7th Annual joint meeting of the EEG, EMG and clinical neurophysiology in Czechoslovakia

Ele('troencephak)grapt O' and clinical Neurophvvwlogv, 1985, 61 : 4P 14P

4P

Elsevier Scientific Publishers Ireland, Ltd.

Society. proceedings 7th ANNUAL

JOINT

MEETING

OF

THE

EEG,

EMG

AND

CLINICAL

NEUROPHYSIOLOGY

IN

CZECHOSLOVAKIA Prague, April 24 27, 1984

Secretary: Dr. S. NEVSiMALOV,~ Department of Neurology, Katei"inska 30, 120 O0 Prague 2 (('zecho~'lova/,ia) (Received for publication: November 13, 1984)

1. EEG compared with neuroradiological and pes! morlem findings in patients with cerebrovascular emergencies. - J. Berger, K. Schwartzova and F. Komz~d~ (PIzeh) The authors compared 315 EEG findings during the 1st-3rd weeks following cerebrovascular attacks with angiographic, CT and post mortem findings. Patients in whom no such attack was confirmed by any of the methods applied were excluded. The EEG in stenosis and closure of the internal carotid or brain haemorrhage revealed major electrical depression with a maximum over the area of the lesion, surrounded very often by delta waves or FIRDA. In stenosis or closure of intracerebral arteries there were significant focal EEG findings but, compared with lesions of the extracranial arteries or haemorrhage, no electrical depressions. Subtentorial affections manifested themselves by flattening, diffusely, or by background activity changes. When a hemispheral maximum appeared it was caused by a simultaneous lesion of the hemisphere. Focal findings were seen in 61-83% in different groups of diseases. The high proportion of non-focal findings is not surprising. Foci are known often to become visible in repeated records only after the brain oedema has abated. Serial EEGs can record the dynamics of the process, and are thus an indispensable complement to other diagnostic methods.

2. The significance of EEG examination in the diagnosis of focal cerebrohaemodynamic disorders in children. - - A. Zouhar and H. Zemanov/~ (Brno) Focal cerebrohaemodynamic disorders were diagnosed in 25 children (3-15 years) out of 1823 inpatients (1.378e). Angiography revealed occlusive ischaemia in 7, non-occlusive ischaemia in 9 (verified by rCBF), and a further 9 cases were diagnosed as migraine accompagnbe. The first EEG showed gross focal disturbances (mostly delta waves) in 6 of the 7 cases of occlusive ischaemia, in 8 of the non-occlusive cases, and in 4 of the 9 with migraine. After a month, no EEG normalization was seen in the occlusive cases (clinical improvement in 4), the EEG had normalized in 3 of the non-occlusive cases (clinical improvement in all), and in the migraine patients both the EEG and the clinical focal findings had disappeared. Longitudinal

EEG evaluation was found of great importance for diagnosing focal cerebrohaemodynamic disorders in children, even in comparison with CT.

3. Comparison of EEG and CT findings in cerebrovascular diseases. - - I. Szirmai, Z. M6ro, P. Kosaras and L. Fodor (P~cs, Hunga~) Ninety-one cerebrovascular patients (36 bleedings- H, 55 anaemic infarctions = CI) had CT and parallel EEG investigations performed. To estimate the statistical relations between CT and the 'lateralization of EEG signals' (y) the following equation was established:

~//

(Ap

Y=

A n ) 2 ( F" , - F p ) 100

(8-Vp)10 +('% +

%,)2

8

where A = amplitude, p = pathological side, n = normal side, F = frequency, a = actual alpha frequency in the unipolar record. The CT codes expressed the extent and localization of bleeds and infarcts. A positive correlation was found between the extent of bleeding and the projecting fields of pathological EEG signals. Relation functions for the EEG and CT codes were different in the periodic (P) and non-periodic (non-P) EEG groups. Capsular and midline localization was found more frequent in the P as distinct from the non-P group. In the non-P group of CIs one negative correlation coefficient means inverse proportion between the extent of lesions (CT) and their pathological EEG. In the CI group there were 14.55% negative EEG findings. The uses of the evaluation score were illustrated in individual cases.

4. Hemiplegic migraine in childhood. Differential diagnosis and EEG aspects. - - V. Farkas, L. Szego and O. Kohlheb (Budapest, Hungary.) Intermittent hemiplegia with characteristic headache was present in 6 children. The attacks began between 8 and 12 years of age, recurring at intervals of 6 12 months. The symptoms lasted no longer than 2 h, followed by complete recovery without any residual neurological signs. Serial interictal sponta-

0013-4649/85/$03.30 ~') 1985 Elsevier Scientific Publishers Ireland, Ltd.

7th A N N U A L J O I N T M E E T I N G 1N C Z E C H O S L O V A K I A neous EE(i (with hyperventilation and photic stimulation) and sleep EEG (after sleep deprivation) were performed. In 4 patients all EEGs were normal. Inconstant abnormalities were noted in 2 patients shortly after attacks: in one case rolandic sharp waves, in the other focal slow waves. Differential diagnosis of paroxysmal neurological diseases such as complicated migraine, partial epileptic seizure and, e.g., transient ischaemic attacks may prove difficult particularly in children. A normal EEG can be useful in diagnosing a non-epileptic disorder. Symptoms such as a brief prodromal episode (aura), abrupt onset of neurological impairment syndromes, occasional convulsions, postictal sleepiness, interictal epileptiform EEG findings, effective treatment with anticonvulsants, all these may be characteristic of migraine as well as epilepsy.

5. Visual and auditory brain-stem evoked potentials in patients with focal ischaemic cerebral lesions. - - D. Bartko and M. Kond~t~ (Bratislava) Checkerboard pattern reversal (VEP) and auditory brainstem (ABEP) evoked potentials were studied in 150 patients with focal cerebral ischaemia. The data were compared with control group I (50 healthy subjects) and with control group II consisting of 30 arteriosclerotics and hypertensives threatened with cerebral infarction. The latter had longer latencies and lower VEP amplitudes (N1, P1) and ABEPs (P3, P5) than the former. The focal brain ischaemia group showed these changes to be more significant. The 3 S.D. normative interval was used for the elderly patients. According to these criteria, the authors found 33% abnormalities of VEPs in arteriosclerotics, 67% in supratentorial and 28% in infratentorial ischaemic lesions. ABEPs were rated as abnormal in 27% arteriosclerotics, 35% supratentorial and 56% infratentorial ischaemic lesions. The EP changes were more conspicuous in the group with severe neurological impairment. Evoked potentials were found useful for the detection of not only small cerebral ischaemic lesions but also diffuse vascular lesions without straightforward symptoms of brain dysfunction.

6. Multimodality evoked potentials in focal brain ischaemia following middle cerebral artery occlusion in cats. - - D. Bartko, M. Kondb~ and J. Pancak (Bratislava) Multimodality evoked potentials (MEP) can be used for ascertaining quantitative changes in electrical activity corresponding to changes in cerebral ischaemia and for monitoring the functions of sensory pathways. The authors report on their investigation of MEP following middle cerebral artery occlusion (MCAO) in 20 cats. Visual, somatosensory and auditory responses (both cortical and brain-stem components) were obtained before occlusion, 30 and 90 min after MCAO. The latencies and amplitudes of surface recorded potentials were analysed, indicating latency increase as well as amplitude reduction (approx. 40% initial value) in the somatosensory evoked response following MCAO, Peaks III and IV of the somato-

5P sensory brain-stem components were affected as well as the mean conduction time ( P < 0.05). Visual evoked potentials showed a similar latency increase ( P < 0.05). Auditory cortical and brain-stem evoked responses were unaffected by the occlusion. MEP could offer a means for the objective assessment of various brain pathways and thus be of use for monitoring the functional state of the brain during experimental cerebral ischaemia. 7. Changes in visual and auditory brain-stem evoked potentials due to ischaemic cerebral infarction. A study of dynamics. - M. Kond/t~ and D. Bartko (Bratislava)

Visual and auditory brain-stem evoked potentials (VEPs, ABEPs) were recorded in a group of 155 patients with focal brain ischaemia - - at the onset, 14 and 28 days and 6 months afterwards. At the onset the latency of VEP peak N1 was delayed ( P < 0.01) and the amplitudes of VEP peaks P1 and N2 were reduced (P < 0.01). The incidence of abnormal records was significantly increased (84% VEP, 43% ABEP). Two weeks following the attack the latency of VEP peak N1 had decreased and the P1 and N2 amplitudes had increased. Abnormal findings were present in 58% of VEPs and in 37% of ABEPs. A statistical analysis of the evoked potentials recorded 28 days and 6 months after the attack showed no further significant differences. There was no significant correlation between VEP and ABEP and cerebral blood flow, although the anticipated trend was noted. The study suggests the possibility of assessing altered brain function in the recovery of ischaemic cerebral lesions, which is not a 'steady state' but a dynamic process.

8. Somatosensory evoked potentials in focal brain ischaemia. Dynamics of alteration. - - D. Buranova and D. Bartko (Bratislava) The purpose was to ascertain the dynamics of changes in cortical and spinal somatosensory evoked potentials (SEPs) in cerebral focal ischaemia. One hundred and thirty-one patients, aged 35-78 years, with focal ischaemia of the right or left brain hemisphere with the clinical picture of motor disturbance due to damage to cortico-spinal pathways, were followed up. Ninety-three had rather mild strokes (BI score less than 170 points), 38 had severe ones (B1 score more than 170 points according to Bartko (1982)). The following postictal changes were observed: SEP changes immediately after the stroke, on the 14th and 28th days, and more than 3 months after the stroke. In mild cerebral ischaemia, an amplitude decrease in waves P~s and N20 was observed. In severe cerebral ischaemia the alterations were more marked, on the 14th day after the onset of the disease, a decrease in amplitude occurred, and a latency prolongation of waves N20 and N55 was found. In patients examined after a 3 m o n t h interval, a significant shortening of the latency in wave P45 as well as a deformation of the cortical SEP were observed.

6P 9. Somatosensory evoked potentials in focal brain ischaemia. - D. Bartko and D. Buranov/~ (Bratislava)

The aim of the present study was to establish some characteristics of cortical and spinal somatosensory evoked potentials (SEPs) in focal cerebral ischaemia, and to compare them with a group of normal healthy subjects (control group I) and with a group of hypertensives and arteriosclerotics (control group 11). The 75 healthy subjects were divided according to decades of age. The N20 latencies were significantly increased in the 41-60 and the 61-80 year age groups. In the elderly, over 80 years of age, the latencies of other waves were also changed. Unlike the healthy controls control group 11 (46 subjects) exhibited significantly increased latencies of all except waves P15 and P25- In the authors' view, these SEP changes could well be due to clinically silent transient ischaemic attacks. Similar changes were also found in the groups of supratentorial (131 persons) and of infratentorial (19 persons) ischaemia. The latencies of waves N20 and N55 were significantly delayed in patients after cerebral infarction in comparison with the healthy controls,

I0. Early acoustic evoked potentials in vascular lesions of the brain-stem. - - F. Komzak, J. Berger, Z. Mra~ek and J. Seidl (Plzeh)

The authors examined 3 patients suffering from brain-stem haemorrhage and 42 patients with ischaemic lesions of the brain-stem within 2 weeks of the attack. Other neuroradiological examinations were performed simultaneously. Pathological signs were detected in 53.3%, Brain-stem symptomatology of various extent and combinations was present. The following lesions were found: (1) Wallenberg's syndrome, (2) in the region of the ports, (3) in the pontine and mesencephalic regions, (4) in the pontine and cerebellar regions. Four patients with Wallenberg's syndrome had protracted latency of waves 111 and V with normal interpeak latency of waves III-V. In 6 patients with pontine lesions there was protracted latency of wave V and protracted interpeak latency of waves III-V. Six patients with mesencephalic lesions exhibited protracted interpeak latency of waves I V - V and V - V I but no protracted latency of waves V and VI. In 12 cases there were pathological AEP findings as distinct from normal findings when other methods of examination were used.

11. EEG changes in gross metabolic abnormality in children, due to renal and hepatic failure. - - M. Lehovsk~ and L. Misiaczkovit (Prague)

Three groups of children were studied: 17 with acute renal failure, 30 with chronic renal failure, and 36 with acute hepatic failure due to Rey's syndrome. The clinical picture was similar in all children: changes in consciousness and seizures in the most affected cases. The EEG changes were in agreement both with the clinical condition and with the metabolic disturbances.

SOCIETY P R O C E E D I N G S The EEG abnormality, however, persisted after biochemical recovery, and some temporary deterioration of curves could be detected. The changes were less severe in cases of chronic renal failure, and also the prognosis was better in these cases. No specific graphoelements were found in these groups of patients, and there was only a lack of normal rhythmic activity, with general slowing down. In the most severe cases slow delta waves with periodic suppression were seen. The EEG changes were in agreement with the level of consciousness.

12. Relationships between neurographic and EEG findings in chronic renal insufficiency. - - R. Matthes, R. Both and G. Muhlau (Jena, G.D.R.)

Twenty-one patients participating in a chronic intermittent haemodialysis program underwent a total of 42 EEG and neurographic examinations. The electroneurographic examination included the determination of the tibial nerve motor conduction velocity and Hoffmann reflex latency measurement at the soleus muscle. The EEG revealed slowing of background activity and general bursts of slow waves. A statistical examination of the interrelationships between different electrophysiological parameters revealed a close connection between the motor nerve conduction velocity and Hoffmann reflex latency ( P < 0.01). However, there was no significant correlation between motor nerve conduction velocity ( P > 0.05) or Hoffm a n n reflex latency and pathological EEG changes ( P > 0.05). These findings suggest that encephalopathy and polyneuropathy in haemodialysed patients are produced by different pathogenetic mechanisms. 13. EEG and chronic renal insufficiency. - - R. Both, G. Mt~dau and H. Sperschneider (Jena, G.D.R.)

Sixty-five patients with chronic renal insufficiency taking part in a chronic intermittent haemodialysis programme were given a total of 265 EEG examinations. Spontaneous resting EEG and EEG during 3 rain of hyperventilation and in response to photostimulation were taken. The EEG evaluation involved the slowing of background activity, general bursts of slow waves, and the occurrence of epileptiform activity. With regard to the duration of dialysis, the patients - - including 19 with dialysis encephalopathy - - exhibited the following findings: after initial improvement, background slowing, in terms of frequency and severity, progressed as the dialysis grew in length. The frequency and severity of the general bursts of slow waves showed no relationship to the duration of dialysis. Only in 1 case was epileptiform activity observed among the EEG changes that appeared during dialysis encephalopathy. 14. EEG changes in patients with Wilson's disease and their heterozygous relatives. - - S. Nev~imalov/t, B. Roth, J. Vymazal and Z. Mare~3ek (Prague)

The study is based on the clinical, biochemical and EEG correlations in a group of 40 patients with Wilson's disease and

7th A N N U A L J O I N T M E E T I N G IN C Z E C H O S L O V A K I A their 57 heterozygous relatives (25 children, 30 patients and 2 siblings). EEG abnormalities in the patients were found in 84.2% of the records with only a slight preponderance in patients with clinical neurological manifestations. Rather m a n y abnormalities were observed also in the hepatic (70%) or asymptomatic (75%) forms of the disease. Abnormalities of episodic nature predominated in all groups. In the group of heterozygous relatives, EEG abnormalities were found in 80% of the children and in 48% of the adults. Both values show a higher percentage of pathological findings connected, probably, with the state of heterozygosity, the difference in children compared with the controls being highly significant. The most pronounced EEG changes were found in the youngest age groups (under 10 years) with paroxysmal or specific epileptic manifestations. The toxic influence of cumulated copper pervading the placental barrier in pregnant women with Wilson's disease is discussed. A favourable effect of penicillamine treatment, with disappearance of these changes in a few cases, was observed.

15. The significance of EEG findings for interrupting dietary treatment for phenylketonuria in children. - - J. P~tov~t and J. Hy~mek (Prague) EEG findings after protein load tests in 12 children suffering from classical P K U (mean age 12 years) were used as a possible criterion for the termination of dietary treatment for PKU. During the treatment with phenylalanine-low products, EEG was performed regularly twice a year at therapeutic phenylalanine blood levels. For the estimation of phenylalanine tolerance a protein load of 3.5 g p r o t e i n / k g body weight was used. A direct correlation between the phenylalanine level and EEG changes was observed. The most typical were background changes with slow activity in 9 children, in two of them with hypersynchrony. In two cases there was severe generalized abnormality with epileptic activity, and only in 1 case was the EEG normal. EEG normalization within 1 h of the protein load test might be an important criterion for the discontinuation of dietary treatment for PKU.

16. Benign eentro-temporal epilepsy of childhood. EEG and clinical follow-up of 80 cases. - - G. Ger~by (Budapest, Hungary) Twenty-five girls and 55 boys with centro-temporal epilepsy were followed up for 3-13 years. Mean age at the first clinical manifestation was 5.5 (girls) and 6.4 (boys). 11.2% had a family history of epilepsy. Organic brain damage could not be detected at the first evaluation or during the observation period. Eighteen showed right-, 20 left-sided foci only, 42 had bilateral loci with changing predominance on one side. Beside focal spike activity, generalized epileptiform discharges (usually polymorphous S-W synchronization) also appeared in one or more records of 30 patients, mostly with bilateral focal spiking. Seventy-one children became seizure-free (53 within 2 years)

7P though uni- or bilateral spike activity outlasted the cessation of the seizures in 50 patients for 0.5-5 years, and in 10 for 5-10 years. Patients with bilateral spike loci and those with generalized discharges besides the uni- or bilateral focal spiking showed no prognostic difference (total number of paroxysms, the time necessary for full seizure control) from those with unilateral spike foci only.

17. A longitudinal study of EEG records and clinical course in patients with absences. - - D. Fiedlerova and L. Chromova (Hradec Krhlove) The development of EEGs correlated with clinical data on 46 adults suffering from absences was followed up over periods lasting 9-30 years. The patients were divided into 4 groups depending on their age at the first appearance of absences. The nature of the EEG recorded before the age of 26 was variable, in those after the age of 30 it remained unaltered. The absences in 80.3% of the patients could be rated as transient pseudoabsences, in 17.5% as being of the primary type, and one (2.2%) was a case of atypical absence in the frontal lobe area. The origin of the absence could not be identified in 1 patient with a continuously normal EEG but was clinically supposed to be of secondary origin. Patients resistant to treatment and those socially unsuccessful mostly belonged in the group with temporal foci and with a frontal focus. Patients showing late signs of impaired intelligence or psychosis invariably belonged in the temporal foci group.

18. A clinical and EEG study of 856 epileptic children. - - S. W ~ s e r and J.M. Kasper (Leipzig and Eisenach, G.D.R.) Of 856 epileptic children receiving inpatient treatment (generalized primary epilepsy 21.6%, generalized secondary epilepsy 38.8%, unclassified 0.7%), 805 were subsequently followed up as outpatients; their different clinical features were examined and analysed by means of data processing (EDVA 40). The following were seen to be prognostically favourable (i.e., free from attacks or neuro-psychiatric findings): later manifestation, convulsions during fever as a type of manifestation, absences and grand mal as types of paroxysm, familial predisposition, no exogenous possibilities of damage, normal neurological a n d / o r psychic findings, uneventful initial EEG and unchanged type of seizure during the disease.

19. EEG findings in children of epileptic fathers. - - Z. Salcmanova (Plzeh) Twenty-five epileptic fathers and their 41 children were studied. The average paternal age was 36, the average history of the disease was 23 years. Sixteen fathers suffered from primary generalized epilepsy, 9 from partial epilepsy. Sixteen had gone without seizures for more than 3 years, 5 had seizures 4 times a

8P year, 4 of them several times monthly. Their wives were free from any neurological involvement. The children's average age was 10 years. Thirty-eight had normal neurological findings, 1 child with a meningocele had paraparesis of the legs, 2 suffered from the central hypotonic syndrome with psychomotor retardation. Enuresis nocturna appeared once. The children's EEG was normal in 14 instances, bioccipital slow waves were seen twice, synchronous spike-slow wave discharges were diagnosed in 13 cases, and frontal, temporal and occipital spike foci were seen in 14 cases. Six children had febrile seizures, from which epilepsy developed 3 times. Nine suffered from epilepsy, thereof eight of a mild type. The disease appeared earlier in the children than in their fathers. While the paternal involvement was mostly of the mild type, pathological EEG patterns were found in two-thirds of the children.

20. EEG and long-term clinical follow-up of children with manifestations of borderline epilepsy. - - K. Schwartzov/l and L. Oudov'a (PIzeh) Three hundred and ninety-seven children with various manifestations of borderline epilepsy (febrile convulsions, mixed paroxysms, respiratory spasms, visceral fits, syncopes, payor nocturnus, enuresis nocturna, vertigo and tics) with bursts of rhythmic sharp waves, bursts of SW or focal epileptic graphoelements received neurological and EEG follow-up care for 2-15 years. More than 1200 records were studied. The clinical effects were favourable and manifest epilepsy never developed. Diazepam was the therapy of choice. Hydantoinates had to be added in a few cases (pavor nocturnus and abdominal fits). EEG normalization appeared later than the clinical compensation. In some cases, non-specific abnormalities persisted in the records of clinically normal, healthy or vegetatively stigmatized adolescents.

21. An EEG study of temporal lobe epilepsy in childhood. - - O. Kohlheb, V. Farkas and L. Szeg6 (Budapest, Hunga~) Eighteen patients with complex partial seizures were found among 466 epileptic children. Patients affected by other types of epileptic paroxysms, especially by benign focal epilepsy with rolandic spikes, were excluded. The history, clinical phenomena of seizures, therapeutic outcome and prognosis connected with electrophysiological manifestations were examined. Repeated interictal spontaneous EEGs and sleep EEGs after sleep deprivation were performed. The former were abnormal in 14 children: 7 patients had temporal spikes, 3 had temporal spike-slow wave complexes, 4 had slow temporal activity. In 4 patients temporal epileptiform abnormalities were present solely in the sleep EEG records after sleep deprivation. Uni- and bilateral EEG changes occurred in equal proportions. As regards the symptomatology and clinical data, the differential diagnosis of temporal lobe epilepsy may sometimes prove rather difficult. Consequently, the recently established decreasing number of children with temporal lobe epilepsy may be due to correct differential diagnosis.

SOCIETY P R O C E E D I N G S 22. The value of activating methods in the diagnosis of epilepsy. - - D. Bartko, D. Buranov/~ and I. Bre~n~' (Bratislava) The purpose of the study was to assess the value of 3 EEG activating methods: (1) sudden discontinuation of anticonvulsants, (2) sleep deprivation, (3) convulsion-provoking drugs (Bemegride, SPOFA). In a group of 91 patients with suspected epilepsy and disorders of consciousness of uncertain origin the EEG findings were normal in 72.5%, non-specific abnormalities in 21.9% and specific graphoelements in 5.4%. The highest proportion of specific graphoelements occurred following i.v. Bemegride administration (40.5%) and in combination with sleep deprivation (50.0%). The lowest percentage of positive specific epileptic graphoelements was [k)und after the discon0nuation of anticonvulsants (20.0%) and sleep deprivation (8.5%) respectively. No epileptic seizures were observed. The following diagnostic programme seems to arise logically from those facts: (1) sudden omission of anticonvulsants, (2) EEG on the 3rd and 4th days after sleep deprivation, (3) with negative EEG findings - administration of Bemegride i.v. with EEG recording.

23. EEG findings in addition to spike and wave complexes in petit real epilepsy. A preliminary report. - - D. Pozo and J. Pascual (Havana, Cuba) Background EEG activity was studied in 74 children with generalized discharges of 3 c / s e c spike-wave complexes. From the clinical point of view 2 groups were formed: one consisting of 65 children was rated as primary epilepsy (petit mal), the other (9 children) met the criteria of secondary epilepsy. Both groups included children with simple and complex seizures. Abnormal background EEG activity was observed in 68.9%. In group 1, a significant correlation at 0.01 of confidence was found between normal background EEG activity and simple absences (94.7%). In group II, the abnormal record was associated with complex absences in 80%. The majority (70.6%) of the background EEG abnormalities were characterized by focal discharges. The study showed the need for establishing a more flexible definition of absences based on various EEG pictures and clinical characteristics of petit real. A significant correlation was found between the background EEG activity and the type of absence.

24. EEG in sporadic epileptic seizures occurring in alcohol/ drug-dependent patients. - - P. Rajna and J. Veres (Budapest, Hungary) Accidental epileptic symptoms without any real epileptic mechanism are rather frequent in alcohol or drug dependence. About 10% of the population are affected. EEG records of 150 patients admitted after their accidental grand mal were analysed. Their EEGs showed no signs of an electrical epileptic mechanism but there were signs of altered states of vigilance such as exist in alcohol/drug abuse or withdrawal syndromes. Diffuse slow alterations were seen as being due to the intake of drugs.

7th A N N U A L J O I N T M E E T I N G IN C Z E C H O S L O V A K I A

9P

Caution is advisable in cases of paroxysmal discharges like genetically based patterns (spike and wave complexes) and in some alterations of dubious relevance (i.e., 6 - 1 4 c / s e c positive spikes). These can easily appear in similar situations without any clinical meaning - - especially during hyperventilation and photostimulation. Their transitional character can be verified by an EEG check-up. The authors try to determine some of the specific circumstances explaining the presence of accidental epileptic manifestations in alcohol/drug dependence as distinct from the special forms of genetically based epileptic mechanisms.

primary neuromuscular mitochondriopathies (3 cases of chronic progressive external ophthalmoplegia such as the muscular descending and oculo-pharyngeal types, as well as Kearns disease, 2 cases of lipid storage metabolism - - carnitine deficiency - - and 1 case of exercise intolerance due to AMPdeaminase deficiency). Diagnostic clues to those primary neuromuscular mitochondriopathies were obtained from morphological and biochemical findings. Electrodiagnostic findings were often slightly pathological. It is emphasized that electrodiagnostic disturbances are often multisystemic in origin; more investigations are necessary.

25. Disappearance of pathological EEG changes after the discontinuation of anticonvulsants. - - A. Hal~sz and A. Mattyus (Budapest, Hungary)

28. Nerve conduction velocity in type 1 diabetics treated with continuous subcutaneous insulin infusions. - - G. Reichel, W. Felsing and H. Bibergeil (Greifswald, G,D.R.)

In most cases of our 500 in- and outpatients EEG recording failed to show any improvement even after a 3 or 4 year period free of attacks. The anticonvulsant treatment of these patients went on for another 3 years on average until it was gradually discontinued. In most cases, the EEG remained pathological except in 25 cases in which improvement was registered when or after the anticonvulsants were phased out.

Twelve insulin-dependent diabetics were studied over 6 26 months while they were treated with continuous subcutaneous insulin infusions. All had total insulin deficiency. Mean blood glucose, glycosylated haemoglobin A1, motor and sensory nerve conduction velocity (median, tibial, peroneal) were measured. Significant metabolic control improvement was noted. Motor and sensory nerve conduction velocities increased gradually.

26. EMG examination of the masseter and other muscles in children with cerebral palsy. - - J. Przedpelska, G. Wasilewska, A. Serafinowska and B. Adamczyk (Poznan, Poland)

29. Sulcus ulnaris syndrome ( S U S ) - - course and prognosis. - G. MiJhlau and R. Both (Jena, G.D.R.)

The following examinations were carried out in 20 children with cerebral palsy and in 20 normal children: (a) E M G of the masseter, temporalis, orbicularis oris, gastrocnemius and tibialis anterior muscles, (b) mastication capacity examination using the Gelman functional method, (c) general assessment of physical efficiency, (d) clinical functional examination of the tongue and lips. The pathological features of the masseter muscles in spastic children are similar to the E M G patterns of the leg muscles. Involuntary myoelectrical activity during relaxation and after voluntary contraction was observed. Paradoxical myoelectrical activity could be found, i.e,, activity during passive stretching was often greater than during voluntary contraction. The intensity of the E M G pathological signs correlated with a decrease in masticatory capacity, with general physical deficiency and with the degree of cranial nerve lesions.

27. Electrodiagnostic findings in neuromuscular mitochondriopathies. - - G. Sack, T. Krause and J. L~ssner (Leipzig, G.D.R.)

Primary neuromuscular mitochondriopathies, according to Walter, including muscular disorders of lipid storage metabolism, represent an important subgroup in clinical myology. Electrodiagnostic investigations (EEG, EMG, MCV, SCV, TFR, AEP, SSEP) were carried out in 6 patients suffering from

Out of 1028 patients with 1138 peripheral nerve lesions 142 suffered from electrophysiologically proven SUS, the most frequent ulnar nerve lesion. The male-female ratio was 1 : 2.6. In 58% of the cases the disease was right-sided, in 42% left-sided. The patients with SUS were younger than those with the carpal tunnel syndrome in the same patient group. The length of history ranged from weeks to over 10 years. At follow-up, 93 patients could be restudied. The follow-up examination was performed after healing or not earlier than 2 years after the initial examination. Spontaneous regression was observed in patients under the age of 40 and in those with a history of less than 6 months. Surgical treatment yielded the best results where the aetiology was known. Late paresis never receded without surgical displacement of the ulnar nerve. Where the aetiology is unknown, however, the present results of investigation call for caution with regard to surgical therapy.

30. The value of half-field stimulation in clinical VEP testing. - - A.M. Halliday (London, England)

VEP abnormalities may manifest themselves as amplitude, latency or wave form changes, or by changes in the topographical distribution of the response over the back of the head. The most useful feature of the characteristically delayed pattern response is the high incidence of delays in patients with demyelinating disease but no previous episode of visual impairment. Compressive lesions seem to be particularly liable to

10P produce distortions of the normal wave form of the response. More specific wave form changes are seen with central scotomata, where the normal positivity becomes replaced by a negative component of similar latency derived from paramacular stimulation, and also in toxic optic neuropathy and Leber's optic atrophy. Half-field stimulation has two main advantages in clinical testing: (a) limits of normal can be more tightly set as the variability of the topographical distribution for the whole-field response is considerably greater than for the separately measured half-field responses, (b) easier component identification in suspected demyelinating disease and similar situations. This helps to interpret apparently bifid major positivities and other variants of the so-called W wave form problem.

31. Topographical diagnosis of brain-stem lesions with brainstem evoked potentials (BAEPs). - - L. Ciganek, A. Smie~kova and M. Hrub~ (Bratislava) BAEPs registered and processed by means of an original and exact, fully automated, computer method were used for the topographical diagnosis of different kinds of brain-stem lesions in 77 patients. Pathological changes in the BAEP were automatically identified, comparing the patient's BAEP with a statistical model obtained from 60 healthy subjects. The criteria for the identification of each wave and for the interpretation of pathological findings are presented. The BAEP findings were in fairly good correlation with the symptomatology and with the results of imaging methods. The method appears to be very sensitive, reflecting functional rather than morphological changes. The most frequent were cases with brain-stem tumours and infarcts.

32. EEG maturation, prognosis and EEG evoked potential relationship in premature infants. - - Z. Vitova and L. Faladov[t (Prague) Serial and continuous EEG polygraph records were made in 30 premature infants (coital age 28-38 weeks). The EEG data were processed in visual and compressed power-spectral analyses. In 19 prematures, visual evoked potentials were also investigated. Neurological sequelae were found in 30% of the cases. Normal or slightly abnormal EEG cases invariably indicated a favourable outcome while EEG abnormalities were related to an uncertain (40%) or unfavourable (50%) development. Pathological EEGs were found in 43%. The following E E G patterns were associated with unfavourable prognosis: absence of E E G lability, reactivity or spatial organization, low-voltage tracing in R E M and n o n - R E M sleep, marked EEG immaturity, persistent multifocal spikes. Investigations of the neonate visual evoked potentials reliably detected even minor neurological sequelae but no differentiation between minor and major handicaps was possible. The simultaneous recording of spontaneous and evoked EEG activities proved to be of high prognostic significance.

SOCIETY P R O C E E D I N G S 33. Assessment of auditory brain-stem evoked potentials in the localization of brain-stem tumours in children. - - J. Kraus, L. Faladov~ Z. Vitov~t and M. Lehovsk¢ (Prague) Brain-stem auditory evoked potentials (BAEPs) were recorded in 10 children (aged 2 - 1 4 years) with posterior fossa tumours involving the cerebellum and brain-stem. All the neoplasms were confirmed by computerized tomography and at operation. Ipsilateral BAEPs were elicited by monaural click stimulation. Peak latencies, wave intervals, interpeak latencies, peak presence and amplitude were all calculated for BAEP assessment. The results were compared with normal reference values. Abnormalities consisted in increased latencies of components generated rostral to the lesion in all cases. In 4 cases with severe brain-stem involvement the affected components were missing. In 9 patients, BAEPs elicited by monaural stimulation of the ear ipsilateral to the lesion helped to localize lesions in the brain-stem correctly. In 8 cases, bilateral wave V abnormalities were found. The time between successive peaks appears to be the most sensitive parameter.

34. Changes in the Pi Pu segment of BAEPs and their diagnostic value. - - H. R6der and B. Freigang (Greifswald and Magdeburg, G.D.R.) The most frequent alterations in the auditory evoked brainstem potentials appear between waves I and II. Tumours of the cerebello-pontine angle lead to a more of less typical pattern. Similar configurations are rare in patients with multiple sclerosis or brain-stem tumours. Other diseases (vascular lesions, tumours of the cerebellum, traumatic brain-stem lesions, increased intracranial pressure) cause changes in the early segment of the BAEP which, as a rule, differ from the potential configuration produced by tumours of the cerebello-pontine angle. In very rare cases of acoustic neuroma, the tumour leads to atypical changes of the BAEP.

35. P3 wave during correct and intentionally false answers concerning visual stimuli. - - J. Radilov/i (Prague) A technique was used of computer-aided single evoked potential classification and separate averaging into two groups using the criterion of correct or intentionally false answers on the recognition of a certain number of visual stimuli simultaneously presented tachistoscopically (for 200 msec). The P3 wave was analysed. Healthy paid subjects counted the number of items presented with additional cues. In the subsequent presentation they intentionally lied and then again responded correctly. Depending on the 'intensity' of the lie the P3 was lower or higher than in correct answers. As the intensity of the lie increased the difference between the two groups became smaller. With very elaborate lies no differences in comparison with correct answers were found. The enhancement of the P3 amplitude may be due to equivalent neuronal activity enhancement either during intensive concentration on the correctness of the answer or on the elaboration of a complicated lie.

7th A N N U A L J O I N T M E E T I N G IN C Z E C H O S L O V A K I A 36. Evoked potential audiometry in neurologically affected children. - - A. Smiegkov/l and M. Hrnb~ (Bratislava) Brain-stem electric response audiometry (BERA) is used in clinical practice for auditory acuity estimation and as a means of neurological diagnosis. The aim was to establish normative BERA readings as criteria for (a) hearing ability tests in infants born with the risk of hereditary sensorineural hearing loss, conductive hearing loss, meningitis, intracerebral haemorrhage, and (b) the detection of the causes of retarded speech development in older uncooperative children. Auditory brain-stem responses were recorded in 30 healthy newborn infants and in 30 healthy toddlers aged up to 2 years. Any pathological signs of the BAEP were automatically identified in both groups when compared with a statistical model obtained from healthy newborns and older children using a fully automated computer method. The normative reference data were found useful for the diagnosis of BERA abnormalities in young children.

37. Short-latency visual potentials evoked by pattern stimulation. - - L. Lipovsk~ (Bratislava) Pattern reversal and pattern flash stimulation (1 Hz) elicited oscillatory responses in a group of 13 healthy volunteers (aged 18-45 years). Checkerboard stimuli were of one square visual angle of 1.15 °, mean luminance 48.8 c d / m 2, contrast 80%. Five oscillator 3 W shaped waves of very small amplitude (2-3 ~V peak to peak) and lasting 3 - 6 msec occurred, though only in the high frequency filtered bandpass of 50-2000 Hz. The latency of these complex oscillatory waves was 14.5-31.0 msec on pattern reversal stimulation, and 7,1-18.7 msec on pattern flash stimulation. The oscillatory wave complex spread all over the scalp area and exhibited the same latency. It was recorded from the scalp midline (infraorbital, Fpz, Fz, Cz, Oz) electrodes to the ear. There was very little individual variability. No such oscillatory, waves occurred when diffuse light flashes were used. The characteristics of this new complex of oscillatory waves observed suggest that they originate in the subcortical structures of the visual pathway.

38. Spinal somatosensory evoked potentials. The value of the method for localizing lesions in the central and peripheral nervous systems. - - D. Bartko and P. Varsik (Bratislava) The aim was to establish the possibilities and the value of spinal somatosensory evoked potentials (SSEPS) in central and peripheral nervous system lesions. SSEPs were investigated after median and anterior tibial nerve stimulation in 15 patients with polyneuropathy localized in the legs alone, in 10 patients with lumbar radiculopathy, and in 8 patients with spinal lesions. The control group consisted of 54 normal subjects of both sexes and the same age range. Responses to bilateral stimulation were recorded from Erb's point, from the C 5 and Thl2 spinous processes and from the scalp. The latency of the P9 and Ni3 waves was prolonged in all members of the polyneu-

11P ropathy group following median nerve stimulation. Signs of spinal lesions in the cervical and lumbar regions were recorded, too. Unilateral deformation of the 3-phase complexes was observed in the radiculopathy group. Decreases in the amplitude and prolongation of the latencies at the site of the lesion were observed in the group of patients with spinal lesion. SSEP changes may be indicative of spinal cord and peripheral lesions.

39. Spinal somatosensory evoked potentials in multiple sclerosis. - - P. Varsik and D. Bartko (Bratislava) Somatosensory evoked potentials (SEPs), both spinal and cortical, were recorded from the C 5 and Th12 spinous processes and from the scalp (C3-C 4 and C z using the 10-20 system). The median and anterior tibial nerves of both sides were stimulated. Fifteen patients with straightforward multiple sclerosis (MS) were compared with 52 normal control subjects of both sexes and similar age distribution (21 52 years). Furthermore, 6 patients with the spinal form of MS were examined using the Cracco et al. method (1980). The latencies and the amplitudes of the 3-phase complexes were analysed within 50 msec. After median and tibial nerve stimulation, unilateral or bilateral delayed latencies of the P9 and P14 waves were found in 70-80% of the MS cases. This suggests the true value of electrophysiological investigation in MS for localizing lesions in the spinal cord and the peripheral nervous system. In the spinal forms of MS, amplitudes and latencies were changed on the side of the spinal lesion. Cortical SEPs were affected similarly.

40. Visual and auditory brain-stem evoked potentials in comatose patients. - - M. Kond~, D. Bartko and S. Jan~o (Bratislava) Visual and auditory brain-stern evoked potentials were studied in 10 comatose patients with hemispheral or brain-stem lesions. The authors compared the predictive accuracy of evoked potentials with the clinical neurological signs and with the quantitative neurological deficit according to the BI score. The results suggested some electrophysiological-anatomical correlations between the evoked potential wave forms and CT or necropsy findings, as well as with the degree of consciousness deterioration (according to the Glasgow Coma Scale). Evoked potential tests in unconscious patients are an extension of clinical neurological examinations and may be useful in differentiating brain-stem from hemispheral lesions. Experience with assessments of the prognostic accuracy of evoked potentials continues to be gathered.

41. The clinical significance of periodic lateralized epileptiform discharges (PLEDs). - - P. Tariska, G. Gereby and K. Majtenyi (Budapest, Hungary) Electro-clinical data are discussed on 25 adults (collected between 1971 and 1983) with PLEDs in at least one of their

12I) EEG records marked by precisely identifiable aetiology. Extracercbral metabolic disturbances occurred in 16 cases, the subgroup of watershed ischaemia (n = 12) being by far the most benign category. Other than vascular conditions were as follows: intracerebral tumour (2), subdural haematoma (1), cerebral abscesses in aspergillosis (1), Jakob-Creutzfeldt disease (5). In 2 Jakob-Creutzfeldt cases the PLEDs remained unilateral while in 3 the earlier lateralized pattern subsequently became generalized. The neuropathological picture ( n - 1 1 ) was not uniform. In cerebrovascular cases (4) infarcts of variou~ ages were characteristic of the same supplying territory or watershed zone; in Jakob-Creutzfeldt disease (5) the marked astmcytosis, cortical and subcortical spongy state may favour the development of periodic activities. Considering the electroclinical differences between the aetiological categories it would be useful to pay attention to the different aetiological subgroups.

42. Diagnostic problems in incipient myasthenia gravis (MG). - - P. Spalek and S. Hupka (Bratislava) The diagnosis of incipient M G is often difficult to confirm, especially in mild and atypical forms. Stapedius muscle contraction can be measured with an electro-acoustic impedance bridge. Using a Peters AP 61 set the diagnostic significance of stapedius tel'lexometry was tested in 20 patients with incipient M G and compared with the results of repeated nerve stimulation. Stapedius reflex fatigue was found in 17 patients. After prostigmine, fatiguability normalized in 8 and improved in 9 patients. With repeated brachial plexus stimulation, an ulnar and femoral nerve evoked potential E M G decrement was noted in 15 patients (deltoid muscle - 13, abductor digiti minimi - 5, rectus femoris - 8 ) . The results suggest that neuromuscular junctions in the stapedius muscle are particularly predisposed to be affected by MG. Diagnostically significant positive findings were seen in 4 patients with localized ocular and oculobulbar forms of M G who had normal findings in extremity muscles when their neuromuscular transmission was tested with repeated nerve stimulation. In addition, stapedius reflexometry is easy to realize, painless, and requires only little cooperation from the patient.

43. Rare EEG findings in occupational health investigations. - H.J. Laux (Berlin, G.D.R.) Twenty-nine out of a total of 492 EEG records were selected for closer scrutiny for purposes of occupational medicine. In each of the 29 cases singled out there were artifacts or errors, eliminated by control registration, including EEG spectral analysis. In 11 cases it proved impossible to correlate these rare EEG findings with any particular clinical disturbance. Also, the investigated subjects, subsequently included in the healthy control group, reported "feeling well.' Some more examples of non-correlatable EEG abnormalities are demonstrated and discussed, such as the phenomenon of diminished or absent

SOCI E'IY P R O C E E D I N G S hyperventilation reaction. Nevertheless, rare EEG findings ought to be interpreted with some caution.

44. The influence of psychic and physical performances on paroxysmal activity. A telemetric study. - - (~. Hrazdira, M. Svejdova, I. Rektor and V. Ruta (Brno) Telemetric EEG testing was performed in 40 adults with different types of epilepsy. Pathological paroxysmal activity (PPA) was present in 27, in the rest (13) it has been diagnosed not long before but had disappeared by the time of testing. The test started with the subjects at rest in the lying position with eyes closed. Then records were made in different situations: eyes open, sitting, walking, exercise with a dumb-bell in the right and left hands, and in the course of two psychological tests (to examine attention). The records were evaluated visually. In the 27 PPA patients, mere opening of the eyes produced a significant depression of the discharge rate. The changes in the other test situations differed non-significantly from the starting situation (lying, eyes closed) though they were significantly different from the resting record with the eyes open. The simple opening of the eyes proved to be the most effective factor in PPA depression. The other performances influenced that depression to a different degree but not significantly with regard to the starting situation. In a group of 13 patients no discharge appeared throughout the testing session.

45. Quantification of diurnal sleepiness in patients with narcolepsy and hypersomnia. - - B. Roth, S. Nev~imalov~, K. Sonka and P. Do~ekal (Prague) The authors propose a method of quantitative evaluation of excessive diurnal sleepiness. They perform in each patient a 45 min polygraphic examination to evaluate the occurrence of manifestations of wakefulness as well as all forms and stages of sleep, together with their latencies and total durations. In this way it is possible to describe the patients' sleepiness both quantitatively and qualitatively. The above test was used in the study of 8 healthy controls, 8 patients with narcolepsycataplexy, 8 patients with idiopathic hypersomnia and 8 patients suffering from the syndrome of hypersomnia with sleep apnea. All 3 groups of patients differed significantly from the control group, showing deeper sleep stages of shorter latency and longer total duration. The 3 groups of patients differed also in some aspects from each other.

46. The microstructure of night sleep in arousal disorders. Somnambulism and night terrors. - - P. Halb.sz, J. Ujszaszi and J. Gadoros (Budapest, Hungary) Nine young adult somnambulists and night terror patients had their night sleep investigated and compared with 8 agematched controls. Unlike the sleep stage distribution, the patients' night sleep microstructure was found to be highly char-

7th A N N U A L JOINT MEETING IN CZECHOSLOVAKIA acteristic. The microarousals were classified as MA with and without synchronization. MA with synchronization (SMA) was defined as preceded by K complexes or groups of slow waves. While the peak of the MA count was found in REM and intermediate sleep stages, SMA appeared in NREM stages with a peak in stage 2. The amount of SMA in NREM sleep was significantly higher in the patients' group. The greatest differences appeared in stage 2 where the SMA count in the patients was more than 3 times higher than that in the controls. The SMA values plotted against the waking times in sleep revealed an inverse relationship between the amount of SMA and the time spent awake during night sleep. The microdynamics of somnambulists and night terror patients (arousal disorders) showed a characteristic increase in a special type of microarousal which could be regarded as a microevent of dissociated arousal, a central characteristic feature of the arousal disorders.

47. Thresholds of perception in relation to the type of ongoing EEG activity. - - Z. Bohdanecky, V. Bo~kov and T. Radii (Prague) The route of perception in brain information processing is believed to be related to EEG alpha activity, one of the most prominent forms of human brain work. The authors' experiments were designed to determine whether acoustic and visual thresholds were dependent on the EEG alpha or non-alpha epochs, respectively. Fifty epochs of either activity lasting 300 msec were required for threshold estimation. A 1000 Hz tone lasting 20 msec or a dim light spot of equal duration served as stimuli, presented by means of the computer-aided staircase method. Significantly lower values for acoustic thresholds were observed during non-alpha periods with the differences reaching in some subjects almost 3 dB. The values of visual thresholds for both epochs, however, exhibited no difference.

48. Statistical behaviour of the vocabulary of neuronal activity,. - - D. Svorad (Bratislava) A sample of unit activity can be hypothesized as a neuronal text, i.e., a train of symbols (units) generated according to certain rules from the stock of the symbols (vocabulary) which, in the case of bursting neuronal activity, consists of 2 to n intraburst interspike intervals. The vocabulary of 30 sec samples of extracellularly recorded unit activity (its bursting) of the rat striatum was analysed off-line on a PDP 11-40 computer, using the characteristic (introduced in statistical linguistics by Udny Yule and Herdan)

13P item) occurrence, that is, frequency of use. in a given literary text or author, It appeared that whereas neither the arithmetic mean nor the standard deviation can he used as a characteristic of the neuronal text, since they significantly vary with the number of occurrences and with the size of vocabulary, K remains constant (e.g,. in a neuronal sample K = 186.2 when N 689, V = 151, and K = 186.4 when N 225, V - 94: N = the size of text, V - the size of w~cabulary).

49. Interhemispheric asynchruny o f the scalp EEG lateral derivation as a valid parameter of normality in time series of EEG curves. - - F. Krej~i and S.E. Petranek (Prague) Precise simultaneously registered EEG curves from the lateral areas of the scalp, i.e., the electrodes Fp, Flat, Treed and Tpost are evidently characterized by asynchrony as documented in the authors' poster. This phenomenon brought out by special technology is of great importance as a parameter of normality in connection with the simultaneous synchrony in the leads from the medial parts (electrodes F3-4, C3-4, P3-4 O1-2). In abnormal cases, these parameters undergo characteristic changes in relation to the degree of the pathological process present and its development in time.

50. Transcerebral electrostimulation (TE). - (Prague)

S.E. Petr~mek

Ten healthy volunteers were investigated in a blind test involving a 2 h application of the Electroson-4T machine (current pulses 0.5 msec, f = 90 Hz). Sleep polygraphy was carried out by means of interval recording. The difference in sleep indices was non-significant and so was the shift to the more superficial stages. Neither REM nor the quantity' of dreaming as reported by the volunteers showed any change although significant variations occurred in some individuals. One woman had to be excluded from the test group because of severe migraine-like cephalalgia repeatedly provoked as the current was switched on. In another patient suffering from insomnia, epileptic abnormality in the EEG was found after 10 applications of TE. The observations are of considerable importance for their clinical implications. The problem of TE contraindications continues to be dealth with, and the possibility of epileptic paroxysms aroused by kindling is under study.

51. The combined effect on hippocampal theta activity of reticular stimulation and cholinergic system drug influence. - - P. Hlavi~ka and T. Radii (Prague)

s

K ~ y ' p~2n~ r-I

where n is the number of different units occurring with the frequency r, and p~ stands for the probability of r. Yule's characteristic is a constant of the word count distribution epitumizmg the relation between vocabulary and word (unit,

The influence of physostigmine (P -- 0.5 m g / k g ) and atropine (Atr - - 3 m g / k g ) on hippocampal theta activity (TA) was studied in rats with implanted electrodes, Periods of reticular formation stimulation (8 sec) were repeated 10 times at different voltage levels. Measurements were performed before, and 10 and 60 rain after drug (or saline) administration. After

14P Atr only brief epochs of TA were observed with increased frequency. P induced increasing incidence of TA ( P < 0.05), and its average frequency decreased ( P < 0.1) when compared with electrical stimulation alone or with the frequency of spontaneous TA. The effect of reticular stimulation and P did not fit the 'additive' model any more than that of reticular stimulation and Atr tallied with the 'subtractive' one.

52. Electrocorticographic changes induced by 3-mercaptopropionic acid and bicuculline in young rats. - - A. Zouhar and P. Mareg (Brno and Prague)

The effect of 3-mercaptopropionic acid (3-MPA, a G A B A synthesis inhibitor) and bicuculline (Bic, a receptor GABA antagonist) was studied in acute experiments in 81 rats aged 7, 12 or 18 days. Both drugs were injected intraperitoneally. 3-MPA induced spikes in the frontal regions as the first change in all age groups. The spikes increased in amplitude as well as in incidence, and generalized paroxysmal activity started from the continuous localized spike (or sharp wave) activity. The first signs of Bic action were similar to those following 3-MPA. As for the localization of the first ECoG signs of action the difference between 3-MPA (spikes in the frontal region) and Bic (theta waves occipitally) seen in adult rats failed to appear in rats aged 7, 12 or 18 days. Failure to induce occipital changes was due to the occipital region immaturity.

53, Behavioural correlate of rhythmic metrazol activi~' - - a model of human absences. - - R. Schickerova, P. Mareg and S. Trojan (Prague)

There is lack of an adequate animal model of h u m a n primary generalized seizures of the absence type. We propose as a model rhythmic metrazol activity (RMA), i.e., periods of spike-and-wave rhythm appearing after subconvulsive doses of m e t r ~ o l accompanied by locomotor arrest and minute jerks of head musculature. In the present experiment we study the interaction of R M A with a motivated behaviour. Adult rats with chronically implanted electrodes were trained to lick water from a narrow tube. Before each experimental session (either control or after one of the two doses of metrazol) they did not have access to water for 40 h. Under control conditions thirsty rats licked water continuously for at least 2 min. After metrazol injection (25 or 50 m g / k g s.c.) the behaviour of the animals depended on the ECoG pattern. At the beginning before the appearance of R M A the rats licked water but slowly and only for some seconds. Similar behaviour was observed when R M A appeared in restricted regions of the cortex Generalized episodes of RMA always abruptly stopped licking. Licking was completely blocked if approximately one third of the record was filled with RMA. These results confirm the adequacy of our model.

SOCIETY P R O C E E D I N G S 54. Influence of dipropylacetate and ethosuximide on self-sustained after-discharges (SSADs) elicited by electrical stimulation of subcortical structures in rats under chronic conditions. - - L. Chocholovii (Prague)

In freely moving rats rhythmic electrical stimulation (4 -16 V, 9 Hz, 20 sec) was repeated 10 times in control experiment and after the drug administration (ethosuximide 125 m g / k g i.p., dipropylacetate 200 m g / k g i.p.). Hippocampal stimulation elicited SSADs in 85%, 79% of them being biphasic (recurrent rSSAD). They were characterized by serrated waves and immobility of the animal. Thalamic stimulation elicited 77~ of SSADs (58% of rSSADs), formed by spike-wave ,activity and partial clonic jerks. Ethosuximide did not influence the incidence of SSADs or of rSSADs, or the type and duration of both thalamic and hippocampal after-discharges. Dipropylacetate decreased significantly the incidence of hippocampal SSADs and rSSADs, and reduced the incidence of thalamic SSADs during the 2nd h of its action, Neither the electrographic nor the behavioural character of the SSAD and the rSSAD was altered qualitatively. The influence of dipropylacetate on hippocampal SSADs corresponds with the clinical effect of the drug on h u m a n partial seizures with complex symptomatology. The poor effect of ethosuximide on thalamic SSADs brings some doubts about the possible reliability of thalamic after-discharge as a model of h u m a n thalamo-cortical absences. 55. The genesis of the rhythmic EEG activi~" elicited by metrazol in rats. - - M. Pohl and P. Mare,~ (Prague)

Metrazol is a convulsant drug commonly used in experimental epileptology. Dose-dependent EEG changes could be induced by metrazol: (1) rhythmic metrazol activity (RMA), i.e., periods of spike-and-wave rhythm; (2) isolated spikes: (3) ictal activity formed by spike-and-wave rhythm lasting tens of seconds. The role of the brain-stem structures, thalamus, hippocampus and cortex in the genesis of rhythmic activities, especially RMA, was studied, using surgical as well as functional ablations. Cerveau isolb preparations (with intercollicular brain-stem section) generated R M A but the incidence of spike-and-wave ictal activity was depressed. Another type of ictal activity (serrated waves) frequently appeared in these preparations. Thalamic spreading depression abolished the appearance of R M A in the ipsilateral cortex. Cortical spreading depression blocked R M A in ipsilateral thalamus. Rhythmic activity of completely different shape remained in the hippocampus under the conditions of cortical spreading depression. The importance of the thalamo-cortical system for the genesis of generalized R M A is stressed. The hippocampus is able to produce a different kind of rhythmic activity, lctal activities induced by metrazol could not be studied by means of spreading depression.