Spanish society of clinical neurophysiology, XXXI annual meeting

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Electroencephalography and clinical Neurophysiology 94 (1995) 73P-81P

Society proceedings

Spanish Society of Clinical Neurophysiology, XXXI annual meeting Madrid, 16-17 December 1993

Secretary: Dr.

S.A. Hernandez

SENFS, C / Cantelejos 13, 28035 Madrid, Spain Received for publication: 22 August 1994

1. Functional presurgical assessment in partial epilepsy: stimulation procedures and sodium amytal test. - G. Alarcon and C.D. Binnie (EEG Department, The Maudsley Hospital, London, UK) Neurophysiological assessment of patients with partial epilepsy being evaluated for surgery ought to address two important issues: (a) localisation of functionally abnormal tissue involved in originating seizures; and (b) estimation of potential functional deficits which could result from surgical removal of brain tissue. Although localisation of abnormal tissue is usually emphasised, the final surgical procedure should be tailored according to findings on both grounds. A surgical procedure that achieves good seizure control at the expense of leaving significant neuropsychological deficits is unacceptable. In the present lecture we review two important neurophysiological techniques aimed to estimate potential functional deficits which could result from the removal of specific structures. Electrical stimulation through mat electrodes is useful to identify neocortical sensory or motor areas in patients with frontal or parietal epilepsy. Sequential stimulation at different pairs of neighbouring electrodes with progressively increasing intensities (1 rnsec pulses of 1-10 mA at 50 Hz during less than 6 sec) with simultaneous EEG recordings can be used to identify functionally relevant areas. Current intensity is progressively increased until one of the following takes place: (a) positive signs are observed (muscle twitches, tonic flexion of limb or facial muscles) or reported by the patient (tingling or burning sensations); (b) negative signs (speech arrest) are observed; (c) afterdischarges are observed on the EEG; or (d) a 10 mA intensity is reached. Positive or negative signs without afterdischarges indicate the location of relevant functional areas underneath the stimulated electrodes. Positive or negative signs in the presence of afterdischarges are of little value because signs may be due to the propagation of neuronal activity to cortex located relatively far from the stimulating electrodes. Multiple subpial transections would be the surgical procedure of choice in patients with a presumed epileptogenic zone in sensory, motor or speech areas located over the cerebral convexity. Sodium amytal test is useful to identify the dominant hemisphere, particularly for memory and speech, in patients where a temporal lobectomy is contemplated. A more restricted resection (for instance amygdalo-hippocampectomy) should be performed if the presumed epileptogenic zone lies in the dominant hemisphere for memory or speech. Sodium amytal test under general anaesthesia has also value in identifying the hemisphere involved in epileptogenesis in patients with secondary bilateral synchrony (only injection of the epileptogenic hemisphere is associated to complete abolition of generalised discharges). This is important in patients with Landau-Kleffner syndrome who can improve dramatically after multiple subpial transection of the speech areas.

2. Involvement of nervus thoracicus Iongus in progressive scapulohumeral muscular dystrophy. - J.M. Castilla, IL Jim6nez-Castellanos, S. Barrera and M. Del Mar Quesada (Neurofisiologla Cllnica, Hospital Universitario "Virgen Macarena," Madrid) Early stages of limb-girdle muscular dystrophies, particularly in the scapulo-humeral form, are characterised by winging of the scapulae which is due to weakness of the scapular girdle, affecting in particular the musculus serratus anterior which is innervated by the nervus thoracicus longus. Lesions of the nervus thoracicus longus are not rare. Its long trajectory from spinal roots C5, C6 and C8 to the musculus serratus anterior along the thoracic wall makes this nerve susceptible to lesions, mainly mechanical in origin. With regard to a case of girdle muscular dystrophy who presented with acute paralysis of the nervus thoracicus longus provoked by lifting a heavy load, we have studied the thoracicus longus neuromuscular system by recording the nerve conduction velocity and electromyogram of the musculus serratus anterior in 10 patients with rhizomelic muscular dystrophy. Eight patients showed a clearly neurogenic electromyographic pattern and slowed conduction velocity. In two cases these abnormalities were present at early stages of the disease. In view of the high incidence of nervus thoracicus longus involvement shown by electromyographic and electroneurographic recordings obtained in patients with rhizomelic muscular dystrophy, we consider that the pronounced winged scapula, often present since early stages, is secondary to lesions of the nervus thoracicus longus rather than to weakness of scapular musculature provoked by the disease. Early fixation of the scapula to the rib cage is recommended as a preventive measure.

3. Neurophysiological evaluation of axonai optic neuropathy. - T. Su~irez and F. Fern~indez-Gonz~ilez (Servicios de Neurofisiologia Cllnica, Hospital "Valle del Nal6n," Riafio-Langreo Hospital "Central de Asturias," Oviedo) It is known that demyelinative diseases affecting the second cranial nerve show a delayed P100 component in pattern visual evoked potentials (PVEPs) as the most significant neurophysiological change. In order to determine neurophysiological features present in axonal optic neuropathies we have reviewed recordings from 27 patients referred by ophthalmologists whose diagnosis was based on clinical criteria (aetiology, examination, evolution, ... ).

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Society Proceedings / Electroencephalography and clinical Neurophysiolo~,~, 94 (1995) 73P-81P

An electroretinogram (ERG), flash visual evoked potentials (FVEPs) and PVEPs were recorded. PVEPs were abnormal in all cases: PVEPs were absent in 74% and poorly defined in 26% of patients. FVEPs were normal in 48%, absent in 22%, showed amplitude asymmetries in 18% and latency asymmetries in 11% of the patients. The ERG was normal in 89% and showed amplitude asymmetries in the remaining 11% of patients. The use of FVEP in the differential diagnosis with maculopathies (6 cases) is discussed. In addition, we observed abnormalities similar to those found in severe disorders of refraction (10 cases).

4. Neurophysiological monitoring in endovascular treatment of intracranial aneurysms via electrical coils. - S. Ant6n a, M.D. Garcia n, L. Nombela b, j. Brasa b and A. Fernfindez-Zubiilaga b (a Servicio de Neurofisiologla and b Servicio de Neuroradiologla, Clinica Puerta de Hierro, Madrid)

We have studied 13 patients who had EEG monitoring during the implantation of electrical coils in intracranial aneurysms at the C1 Puerta de Hierro. Patients were sedated and heparinized. A microcatheter was introduced until the aneurysm was reached. Within the microcatheter, a coil comprising a wire guide of stainless steel and a platinum circular memory at the distal end was introduced inside the aneurysm. A positive electrical current was then applied to the proximal end of the guide to induce electrothrombosis at the platinum end (due to the negativity present in blood cells) and electrolysis at the steel-platinum interface which is followed by detachment of the platinum end and withdrawal of the guide. The procedure is presently indicated as an alternative to surgery when the latter is not feasible. An initial awake EEG was recorded, followed by continuous EEG monitoring and clinical examination during the procedure. Attention was paid to early detection of potential complications: vascular spasm, haemorrhage, coil migration and embolism. Early results from treatment were occasionally observed. Thirteen patients were studied (9 women and 4 men), ages between 18 and 88 (average 49). Clinical presentation consisted of headaches in 10 patients, exophthalmos in 1 patient, amaurosis in 1 patient and 1 patient was asymptomatic. Aneurysms were most frequently present in the carotid artery (8 patients), but were also present in the vertebro-basilar territory (4 patients). One patient presented a carotid cavernous fistula. The size of the aneurysms was between 0.6 and 3 cm. The CT showed signs of haemorrhage in 6 patients, infarct in 3 and a space occupying lesion in 1 patient. The number of coils introduced during each session was between 1 and 10, most frequently 2-3. The time taken to release each coil was between 8 sec and 39 min (average 11.7 min). Two patients presented transitory complications (headache, ocular pain) during the procedure, with no EEG manifestations and no sequels. One patient subsequently presented inguinal haematoma. The procedure had to be abandoned in 3 patients due to the presence of EEG abnormalities with clinical manifestations and it was later performed. We consider that EEG monitoring during coil implantation in intracranial aneurysms is useful as an objective method to assess the ongoing brain activity and helps the neuroradiologist decide whether to continue or halt the procedure.

5. Neurophysioiogical study of the cerebellum: application to one case of alcoholic cerebellar atrophy with slow tremor in legs. - J. Monells, H.M. Espadaler, A. Vails, J.L. Seoane, V. Ambros and D. Solsona, (Servicio de Neurofisiologla Cllnica "Hospital del Mar," Barcelona) (1) Review of neurophysiological methods previously described in the literature to study cerebellar function. (2) Application of these methods to

one case of alcoholic cerebellar atrophy with slow tremor in lower limbs and interpretation of the results. The following methods were used. (1) EMG recordings of ballism (M. Hallett et al., 1993). (2) Premotor potential (H Shibasaki et al., 1978). (3) EMG recordings of tremor (B.P. Silfverski61d, 1977). (4) Recordings of long latency reflexes (LLR) (G. Deuschl, 1990). (5) Acquisition of conditioned reflexes (H. Yopka, J. Vails-Sol6 et al., 1993). A 67-year-old chronic alcoholic man who presented with unstable gait and rhythmic slow movements in legs which prevented him from walking. CT and MRI showed marked cerebellar atrophy. Results were: (1) EMG recordings of ballista: increased duration of the first discharge in the agonist muscle. (2) Premotor potential: normal onset latency. Amplitude in the lower range of normal limits. (3) EMG recordings of tremor: 3 Hz, alternating agonist-antagonist, triggered by action, intention, standing, walking, eye closure and passive muscular stretch. (4) LLR: LLR of high amplitude in lower limbs, provoked by electrical stimuli. (5) Acquisition of conditioned reflexes: deficient conditioning. Conclusion. (1) The methods previously described allow the study of cerebellar function at the different stages of motor control where it is involved: programming (ballista, premotor potential), correcting (recordings of tremor, LLR) and motor learning (conditioned reflex). (2) The abnormalities described in this patient support the use of these tests in the evaluation of cerebellar function and suggest a pathophysiological hypothesis in the generation of this type of tremor.

6. Electromyographic study of musculus iatissimus dorsi activity during respiration. - J. Monells, J.M. Espadaler, M. Orozco-Levi, J. Gea, A. Vails, J.L. Seoane and J.M. Broquetas (Servicio de Neurofisiologia Clinica y Pneumologla, "Hospital del Mar," Instituto Municipal de Investigaci6n M~dica, Universidad Aut6noma de Barcelona, Barcelona)

The musculus latissimus dorsi (MLD) is used as a control for structural studies of respiratory muscles since it is assumed that it is not involved in respiratory movements. However, structural changes (hypertrophy) have recently been described in MLD biopsies from patients with chronic obstructive lung disease (COLD). The objective of the present study is to show MLD electromyographic activity during inspiration after the application of progressive inspiratory loads. Eight healthy subjects were studied (average age 31 +_ 2 years, FEVI 98_+ 4%, PIM 110_+ 6%). Electromyographic activity from the nondominant MLD was recorded with surface electrodes. The signal was rectified, integrated and ECG activity was subtracted. Similar simultaneous recordings from the ipsilateral biceps were used as a control. The activity of both muscles was recorded during maximal voluntary contraction (MVC) and during the application of progressive inspiratory loads (20, 40, 60, 80 and 100%). Basal MLD activity was 1.9 _+ 0.5 compared to activity during MVC. During the application of inspiratory loads there were linear increments in activity which were significant for loads of 40% ( P < 0.01), 60% ( P < 0.01), 80% ( P < 0.001) and 100% ( P < 0.001). In the latter case MLD activity reached 31.5% compared to MVC. No significant changes were seen in the control muscle. In healthy subjects MLD is progressively recruited during the application of inspiratory loads. This could explain the presence of MLD hypertrophy in patients with COLD and would cast a doubt about the use of MLD as a control in the study of structural changes of respiratory muscles in these patients.

(Sponsored by FIS 92/0314, CIRIT AR 91-367 and IMIM 1642380.)

Socie~ Proceedings / Electroencephalography and clinical Neurophysiology 94 (1995) 73P-81P 7. Photosensitive reflex epilepsies: a study of 4 cases. - V. Izura and C. Pastore (Hospital Universitario "San Juan de Alicante," Alicante)

Approximately 5 - 6 % of patients with epilepsy refer triggering of some seizures by some form of sensory stimuli. However, the frequency of pure reflex epilepsies (REs) is estimated in about 1%. REs are defined as those in which seizures are provoked by a specific sensory stimulus and are classified in two types: (1) RE with seizures triggered only by the corresponding stimulus; (2) RE with spontaneous seizures and seizures provoked by specific stimuli. REs are also classified according to the sensory modality involved: (1) seizures induced by visual stimuli (photosensitive epilepsies); (2) seizures induced by somatosensory stimuli; (3) seizures induced by complex stimuli; (4) seizures induced by acoustic or vestibular stimuli; (5) self-induced seizures. Photosensitive epilepsies can in turn be classified according to different clinical or electroencephalographic parameters. We present 4 cases of photosensitive epilepsies as a sample of the variety of alternatives which can be found.

8. Efficiency of neurophysiologicai examinations in differential diagnosis of tremors: three cases of 3 Hz tremors of different aetiology. - A. Vails, J.M. Espadaler, J. Monells, J.L. Seoane, J. Pascual and C. Oliveras (Servicio de Neurofisiologla y Neurologia, "Hospital del Mar," Barcelona)

The study of tremor in 3 patients with similar semiological features by different electrophysiotogical techniques allows a differential diagnosis and the distinction of different lesional topographies. This requires the establishment of investigational protocols in tremor disorders. Case 1: a 43-year-old patient suddenly presented continuous rhythmic movements in left hemiface and left upper limb with confusional mental state. He was treated as partial status epilepticus with no significant improvement and a neurophysiological study was requested. EEG: mild signs of diffuse encephalic involvement. No epileptiform activity was observed. Brain-stem auditory evoked potentials (BAEPs): absence of wave V to right ear stimulation. EMG: recordings from flexor and extensor muscles in the forearm showed continuous (not ceasing at rest) rhythmic discharges and alternating agonist-antagonist activity at 3 Hz. Neurophysiological diagnosis: (1) BAEP compatible with a mesencephalic lesion; (2) EMG compatible with red nucleus type tremor. CT: mesencephalic haematoma. Case 2: a 67-year-old alcoholic patient had suffered from progressive instability on walking and rhythmic movements of both legs for several months. It was considered as alcoholic polineuropathy and syndrome of restless legs. An EMG study was requested. EMG: mild chronic sensorimotor axonal polyneuropathy. EMG recordings from both lower limbs showed rhythmic alternating agonistantagonist discharges at 3 Hz during intention and action which ceased at rest. Neurophysiological diagnosis: (1) mild chronic neuropathy of toxic deficiency origin; (2) slow leg tremor (3 Hz) with cerebellar characteristics. MRI: marked cerebellar atrophy. Case 3: a 32-year-old patient, ex-parentheral drug abuser, H I V + was admitted with subacute instability on walking and rhythmic involuntary movements of left hand. An electrophysiological study was requested: BAEP: bilaterally increased duration of the interval I-IlL EMG: rhythmic discharges at 3 Hz in the left musculus abductor pollicis during intention and action, which ceased at rest. Neurophysiological diagnosis: (1) BAEP compatible with a pontine lesion; (2) tremor with cerebellar characteristics.

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MRI: lesion in the left cerebellar hemisphere which compressed the brain-stem and was compatible with toxoplasmosis. In all 3 cases neurophysiological studies allowed a diagnostic orientation about the lesion topography and aetiology which shows the usefulness of neurophysiological studies in this type of patients in order to identify abnormalities in the different structures of the central nervous system as potential causes of tremor.

9. Normal patterns in trigeminal somatosensory evoked responses to gingival stimulation of the nervus mentalis. - J.A. Villanueva, C. Montes and M~I. Vi~uales (Grnpo de Investigaci6n de Neuroanatomia Funcional, Departamento de Ciencias Morfol6gicas, Facultad de Medicina, Universidad de Sevilla, Seville) Trigeminal somatosensory evoked potentials from 30 healthy volunteers (12 men and 18 women), aged between 17 and 20, were studied. The nervus mentalis was stimulated at its foramen in the mandibula by a surface electrode over the gum and electrical responses were recorded over the contralateral primary somatosensory area. A " W " complex was recorded with an average duration of 31.6 msec and 4 amplitude deflections Nll.24, P18.64, N21.89 and P33.75. The design of the stimulator allows its automatic placement over the desired area and therefore the use of low stimulation intensities which minimises muscular and conduction artifacts. We think that the technique described above could be relevant as a complementary test to traditional PES in the everyday clinical work.

10. Diagnosis of the carpal tunnel syndrome in borderline cases: evaluation of asymmetries in median nerve conduction parameters. - A. S~ez de Cabez6n Alvarez and F. Romero Puertas (Servicio de Neuroflsiologia Cllnica, Hospital "Miguel Servet," Zaragoza) One way to approach the diagnosis of unilateral carpal tunnel syndrome is based on evaluating latency asymmetries obtained from bilateral examinations. We present 18 cases where wrist latencies in the affected side were within normal limits but sufficiently delayed when compared with the healthy side. In addition, this abnormality was accompanied by other asymmetries in the sensory branch, such as a relative reduction in the segmental conduction velocity (100% of patients) and reductions higher than 40% (77.7 in this series) in the amplitude of the potential. This summation of abnormalities confers this method sufficient reliability and makes it suitable to be used in mild focal neuropathies.

11. Modifications in the periodic EEG pattern in herpetic encephalitis treated with acyclovir. A study of nine cases. - A. Benet6, E. G6mez Siurana, P. Rubio, A. Esparza, R. Sobrino and P. Smeyers (Servicio de Neuroflsiologla Cllnica, Hospital Universitario "La Fe," Valencia) The presence of localised periodic activity in encephalitis by simplex herpes virus is a characteristic feature and has been intensively documented in the literature. However, its clinical significance is still under controversy. In addition, the use of new antiviral drugs in the last few years has dramatically changed the grim survival prognosis and poor sequels secondary to this disorder. We present an EEG study in 9 patients diagnosed of herpetic encephalitis and treated with acyclovir. Special attention has been paid to the presence or absence of periodic activity and its characteristics. We have observed that periodic activity is either absent or shows mild differences with respect to the classical pattern. It appears as an objective clinical sign which is tightly linked to the patient's clinical response to treatment.

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12. Chronic lathyrism. Electrophysiological findings. - M.I. AndrOs, A.L. Serrano, J.J. Ortega and M. Gil (Servicio de Neurofisiologia Clinica, "Hospital General," Castell6n) Lathyrism is a neurotoxic disorder caused by prolonged ingestion of certain types of vegetables which contain fl-N-oxalyl-L-a,fl-diamino-propionic acid and is characterised by spastic motor paraplegia. Patients show signs of lower motoneurone disease. We present electrophysiological findings observed in EMG, ENG, H reflex, F wave and somatosensory evoked potentials recorded from patients with neurolathyrism after ingestion of chick peas (Lathyrus

sativus). 13. Hepatic transplant in Corino Andrade's disease: results from successive electromyographic controls. - P. De Mingo Casado, M.L. Ruiz-Cabello Osuna and F. Biec Alem~in (Servicio de Neurafisiologia Cllnica, Hospital Universitario "Virgen de Arrixaca," Murcia) Hepatic transplant (HT) has been recently suggested as an effective treatment for familiar amyloid polyneuropathy (Corino Andrade's disease). There is not a large experience referred in the literature about the evolution of these patients after HT due to the small number of patients treated and to the short time which has elapsed since the first transplants. We present results on electromyographic examinations performed previously to HT and 3, 6, 12 and 24 months after HT on 9 patients. Identical neurophysiological parameters were compared on successive investigations. The complete series of examinations was not recorded in all patients due to some shorter periods of evolution after HT. Patients belonged to two different familiar traits. Mild improvements of several parameters were found during successive examinations and no significant deterioration in the degree of involvement of the peripheral nerve was found in any patient. This confirms the hypothesis that HT substantially changes the dramatic evolution of familiar amyloid polyneuropathy type I.

14. EEG study in patients treated with clozapine. - M.A. Garcia Jim(~nez, J.L. Santos, M.C. S~nchez Gonz~lez and J.C. Guill~n Izquierdo (Servicio de Neurofisiologia Clinica y Psiquiatrla, Hospital "Virgen de ia Luz," Cuenca) Clozapine is an antipsychotic drag used in the treatment of patients with refractory schizophrenia after failure of conventional treatment due to lack of therapeutic response or the onset of pyramidal symptoms. Electroencephalographic abnormalities have been described during treatment in a high percentage of patients. We have studied 40 patients diagnosed with schizophrenia, 27 men and 13 women, with an average age of 31.45 years (20-63), who had an electroencephalographic study mostly between 6 and 24 months after onset of treatment with clozapine. Twenty-one patients had a previous basal study and 19 patients only had EEG studies during treatment. The average age of onset of psychiatric symptoms was 20.5 and the average time of evolution was 10.6 years. None of the patients had personal or family history of epilepsy. A very wide range of clozapine doses was used. Treatment effectiveness was evaluated clinically with a psychopathological scale (BPRs). The clinical situation, present mental state, therapeutic and side effects were quantified with a scale or index. During treatment the EEG was normal in 35% of the patients and abnormal in the rest. The most frequent abnormalities observed were bursts of generalised theta and delta waves (42.5%), focal activity (10%) and slow background activity (5%). Paroxysmal epileptiform activity was not observed in any patient. Among the patients who had records before and during treatment, the EEG continued to be normal in 9 patients (22.5%). EEG abnormalities were correlated with the clinical evolution of patients, dose, therapeutics and side effects of clozapine. Our results are discussed in the context of previous findings referred by other authors.

15. Infantile epilepsy and disorders of neuronal migration. Electroclinical study of 62 patients. - A. P6rez Jim6nez a, E. Fontana, V. Colamaria, F. Piardi, E. Santorim, A. Franco and B. Dalla Bernardina (Catedra de Neuropsiquiatrla Infantil, Universidad de Verona, Verona, Italy, and a Servicio de Neuroflsiologia Clinica, Hospital "La Paz," Madrid)

Disorders of neuronal migration (DNM) constitute an important aetiological factor in epilepsies of infantile onset. Despite our present neuroradiological techniques, diagnostic and prognostic evaluations remain difficult in a high proportion of these patients. We have performed a longitudinal study of electro-clinical features in 62 patients (ages 5 months to 19 years) with DNM diagnosed by CT and/or NMR and epileptic seizures with onset between 1 day and 3 years, and 9 months (average 9 months). According to topographical criteria, 28 patients showed a diffuse abnormality (e.g., lissencephalia), 15 showed focal bilateral abnormalities and 19 patients had focal unilateral abnormalities (e.g., pachygyria). Epilepsy started during the first year of life in 69% of patients, being more precocious the more extensive the DNM (in 85.7% of diffuse DNM). Seizures had a neonatal onset in 30% of patients. Once age was accounted for, EEG follow-up identified abnormal activities, anachronic for amplitude (in 30%) or frequency (diffuse fast rhythms in 32.2%). An EEG pattern of early diagnostic value, characteristic of diffuse DNM and already present during neonatal life in 68% of patients, is formed by association of high voltage (130-3000 /zV) slow components and bursts of high frequency (alpha-like) activity which take place in an alternating and asynchronous fashion. This EEG pattern often evolves to a different pattern better known to the literature (non-reactive high amplitude diffuse fast rhythms). Among the different electro-clinical entities it is possible to recognise well defined entities such as partial seizures associated with pseudoperiodic spasms (45%), electrical status epilepticus during slow sleep (ESES, 14.5%) or continuous partial epilepsy (8%), all of them showing a high diagnostic and prognostic value.

16. Neurometric studies with quantitative EEG. - D. Mendonca, S. Abreu, M. Oliveira e Silva, J.P. Cunha, J. Lopes, J. Ramalheira and A. Martins da Silva (Instituto de Ciencias Biom~dicas Abel Salazar, Universidad de Porto, Servicio de Neurofisiologia, Hospital de Santo Antonio, Porto, and INESC, Universidad de Aveiro, Aveiro, Portugal)

The analysis of the functional state of the brain could be better approached by quantitative EEG studies based on neurometric methods (Jhon et al., 1987). Banks of normal data have been obtained and validated in large population samples. Factors such as sex, age, literacy, handedness, etc. have been accounted for when this methodology is used. It has been suggested that parameters obtained with such data banks can be applied to the population in a general manner, independent of cultural, ethnical, socioeconomic factors, etc. In order to study the applicability of such values to our population we have developed a computerised system which includes data acquisition, segmentation, data processing (similar to the one described by Jhon et al., 1987) and statistical analysis. Data from 40 healthy subjects (15 children between 7 and 16 years old and 25 adults between 20 and 26) were recorded with a conventional bipolar montage and compared with values reported by previous authors. A monopolar common average EEG was also obtained from the same subjects in order to perform a similar analysis. The objectives of this research are: (1) to define a bank of normal EEG data for the population we attend daily: children, adolescents and young adults, (2) to use these data as a reference for the analysis of EEG background activity in specific disorders such as epilepsy or metabolic abnormalities.

Society Proceedings/Electroencephalography 17. Review of activities accomplished by the sleep unit at the Hospital Comarcal de Xativa: technical and methodological aspects. B. Hoyo Rodrigo a, E. Lopez Gomariz a, j. Minguez Villena b, T. P~rez Garrigues c and I. Rodriguez Nieto a (a Servicio de Neurofisiologia Clinica, b Servicio de Neumologla, c Servicio de Otorrinolaringologia, Hospital Lluis AIcanyis, Xativa) Xativa's NHS services cover a population of 189.000 inhabitants distributed over 53 villages, towns and cities. The "sleep unit" is set up within a multidisciplinary approach with the contribution of different specialties: clinical neurophysiology, pneumology, otorhinolaryngology and others (neurology or psychiatry). We have created a decision protocol to filter and choose the most appropriate sleep study for a particular patient: polysomnography of nocturnal sleep (PNS) or multiple latency tests (MLT). Each patient with a suspected sleep disorder is asked to fill in a questionnaire with questions about h i s / h e r sleep characteristics and about symptoms suggesting a sleep disorder, paying special attention to sleep apnoea syndrome (SAS). Several criteria have been established: greater criteria: essential arterial hypertension, polyglobulia, presence of respiratory pauses during sleep; lesser criteria: moderate SED (falling asleep during periods of inactivity), snoring, excessive sudation during sleep, wide neck. Patients who fulfilled criteria for high suspicion of SAS showed 1 out of the 3 following conditions: (a) severe SED (falling asleep during activity) plus one greater or lesser criterion; (b) 2 greater criteria; (c) 1 greater criterion plus two lesser criteria. Such patients are referred to the Department of Pneumology in this hospital to perform a number of examinations: biochemistry, haemoglobin levels, thyroid hormone levels, arterial gasometry, otorhinolaryngological examination, cephalometry, thoracic radiography and electrocardiogram. In addition a polysomnography is requested. Patients who do not fulfill the criteria but show some isolated suggestive symptom would have periodic controls. Patients who suffer from a sleep disorder not suggesting SAS are referred to the Department of Clinical Neurophysiology where the presence of SED is evaluated by MLT if they show SED or if narcolepsy is suspected. (A) Polysomnography of nocturnal sleep. Technical methods used to fulfill the ASDA criteria. We found it worthwhile to connect an oxymetry meter to a polysomnography channel in order to correlate each apnoea/hypoapnoea with oxygen saturation and to dispose of a record of the sympathetic-cutaneous response as an indirect index of the central nervous system response. In order to shorten time when an OSAS is diagnosed, the patient is directly appointed for a PNS in order to adjust the continuous positive air pressure. A report on results from each PNS together with a hypnogram are remitted to the specialist who requested the test. (B) Sleep multiple latency tests. Four 20 min naps are attempted if the patient does not fall asleep and 30 min naps are recorded if the patient does fall asleep (with 2 h awake intervals in between), starting at 9 a.m. Sleep latencies for each nap, the mean sleep latency for all 4 naps and REM latencies are then calculated. At least 2 naps with a sleep latency shorter than 5 min and at least 2 naps with REM latency shorter than 15 min are required for the diagnosis of narcolepsy. A 4 nap mean sleep latency shorter than 5 min is required for the diagnosis of hypersomnia.

18. Review of activities carried out in the sleep unit of the Hospital Comarcal de Xativa. Analysis of results. - E. Lopez Gomariz ~, B. Hoyo Rodrigo a, T. P~rez Garrigues b, j. Minguez Villena c and I. Rodriguez Nieto a (a Servicio de Neurofisiologla, b Servicio de Otorrinolaringologia, c Servicio de Neumoiogla, Hospital de SVS Lluis Alcanyis, Xativa) Since the sleep unit was set up, 129 polysomnographies have been recorded, 7 diurnal and 122 nocturnal.

and clinical Neurophysiology 94 (1995) 73P-81P

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At present there are no urgent or preferential patients on the waiting list and the waiting period for ordinary patients is 6 months. Polysomnographies to adjust continuous positive air pressures are recorded after UPFP, significant weight loss or low tolerance to high pressures. Eight polysomnographies were repeated either because no diagnoses were achieved or because a reliable adjustment of the continuous positive air pressure (CPAP) was not obtained. Only in patients with very severe obstructive sleep apnoea syndrome (OSAS) who easily fell asleep was it possible to obtain a diagnosis and an appropriate CPAP adjustment during the same night. Sex analysis of patients yielded that 81.4% were males, the average age was 54 years (range 29-76) and the average body mass index was 30 (range 22-42). A diagnosis of OSAS was obtained in 53%, central apnoeas in 6%, myoclonus in 12%, and no specific diagnoses were obtained in 15%, in which polysomnography was repeated or a multiple sleep latency test (MSLT) was carried out if narcolepsy was suspected. Eleven per cent were normal. We think that the selection procedure established by the Departments of Pneumology and Otorhinolaryngology is efficient. We have tried to correlate different biological parameters. The most significant correlation was between the index of apnoea/hypoapnoea and the final value of CPAP (correlation coefficient (r) = 0.53) and between the duration of apnoea/hypoapnoea and minimal oxygen saturation reached (r = 0.608). The mean REM latency was shortest in CPAP adjustments, followed by OSAS and by normal patients. Sixteen MSLTs were performed, also with a higher proportion of males (68.75%). The average age was 56 years (range 34-75). Narcolepsy was confirmed in 50% of patients, 43.75% went on to a polysomnographic study, after the presence of excessive diurnal somnolence with no REM disturbances was established, and 6.25% were normal. We feel that the Sociedad Espafiola de Neurofisiologia should promote the development of multidisciplinary sleep units in local hospitals because the existing demand, which is not presently met, justifies their creation in centres which cover populations between 100,000 and 200,000 inhabitants.

19. Post-poliomyelitic syndrome: electrophysiological study of 28 cases. - P. Rubio a, MJ. Chumiilas a, I. Vfizquez b, A. Esparza a and P. Smeyer a (a Servicio de Neurofisiologia Clinica, Secci6n de Electromiografia, Hospital "La Fe," Valencia, and b Servicio de Rehabilitaci6n, Hospital "Marina Baixa," Alicante)

The onset of a late deterioration several decades after suffering poliomyelitis is a presently recognised syndrome whose nature is still unknown. The existence of dynamical changes in motor units as a result of denervation-reinnervation processes with superimposed signs of recent denervation is an electromyographical finding which has been discussed by several authors. There is controversy in comparing results from patients with and without new symptomatology. The most widespread opinion seems to be the existence of significant differences between both groups. We have studied 28 patients between 27.5 and 55 years old who had previously suffered from acute poliomyelitis. 67.9% presented clinical symptomatology of post-poliomyelitic syndrome, according to Bradley's criteria, and 32.1% did not. A clinical evaluation, conventional EMG, quantitative EMG and single fibre studies were performed. Results from comparing both groups are shown.

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20. lctal and interictal electro-clinical analysis in one case of Aicardi syndrome. - R. Grimau Merino, L. Giardina, E. Avesani, E. Zullini, A. Montagnini, F. Darra and B. Dalla Bernardina (Catedra de Neuropsiquiatria Infantil, Universidad de Verona, Verona, Italy) Aicardi syndrome is a congenital polymalformative disease with central nervous system dysplasias (agenesia of corpus callosum, heterotopias and disorders of neuronal migration), ocular system and skeletal muscle. Clinical characteristics include severe psychomotor delay and refractory epileptic encephalopathy with series of atypical spasms of early onset and partial seizures. EEG features have been previously described. Initially they include multifocal epileptiform abnormalities organised in an alternating fashion and complete interhemispheric asynchrony. EEG signs tend to evolve to hypsarrhythmia showing multiple epileptic foci within the first year of life. We present the awake and sleep electro-clinical profile of an 8-year-old patient. In addition to the EEG pattern described above, some polygraphic EEG features appeared important: (1) presence of clusters of repetitive subclinical focal seizures where both hemispheres are alternatively and asynchronously involved; (2) asynchronous, asymmetrical bilateral or focal unilateral clinical and EEG manifestations during a cluster of pseudoperiodic spasms; (3) onset of electro-clinical partial ictal episodes which precede and overlap with the cluster of spasms. The EEG characteristics of this case encourage the analysis and review of the possible pathophysiological mechanisms of infantile spasms.

21. Evoked potentials in a reanimation unit: study of 50 patients. R. Sobrino a, A. Esparza a, p. Rubio a, M. Vallet a, C. Vilela a and L. Crespo b (a Servicio de Neurofisiologla Clinica, b Servicio de Reanimacirn, Hospital Universitario "La Fe," Valencia) Somatosensory and auditory brain-stem evoked potentials have been recorded in 50 patients in deep coma (a requirement at the Unidad de Reanimaci6n) who were suffering from the following disturbances: head injury in 38 patients, vascular disorders in 6 patients, ischaemic-anoxic encephalopathy in 4 patients, tumours in 2 patients. The number of parameters under study has been limited to 3 for brain-stem evoked responses and 4 for sensorimotor evoked potentials. Results were analysed and correlated with clinical evolution of patients. These results are compared with those obtained by other authors.

22. Multimodal electrophysiological study of a family with probable borderline hereditary sensorimotor neuropathy. - A. Garcla, C. De Pablos, J. Berciano and J. Calleja (Hospital Universitario "Marqu(~s de Valdecilla," Santander) Sensorimotor hereditary neuropathies (SMHN) are classified in types I and II according to clinical, genetic, histological and electrophysiological criteria. The neural conduction velocity (CV) is severely reduced in type I whereas it is normal or slightly reduced in type II. Bradley et al. (1976) reported that there are families with homogeneous motor median nerve CV between 25 and 45 m / s e c that were classified as borderline SMHN which appear to show greater severity than type I. In addition, Dyck and Lambert's classification (1975, 1984) defines other types which correspond to Dejerine-Sottas disease (type III), Refsum's disease (type IV) and SMHN associated with hereditary spastic paraplegia (type V), optic atrophy (type VI) or retinitis pigmentosa (type VII). Furthermore authors occasionally refer to families which are not classifiable within any of the above mentioned groups. We present a neurophysiological study carried out on a family comprised of a 37-year-old mother and her 3 children, aged 17, 15 and 14. They all showed clinical characteristics of the autosomal dominant form of SMHN with no observed neural thickening. No ataxia, cerebellar or Babinski signs were present. Neural conduction studies did not classify

this family into any of the main SMHN types. In addition, multimodal evoked potentials (EPs) showed severe abnormalities in somatosensory evoked responses, brain-stem evoked potentials and motor responses to magnetic stimulation whereas visual evoked potentials were normal. Studies of multimodal PE and of the cortico-spinal pathway in this family showed the involvement of multiple neural systems. Even though motor CV of the median nerve would correspond to the borderline form described by Bradley, it is possible that the torpid clinical evolution of this form could be due to the multisystemic involvement. We therefore consider these tests as highly useful in the nosological classification of "atypical forms" of SMHN.

23. Treatment with botulinic toxin does not modify the recovery cycle of blink reflex in patients with blepharospasm. - J. Prieto, A. Traba, F. Grandas and A. Esteban (Secci6n de Neurofisiologla Clinica, Servicio de Neurologia, Hospital Universitario "Gregorio Marafirn," Madrid) An increase in excitability in brain-stem interneurones involved in blink reflex has been described in blepharospasm. In order to investigate in botulinic toxin (BOTOX) which is used to treat blepharospasm has an action on the central nervous system, we have studied the recovery time course of the R2 component of the blink reflex (RCBR) in 12 patients with blepharospasm present before and 3 weeks after a BOTOX injection. To avoid difficulties in recording the EMG of denervated muscles, BOTOX (20 units) was only applied to one muscle orbicularis oculi in one side. The RCBR was studied by applying pairs of electrical stimuli to the nervus supraorbitalis consecutively on both sides with interstimulus intervals between 100 and 1500 msec. If BOTOX alters the excitability of brain-stem neurones we would expect changes in the RCBR from the untreated muscle orbicularis oculi because R2 responses are bilateral and mediated by the same bulbo-pontine interneurones. However, no significant differences were found between RCBR recorded before and after BOTOX in the untreated muscle orbilularis oculi either after ipsi- or contralateral stimulation (ANOVA, P > 0.1). The present results suggest that treatment with BOTOX does not change the underlying pathophysiological abnormalities in blepharospasm.

24. Somatosensory evoked potentials from dermatomes. Methods of study and normal values. - J. Prieto, A. Traba and A. Esteban (Hospital General Universitario "Gregorio Marafi6n," Madrid) With the common present methodology it is difficult to achieve an adequate accuracy in the topographical identification of medullary lesions, especially for those located in thoracic segments. Somatosensory evoked responses to upper or lower limb stimulation yield a global evaluation of medullar conduction along the dorsal columns, also including peripheral and encephalic structures, that determine the recorded response. Despite multiple attempts (somatosensory evoked potentials with percutaneous rachidial recordings or somatosensory evoked responses to stimulation of supposedly monoradicular segmental nerves), no conclusive results can be achieved at present. Dermatome somatosensory evoked potentials (DSEPs) can be an alternative to habitual techniques due to their higher localising value. Before clinical use, an analysis of normal subjects is required in order to establish a reasonable methodology and criteria of reliability. Methodology employed and normal values are presented here. DSEPs were recorded from a control group comprising 30 normal subjects. In 15 of them, bilateral percutaneous stimuli were applied to well established dermatomes corresponding to C4, T2, T8 and L2. Recordings were carried out through scalp subcutaneous electrodes at C'3, C'I, C'z, C'2 and C'4 referred to Fz. A cortical response was always obtained in all subjects. The latency of the first positive peak (P1) and the peak-to-peak amplitude P1-N2 were evaluated. Latency increased directly related to the distance from the stimulated dermatome. No relation to subject size or sex was found.

Society Proceedings/Electroencephalography In the remaining 15 subjects responses to unilateral stimuli were analysed. As in the previous group a cortical response was evoked by the stimulation of all studied dermatomes (C4, T6, T8, T10 and L2) in all subjects. No significant latency or amplitude asymmetries were found related to the stimulated side. A clear tendency to lateralisation of the response was evident. The amplitude was usually greater (with no differences in latency) when recorded over contralateral cortical areas to the stimulated side, even in the most caudal dermatomes. DSEPs could be a valuable technique to study medullar disturbances given their reproducibility and the simple methodology required.

25. Retinitis pigmentosa. Electrophysiologicai study of 6 families. P. Marln, R. Roldin and A. Esteban (Secci6n de Neurofisiologia Clinic& Hospital General Universitario "Gregorio Marah6n," Madrid) Retinitis pigmentosa (RP) is a chronic, progressive degeneration involving retinal atrophy with characteristic pigment deposits. It is a hereditary disorder which affects 1/5000 of the population. The main symptoms are photophobia, bad adaptation to darkness, nictalopia and concentric retraction of the visual fields. The usual onset takes place at about 20 years of age but it can appear later (40-50 years of age). Patients can be asymptomatic, and ophthalmoscopic examination can be normal during early stages in the disease. In the present communication we present results from visual evoked potentials (VEPs) and electroretinograms (ERGs) from 20 members of 6 families suffering from RP. All members were studied, including asymptomatic subjects, with VEP (to reversal patterns and red flashes) and whole field ERG with and without adaptation to darkness. VEPs were normal in 15 cases, including subjects in advanced stages of the disease. The ERG was abnormal in 13 cases including clinically and ophthalmoscopically normal subjects. The most frequent abnormalities were: increased latency and decreased amplitude of b wave (4 cases), decreased amplitude of b wave (4 cases), complete abolition of ERG (3 cases), and complete abolition of b wave (2 cases). The ERG allows detection of early retinal abnormalities and should therefore be obtained in all members of families with RP, including asymptomatic subjects. VEPs remain intact until the advanced stages of the disease.

26. Somatosensory evoked potentials from nervus cutaneus femoris lateralis. - P. Marin, A. Espi and A. Esteban (Seccion de Neurofisiologia Clinica, Hospital General Universitario "Gregorio Mara," Madrid) Recording of somatosensory evoked potentials (SEPs) in root and peripheral nerve lesions is a common technique which generally yields good results. We have recently described favourable results yielded by SEP studies from the nervus cutaneus femoris lateralis (NCFL) compared to its peripheral conduction in patients with meralgia paraesthetica. It was, however, difficult to evaluate scalp midline responses (C'z) recorded by the usual SEP techniques and evoked from lower limbs in some subjects, either in the control group or from the healthy side in the patient group. A series of normal subjects has been studied with subcutaneous simultaneous recordings at 3 sites (C'3, C'z, C'4) evoked by percutaneous stimulation of the territory innervated by the nervus cutaneus femoris lateralis (line between spina iliaca anterior superior and outer patellar edge, 17 cm below the spina iliaca anterior superior). Low stimulation frequency (2.9 Hz), narrow recording bandwidth (10-500 Hz) and low number of averaged epochs (100-200) were used. The latency of P1 and the amplitude P1-N2 form all 3 recording sites were evaluated. Responses were generally lateralised with greater amplitude over the contralateral side with respect to the stimulated side. The most outstanding finding was a marked absence or attenuation of the response along the midline in 2 out of the 12 studied subjects. In these, the lateralised

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response showed normal characteristics. This finding is not properly mentioned in the literature but should be considered in order to avoid false positive diagnostic errors.

27. Ischaemic neuropathy with conduction block. - A. Traba and A. Esteban (Secci6n de Neurofisiologia Cllnica, Hospital General Universitario "Gregorio Marafi6n," Madrid) The presence of a nerve conduction block (CB) has been described in a great variety of clinical situations, usually related to compressive or immuno-allergic disturbances. During recent years it has been suggested that ischaemia might have a role as an aetiological factor in the generation of CB. A patient is presented here with symptomatology of sensori-motor polyneuropathy and nervus suralis biopsy showing vasculitis (polyarteritis nodosa). The electrophysiological examination showed classical signs of axonal lesions and multifocal CB in all explored nerves. Their time course had some peculiar characteristics in relation to their topography, the most distal CB disappearing earlier and the more proximal CB showing a later onset and longer duration. It is possible that CB would be detected more often and would stop being an exceptional finding in ischaemic neuropathy if an early and conscientious electrophysiological study together with repeated follow-up examinations, including proximal nerve segments, are carried out when this type of disorder is suspected.

28. Single fibre EMG (SFEMG) in oculo-pharyngeal dystrophy (OPD). A study of 3 cases. - E. Franco a, M. Sueiras b, M. Gratacos b and J.M. Fermindez a (a Servicio de Neurofisiologia Clinica, Hospital "Arnau de Vilanova," L~rida, and b Hospital Universitario "Valle d'Hebr6n," Barcelona) Even though the diagnosis of OPD is easy when the complete clinical and genetic picture is present, the differential diagnosis with other ocular myopathies or myastenia gravis can be problematic. The objectives of the present work are to evaluate the sensitivity and specificity of SFEMG in OPD. Two males and 1 female have been studied (average age = 60.3 years) who suffered from OPD and belonged to 2 families. They all were otherwise healthy. An electroneurogram (ENG), conventional electromyogram (EMG), turns/amplitude test ( T / A ) and frontal muscle SFEMG were recorded. The ENG was normal in 3 patients. Conventional EMG and T / A were normal in distal muscles and slightly myopathic in the deltoid and biceps in 2 patients. Polyphasic, brief and low amplitude motor unit potentials were predominant in cranial muscles in all patients. Fibre density (FD) was significantly increased in the 3 patients (average = 2.36; S.D. = 0.2; normal values < 1.7; P < 0.001). Mean interspike interval was also very increased (average = 1.28; S.D. = 0.32; normal values < 0.7; P < 0.001). Jitter measurements were always within normal limits. SFEMG is very sensitive and relatively specific in OPD, allowing unequivocal differentiation between OPD and myastenia gravis.

29. Identification of sensorimotor hereditary neuropathy type I through neural conduction in the early years of life. - A. Garcia, C. De Pablos, J. Berciano and J. Calleja (Servicio de Neuroflsiologia y Neurologla, Hospital Universitario "Marquis de Valdecilla," Santander) Hereditary sensorimotor neuropathy (HSMN) type I is a genetically heterogeneous disease which does not express clinically in all patients until after the first decade of life. Even though peripheral nerve conduction studies have been widely used for diagnostic purposes, few authors have measured this parameter in early life.

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We have carried out a neurophysiological study in 21 subjects belonging to 6 families (aged between 1 month and 5 years) who were at risk of suffering HSMN type I. Motor conduction velocity (MCV) and distal motor latency (DML) were jointly evaluated in order to identify this disorder as early as possible and to study the evolution of nerve conduction in intermediate and distal segments of peripheral nerves. Patients were classified in groups according to the age when the first neurophysiological examination was performed. Twelve patients were affected. Isolated evaluation of MCV yielded a diagnostic suspicion in 50% of those with ages below 2 years and in all patients above 2 years of age due to a different time course in MCV deterioration in these patients. Joint evaluation of MCV and DML detected the disorder from the first months of life since DLM abnormalities preceded decreases in MCV. We therefore consider that both parameters must be evaluated in combination in order to establish the diagnosis of HSMN type I.

30. Long latency EMG response after muscle stretch. Variations with age. - M.C. Maeztu, D.S. Goodin and M j . Aminoff (University of California, San Francisco, CA, USA) Brisk stretch of a muscle in isometric contraction originates a long latency EMG response (M2 and M3) which takes place after the EMG correlates of the myotatic stretch reflex (M1). Long latency response is known to be abnormal in certain diseases of the central nervous system which take place in old age such as Parkinson or Huntington disease. The effects of aging on this response are, however, ill defined and have motivated the present study which has been carded out on 30 normal subjects with ages between 24 and 84 years. Subjects were asked to keep their wrist fixed in a position against a basal flexor-to-extensor load of 2.3 N and to oppose any brisk increment in load. Random 18.4 N load variations were then applied in flexing or extending directions. Rectified EMG responses were recorded by surface electrodes placed over the motor site of flexor and extensor carpi radialis muscles with reference to the back of the contralateral hand. Responses were later integrated within specific time periods and basal EMG activity was subtracted in order to determine the areas of M2 and M3 components. M2 and M3 responses were always larger in the stretched muscle (agonist) but appeared simultaneously in agonist and antagonist muscles in all subjects. The agonist/antagonist EMG ratio was larger for M2 than for M3. Nevertheless no significant relationship was observed with respect to age in the integrated area of M2 and M3 responses, even though age has an important influence on the neuromuscular system.

31. Evolution of Spanish scientific production on electroencephalography during the last decade. A comparative study. - M.C. Martin Miguel a, J.M. Ortiz Blasco b and J.J. Garcla Seoane b (a Servicio de Neurofisiologla Cllnica, Hospital Universitario "San Carlos," Madrid, and b Departamento de Fisiologia, Facultad de Medicina, Universidad Complutense, Madrid) Developments in EEG during the last decade have been studied by analysing Spanish and international scientific production in the databases IME (Indice Medico Espafiol) and MEDLINE (Index Medicus) respectively. Scientific production in EEG was compared with production in other scientific fields. Papers on EEG compiled by both databases were processed by programming a word processor and creating a data file which was then analysed by two statistical packages. Equations were best fitted by the least squares method. Correlation analysis between variables was carried out with non-parametric coefficients of Spearman and Kendall. Significance level was less than 0.01. Global productions compiled by IME and MEDLINE grow exponentially and are mutually related by a linear model which is statistically significant. Papers on EEG do not change significantly with time, remaining around an average value.

The finding that global scientific production shows an exponential growth whereas Spanish and international contributions on EEG remain constant indicates that scientific production in this field is in a stationary situation, in contrast to what is happening in other areas.

32. Sensory-ataxic neuropathy. - M. Gonzfilez Hidalgo, J. Mejuto, A. Guerrero Sola and C. Franco Carcedo (Secci6n EMG, Servicio de Neurofisiologla, Hospital Universitario "San Carlos," Madrid) Nerve dysfunction affects sensory and motor components in most polyneuropathies. At early stages the first clinical manifestations are sensory, especially cutaneous. As the disorder becomes chronic, motor weakness takes place and kinesthetic disturbances can appear at this stage. Pure sensory neuropathies are not common at present, predominantly affect proprioceptive sensitivity and clinically present as sensory ataxia with preservation of motor strength. Their reduced incidence at present is due to a decrease in the prevalence of disorders which classically originated them: dorsal tabes dorsalis, diphtheria and arsenic poisoning. In 1948 Denny-Brown identified two patients with sensory neuronal degeneration and subclinical carcinoma. This is the most frequent cause of acquired ataxic neuropathy although it has also been described in patients without neoplasia. We present two patients with clinical symptomatology dominated by ataxia. Electromyographic studies showed pure axonal sensory neuropathy but no neoplasia had been detected at the time of diagnosis.

33. Early infantile epileptic encephaiopathy with suppression bursts. - M.C. Martin Miguei a, j. Campos Castell6 b and J. Espinar Sierra a (a Servicio de Neurofisiologia, b Servicio de Neuropediatrla, Hospital Universitario "San Carlos," Madrid) Early epileptic encephalopathies usually are entities which require complex management and generally have fatal prognosis. The differential diagnosis with more benign disorders a n d / o r known treatable aetiologies is therefore of paramount importance. We present 3 clinical cases of early encephalopathy which showed several clinical manifestations and shared an electroencephalographic pattern in common: pattern of suppression bursts. The electro-clinical findings and the value of the electroencephalogram in the syndromic diagnosis of this entity are discussed in the view of these 3 cases and after a literature review in order to establish guidelines for differential diagnosis.

34. Long-term effects of nasal continuous positive pressure (nasal CPAP) in sleep apnoea syndrome (SAS). - J. Mejuto, S. P~rez and J. Espinar (Servicio de Neurofisioiogia Cl~nica, Hospital Universitario "San Carlos," Madrid) The treatment of choice in sleep apnoea syndrome is domiciliary administration of nasal CPAP. Its immediate effectiveness is thoroughly established but long-term studies are scarce and use small samples. In this unit we have started treatment with nasal CPAP in 212 patients with severe SAS since 1987. All patients showed an immediate remission of symptoms and of polygraphic signs of SAS. Preliminary results from 41 patients are presented (34 males and 7 females), with an average age of 50.6 _ 4.1 years, who had had polygraphic follow-up and had been submitted to CPAP for periods between 7 and 63 months. Significant reductions in the apnoea-hypoapnoea index (AHI: from 58 _ 6.7 to 37.8 _+ 9.5 apnoeas/hypoapnoeas per hour of sleep, P < 0.05) and in the positive pressure used (from 7,3 + 0.8 to 6.5 ___0.9 cm of water, P < 0.05). Weight did not change significantly during treatment and there was no correlation between AHI or positive pressure and duration of CPAP treatment or weight changes.

Society Proceedings/Electroencephalography and clinical Neurophysiology 94 (1995) 73P-81P The present findings seem to indicate that CPAP acts symptomatically, controlling SAS since treatment onset, but should be maintained for as long as additional factors (obesity, alcohol intake, malformations) are not corrected.

35. Associated movements in Alzheimer disease (preliminary note). T. Ortiz a, JoM. P~rez-Serrano a, F. Jim~nez a, J.C. Oliveros b, j. Ferrero b and M. Garcla de Leon b (a Hospital Universitario "San Carlos," Madrid, b Hospital Militur Central "Gomez Ulla," Madrid) Associated movements take place during the first years of life. The onset of such movements in adult life has been associated with several disorders but never with Alzheimer disease (Shibasaki and Nagae, 1984; Cohen et al., 1991; Danek et al., 1992). Present data imply that neurophysiological mechanisms involved in the generation of associated movements in adults are as yet unknown. We have carried out an investigation on the presence or absence of associated movements in some dementias. Patients were asked to perform a certain movement with the right hand as a response to a stimulus. The presence of associated movements in the contralateral limb was studied. We have already studied 12 patients with Alzheimer disease, 5 patients with non-Alzheimer dementias and 10 normal controls. Eight Alzheimer patients presented associated movements, but no controls or non-Alzheimer dementias presented associated movements. A " n o r m a l " subject studied for some other reason and therefore not included in the above-mentioned results presented associated movements

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when explored last year. This subject had again been explored 2 months ago and presented MMT of dementia. These preliminary results seem to suggest that: (1) 66% of cases with Alzheimer show contralateral associated movements; (2) this does not happen in normal controls or in other types of dementias; (3) the onset of associated movements in a "healthy" subject can predict a future onset of Alzheimer dementia.

36. Study of palmar conduction velocity of the median nerve in the diagnosis of carpal tunnel syndrome. - M. Gonz~lez Hidalgo, I. Villalibre Vaiderrey, A. V~zquez Feito and C. Franco Carcedo (Secci6n EMG, Servicio de Neurofisiologla Clinica, Hospital Universitario "San Carlos," Madrid) The several neurophysiological techniques used for the diagnosis of carpal tunnel syndrome (CTS) show a variable degree of diagnostic efficiency. One of the alternatives for CTS diagnosis is to compare the values of median nerve sensory conduction velocity obtained for the segment palm-wrist and for the segment finger III-wrist. The objective of the present study is to evaluate the diagnostic effectiveness and usefulness of the above-mentioned technique in the diagnosis of CTS and whether a greater drop in conduction velocity in the segment palm-wrist compared to the values for finger Ill-wrist is a sufficient diagnostic criterion for a median nerve lesion at the carpus. One hundred electroneurographical studies from the distal segment of the median nerve were evaluated in patients diagnosed with CTS. The neurophysiological study protocol and results are presented.