Measurement of tongue fatigue

NMDA ANTAGONISM BLOCKS DEPRESSION, BUT NOT ANOXIC DEPOLARIZATION. M. I,aurrrzen, (University

E. Zhang,

T. Wieloch

of Copenhagen,

LEAO’S SPREADING OR HYPOGLYCEMIC

as spasticity can be described with a minmwh number 01 parameters of the highest clinical value. is now under tnwstlgation.

and A.J. Hansen

Copenhagen,

Denmark)

Leao’s cortical spreading depression (CSD), anoxic (AD) and hypoglycemic depolarization (HD) are conditions where brain ion homeostasis fails dramatically, causing high-amplitude changes in extracellular ion concentrations. CSD is spontaneously reversible, while repolarization of AD and HD require restoration of oxygen or blood glucose. The purpose of this study was to examine effects of glutamate blockade using MK801 which binds to the NMDA site of glutamate receptors. Extracellular [K+ ] and [Ca*+ ] was measured in parietal cortex in anesthetized, craniotomized rats by ion-selective microelectrodes. (1) CSD was induced by tetanic electrical stimulation of the cortex. MK801 at 3-10 mg/kg iv. or i.p. blocked CSD completely and irreversibly (n =lO). (2) AD occurred about 120 set after circulatory arrest, [K+ 1, increased from 3 to 60-70 mM, [Ca”], declined from about 1 mM to 0.1 mM. MK801 did not influence these variables (n =lO). (3) HD occurred about 32 min after blood glucose declined below 1 mM, ]I( ’1, increased to 55 mM, and [Ca*+ 1, declined from 0.9 to 0.08 mM (n =lO). MK801 did not influence these variables either. In conclusion, CSD in rats is closely linked to glutamatergic neurotransmission and the NMDA subreceptor. AD and HD are probably mediated by other mechanisms. dependent on available substrate, such as second-messenger operated ion channels or translocator coupled ATPases.

AUGMENTATION OF DURING SURGERY.

M.K. Lebiedowska, (Child Health

M.J. Lebiedowski

Centre.

Warsaw,

OF

EVOKED

POTENTIALS

C.-S. Lee and T. Kurokawa (University

of Tokyo,

Tokyo,

Japan)

Monitoring of spinal cord function during spinal and aortic surgery is performed using epidural stimulation and recording. Although amplitude reduction is well recognised as a sign of spinal cord dysfunction, little is known about amplitude augmentation during surgical procedures. We have observed amplitude augmentation during surgery in the following situations and for the associated reasons: (1) anterior to a spinal cord lesion, due to conduction block in the volume conductor; (2) following excision of a spinal cord tumour, due to recovery of conduction in the compressed tracts; (3) during correction of scoliosis or after incision of the dura mater, due to physical changes in the intradural volume; (4) within a few minutes following a sudden reduction in blood pressure during aortic surgery, due to a transient increase in the response of spinal tracts because of spinal cord ischemia. Although augmentation of spinal cord potentials is not a common occurrence, it can have implications for surgical procedures and should be taken into account along with amplitude reduction.

MEASUREMENT THE QUANTITATIVE EVALUATION MATIC SPASTICITY IN CHILDREN.

SPINAL

OF TONGUE

FATIGUE.

POST-TRAU-

and J.S. Ekiel

Poland)

A new system for the quantitative evaluation of spasticity has been developed and used to describe chosen features of the motor system in 20 post-traumatic and 10 healthy children. Appropriate methods have been developed or used to measure the chosen parameters of the following spasticity features: (1) muscle tone (the stiffness of the knee joint muscles attempting relaxation); (2) maximal voluntary activity (maximal voluntary knee extension and flexion torque); (3) antagonistic muscle coactivation during voluntary knee extension and flexion; (4) hyperactivity of short latency reflexes related to voluntary activity (the short-latency knee reflex reaction during voluntary extension). The results of the measurements have been normalised and a comparable, objective description of each spasticity feature achieved. Summation of the surpluses and deficits at the range of each feature correlates with the clinical patient status. To what extent such a multidimensional phenomenon

C.J. Lee, D.P. Romilly (G.F. Strong

and C. Hershler

Rehabilitation

Centre.

Vancouver,

BC, Canada)

We are investigating tongue strength and control using a strain gauge-based cantilever beam transducer designed to measure tongue force in any of three directions: up, left, or right. Two types of test are performed: (1) a static fatigue test which requires subjects to exert and maintain their maximum tongue force throughout the measurement; and (2) a cyclic fatigue test which requires subjects to exert their maximum tongue force, relax, and then re-exert at a preset frequency. Each type of test is performed on separate patient visits. During a particular visit, a measurement, lasting 30 seconds, is repeated twice for each of the three directions. with a 60-set recovery period between measurements. Five normals and 3 patients (2 stroke, 1 polio) have been tested for fatigue. Normal subjects obtain higher instantaneous ( < 1 set) and extended ( > 1 set) maximum tongue force values than patients. There are no significant differences in instantaneous force between the two lateral directions in both the subjects and patients. However, the fatigue test data reveal a

S.81 distinct djf&rence between the left and right extended maximu+m tongue force values in the patients, which is not observed in the normals, suggesting that tongue force fatigue may provide a more suitable means of assessing oral phase swallowing disorders than instantaneous measurements.

AN UNUSUAL CASE OF HYPERINSULINOMA WITH CONFUSIONAL STATES AND TONIC-CLONIC SEIZURES DIAGNOSED WITH THE HELP OF LONG-TERM VIDEO-EEG RECORDING. Ch. Lej;bre,

B. Lefebre

(Free University,

and B. Skotzek

Berlin, F.R.G.)

About one year prior to admission, this otherwise healthy, intelligent young man suffered from several episodes of confusion at night which he did not remember. Nine months later he had his first tonic-clonic seizure at night which was followed by another four seizures, all occurring at night over the next 3 months. Physical and neurological examination, blood glucose, EEG and CT scan were, besides a slight adiposity, normal at admission. The patient did not report any ravenous hunger or changes in appetite. The patient’s own idea that seizures may be psychogenic was excluded by recording a long-term EEG where we observed a tonic-clonic seizure at about 4 a.m. Blood glucose postictally was normal. During a confusional state the following morning, beginning at about 8 a.m. when the patient seemed to be awake but disoriented, we observed in the 16-channel video-EEG diffuse slowing with inserted parts of sharp waves and an increasing number of spikes, as will be demonstrated on video. Blood glucose level was 28 mg/dl at that time. Further diagnostic procedures led to the diagnosis of a hyperinsulinoma which was surgically localized and operated. After surgery the patient was seizure-free with no further episodes of confusion.

SEVEN-CHANNEL-MAGNETOENCEPHALOGRAPHY (MEG) IN FOCAL EPILEPSY. Ch. L&bre,

gradiometer in the Berlin shielded room. We will demonstrate with clinical data, interictal and ictal EEGs, CT, SPECT and MRI, that using a special procedure during the MEG measurement, it seems possible to localize single foci in the MEG of multifocal patients. We will discuss the necessity and usefulness of multichannel MEG, the problems in clinical routine and the possible origin of some artefacts identified and corrected during our measurements.

PRINCIPLES OF EEG MAPPING AND MAP

ANALYSIS.

D. Lehmann (University

Hospital,

Zurich,

Switzerland)

The spontaneous EEG can be viewed as series of momentary potential distribution maps (Lehmann 1971. EEG Journal). The spatial configurations (landscapes) of such maps are reference-independent. Momentary map landscape might be assessed using locations of extreme potentials (invoking a 2-D-dipole concept). The maps periodically (for alpha about 20/set) wax and wane in relief strength and reverse in polarity. In wakefulness, landscapes tend to be stable over several reversals; changes to a new landscape occur quickly. If map landscapes differ, different neural generators must have been active, executing different brain processes. Thus, adaptive segmentation of map series according to landscapes into different, spatially stable epochs of varying duration identifies global, functional micro-states. (Segmentation of the time function of relief strength can identify gross states.) Different map-defined micro-states are associated with different cognitive modes and reaction times. Mental pathology might be manifest in aberrant frequency or concatenation of the micro-states. Landscapes of FFT power are reference-dependent. Only maps of FFT power vs. the average reference correspond to maps of extreme potential incidence accumulated over the analysis epoch, and thus are functionally interpretable. Map transformations (gradients or current densities, i.e.. spatial high-pass filtering) emphasize selected features. Fourier coefficients can be used for the computation of the intracranial source localization of long epochs of ongoing EEG activity.

R. Stehr and D. Jam

(Free University,

Berlin, F.R.G.)

One of the first, most promising clinical applications of the new biomagnetic methods could be the possibility to localize deep sources of epileptogenic foci in patients suffering from focal epilepsy, especially in cases of drug resistance where epilepsy surgery could be helpful. Most important for surgery is the exact localization of the epileptogenic focus if there is interictal and/or ictal multifocality. Conventional evaluation methods include invasive long-term EEG monitoring for seizure and interictal EEG recordings among others. In our project we examined 4 patients suffering from intractable focal epilepsy because of multifocal EEG abnormalities using a 7-channel

INFLUENCE OF LIGHT-DARK CYCLE ON SPONTANEOUS RECURRENT SEIZURES INDUCED BY SYSTEMIC PILOCARPINE IN RATS. J.P. Leite, Z.A. Bortolotto (Escola

Paulista

and E.A. Caualheiro

de Medicina,

SZo Paulo, Brazil)

The seizures induced by pilocarpine (PILO) in rodents have proven to be a useful experimental model for studying the basic mechanisms of partial seizures which follow neuronal damage. particularly those seizures originating from the tem-