeks often increases the EMG activity and the muscle strength by at least 100%. A severely spastic patient learned to control the clonus of her triceps surae m u ~ through voluntary activation of tile peroneal musculature, although the actual dorsiflexion of the ankle remains minimal. The main drawbacks and difficulties of EMG feedback training is that every patient and muscle group needs an individual program. A change of position, e.g.from sitting to standing, brings new reflexes into play and may necessitate a new training program for an activTty that the

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patient already has mastered in the sitting position. However, for the rehabilitation of a well defined action of a centrally paralysed muscle EMG feedback seems ®utstanding.

M 082. INFLUENCE OF PERCUTANEOUS STIMULATION OF PERIPHERAL NERVES ON EXPERIMENTAL PAIN. P.Hiedl and A . S t r u p p l e r . (M~nchen, W.Germany). In healthy subjects an experimental pain was produced by radiant heat stimulation. Therapeutic percutaneous nerve stimulation was performed on several sensible nerves. Statements of subjects about analgetic effect were recorded and compared with the antalgetic effect of transcutaneousnerve stimulation. A second point was to study longloop-effects of percutaneous nerve stimulation.

M 083. PLURISEGMENTAL EFFERENT AND AFFERENT CONDUCTION VELOCITY AND EVOKED MUSCLE AND NERVE POTENTIALS IN THE DETERMINATION OF THE LEVEL OF NERVE LESIONS. A.Jusic. (Zagreb, Yugoslavia). Since 1966 the EMG team of the institution has dealt with pludsegmental conduction velocity determination. Representative cases are described in detail. I. A typical case of ulnar groove syndrome is presented with values of 7 m/s in elbow region, 2. In a more advanced case with additional slowing below the elbow M-potential width had localising value. 3. In lower plexus brachialis compression the conduction velocities decreased approaching axilla. Width of M-potentials increased progressively. 4. Of special interest was a case with spinal amyotrophy and additional clavicular fracture. The patient developed atrophyof small hand muscles with hypoesthesia and was suspected of low plexus brachialis compression. Plurisegmental motor conduction velocity measurements displayed slowing in the elbow segment. The additional thenar muscle atrophy was proved to be due to "all ulnar hand". 5. A case of strangulation of the upper arm region had a conduction slowing there. 6. With a traumatic aneurysm of the ulnar artery an isolated slowing of the motor conduction velocity over the tumefaction was recorded. The nerve potentials were elicitable over the elbow and in the upper arm segment, not in the lower. 7. Over a tumour compressing the median nerve in the lower arm slight slowing of motor fibres and extreme slowing of sensory fibres were found. 8. In cases 6 and 7 afferent fibres proved to be more sensitive to compression than the efferent ones. In case 8 (radial bone fracture and haematoma connected with it) the results were the opposite.

M 084. LOW FREQUENCY ELECTROSTIMULATION OF THE MUSCLES IN TREATMENT OF PARKINSON'S DISEASE. A.Jusic. (Zagreb, Yugoslavia). Since 1968 low frequency,

rhythmic electrostimu-

lation following the method of Hufschmidt has often been appiied in patients with Parkinson's disease. The method employed was a modification of the technique used in spastics. Rigor and akinesia were improved, but tremor sometimes enhanced. The stimulation effect crossed over the segment of muscle stimulated, the motility as a whole improved. Hand deformities suggesting another disease disappeared almost entirely, p r ~ i ~ that their origin was functional. The additional local stimulation improved speech and swollowing difficulties. Stimulation with special distribution of stimulation point resolved urinary retention. The effects outlasted the treatment for many days or weeks. No correlation with duration of illness or age of patient has been observed. The effects are less impressive thar those obtained by drugs and are of more theoretical interest. The treatment can be recommended as adjuvant.

M 085. THE EVOKED NERVE POTENTIALS OF DEEP PERONEAL, TIBIAL AND SURAL NERVES IN THE DIFFERENTIPL DIAGNOSIS OF LESIONS OF AFFERENT FIBRES. M.Sostarko and A.Jusic. (Zagreb, Yugoslavia). The clinical distribution of sensory disturban~s may be indicative of the level of a lesion of peripheral afferent nerves. The evoked sensory nerve potentials can localize the lesion in more precise and repoducible manner. The subjects of analysis were healthy adults (28) patients with spinal amyotrophy and slight sensory loss (19), patients with radicular compression (20), patients with po]yneuropathy (uremic 29, alcohol~ 32, diabetic 38) and patients with peroneal muscular atrophy (12). The analyses were performed on the distal segments of the deep peroneal, tibial and sural nerves by percutanecus stimulation and with entomological needle recording electrodes. In spinal or radicular lesions the results were identical to those obtained in healthy adults. The evoked potentials nearest to normal were found in uremic polyneuropathy. More pathological changes of evoked sensory potentials were present in alcoholic patients and s~ill more in diabetics; sensory nerve potentials were absent in many cases in both groups. In most patients with peroneal m ~ c u l a r atrophy no nerve potentials were evoked.

M 086.EVOKED MUSCLE POTENTIALS IN THE DIFFERENTIAL DIAGNOSIS OF LESIONS OF THE DEEP PALMAR BRANCH OF THE ULNAR NERVE. M.Sostarko and A . J u s i c . (Zagreb, Y u g o s l a v i a ) . Atrophy of the interosseal muscles with hypothenar sparing ~ut without sensory disturbances appears sometimes in the initial stage of amyotrophic lateral sclerosis. The same clinical pictum may be produced by a lesion of the deep palmar branch of the ulnar nerve. The authors have observed four cases of this kind and two of them are reported in full detail. The first developed

608 interossea] amyotrophy during the maize harvest. The terminal latency for stimulation in the wrist and recording in the adductor pollicis muscle was 18 ms/10 cm, with the same stimulation point in the wrist and recording in hypothenar bulk the values were 2,7 ms/6,5 cm. The terminal latency for the adductor pollicis muscle approached the normal value after a four months period of rest and physical therapy. The action potential of adductor pollicis was polyphasic and prolonged in duration and follow-up showed normalization. The next patient had some swelling in the proximal part of the hand. The values for the hypothenar muscles were normal and terminal latency for adductor pollicis muscle was 7,5 ms/7cm with highly polyphasic and wide potential. Aftera ACTH course the values came back near to normal.

M 087.CLINICAL EVALUATION OF TONIC VIBRATION REFLEX (TVR). S.Watenabe, S . K a w a g u c h i , S . T o c h i g i , Y.Nakano and T.Matsuda. (Chiba-shi, Japan). T-reflex, H - r e f l e x , TVR and i n f l u e n c e o f v i b r a t o ry s t i m u l i on H - r e f l e x were examined in the same s u b j e c t s to d e t e r m i n e any d i f f e r e n c e s in r e s p o n s e t o r e f l e x s t i m u l i between normal s u b j e c t s and nervous disease patients. A Hagbarth type vibrator (Heiwa Denshi Co. L t d . ) was a p p l i e d t o the A c h i l l e s tendon ( a t I00 Hz) t o e v a l u a t e c a l f muscle TVR and the i n f l u e n c e o f vibratory s t i m u l i on the H - r e f l e x . The i n f l u e n c e o f v i b r a t o r y s t i m u l i on the H - r e f l e x was examined 5 s. a f t ~ a p p l i c a t i o n and r e p e a t e d a t 30 s . i n t e r va]s. The TVR is a sensitive method in detecting hyposensitivity of muscle spindles and mild demyelination of 1-a fibres. In spastic paralysis, the TVR appeared occasionally as a clonic movement. The TVR could not elicited in spino-cerebellar degeneration, ~ m e cases of basilar artery insufficiency and in early stages of central cervical cord injury. Though unconfirmed by autopsy, the common lesion in the above mentioned cases was postulated to be in the spino-cerebellar tract. A recovery curve of the H-reflex was drawn during application of vibratory stimuli to the Achilles tendon. In normal subjects, the amplitudes of H-waves were depressed; however, the curve showed apparent early facilitation and supernormality. As for the recovery curve, the vibratory stimuli acted as a facilitatory factor. Patients with nervous diseases reacted variously. An influence on the amplitude was not always associated with a change of the ratio. Besides, the change in the early facilitation period did not always bring the change in the supernormal period.

M 088.F~AVE P R O X I M A L M O ~ R NERVE CONDUCTION VELOCITY IN THE PERIPHERAL NERVES OF PATIENTS WITH AMYOTROPHIC LATERAL SCLEROSIS. C.Argyropoulos, S.Scarpalezos and C.P.Panayiotopoulos. (Athens, Greece).

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The F-wave has been used for estimations of motor nerve conduction velocity (MNCV) along the centr~ segments of the axons of the deep peroneal (anterior horn cells to the knee) and the ulnar nerve (anterior horn cells to the elbow) in patients with amyotrophic lateral sclerosis (ALS) and matched control subjects, MNCVs have also been estimated with conventional methods. We applied the method described by Panayiotopoulos et al, 1977 (J.neurol.Sci.,31:331-341) for the deep peroneal nerve and Kimura, 1974 (Neurology, Minneap. 24:539-546) for the ulnar nerve. One hundred Fwaves were obtained from each nerve in order to assure that the F-waves with the shortest latency did not escape detection. We found that MNCV in the central segments of these nerves is faster than in their distal parts. In a very small minority of patients the central MNCV in the ulnar nerve only, was slightly slower than the distal MNCV. Our results do not confirm findings of other authors who found a consistent progressive decrease of MNCV from the distal to the proximal segments of the peripheral nerves.

M 089. F-WAVE CONDUCTION VELOCITY IN THE CENTRAL SEGMENT OF THE TIBIAL NERVE. C.P.Panayiotopoulos and S. Scarpalezos. (Athens, Greece). The F-wave has been used for estimations of motor nerve conduction velocity (MNCV) along the central segment (a~terior horn cells to the knee) of the tibial nerve, in 100 control subjects and in patients with various neuromuscular diseases. The method is similar to that described for MNCV estimations in the central segment of the deep peroneal nerve (Panayiotopoulos et al. J.Neurol. Sci.1977, 31,331-341). Recording surface electrodesare placed over the small plantar muscles; the tibial nerve is supramaximally stlmulated at the knee and ankle. F-waves were easily elicited and measured in all control subjects and in the majority of patients. In a few patients, with severe atrophy of the small plantar muscles, F-waves were not obtained. In the latter cases, MNCV of the central segment of the tibial nerve was estimated from responses obtained from the gastrocnemius muscle. MNCV was found to be faster in proximal than distal segments of the tibial nerve in the control subjects and in the majority of tile patients. In patients with neuropathies the central MNCV was slowed even if the proximal muscles were normal. Patients with muscular dystrophies have normal a MNCV with the exception of dystrophia myotonica. It is concluded that the F-wave method is a useful tool in clinical neurophysiology and should be routinely applied in the investigation of patients refered for MNCV estimations.

M 090. STATISTICAL ANALYSIS OF THE VARIATION OF NERVE CONDUCTION VELOCITY. A.H.Lang and S.E.Bj~rkqvist. (Turku, Finland).

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The maximal nerve conduction velocity (NCV) of six sensory nerves (N.radialis, suraiis and peronaeus superficialis,bi]ateral]y) was measured in 59 uraemic patients and 88 normal adults. When the effect upon NCV of age and temperature was eliminated by means of partial correlations, it became possible to establish a significant negative correlation between height and NCV. This explained as much as 35 per cent of the remaining variance in males. A set of "statistical corrections" (grouping of NCVs according to the subject's sex, computing of the average NCVs of an individual, and height-, age- and temperature normalization of single or mean NCV-values) substantially decreased the variability of NCV and increased the diagnostic sensitivity of the measurements. In a group of 129 normal children and adolescents, age 3-19 years, the corresponding "statistical corrections" revealed a significant positive correlation bel~een age and NCV but a negative correlation between height and NCV. In other words, maturation and increase in height are factors which have opposite effects upon NCV. These factors can be differentiated only by statistical means when analyzing NCV values in a particular population. The existence of the height -NCV correlation has both practical and theoretical implications.

M 091. STUDIES OF THE PROPRIOSPINAL SYSTEM IN MAN. J.Faganel. (Ljubljana, Yugoslavia).

INTERNEURONE

Characteristics of the spinal interneurone sys~m were studied in patients with severe transverse spinal cord injuries which completely or incompl~ tely isolated the spinal cord from the supraspinal s e d G y - m o t o r integrative mechanisms. Propdoceptive and exteroceptive reflex mechanisms were examined for this purpose. The excitability of motoneurones tested by repetitively elicited myotatic reflexes was influenced by additional stimulation of various skin areas and by vibration of mugcles of the trunk and lower extremities. Noxious plantar stimulation activated interneurones of the spinal gray matter and caused inhibition of the myotatic reflexes in extensor muscles and facilitation of the myotatic reflexes in flexor muscles. Noxious stimulation appli~ to more distant dermatomes activated intersegmental interneurones of the spinal white matter which mediated ascending and descending excitation with a mainly facilitatory influence on the myotatic reflexes. Additional stimulation by muscle vibration a]so activated propriospinal interneurones, however, this influence on myotatic reflexes was inhibitory. The activity of the segmental interneurone s y s t ~ of the spinal gray matter and intersegmenta] interneurone system of the spinal white matter depends on the supraspinal motor control mechanisms. The residual descending motor control can be preserved even in patients with severe spinal cord injuries to a degree that can modify the

activity~

the spinal

interneurones.

M 092. CARPAL TUNNEL SYNDROME AFTER BRACHIAL XUS LESIONS. F.M.Dyro. (Portland, Maine, USA).

PLE-

This report concerns fourteen patients, previously a s y m p t o m a t i c who had e i t h e r b r a c h i a ] F l e x u s s t r e t c h i n j u r i e s o r P a r s o n a g e - T u r n e r Syndrome w i t h r e s i d u a l p a r e s t h e s i a s . Six p a t i e r t s w i t h r e s i d u a l symtoms in median n e r v e d i s t i b c t i o n requir~ s e c t i o n o f the t r a n s v e r s e c a r p a l l i g a m e n t . Of the f o u r t e e n p a t i e n t s s t u d i e d , f i v e had m i l d p r o l o n g a t i o n o f the median s e n s o r y l a t e n c y on the s i d e o p p o s i t e the i n j u r y . Two p a t i e n t s had b i l a t e r a l c h r o n i c c a r p a l t u n n e l syndrome t h a t became s y m p t o m a t i c o n l y a f t e r a l e s i o n in one p ] e x u s . These ~ o were in a g r o u p o f p a t i e n t s w i t h p l e x u s neuritis. The t h i r d p a t i e n t in t h a t g r o u p had p r o l o n g e d s e n s o r y l a t e n c i e s on the o p p o s i t e s i d e . In one p a t i e n t , u l n a r e n t r a p m e n t a t the c u b i t a ] t u n n e l was found a f t e r i n j u r y and in f o u r o t h e r p a t i e n t s u l n a r d i s t a l mot or o r s e n s o r y ] a t e n c i e s were p r o l o n g e d . T h e r e d i d not a p p e a r i:o be any d i f f e r e n c e between upper and l o w e r piexus injur i e s in terms o f r e s i d u a . The p o s s i b i l i t y that a pre-existing subclinical ] e s i o n a t the w r i s t m i g h t be unmasked by a subs e q u e n t r o o t l e s i o n has been r e c o g n i z e d . Upton and Mcgomas have r e p o r t e d on the phenomenon o f the " d o u b l e c r u s h " , p o i n t i n g o u t the " e l a t i o n s h i p between n e u r a l l e s i o n s in the neck and c u b i t a ] o r c a r p a l t u n n e l syndrome. W h i l e i t may be d e b a t ~ t h a t t h i s paper is d e s c r i b i n g a v a r i a n t o f the d o u b l e c r u s h , the p e r s i s t a n c e o f p a r e s t h e s i a s in the median n e r v e d i s t r i b u t i o n , and ]e~s commonly in u l n a r d i s t r i b u t i o n , in a p a t i e n t w i t h h i s t o r y o f a b r a c h i a ] p l e x u s i n j u r y s h o u l d not be a t t r i b u t e d to the injury itself. There may well be a median nerve entrapment requiring decompression.

M 093. THE FREQUENCY RESONANCY THE H-REFLEX. Sz.Toth, A.Solyom and J.Vajda.

INVESTIGATION

OF

(Budapest,Hungary).

On p a t i e n t s w i t h c h r o n i c i m p l a n t e d e l e c t r o d e s w i t h i n the m o t o r system ( m o t o r c o r t e x , n u c l e u s ventrolateralis o f the t h a l a m u s , p a ] l i d u m , n u c l e ~ d e n t a t u s ) we have d e m o n s t r a t e d enhanced mot or e f f e c t in a g i v e n f r e q u e n c y band ( 5 - 7 c p s ) o f s t ! m u ]ation of the different target points (Toth,Zara~, Lazar 1974). In t h i s s t u d y we i n v e s t i g a t e d the H - r e f l e x a t r e s t and d u r i n g v o l u n t a r y c o n t r a c t i o n on s t i m u l a tion with different f r e q u e n c i e s ( 0 , 1 - 2 0 c p s ) . The investigations were c a r r i e d o u t on normal i n d i v i d u a l s . In t h e f r e q u e n c y band 1-10 cps t h e r e were a "resonancy" like increase of the reflex resporr:es, witha peak in 5-7 cps frequency band. These results were compared with our previous observations of patients with chronic implanted electrodes, with the frequency resonance investigations of patients with spinal cord lesions and with normal alternating movements. Accordingto this study the frequency resonance

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610 investigation is a useful of central motor lesions.

technique

for the study

M 094. STUDY OF THE MOTOR UNIT ACTION POTENTIAL (MUAP)BY MEANS OF A SIMULATION MODEL. P.A.M. Griep and K.L.Boon. (Enschede, The Netherlands). A compLEter simulation model has been developed (Boon, K.L. and Griep, P.A.M.Proceedings ISEK, A. Arrigo (Ed.) Pavi~,1976:22-26) based on geometrical stucture and physiological characteristics of motor units and using volume conduction theory principals (tripo]e modell. Parameters of each fibre were: spatial position, diameter and arrival time of its potential at the electrode. Dimensions and spatial position of the electrode were specified. In a more recent version of the model also anisotropy and geometrical structure of the endplate region were taken into account. From the model studies it was concluded: ].Within a motor unit territory, a microe]ectrode records mainlythe activity of fibres ]ying next to the electrode; while a macroelectrode is less selective. Signals outside the territory yield hardly any differences between the two electrodes. 2.The square root of the low frequency maximum (Pmax) ofthe power spectrum of a simulated muap is ]inearly dependent ~ the number of fibres in a given territory; there is a clear c o r r e ] a d ~ with the territory dimensions if the fibre density is constant. The variability of Pmax is much less than the variabi]ity of the muap-amp]itude. 3.The distribution of the endplate ]ocations is an important parameter which influences str~g]y the degree oF polyphasicity.The fact thatin reality action potentials recorded intraterritorially are seldom po]yphasic can be explaind by assuming correlations between fibre position and endplate position. 4.1f the intere]ectrode distance is small enough, the bipolar recording of muaps is more selective for measuring motor unit behavior than unipolar recordings.

M 095. THE EVOLUTION OF MOTOR NERVE CONDUCTION VELOCITY COMPARED WITH THE CONTROL IN DIABETICS: PHYSIOPATHOLOGICAL CORRELATIONS OF NEUROPATHY. J.J.Papy, J.Conte Devolx, B.Conte Devolx,L.J. Benaim and J.L, Codaccioni. (Marseille, France). Measurements of the motor conduction velocity (MCV) in the latera] popliteal nerve have been made at different interva]s on one hundred diabetic patients. The control of their diabetes has been determined on the b]ood sugar levels, the glycosuria and the acetonuria of the last 24 hours.A first measurement was done when the patient entered the Hospital. A second one, a week or a fortnigbtlater, when the patient had remained in a good metabolic steady state for more than five days or when it appeared it

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was impossible to obtain good contro]. Eventually a third measurement fol]owed the second at least eight days later. Our population has been classified into two categories of patients with or without clinical signs of neuropathy: Patients with a recent onset of diabetes, without any degenerative complications as retinopathy nephropathy or cardio-vascular lesions: a better metabolic control is accompanied by a very significant augmentation (P 0.005) of the MCV when this one was reduced. Its normalisation may occur later if not observed at the second examination. However one observes no change of the MCV when the metabo]ic state remains uncontroled. Patients with a former diabetes with one or severa] degenerative complications. In these cases, on the contrary, the MCV changes on]y exceptionally, even if it was reduced at the beginning. There is no correlation with the metabolic control,usually good. These results seem confirm the existence of two types of neuropathic affections in diabetic patients: one is purely functional and regresses when the metabolic state is stabilized, the other one probably due to an alteration of nerve structure, which evolves simultaneously with the o t ~ r degenerative complications and totally independently of the metabolic contro]. These physiopathological considerations are discussed.

M 096.ELECTROMYOGRAPHY OF ANAL AND URETHAL SPHINCTERS IN FEMALE URINARY STRESS INCONTINENCE. J.J.Papy, L.J.Benaim, J.Conte Devolx and G.Serment. (Marsei]le, France). Theauthors have made a systematic: EMG survey of anal and urethal sphincters on one hundred and fifty women suffering from urinary stress incontinence. More or less severe signs of pheripheral and partial denervation o~: urethal sphir~ter have been found in one third of the cases. A total denervation and an atrophy of the striated sphincter have not often been seen. The anal sphincter is definitely less affected,it is often normal when the urethal sphincter is affected and on the whole it presents less severe signs of denervation than the uretha]. Some correlations have been made with the operative results of fifty patients. Results are good whenever the EMG is found to be normal. They are equally good when a partial denervation of moderate severity is present. They are bad in the case of a partial but severe,or total denervation; bad too when the sphincter can't be found by an experienced electromyographer probably owing to the fact that it is atrophied. On the basis of these observations the authors have drawn up an electromhographic classificat~n of sphincteric disorders. This seems to provide a basis for predicting the probable outccme of surgical treatment in urinary stress incontinence.

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M 097. SOME SINGLE FIBRE EMG FINDINGS IN MYOTONIC DYSTROPHY. R.Schoenhuber, C.Pagani and F.Prattichizzo. (Modena, Italy). Three brothers aged 34, 38 and 50, affected by myotonic dystrophy (MD) confirmed by cJinical, EMG and enzymological data, were studied also with single fibre EMG (SFEMG). In all patients the fibre density (FD), i.e. the number of muscle fibre spikes belonging to one motor unit picked up by the electrode, was significantly elevated: 2.2, 2.05 and 2.3 (normal 1.45 or less). There were also some blockings and a high jitter. An increased FD is found in diffuse or selective muscle fibre atrophy and in reinnervation, but only in the latter are there also signs of end plate instability as high jitter and blockings. In MD there is a type I fib~atrophy, that may contribute to the increased FD. However, the presence of high jitter and blockings found in our patients stresses reinnervation as the main cause of increased FD in MD. This reinnervati~on may be due to collateral sprouting secondary to motor neuron loss or to recapture of muscle fibre segments denervated by focal necrosis or splitting. SFEMG so demonstrates the presence of reinnervation in MD, although it cannon differentiate the pathogenic mechanism involved.

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Using SFEMG H reflexes and F responses can clearly be distinguished. This distinction is often difficult with conventional methods. All 120 motoneurones studied with SFEMG showed F responsses, on the average I response/100 stimuli. Responses occurred irreg @arly, with silent periods of up to 600 stimuli. Varying the stimulation frequency in the range I to 5/sec did not influence the frequency of the F response. The discharge characteristics of the motoneurones could be changed by activation of muscles of the same spinal level. When the neurone produced many F responses at rest, their frequency decreased under activation and vice versa ( p<0.05. Neurones of spastic limbs showed a significantly higher number of F responses compared both with a normal limb of.the same patient, and with normal subjects. The F response (a recurrent discharge), results from a somatodendritic spike potential, if the membrane at the axonal hillock is excitable. There is a critical time window, which may be too narrow in cases where the membrane is too much predepolarized, such as in spastic patients under activation. In contrast, a slight predepolarisation facilitates both the invasion of a soma-dendritic spike and repolarisation at the hillock with a concomitant increase of F responses.

M 098. CORRELATION

BETWEEN SINGLE FIBRE EMG JITTER AND ENDPLATE POTENTIALS. HH.Schiller and H.Lundh. (Z~rich, Switzerland).

M I00. MYOELECTRIC CONTROLLED HAND PROSTHESES IN CHILDREN. R.S~rbye. (Orebro, Sweden).

~ e SFEMG jitter is known to represent mainly the safety factor of neuromuscular transmission (Staolberg, Schiller, Schwartz 1975). To study the correlation between SFEMG jitter and endplate potential amplitude, neuromuscular transmission was studied in rats paralyzed with botulinum toxin type A, with SFEMG in vivo and with intracellular microelectrode technique in vitro. In muscles that were not completely paralyzed, SFEMG showed an increased neuromuscular jitter on nerve stimulation and in these muscles endplate potentials were of reduced amplitude. When the nerve stimulation frequency increased, the jitter decreased. On intravenous injection of drugs that increase acetylcholine release (such as tetraethylammonium and guanidine), endplate potentials increased, the jitter was reduced and the frequency dependence disappeared. Similar SFEMG resul~ have been obtained in disorders of acetylcholine release such as botulism (Schiller and Staolberg 1977) and myasthenic syndrome (Schiller, Rosen, Elmqvist, Nilsson 1977). SFEMG allows the evaluation of phenomena at the endplate in man in vivo.

From May 19,71 15 p r e - s c h o o l c h i l d r e n w i t h congen i t a l b e l o w - e l b o w phocomelia have been s u p p l i e d w i t h m y o e l e c t r i c c o n t r o l l e d hand prostheses in Orebro, Sweden. The ages at f i t t i n g have been 18 months - 5 years. Maximum follow up time is 6 years, in a girl aged 3 years at application. As pre-school children were earlier not considered able to manage such prostheses, the first 8 children had to be supplied with myoelectric controlled hand prostheses inappropriately large and heavy for their ages. A smaller prosthesis of the same type, developed in Sweden during the last years, has later been fitted in 2 of these children and in 7 others. The prostheses have been well accepted, without any rejection up to now. The control of the devise can obviously be integrated with the normal psychomotoric development. Most of the children have got a body image in their prosthesis. The active use of the stump muscles has greatly inhibited the expected atrophy, which means greater capability of socket retension and better control sites for even more advanced prostheses later on. Some patients have indicated development of a natural sensory feedback, supporting the device control. For most patients and parents the application of the prostheses has also brought great psychological advantages. We think that myoelectric controlled hand prostheses should be applied at an early pre-school age.

M 099. F RESPONSES STUDIED WITH SINGLE FIBRE ELECTROMYOGRAPHY (SFEMG) IN NORMAL MAN AND IN SPASTIC PATIENTS. H.H.Schiller and E.Staolberg. (ZBrich,Switzerland and Uppsala, Sweden).

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M 101. PROPRIOCEPTIVE RELATIONSHIP BETWEEN QUADRICEPS FEMORIS AND TRICEPS SURAE MUSCLES IN MAN. Z.Bouaziz, M.Hugon and M.Bouaziz. (Marseil]e, France). Electrical stimulation o f the f e m o r a l n e r v e m o d i fied H reflexes elicited in the Soleus muscle at different time i n t e r v a l s . The e n s u i n g r e c o v e r y cycle consisted of six distinct phases. Similar heteronymous recovery curves were obtained when the electrically evoked monosynaptic reflex in Quadriceps femoris muscle was conditioned by stimulation of the posterior tibial nerve at the politeal fossa. The influence of tactile impulses excited by these sti,muli was negligible. Our findings are related to facilitatory and inhibitory spinal mechanisms and are in agreement with animal physiological data (Cat-Baboon). These heteronymous recovery cycles were dependent upon impulses elicited in I and alpha fiber groups by the conditioning stimulus and resulting motor or reflex response. A diagram of proprioceptive int~c o n n e c t i o n s between t h e s e two m u s c u l a r g r o u p s was d e r i v e d f r o m above d a t a . I t i n v o l v e s e x c i t a t o r y la, inhibitorylb and r e c u r r e n t i n h i b i t o r y and disinhibitory interactions. These r e l a t i o n s h i p s a r e not s y m m e t r i c a l : la a f f e r e n t s from the Soleus n e r v e do not seem to f a c i l i t a t e monosynaptic response in the Q u a d r i c e p s f e m o r i s m u s c l e ; r e c u r r e n t activities from Q u a d r i c e p s do not i n h i b i t the Soleus r e s p o n s e s . I n t e g r a t i o n o f long l o o p f u n c t b n in o u r d i a g r a m is not n e c e s s a r y f o r a d e q u a t e d e s cription of our findings at rest. (Work s u p p o r t e d by "La F o n d a t i o n p o u r la Reche~he M@dicale F r a n g a i s e " ) .

MI02. COMPARISON OF SPINAL EVOKED POTENTIALS AND LATE MUSCLE RESPONSES. A. Siafakas, C.P.Panayiotopoulos and S.Scarpa]ezz)s (Athens,Greece). Somatosensory and spinal evoked potentials as well as late muscle responses (F-waves and H-reflexes) are considered of importance in clinical neurophysiology. However, comparative studies of these responses are not available despite the fact that they travel along pathways which aretopographically closely related for long distances and are common for some of them. In 20 control subjects, we studied simuitaneuously recorded somatosensory cerebral, spinal evoked potentials and F-waves after supramaximal stimulation of the median nerve. H-reflexes were also obtained from the same nerve. We have also estimated the expected latency of arrival in the spinal cord of the shortest F - w a v e s ~ d H-reflexes. It was found that the latency of arrival of these responses coincides with the latency of the initial part of the large negative wave of the spinal evoked potential. Application of these comparative studies in human diseases are important as indicated by these preliminary results.

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M 103. MISDIRECTION OF REGENERATING FIBRES FOLLOWING FACIAL NERVE PARALYSIS. AN EMG STUDY OF 50 CASES WITH OR WITHOUT POST-PARALYTIC FACIAL SPASM. P.Dori, J.Sachinidis and M.Doris.(Athens,Greece). About 50 p a t i e n t s , presenting either post-paralyt i c f a c i a l spasm o r c l i n i c a l r e c o v e r y , have been electromyographically studied. A minute analysis was done, b o t h o f the abnormal i n v o l u n t a r y a c t i v i t y and o f v o l u n t a r y , w i t h s i m u t L a n e o u s r e c o r d ing from the F r o n t a l i s , the O r b i c u l a r i s O cul i and th Q u a d r a t u s L a b i i S u p e r i o r muscles o f the i n v o l v ed s i d e . In a l l cases m i s d i r e c t i o n o f the r e g e n e r a t i n g F a c i a l n e r v e ' s f i b e r s was f ound f o l l o w ing e i t h e r a s i m p l e o r a complex p a t h , o r sometimes b o t h . The d e v e l o p m e n t o f p o s t - p a r a l y t i c facial spasm is due t o a p r e m a t u r e and r i c h r e g e n e r a t i o n of one branch o f the damaged f a c i a l n e r v e in compar i s o n t o the r e s t o f them. Thus, the r a p i d l y r e g e n e r a t i n g n e r v e branch e x t e n d s beyond the a r e a n o r m a l l y i n n e r v a t e d by i t t o a r e a s c o n t r o l l e d by o t h e r b r a n c h e s , which a r e e i t h e r more d i s t a l o r show a r e t a r d e d r e g e n e r a t i o n . T h i s phenomenon depends on the p a t t e r n o f f a c i a l lerve branching, which v a r i e s g r e a t l y , not o n l y among d i f f e r e n t individuals, but even between the two s i d e s o f the f a c e o f the same p e r s o n ; t h i s b r a n c h i n g ranges from a d i r e c t u n c o m p l i c a t e d pentamerous t y p e to a complex p l e x i f o r m a r r a n g e m e n t . In the l i g h t o f these findings, the p o s s i b i l i t y of preventing or, at least, eliminating the p o s t - p a r a l y t i c facial spasm is a l s o d i s c u s s e d .

M 104.ELECTROMYOGRAPHIC STUDY OF A CASE OF SUCCESSFUL HYPOGLOSSAL-FACIAL ANASTOMOSIS. P.Dori, J.Sachinidis and M . D o r i s . ( A t h e n s , G r e e c e ) . A case o f s u c c e s s f u l h y p o g l o s s a ] - f a c i a ] anastomos i s is r e p o r t e d . T h i s a n a s t o m o s i s was done in o r d e r t o p r e v e n t the u n p l e a s a n t consequences o f a complete facial nerve destruction f o l l o w i n g an o p e r a t i o n f o r removal o f an A c o u s t i c Neurinoma. F i f t e e n months a f t e r the a n a s t o m o s i s the e l e c t r o m y o g r a p h i c f i n d i n g s a r e a n a l y s e d and a c o r r e l a t i o n t o the p r e s e n t c l i n i c a l pict ure is at t empt ed . The EMG r e c o r d i n g s , t a k e n s i m u l t a n e o u s l y from the frontalis, orbicularis o c u l i and q u a d r a t u s l a b i i s u p e r i o r m u s c l e s , showed f a i t h f u ] ] y the d e g r e e and p r o g r e s s o f the r e i n n e r v a t i o n t h r o u g h the c r e a t e d newe c r o s s i n g . T h i s i n f o r m a t i o n c o u l d not be o b t a i n e d e i t h e r by t h o r o u g h c l i n i c a l examinat i o n a n d / o r by f a c i a ] n e r v e s t i m u l a t i o n . The a d v a n t a g e s o f the a n a s t o m o s i s d i s c u s s e d a r e q u i t e c o n s i d e r a b l e in c o m p a r i s o n t o the d i s c o n f o r t whi ch is c a u s e d . Thus, a l t h o u g h we l o o k a t t h i s o p e r a t i o n o n l y from the clinical and neurophysiological point of view, we suggest that the anastomosis discussed could be a method of choice for the prevention of the serious side-effects which follow severe and irreversible damage of the facial nerve.

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M 105. THE OCULOAURICULAR PHENOMENON IN DIAGNOSTIC USE (POLYGRAPHIC,COMPUTER ASSISTED EMG STUDIES). M.P.Heuser. (MUnchen, W.Germany). The oculoauricular Phenomenon (OAP) is based on a bilateral interaction between the motor nuclei of the abducens and the facial nerves. In peripheral f a c i a I paralysis the OAP is homolaterally abolished, in nuclear lesions (accompanied for instance by facial myokymia or nystagmus as in E. d.), it is disturbed, whereas in central facial paralysis the OAP is normal. In peripheral (distal) paralysis of the a b d uc e n s nerve or mechanic paralysis of the eye muscle the OAP is undisturbed, with a unilateral nuclear lesion, (MOEBIUS, DUANE, etc.), the OAP is homolaterally disturbed. In central strabismus the OAP isbilaterally normal.

M 106. RECORDED CORNEAL REFLEX:STUDY

IN NORMAL SUBJECTS AND IN TRIGEMINAL NERVE LESIONS. B.W.Ongerboer de visser and K.Mechelse. (Amsterdam, The Netherlands).

The few published data on recorded corneal reflexes are contradictory with respect to constancy of latencies. The clinical value of registration of the reflex has not been studied systematically. Orbicularis oculi muscle responses were evoked by manual application of a metal sphere, 2 mm in diameter, to the cornea. At the moment of touch, contact is established between the subject and an electronic circuit. A shift in the electrical potential is detected by a sense amplifier, switching on a pulse generator, which forms the trigger pulse for the sweep of a dual trace oscilloscope. Parameters were derived from findings in 32 normal subjects. Reflexes were also investigated in 15 patients with unilateral trigeminal nerve lesions. We found with the method used a high degree of constancy of the intra-individual latent periods and did not observe facilitation or habituation. The mean latency increases with age. Recorded reflexes were disturbed, bilaterally delayed or absent ipsilateral to the lesion in all of the patients. In 7 of them the reflexes demonstrated by conventional neurological examination were abnormal, in 3 dubiously normal and in 5 normal. These findings demonstrate the value of bilateral recording of the reflex for the clinician.

M 107. STUDIES ON NERVE CONDUCTION IN THE REFRACTORY PERIOD USING ON-LINE COMPUTER ANALYSIS. J.P.C.deW~rd,H.M.Vingerhoets, S.LoH.Notermans, and J.Kap. (Nijmegen, The Netherlands). It has been suggested (Hopf, 1973; Tackmann and Lehmann,1974) that measurement of the refractory period of sensory nerves may be of importance in the early diagnosis of peripheral nerve disease. The refractory period can be determined

618 by recording nerve response to supramaximal pair~ stimuli with varying intervals, measuring the increase in latency and decrease in amplitude of the second response relative to the first. In order to allow accurate measurements averaging techniques have been used hitherto. To avoid this time consuming procedure we developed a fast online computer analysis technique, essentially based on matched filtering followed by peak detection. In this procedure normally 60 double impulses with in;~rvals ranging from 12 to 0 ms in decrements of 0,2 ms are applied. The time segments directly following the firs: impulse are conventionally averaged, whereas the segments following each second impulse are stored temporary. In the averaged time record, the nerve response is automatically detected. This average response is used as a matched filter for detection of the second response. Latency and amplitude curves as a function of impulse interval are estimated from the matched filter output and fitted with simple exponential curves, characteri~d by three parameters. These parameters, from which relative and absolute refractory periods can be directly calculated are stored for later evaluation. An interesting result, obtained by this method, is the observation, that the large influence of temperature on the refractory period is concentrated mostly at the side of stimulation.

M 108.SPONTANEOUS ACTIVITY WITHIN THE MOTOR UNIT.~ A SINGLE FIBRE EMG STUDY. J.V.Trontlj and E.Staolberg.(Ljubljena, Yugoslavia and Uppsala, Sweden). Spontaneous activity may arise in different pars of the motor unit. In the muscle fibre, fibrillation potentials can be generated. One muscle fibre's action potential may trigger" depolarisation of another muscle fibre, thus resulting in pairs of fibrillation potentials, usually but not necessarily with very small jitter. Electrical stimulation experiments sugges~ that the sites of ephaptic transmission are points of lower electrical threshold along the muscle fibm. So-called bizarre high frequency discharges may similarly be explained as being generated by groups of ephaptically activated muscle fibres, driven by one fibrillating fibre. Low-threshold sites along the muscle fibre (including the motor-end plate region) are responsible for "backfiring" or repetitive spontaneous discharges during the supernormal excitability period follow ing a previous voluntary, electrically induced or spontaneous discharge. The interdischarge intervals may be regular, e.g. in fibrillation and myotonia, or considerably irregular, e.g.in tetany, muscular dystrophies and polymyositis. The extradischarge may occur during profound abnormality of the muscle fibre, as indicated by lower and broader action potential and slowed propagation velocity. Pathological impulses may be generated in axonal branches giving rise to fasciculations in which a part or a whole motor unit may b~ activated.

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The order of muscle fibre action potentials in the discharge may change indicating that the impulses are generated in different branches. The interdischarge intervals tend to be irregular, and there is jitter between the individual spike components. Such discharges may also follow voluntary discharges of a motor unit. In neuromyotonia, complex muscle fibre action potentials may occur in double or multiple discharges at varying intervals, repeated in clusters of two to several. The ventral horn cell may be the site of generation of spontaneous impulses giving rise to fasciculation and recurrent discharges.

M 109.~ECTROMYOGRAPHIC ANALYSIS OF THE GLABELLA TAP SIGN. M.Gregoric. (Ljubljana, Yugoslavia). A brisk blink reflex which does not habituate on repeated tapping the glabella is quite nonspecific as a clinical sign. This phenomenon was studied electromyographically in patients with caFs~ar hemiplegia, amyotrophic lateral sclerosis,parkinsonism and dementia, and was compared to the blink reflex in a control group of healey subjects. The behaviour of bothearIy (RI) and late (R2) EMG responses of the blink reflex was analysed by means of a computer. Increase in the R1 responses was often observed in patients with upper motor neuron lesions, i.e. in patients with hemiplegia and in patients with amyotrophic lateral sclerosis, expecially in those with clinical signs of pseudobulbar palsy. In these patients the R2 responses were often relatively small and had a prolonged latency. In the hemiplegic patients, the blink reflex was altered on both affected and unaffected side. In demen~d patients and in patients with parkinsonism, habituation of the late reflex responses was delayed or even absent. Many parkinsonian patients exhibited markedly stable R2 responses with shorter latency. The observed behaviour of the RI responses shows some characteristics of the proprioceptive reflexes, while the behaviour of the R2 responses resembles the behaviour of some exteroceptive defense reflexes. The glabella tap sign in different disorders is most probably caused by different pathophysiological mechanisms and may be due either to an increase in the RI response or to insufficient habituation of the R2 responses or both.

M 110.STATISTICAL ANALYSIS OF REFLEXIVELY PRODUCED MOTOR UNIT SPIKES DURING TRIANGULAR STRETCH IN NORMAL AND SPASTIC MAN. S.Homma, Y.Maruyama and T.Noguchi. (Chiba,Japan). The human Achilles tendon was tapped by a powerful electromagnetic vibrator which was driven with a triangular time course (4 ms in both pushing and releasing phasesl. The soleus muscle continued to contract during the tapping. Motor unit spikes were recorded bipolarly by a pair of fine polyurethane÷nsulated copper wires in-

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serted into the muscle. Relationships between frequency of motor unit spikes (Mr in ordinate) and tapping frequency (laf in abscissa) were determined. There was no linear portion in Mf-laf relation and the relation could be expressed by a quadratic curve in which the maximum was around 50 Hz. For a convenient standardization of the Mf-laf relation, so called shape indices were measured by the time to peak and its duration at a half amplitude in abscissa. Average of time to peak was 14.40 ms and that of ouration at a half amplitude was 36.80 ms. These values were la~er than those obtained from cat's soleus muscles. On the other hand, experiments in cats revealed that the time course of the Mf-laf relation and that of the excitatory postsynaptic potential (EPSP) were quite similar. Therefore the time course of the Mf-laf relation obtained in this experiment seemed to represent the time course of EPSP of human motoneurones induced by la volleys. It may be that the time course of the EPSP in human motoneurones is somewhat slower than in that of the cat. Further theMf-lafrelations of the quadriceps femoris muscles were measured in spastic patient. The results were compared with those of normal man.

M 111.TRANSIENT CHANGES IN THE LEVEL OF NEUROMUSCULAR BLOCK IN MYASTHENIA GRAVIS PATIENTS FOLLOWING THYMECTOMY. J.A.M.Bergmans, C.Fannes~Breselow, A.Lacquet and N.Rosselle. (Brussels, Belgium). The immediate postoperative evolution of the neuro-muscular (NM) block following thymectomy, in patients with myasthenia gravis, has been assessed by measuring twice daily the decrement of response to short trains of volleys at 3/s, in 3 muscle groups. The study has been conducted in 25 patients, and discloses a partial remission which sets in usually on the first postoperative day and is followed by a more or less rapid (2-15 days) return to the preoperative state. Usually, the lasting improvement to be expected from thymectomy occurs only after longer delays. During the early transient phase of remission, the decrement of response to short trains of volleys fluctuates in parallel in the behaviour of NM transmission during long lasting stimulation series. These observations are interpreted in terms of the known change in immune-responsive ness which occurs during the immediate postoperative period.

M 112. NEUROPHYSIOLOGICAL CHARACTERISTICS OF SPONTANEOUS MUSCULAR ACTIVITY ARISING IN PERIPHERAL NERVE FIBRES. J.A.M. Bergmans. (Brussels, Belgium). A detailed neurophysiological investigation of spontaneous muscular activity arising in the peripheral parts of the motor nerve fibres has been made in 8 patients. Several kinds of spontaneous activity are described, including typi-

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cal series of multiplet dischargesrecurring according to a stereotyped pattern. Spontaneous activity is enhanced by cathodal and anodal polarization of the motor nerve. Repetitive activity is evoked by percussion of the muscle at the motor point. Electrical activation of the nerve discloses increased terminal latencies of the muscle action potential, witha normal distal sensory latency, and triggers a repetitive discharge. When two volleys are given in succession, a depression of the repetitive discharge occurs up to intervals of 150-200 ms. Spontaneous and evoked repetitive activity is progressively depressed during ischaemia and enhanced following release of the cuff, and, usually enhanced after a period of voluntary activity. In single human nerve fibres, long lasting repetitive stimulation induces a hyperpolarization with increased distal latencies and spa7taneous activity similar to that observed in the pathological cases. It is suggested that in these cases a similar state exists in the distal parts of the motor axons.

M 113. THE VALUE OF THE ISCHAEMIC EXERCISE TEST FOR THE DIAGNOSIS OF MYASTHENIA GRAVIS. J.A.M.Bergmans. (Brussels, Belgium). In patients with myasthenia gravis, repetitive stimulation under ischaemia enhances the prevailing level of neuro-muscular block, and this technique has thus been used to detect subclinical involvement in muscles showing no decrement during short trainsof stimuliat 3/s. We have used systematicallya program involving a continuous ~imulation series at 4/s for 8 minutes under ischaemia, followed by testing with short trains at 3/s, before release of the cuff, at 10 minutes. The measurement took place at the level of the median innervated thenar muscles. In 6 out of 190 normal subjects, a decrement ranging between 80 and 91% (5/I ratio) has been found. In 47 out of 50 patients with myasthenia gravis, either an existing decrement was revealed. In 3 patientswith confirmed myasthenia gravis, where the symptoms were limited to the extraocufar muscles, no decrement was evidenced by the above testing procedure, In this test, an overlap thus exists between a normal and a myasthenic group, which can be compared to the overlap in curare sensitivity existing between these two populations.

M 114.VASCULAR SUPPLY OF RABBIT MUSCLE SPINDLES. T.Miyoshi and W.R. Kennedy.(Minneapolis, Minnesota, USA). The vascular bed of the blood supply of rabbit tenuissimus muscle spindles was studied using horseradish peroxidase (HRP) diaminobenzedine (DAB) staining and micro-latex injections. Following HRP injections via the aorta, muscle spindles were dissected from the glutaraldehydefixed tenuissimus muscles Reaction with DAB resulted in clear visualization ~ the spindles' capillary supply. Eleven spindles were studied

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first in whole mount and then by skipped transverse sections after epon embedding. The arterial supply and venous drainage of ten other spindles were studied in whole mount of micro.-latex injected tenuissimus muscles. Spindles in tenuissimus muscle lie very close and parallel to the large central arteriole. Capillaries to spindles were among the first branches of the smaller arterioles, providing a very short path from large arteriole to capillaries in the spindle compared to the capillaries in extrafusal muscle. Capillaries entered the spindle at or near the equator. One or two other entries were seen near the poles. Spindle capillaries were larger than those to extrafusal musclesto a degree that allowed their recognition in the latex preparations before verification of spindle location by Nomarski interference microscopy. In the equatorial region two or three capillaries were within the periaxal space. These formed a characteristic longitudinal loop around the sensory endings. Usually one capillary was found to run parallel to the intrafusal muscle bundle and exit near one pole. These characteristic features probably have the functional significance of allowing sufficient circulation to reach the region of the sensory endings where the metabolic demand for oxygen and energy sources is presumed to be great.

M 115. PERMEABILITY OF MUSCLE SPINDLE CAPILLARIES. W.R.Kennedy and K.S. Yoon. (Minneapolis,Minn. USA). Muscle spindles are enclosed within a perineurium-llke capsule that is continuou~ with the perineurium of the motor and sensory nerves to the spindle. The sensory endings have clumps of mitochondria and are believed to have high metabolic activity. Substances like d-tubocurare do not affect spindle function for 10 to 20 minutes, suggesting the existence of a blood-spindle barrier like the barrier between blood and brain or peripheral nerve. Horseradish peroxidase (HRP) injected intravenously escapes from capillaries of diaphragm in 60-90 seconds, (Simionescu, et ai,1975), either via a transcytoplasmic vesicular system (Simionescu, et al. 1973) or via the intercellular junctional clefts (Karnovsky, 1967).HRP does not escape from capillaries of brain, specific areas excepted, (Beightman and Reese, 1969), or peripheral nerve (Olsson and Reese, 1971). Rabbits were given 200 mg/kg of HRP (Sigma Type II) intraaorta. The tenuisslmus mus~le was fixed in situ with glutaraldehyde at varying times after injection. Spindles with some extrafusal muscle attached were isolated and treated by standard procedures for visualization of HRP by electron microscopy. Escape of HRP from tenuissimus capillaries is more sporadic than from mouse diaphragm. Stimulation of the motor nerve before and during the injection improved uniformly. HRP escaped into the extracellular space two minutes after

616 injection. The extrafusal capillary lumens were uniformly dark with the HRP reaction product, and vesicles facing lumenaland extracellular space were often filled. In contrast, capillaries within spindles never leaked HRP, contained only granular deposits of HRP in their lumen, and rare]y any within vesicles. Compared to extrafusal capillaries they were 2-3 times larger, had thinner endothelial cell walls with fewer vesicles. They resembled the capillaries of intramuscular nerve in every way. We conclude they are the most terminal part of the blood-nervous system barrier.

M 116.DIFFERENTIATING ACQUIRED FROM FAMILIAL SEGMENTAL DEMYELINATING NEUROPATHIES BY EMG. A.J.Wilbourn. (Cleveland, Ohio, USA).

For ten y e a r s , e l e c t r o m y o g r a p h e r s have d i v i d e d p e r i p h e r a l p o l y n e u r o p a t h i e s i n t o two main t y p e s : axonal d e g e n e r a t i n g and segmental d e m y e l i n a t i n g . The former a f f e c t s m a i n l y nerve c o n d u c t i o n a m p l i tudes and p r o d u c e s s i g n i f i c a n t f i b r i l l a t i o n s distally: thelatter affects predominantly distal latencies and conduction velocities and produces scant fibrillations. Although Segmental Demyelinating Peripheral Neuropathies (SDPN) are known to be a heterogenous group, no attempt has been made to subdivide them electrically. We have compared nerve conduction and needle examination results in 15 familial SDPN's (C.M.T.Type l,Dejerine-Sottas) with 15 acquired ones (GuillainBarre; chronic relapsing) and have found that they can be differentiated, by electrodiagnostic studies alone, with over 85% accuracy. The familial neuropathies are predictable in their appearance,almost without exception; abnormalities are more severe in sensory than motor fibers, in lower than upper extremities; slowing tends to be uniform along a nerve, with conduction velocities m d distal latencies equally affected; partial blocks are not common;needle examination changes are most prominent in the distal lower extremities. In contrast, the acquired SDPN's are quite variable/unpredictable: motor fibers may be involved more than sensory, upper extremity nerves more than lower; partial blocks and/or focal slowing may be prominent along nerves, especially very distally or very proximally; the needle examination abnormalities often don't follow a disto-proximal gradient. The electrodiagnostic findings are most consistent with the idea that acquired SDPN's are actually peripheral polyradiculoneuropathies and not peripheral neuropathies

M 117. SERIAL CONDUCTION STUDIES IN HUMAN NERVE DURING WALLERIAN DEGENERATIOR. A.J.Wilbourn. (Cleveland, Ohio, USA). Little detailed information is available regarding sequential nerve conduction studies on human, mixed nerve undergoing Wallerian degeneration. Recently, we obtained some such data. A middleaged female had almost all (99%) or her left

INTERNATIONAL FEDERATION - 9TH CONGRESS ulnar nerve infarcted in the mid-arm due to rheumatoid arthritis-vasculitis. Extensive motor conduction studies reco.-ding with surface electrodes from hypothenar, first dorsal interosseous (FDI) and flexor carpi ulnaris (FCU) and antidromic sensory studies were performed, at 24-hour intervals, for eleven days, beginning 24 hours after onset. Stimulating distal to the lesion, all results were normal on Day I, and comparable to those of the contra]ateral, asy~ptomatic u l n ~ nerve. The motor amplitudes declined to
M I18.AN ELECTROPHYSIOLOGICAL STUDY OF MYOCLONUS. S.Egloff-Baer, B.T.Shahani and R.R.Young. (Boston, Mass. USA).

" L a t e responses" (LR) were recorded from i n t r i n s i c hand muscles in 10 normal subjects and 5 patients with various myoclonic disorders. Single square wave pulses (0.1 msec, 5-15 V) were applied over the median or ulnar nerve or their digital branches. In addition to an F response and/or homonymous or heteronymous ~ reflex, (latency 24-29msec), LR I (latency 40-47 msec) was seen in tonically contracting abd.pol].brev. muscles of all control subjects at a stimulus intensity subthreshold for the direct muscle (M) response as well as by stimulation of purely cutaneous digital nerves. In 2 normal individuals an additional high threshold LR 2, latency 71-74ms to the peak, was recorded. In contrast to control subjects, LR I and/or LR 2 could be recorded without background EMG activity in all patients. In one patient with post hypoxic intention myoc]onus (PHIM), LR I and LR 2 disappeared after chronic oral administration of baclofen (Substance P antagonist) a finding which suggests that a derangement of substance P neurotransmitter mechanisms may in part be responsible for certain myoclonic syndromes. Since neither stretching of muscles, nor direct stimulation of large afferent fibres (Group IA and IB) is necessary for production of the myoclonic response, the hypothesis that "myoclonic jerks are really deranged cortical stretch reflexes" (Marsden, Merton, Morton, 1973) is questionable. It is concluded that myoclonus is a distinct entity and should not be confused with st:retch refl~es in which the role of transcortical loops still remains to be proven.

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M 119. DIFFERENT METHODS OF MEASURING THE CONDUCTION VELOCITY OF THE SURAL NERVE AND THEIR PRACTICABILITY IN CLINICAL ROUTINE. P.Velho-Groneberg and G.Otterbach. (MCnchen, W. Germany). Standard techniques of measuring sura} conduction velocity(CSV) are time-consuming. Because of the importance of sensory conduction of the lower limbs in polyneuropathy, a method is desirable for routine clinical use which yields sufficiently exact results with less technical effort. We employ a technique of antidromic recording4using surface electrodes for stimulation and recording, which according to the literature is used only by few authors. To evaluate its reliability, a systematic study of a group of patients with polyneuropathy and of normal controls was carried out. With and without electronic averaging SCV was measured at constant temperature over the proximal segrwent (lateral ankle -mid-calf) in 4 different ways (antidromicaIly-surface stimulation, recording with surface and needle electrodes; orthodromically- needle electrode recording, stimulation with surface and needle electrodes). Latency, shape, amp]itude and duration of the evoked sensory action potential (SAP) are compared to the values in the literature. Special interest is payed to the ease and reliabi]ity with which the SAP could be recorded without averaging. In conclusion, antidromic n~easuring of SCV with surface stimulation and recording proves to be a practicable routine screening test for polyneuropathy.

CHRONIC RELAPSING POLYNEURITIS. J.D. Pollard, G.Selby and J.G.McLeod. (Sydney, Australia). M 120.

Acute idiopathic polyneuropathy follows a course usually uniphasic, but chronic progressive and relapsing varities occur. There is a common association between a c ~ e idiopathic neuropathy and some anticedent event such as viral infection, injections of foreign sera, vaccination or surgery, but there is little recorded evidence to suggest that repeated exposure to such events leads to chronic or relapsing disease. However, in experimenta] allergic neuritis (E.A.N.), which is generally regarded as a useful animal model of acute idiopathic polyneuropathy, repeated exposure to nerve antigen has been shown to cause chronic disease in some animals. In this paper we describe a patient who inadvertently received three injections of tetanus toxoid over a period of 14 years, and following each injection he developed an acute demyelinating neuropathy. Immunological studies indicated T.lymphocyte hyperresponsiveness to both tetanus toxoid and peripheral nerve antigen. Examination of the sural nerve biopsy showed a hypertrophic neuropathy with evidence of chronic continuing m o n o -

617 nuclear cell activity, similar to that seen in chronic relapsing E.A.N. The pathogenesis of chronic relapsing neuropathy is discussed with particular reference to H.L.A. studies performed in this patient and in other patients with either the acute or chronic relapsing form of idiopathic polyneuropathy.

M 121. DOES TRANSIENT BLOCKING OF NERVE CONDUCTION OCCUR IN URAEMIC NEUROPATHY? D.Meyer and A.H. Lang. (Turku, Finland). The EMG firing pattern of motor units, isolated and activated voluntarily, were studied in two groups of patients (uraemia and non-uraemic neuropathy) and in controls. Interspike interva]s were analysed by a computer program designed to identify "double interval firing pattern", i.e. an interspike interval whose duration is twice that of the preceding and following mean intervals in a short MUP sequence. A double interval firing pattern was found in both patients and controls, its highest incidence b e i n g in u r a e m i c p a t i e n t s u n d e r g o i n g d i a l y s i s t r e a t m e n t . The f i r i n g p a t t e r n c a n n o t be produced voluntarily, does not c o r r e l a t e w i t h i r r e g u l a r firing p e r se, may be l i m i t e d t o a r e s t r i c t e d mot o r neuron g r o u p o f the c o n t r a c t i n g m u s c l e , and is more common in d i s t a l than in p r c x i m a l muscles. A thorough off-line c h e c k i n g , o f the o r i g i n a l analogue recording revealed, however, that a double interval firing p a t t e r n is u s u a l l y cue t o i n t e r f e r e n c e from a n o t h e r MUP ( i . e . insufficient motor unit isolation) which causes f a i l u r e o f t r i g g e r i n g or to a transient fall in the centr~,l activation of the motor neuron. In some cases ~ double discharge of the motor unit preceded the instantaneous single long inter-spike interval. It is concluded that in most cases a double interval firing pattern is not due to a conduction block of the main motor nerve fibre. In some cases blocking of conduction cannot be ruled out, but neither can it be positively proved

M 122. HABITUATION OF THE BLINK REFt.EX AT DIFFERENT STIMULATION FREQUENCIES. A.J.W. Boelhouwer and C.H.M. Brunia. (Tilburg, The Netherlands). The electrically evoked blink reflex consists of an early ipsilateral component (R I) and a late bilateral component R2.1n previous experiments it has been shown that the state of arousal effects both R I and R 2. During a mental task two effects could be distinguished: increase of R I amplitude (and integral) and an increase of R 2 latency. Although habituation of R I has been denied by many authors using low frequency stimulation, evidence for this phenomenon has been recently demonstrated (Boelhouwer & Brunia, 1977, J. of Neurol., Neurosurg., Psychiat.,40,58-63). Habituation of R 2 is a commonly observe~ phenomenon when stimulation frequencies of about 1/10 sec. or higher are used.

618 The data to be presented now concern the effect of a mental task on R I and R 2 when 4 different stimulation frequencies are applied: 7.5/s,15/s, 30/s, or 60/s. T h e e ~ e r i m e n t was divided into a rest period,e mental task and a final rest period of 15 min. In each frequency condition 21 h e a l t ~ subjects were used. R I habituation was observed at all frequencies during rest and task, but this decrease was independent of stimulation frequency. This is contrary to the habituation criteria of Thompson & Spencer (1966, Psych.Rev.,173,16-43). The habituation of R 2 was directly related to the applied frequency, i.e. at higher frequencies a faster habituat'ion was observed. The mental task clearly showed opposite effects for R1andR 2. While the amplitude and integral of R I increased during mental task, R 2 decreased in amplitude and integral and its latency was prolonged. Although these effects were observed at all frequencies, they were most pronounced at lower frequencies.

M 123.PATTERN OF ELECTRICAL ACTIVITY DURING VOLUNTARY EFFORT AS RELATED TO PROPERTIES OF MOTOR UNIT POTENTIALS. A. Fuglsang-Frederiksen, U.Scheel and F.Buchthal. ( Copenhagen, Denmark). The number of ~ k e s in the pattern of electrical activity during 5 sec of moderate effort was mainly determined (I) the duration of motor unit potentials and (2) the incidence of polyphasic potentials. (I) An increase in mean duration of motor unit potentialsby 40% produced by cooling of the rr~s~cle from 36 ° C to 28 ° C caused the number of spikes to decrease by 50%. The maximum force, the mean amplitude of motor unit potentials and the incidence of polyphasic potentials were the same at low as at normal temperature. (2) The effect of the incidence of polyphasic potentials on the pattern of electrical activity was estimated in 15 patients recovering after a lesion of the brachial plexus. Given the number of spikes to be expected from the loss of motor units (calculated from the diminished force) and from the increase in duration of motor unit potentials, the difference between expected and observed number of spikes was due to polyphasic potentials. In fact, the number of spikes increased 24% as the incidence of polyphasic potentials increased from 10-20%.

M 124. CEREBELLAR DYSSYNERGIA IN MAN-A QUANTITATIVE ANALYSIS. R.G.MiIler, H.J.B~dingen and H.J.Freund. (Freiburg, W. Germany).

Patients ~ith cerebellar lesions and limb ataxia performed two types of continuous tracking tasks involving flexion and extension of the index finger. In both tasks, patients were provided cutaneous and proprioceptive cues but visual

INTERNATIONAL FEDERATION - 9TH CONGRESS feedback was given in the first (visual tracking) and not in the second (arbitrarily termed proprioceptive tracking). Raw records and fourier analyzed power spectra were compared with normal controls. Harmonic distortion was determined for each task. In the power spectra of severely ataxic patients during visual tracking, there was extreme harmonic distortion (HD) (mean ~ standard deviation =135% ~ 24.7), while there was only minimal HD (2.14% ~ 1.16) in normal subjects and intermediate levels of HD (14.9% ~ 14.1) in moderately ataxic patients. Increased HD is at least partly due to movements of excessiw~ velocity observed in records of ataxic patients. In all patients, as well as normal subjects, tracking performance was markedly improved, and HD substantially reduced, during proprioceptive tracking. This surprising and consistent finding may depend upon the much shorter feedback loop for proprioceptive stimuli compared to visual stimuli demonstrated by Evarts. The tracking records, power spectra analysis, and determination of HD provide both qualitative and quantitative data in patients with dyssynergia.

M 125. PROPRANOLOL : HEARTRATE AND REFLEXES DURING A TASK. C.H.M. Brunia. (Tilburg, The Netherlands). The performance of tasks causes an enhancement of sympathetic activity: heartrate increases and catecholamines levels in the urine are elevated. Banker and Girvin (1973) mentioned that muscle spindles, apart from being innervated by the fusimotor system, have also sympathetic-like nerve endings, at least in the dog. Furthermore a change in the firing rate of la afferents has been found under the influence of adrenergically active agents (Kayaalp et al. 1972). It has been demonstrated that during the performance of a task Achilles tendon (T) reflexes show an increase in amplitude, while simultaneously recorded Hoffmann (H) reflexes do not (Brunia 1971) Heart rate increases during the same task significantly. An experiment was carried out to investigate if a rise in adrenergic activity could be an important explanation for the increase of TR amplitudes during the task. 20 normal healthy subjects in a double-blind crossover designed experiment were given a tabl~ of either 40 mg propranolol or placebo, half an hour before the start of the experiment. At rest and during the performance of a task heart rate, T-reflexes and H-reflexes were recorded. The increase of heart rate during the task did not show up in thepropranolol session. The increase of T-reflex amplitudes, which is a common finding during the task under consideration, was larger in the propranolol session. No differences with H-reflexes were found. It is concluded that the increase of T-reflex amplitudes during the task is only caused by fusimotor and not by

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sympathetic activity. It is speculated that if the sympathetic ~stem plays a role at all, the effect is depressive rather than facilitating.

M 126. HABITUATION IN MONOSYNAPTIC REFLEXES. C.H.M. Brunia. (Tilburg, The Netherlands). Hind limb flexion reflexes of the spinal cat are considered to be a good model for the analysis of neural mechanisms of habituation and sensitisation (Spencer and Thompson 1966). It has been shown that habituation processes can be recorded at the spinal level. Thus Groves and Thompson (1973) compared responses of interneurones at the spinal level with amplitudes of flexor reflex amplitudes. A good concurrence of both reflexes was observed. Habituation seems to involve interneuron activity only Therefore it is said that monosynaptic reflexes do not show habituation. Nonetheless the present experimeRts on monosynaptic reflexes indicate that habituation does occur. Three experiments were performed, in each of which 20 subjects were used. Tendon reflexes were evoked at rest and during the performance of a binary choice task, in each experiment with a different stimulus frequency (3/s,7.5/s,15/s). During the task there was an overall increase in amplitude of tendon reflexes. However, over the cause of the task this enhancement progressively diminished, w h i c h w ~ mentioned by Mackworth(1969). She interpreted these results as being due to habituation. At rest a decrement of tendon reflex amplitudes over a period of 10 minutes could be observed. Although it is generally reported that stimulus frequency is directly correlated with the speed of habituation, in the present experiments no evidence for such a relationship could be found. Thus our results are not in agreement with Thompson's interpretation of habituation. The generality of the statement that no habituation occurs in monosynaptic reflexes may be questioned.

M 127. ELECTROPHYSIOLOGICAL STUDIES IN PATIENTS WITH CIRCUMSCRIBED SCLERODERMA. M.F.Monge-Strauss, A.Perrin, M.Falcy, F.Mikol and C.Grupper. (Paris, France). The authors have studied eleven patients with cirmumscribed scleroderma. Twenty five EMG recordings were performed and, in ten cases, sensory nerve conduction velocity was determined for the median nerve using conventional methods. Abnormalities were nearly always encoutered beneath the lesion and at a distance. Several changes were noted in the same patients: interference patterns with low amplitude during maximal voluntarycontraction, motor unit action potentials with short duration, increased incidence of polyphasic potentials, action potentials at high frequency (>25/sec) with mixed patterns. A significant reduction in value of mean conduction velocity was found (3/10). These findings are compared with results in the

619 literature. They suggest both myogenic and neuropathic processes, and corroborate the hypothesis of diffuse involvement in localized scleroderma.

M 128. SOME METHODOLOGICAL CONSIDERATIONS ON LONG-LOOP REFLEX TESTING IN MAN. H.M.Meinch, B.Piesiur and W.Tiedemann. (G~tti~en, W.Germany). (I) In order to test the susceptibility of reflexes to facilitation and inhibition, tricepssurae H reflexes, varying in amplitude, were conditioned by the following ipsilateral nerves: a) tibial nerve (CT-interval 5 ms, intensity 0.9 X reflex threshold), b) ulnar nerve (CT:8Oms, int.:supramaximal), c) tibial nerve (CT: 20 ms, int.: 1.2 X reflex threshold), d) peronea] nerve (CT: 150-200 ms, int.:1.1X motor threshold). Conditioning modes a) and b) caused a facilitation only if the test reflex was evoked with stimuli below 1.1 X reflex threshold. Conditioning modes c) and d) depressed the test reflex markedly only if the test reflex was maximal (1.1-I.4 X reflex threshold). It is concluded that the triceps-surae motoneuron pool is differently susceptible for inhibitory and facilitatory influences no matter whether mediated via segmental or suprasegmental loops. (2) A simple method is proposed for quantification of tonic EMG changes after a conditioning shock. The EMG recorded with surface electrodes is rectified and averaged, the difference between pre-stimulus (=contro]) activity level and zero-level (ground) being defined as 100%. This scale a l l o ~ o n e to express post-stimulus changes in % of control activity and to compare them quantitatively. The method reflects changes not only in the segmental motor apparatus (as H reflexes do) but also those in a major part of the motor system.

M 129. WITHDRAWAL REFLEX PATTERNS IN MUSCLES OF THE HUMAN LOWER LIMB. H.M. Meinck and B.Piesiur. (G~ttingen, W.Germany~ Tibial nerve stimulation at the ankle evoked changes of the tonic EMG activity in extensors and flexors. These changes were evaluated by averaging the raw and the rectified EMG. Generally, the effects were more pronounced in ipsithan in contralateral muscles, being often absent in the latter. Ipsilateral tibial nerve stimulation principally caused a repetitive inhibition-facilitation pattern, the effects being not strictly reciprocal in extensors and flexors but phase displaced. The early inhibition (latency: 20-50ms) was more pronounced proximally than distally (down to 10% of control values of activity, and in flexors it was weak. The early facilitation (latency:40-70 ms, up to 220% of control values) often had 2 peaks in flexors which corresponded in the averaged raw EMG to 2 separate components with different thresholds. A second inhibitory phase (latency:

620 70-~00ms,down to 20% of cont~l activity) was more pronounced in flexors and locked to a second facilitation (latency: 110~30) being weaker than the first one (up to 180% of control activity). Further successivelyweaker inhibitory and facilitatory phases often followed, giving the whole the figure of a damped oscillation. The contribution of different segmental (flexor reflex) and suprasegmental (SBS, transcortical) loops to the withdrawal pattern is discussed.

M 130. DESCENDING INTERLIMB REFLEXES IN MAN. H.M.Meinck and B.Piesiur. (G~ttingen,W.Germany). Descending interlimb reflexes were investigated byaveraging the rectified EMG. Stimulation of different nerves of the arms evoked a non-reciprocal inhibition-facilitation pattern(latencies:50-70 and 80-100 ms for inhibition and facilitation, respectively) in ipsi- and contralateral lumbar extensors and flexors (mm.quadriceps, gastrocnemius, soleus, posterior biceps, tibialis anterior, extensor digitorum brevis), often followed by ~eaker inhibitory and facilitatory phases. The early inhibition was more pronounced in flexors, the later effects were similar in flexors and extensors. Threshold of the effects was between I and 2x perception threshold, conduction velocity of the responsible arm nerve afferents was about 60 m/s. The effects could be evoked by digital nerve stimulation as well. They were stable with stimulus rates up to I/s. Temporal facilitation was marked but spatial occlusion occurred. The effects were evoked also by stimulation of trigeminal, neck, buttock and abdominal skin areas. Percutaneous dorsal root stimulation at C 5 and TI0 level could evoke these effects as well, the latencies being shorter with TI0 stimulation. Tricepsmurae and quadriceps H reflexes were facilitated bu~ not inhibited by arm nerve stimulation. It is suggested that the effects are mediated via a propriospinal pathway.

M 131. QUANTITATIVE ASPECTS OF JENDRASSIK'S MANOEUVRE. P.J.Delwaide and P.Toulouse.(Li~ge, Belgium). The m o n o ~ a p t i c reflexfacilitation brought about bilateral fist clenching has very rarely been studied quantitatively due no doubt to the lack of standardization of Jendrassik's manoeuvre. We have restricted the conditioning contraction to well defined muscular groups and recorded the following: speed, acceleration, duration and force. Provided that these variables are the same, the facilitation is quantitatively reproducible in amplitude and in time-course. We have studied 14 healthy volunteers and measured the facilitation of the tendon jerks of the quadriceps, the soleus and the biceps femoris at different intervals during voluntary contraction of 3 s duration. The effects on the electrically induced reflexes of the quadriceps and the soleus (EIR) were also investigated. The time-course of the facilitation involves 2 phases: after an ini-

INTERNATIONAL FEDERATION -- 9TH CONGRESS tial peak between 150 and 250 ms, the facilitation diminishes and then remains stable after about a 700 ms. The facilitation is a function of the force and the speed of the conditioning contraction. The first phase is influenced more than the plateau. The same conditioning manoeuvre facilitates the reflexes more in the proximal than in the distal muscles of the lower limb and the tendon jerks more than the EIR; meanwhile these latter are greater. Contraction of the hand muscles is more effective than the deltoid contraction when the force is the same; in the same way, wrist extensors are more active than the flexors. The results indicate differences according to the mode and site of the conditioning contraction implying some kind of specific control in Jendrassik's manoeuvre.

M 132. IATROGENIC FEMORAL NERVE LESIONS FOLLOWING HIP-JOINT REPLACEMENT. A.Fiaschi, D.De Grandis and G.Tarolli.(Verona, Italy). Among the EMG investigations carried in 5 years, 21 cases of iatrogenic femoral nerve lesions have been seen. The authors studied particularly the lesions caused by hip-joint replacement in 7 patients. EMG investigations motor conduction velocity of the femoral nerve, and sensory conduction velocity of the saphenous nerve were performed serially for one year. An anatomical study carried at autopsy has been done tc verify the possible site and type of lesion. This study shows that the femoral nerve lesion in hip-joint replacement can be caused either by direct trauma or by stripping of the muscle nerve junctions with different clinical and EMG aspects. All patients present an improvement more evident in vastus medialis, rectus femoralis and vastus intermedius. In some cases there is neurophysiological evidence that the recovery could be related to reinnervation of collateral brances. The authors discuss the possible physiopathological implications also on the basis of the neurophysiological findings.

M 133. RECOVERY OF SENSORY NERVE CONDUCTION AFTER 'I'SCHAEMIC"BLOCK BY PNEUMATIC COMPRESSION. PRELIMINARY OBSERVATIONS ON MEDIAN NERVE! IN NORMAL SUBJECTS. G.Caruso,L.Santoro,A.Perretti and B.Amantea. (Napoli, Italy). In normal young subjects the blood supply to the arm was arrested by rapidly inflating to a pressure of 320 mm Hg at 8 cm wide pneumatic cuff place around forearm, maintaining occlusion for periods of 15, 30 and 45 minutes. During blood occlusion and during 60 minutes after release of cuff pressure, sensory responses evoked by supramaximal stimuli to digit Ill were recorded distal (at wrist) and proximal (at elbo~ and axilla) to the cuff. The progressive reduction in maximum conduction velocity, observed during the period of forearm

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compression, between digit Ill and wrist and between wrist and elbow was not accompained by slowing in velocity along the segment elbow-axi]~. Moreover, at the axilla the decrease in amplitude of the sensory potential occurred significantly slower than at the elbow. Although individual variations occurred, a significant correlation between the duration of compression and the time for recovery of nerve function was observed. As to the time in reaching pre-compression values of potential amplitude and conduction velocity, a remarkable delay was, moreover, seen in the compressed nerve segment as compared to wrist and axiIla. These results confirm the general hypothesis that ischaemia produces a progressive slowing along all nerve fibres, but also emphasize the role of pressure applied to nerve in determining conduction block.

M 134. ELECTROMYOGRAPHY IN ATHETOSIS. D.Linke. (Bonn, W.Germany). The interrelation of reflex, voluntary and involuntary movements in the agonistic'~ntagonistic muscle systems in athetosis is of great interest for the understanding of its pathophysiology. We performed electromyographic analysis of the biceps-triceps system in eight athetotic patient. The silent period was elicited by muscular stimulation during rest and during voluntary and involuntary contraction of the muscle. In addition the influence of antagonistic stimulation upon involuntary agonistic activity was tested, and the ability to suppress involuntary movements v~s measured. The silent period was significantly shortened in comparison with normals. We saw a great variability of the silent period ranging from 30 to ~ms according to the state of involuntary contraction. No significant alteration of involuntary movements could be seen by agonistic and antagonistic stimulation whereas voluntary suppression of involuntary movements was possible at least to a certain degree. It is supposed, that athetotic movements are due to a motoneurone di~ : inhibition at spinal level, which can be influenced much more by central than by peripheral factors.

M 135. ELECTROMYOGRAPHY OF THE TONGUE. D.Linke. (Bonn, W. Germany). The human tongue is a complicated muscular system being able to perform highly organized motor activities such as speech. For electromyographic investigation of the tongue suction electrodes were employed which keep contact with the surface of the tongue during movements. The intrinsic muscles of the dorsum of the tongue could be demonstrated to be involved as antagonists in protrusive and retroflexive movements. Great variation of the innervation pattern could be found in normals. A silent period with a latency of 20 ms and lasting a b o ~

621 30 ms could be elicited by stimulating the hypoglossal nerve and the tongue itself. Voluntary reaction to tongue stimulation shows reaction times down to 40 ms. In pseudobulbar palsy volun ~ tary reaction time was elongated up to 300 ms. Side differences of innervation could be demonstrated in central hemiparesis. In Parkinsonian patients tremor could be detected when movements of the tongue had not yet been observed. Tremor of the tongue showed a higher frequency than tremor of the extremities. In cases of disturbance of peripheral sensibility diminished reactions to stretching and shortening the tongue could be found. Electromyography of the tongue is of high diagnostic and theoretic value and more use should be made of it.

M 136. SINGLE FIBER EMG IN SUSPECTED MYASTHENIA GRAVIS. J.R.Daube. (Rochester, Minnesota, USA). Single fiber electromyographic (SFEMG) measurements of jitter were made in 40 normal control subjects (20-70 years old) and 40 patients (8-10 years old) with suspected myasthenia gravis. Mean jitter was calculated as mean consecutive difference from range of ten values on 50 discharges from a minimum of 20 fiber pairs in the left extensor digitorum communis (EDC). Jitter blocking, fiber density and duration were all recorded with a 25 micra silver SFEMG electrode at a sweep speed of 200 s/cm and filter settin~ of 320 Hz (low) and 32 K Hz (hight). Jitter and blocking were also measured with a standard concentric needle electrode in 10 of the normal subjects and 10 patients with suspected disease at the same filter settings and sweep speed. The mean jitter in 23 normal subjects 20-60 ye~s old was 25.5*3.8 ps (range: 17-33~si. In this group there was no blocking, and only one fiber pair in one subject had MCD over 60 ~s (64 ~s). In normal subjects of 60-70 years the mean ji~er was 31.6±5.8 ~s (range: 25-43ps); 3 of 7 subjects had fiber pairs with jitter over 60 ps, and one of the 7 had one fiber pair with blocking. No significant differences in jitter were found when recording with a standard concentric electrode in the normal subjects. Eighteen of the 40 patients had ocular symptoms only, 7 had only bulbar symptoms and 15 had generalized symptoms. In none of them was there clinical weakness in the EDC, or an abnormality on repetitive stimulation of proximal or distal muscles before or after exercise. In 8 of 18 "ocular patients" a diagnosis of myasthenia gravis was made on clinical grounds (history, Tensilon test and response to medication); six of these had jitter outside the normal range. Two of the 7 "bulbar patients" had clinical myasthenia gravis, and both had abnormal jitter. Seven of 15 "generalized patients ~' had clinical myasthenia gravis, and all had abnormal jitter. One patient with a mean jitter just outside normal (34 ~s) had no blocking and no fiber pairs with jitter over 60 ps, and did not have myasthenia on clinical grounds. In no other case

622 did a patient have abnormal jitter without the clinical diagnosis of myasthenia gravis Measurements of jitter with the standard concentric electrode were not significantly different, and were facilitated by the greater ease of recording fiber pairs. Fiber density and duration were normal in all subjects.

M 137. VIBRATORY REFLEX RESPONSE IN SPINAL CORD INJURY PATIENTS AFTER CUTANEOUS DEAFFERENTATION. M.R.Dimitrijevic, P.C.Sharkey and A.M. Sherwood. (Houston, Texas, USA). While it is kncwn that vibration can induce a well defined tonic vibratory reflex in normal subjects and even in patients with cerebral spasticity, there is controversy over the existence of this reflex in spinal cord injury patients with complete paralysis.Earlier we have shown that a reflex response to vibration does exist in such patients with presumably complete division of the spinal cord. In these patients, the vibration responseconsisted of two components, ashort phasic component and a prolonged tonic component of lower amplitude. The presence of the vibratory reflex in such instances may be challenged since many of these patients have exaggerated withdrawl reflexes which can mask any other response to vibration. We have studied three spastic spinal cord injury patients, before and after neurectomies of the sensory branches of the femoral nerve, and have found that the vibration reflex response does not change, although cutaneous stimuli in the area over the quadriceps can no longer trigger spasms or other skin reflexes. We concluded that the cutaneous receptors do not contribute to the vibratory reflex in spinal cord injury patients with spastic paralysis.

M 138. PERIPHERAL

AND CENTRAL MECHANISMS OF CLONUS. M.R. Dimitrijevic and A.M. Sherwood. (Houston, Texas, USA). Control of the rhythmic 5 to 7 Hz oscillations of clonus h a s t e n attributed either to the mechanical characteristics of the stretch reflex loop, or to a central pacemaker. The necessity of an intact,hyperexcitable stretch reflex loop is commonly recognized. Our studies of clonus in chronic spinal cord injury patients have shown that while the relaxation-induced m ~ c l e spindle activation is an essential component of clonus, the r e g u l a t i o n ~ the response to repetitive afferent volleys and hence the regulation of the clonus frequency is dependent on the centralcy~lic refractory-excitatory periods. Furthermore, the existence of sustained clonus is a sign of preservation of descending brain influence in spinal cord injury patients clinically described as completely paralyzed. The results of experiments involving the application of repetitive tendon jerks at various frequencies, the delivery of tendon jerks, elec-

INTERNATIONAL FEDERATION - 9TH CONGRESS trical stimuli (H-reflexes) and vibration at various phases of the clonus cycle, and the modification of clonus responses with preserved suprasegmental control in completely paralyzed spinal cord injury patier.ts will be used to elucidate these points.

M 139. EVOKED ELECTRICAL RESPONSES OVER THE LUMBAR SPINE IN MAN. M.R.Dimitrijevic, L.E.Larsson, D.Lehmkuhl and A.M. Sherwood. (Houston, Texas, USA). The electrical responses following peripheral nerve stimulation have been studied in healthy adults of both sexes. The recordings were made from lower thoracic, lumbar, and higher sacral vertebral levels with a common mid-thoracic reference. Using these electrode positions, two types of responses were recorded. I) A predominantly negative wave with a duration of 7 to 10ms and an amplitude around 5 V is followed by a slow positive wave of low amplitude. This respo~e is recorded at the vertebral level T12 and above (with decreasing amplitude) and is the first to appear with increasing stimulus strength. 2) A double-peaked negative wave with approximately the same duration and amplitude, is recorded predominantly over the lower vertebral levels. The initial latency at the S I vertebral level is 8 to 9 ms with popliteal tibial nerve stimulation. The latency tends to increase at more rostral levels. Stimulation of several nerves simultaneously will generally increase the response. The results of studieson the interaction of responses to double stimuli and to stimuli delivered to different nerves will also be presented.

M 140. A VERY SHORT REACTION TIME IN MAN. H.J.Hufschmidt, N.Kilimov and D.Linke.(Bonn, W. Germany). By moving the elbow-joint as a stimulus for a voluntary reaction in Biceps brachii, we found reaction times between 40 and 70 f~. No marked time difference was registered in stretching or shortening the Biceps during the joint movement, ipsi-or contralateral. In the extensors of the arm we found reaction times between 70 and 100 ms. Therefore this short r-eaction in the flexors cannot be a delayed or supraspinal evoked stretch reflex.

M 141. MONONEUROPATHY AND FOCAL RADICULITIS WITH ELECTRICAL SIGNS OF DIFFUSED NEUROGENIC PROCESS. H.P.Cathala, L.Beaussart-Boulenge, L.Herrault and S. E.Snault. (Paris, France). In some patients suffering from mononeuritic or panciradicular syndrome, without other clinical neurological symptoms, electrical examination discloses a diffuse neurogenic impairment. In the paralysed extremity one finds slow responses to galvanic stimulation, signs of severe denervation on EMG records and reduced conduction ve-

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locities. In unaffected territories, only the EMG findings are abnormal; conduction velocities usually remain normal. Such cases can be divided into three groups: I. Cases in which the history reveals a high frequency of mononeuritic episodes in the patient's family. 2. Cases in which one can find factors that may have an effect upon the palsy, such as diabetes or alcohol intoxication. Cases in which the c]inical syndrome remains apparently isolated but sometimes with recurrence of the palsies in different territories. The prognosis of all those cases is not necessarily bad. Cases of the first and the third groups suggest the hypothesis of some infraclinical "nerve fragility", pr~ablycongenital , which is a reason for performing without delay possible surgical intervention which would relieve the nerve. Cases of the second group suggest a complementary hypothesis: the pathological effect of cumulated causes that, if they were isolated, would remain inoperant. This work is based upon 15 cases.

M 142. HIGH FREQUENCY DISCHARGES IN SENSORY NERVES RELATED TO ISCHEMIA. S.O.Kayaalp. (Buffalo, N.York, USA). During a previous investigation (Kayaalp, Kucera and Smith, 19729 on the effect of ischemia on muscle spindle afferent discharges evoked by stretch applied to the triceps surae muscle in cats we noticed occasionally high frequency discharges during ischemia induced by clamping the lumbar aorta. In the present work an attempt was made to gain further information on the nature of this phenomenon. The discharges appeared in bursts in the recordings from the dorsal root filaments but not from the ventral ones after the cessation of the ischemia. The number of spikes in each burst rang~d from 6 to 32, the time interval between them being 2-5 ms. This pattern of high frequency discharges lasted for 10-20 min. The burst discharges were not from the spindle afferents. In some experiments ~ e s c i a t i c nerve was cut at the level of trochanter with no change in burst discharges. The post-~chemic burst discharges were not observed in the sura] nerve. They were different from the type 3 injury potentials described by Adrian (1930). One of the possible sources for them is the fibers that arise from the walls of vessels and that adapted to the stretch caused by blood pressure when the circulation was intact. An extinction of the adaptation may activate them when the flow ceased. (In "Research in muscle deve]opment and the muscle spindle" byB.Q.Banker et al., edits, pp. 422-436, Excerpta Medica, Amsterdam, 1972).

M 143. ELECTROPHY~OLOGIC INVESTIGATIONS IN FRIEDREICH'S HEREDOATAXIA AND IN HEREDITARY MOTOR AND SENSORY NEUROPATHY.

623 M.Sauer and E. Schenck.

(Freiburg,

W.Germany).

Much is known about conduction in sensory fibres of the peripheral nerves in patients with Friedreich's heredoataxia (FHA) and hereditary motor and sentry neuropathy (HMSN). On the other hand there is only scanty information concerning afferent conduction within the spinal cord and brainstem in these diseases. A comparison of the latencies of the primary somatosensory cortical evoked potentials (ssEP) with sensory conduction velocities of peripheral nerves allows only indirect conclusions concerning central conduction. We therefore use the spinal evoked responses (spinEP) of the thoracic and cervical cord (CRACCO) to electrical stimulation of the median nerve at the wrist and of the tibial nerve at the ankle. By combining all methods peripheral and central conduction times may be separated. The latencies of the ssEP are greatly prolonged in all cases of FHA and HMSN type I, even where the shape and amplitude of the ssEP are normal. As shown by our studies, in the FHA patients this is due to an increase of the afferent conduction time within the spinal cord (and brainstems), in the presence of normal or only slightly diminished nerve conduction velocity. Sensory ccmpound action potentials of peripher~l nerves are much reduced as a result of extensive axonal degeneration of the largest sensory fibres. On the other hand, in HMSN type I the prolonged latency of the ssEP depends exclusively on the decreased conduction velocity of peripheral nerves, afferent conduction within the cord appearing normal. Accordingly, in HMSN type II the ssEP latencies are in the normal range. Remarkably, there seem to be different conduction patterns in the central and peripheral portion of the same neurones.

M 144. MEASUREMENT OF MOTOR UNIT POTENTIALS USING A POP 8 e COMPUTER. K.Mechelse and J.M.Schipper. (Rotterdam, The Netherlands). The mean duration of motor potentials and the mean number of zero-crossings and peaks are measu~i] using a computer. The motor unit potentials and an amplitude window, whose position can be changed by a potentiometer, are displayed by the computer. The first potential, the absolute amplitude projected within the window, is isolated. Zero-crossings and peaks of the isolated unit are determined and subsequently the unit is displayed. The position of the zero-crossings and peaks is indicated by vertical bars. The number of zero-crossings and peaks is also shown on the screen. This procedure is repeated until, according to the interpretation of the observer,an unit without superposition of other units has been isolated. The computer is then programmed to select motor unit potentials with the observed number of zero-crossings, peaks and absolute amplitude. Thirty potentials fulfilling these criteria are selected and averaged and

624 subsequently the duration of the averaged unit and its zero-crossings and peaks are determined. The average is displayed with vertical bars indicating the position of the peaks, zero-crossing~ beginning and end of the potential. The number of zero-crossings, peaks and duration is also shown on the screen. The procedure is repeated and a chosen number of different mu pptentials is measured. Subsequently the mean duration of the units and the mean number of its peaks and zero-crossings are calculated and a table with all figures printed out bythe computer.

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