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Schweizerische vereinigung für elektroenzephalographie und klinische neurophysiologie
96P
Electroencephalography and Clinical Neurophysiology, 1981, 52: 96P--98P Elsevier/North-Holland Scientific Publishers, Ltd.
Society proceedings SCHWEIZERISCHE VEREINIGUNG KLINISCHE NEUROPHYSIOLOGIE
F()R ELEKTROENZEPHALOGRAPHIE
UND
Interlaken, May 1--2, 1981
President: Prof. G. DUMERMUTH University Children's Hospital, 8032 Zurich (Switzerland) (Accepted for publication: July 24, 1981)
1. EEG changes before and after cranioplasty.-A. Hecker, D. Stula and G. Scollo-Lavizzari (Basle) Yamaura et al. reported that patients with decompressive craniectomy who developed the 'syndrome of the sinking skin flap', showed significant improvement of the neurological deficits and EEG changes following cranioplasty. In our study on 20 patients we could confirm that there was clinical improvement in 60%, an EEG improvement in 55%, an EEG deterioration in 25% and an unchanged EEG in 20%. The physiopathological basis for these improvements is the normalization of the cerebral structures, which can be demonstrated with computerized tomography.
2. Transient EEG patterns during sleep in healthy newborns. -- A. Statz and G. Dumermuth (Zurich) Twenty-four healthy full-term newborns underwent polygraphic recording of EEG, EMG, EOG, ECG and abdominal and thoracic respiration during day-time sleep. The alpha and beta activity patterns, spikes and sharp waves and 'frontal sharp transients' were visually evaluated and quantified. They showed a high degree of variability in terms of frequency and morphology. Apart from individual differences these depended on the state of sleep. Rhythmic alpha and beta activity are not very prominent. They are found in all states of sleep. Rhythmic alpha activity appears only as scattered waves and interrupted sequences. Their duration varies from 1 to 5 sec. Beta activity is found in spindle-like formations. In a few cases it appears in the form of the 'delta brush' pattern. Spikes/sharp waves are sporadic in appearance, non-repetitive in nature and mostly multifocal, with
parietal predominance. They are more frequent in quiet sleep (1/2--3 min on average) than in REM sleep (1/18 min) and are rare in transitional states of sleep (2/h). 'Frontal sharp transients' occur most frequently in quiet sleep. Often they appear only unilaterally. Their voltage maximum is frontal, frontotemporal or precentral. They are more frequent in REM sleep after wakefulness than after quiet sleep.
3. Prognostic value of the inactive and paroxysmal EEG in prematures and full-term b a b i e s . - P.A. Despland (Lausanne) In premature or full-term babies, EEGs recorded during the first 24 h of life may give useful information for predicting a severely unfavourable outcome. If the favourable prognostic significance of a normal EEG is clear, criteria of normality are still difficult for prematures. The present study is a follow-up among 1525 babies during 1971 and 1980 for some specific tracings with an unfavourable prognostic significance for both newborns and prematures, such as inactive and paroxysmal tracings. Among 82 inactive and paroxysmal EEGs, only 15 were alive and 3 with no sequelae. The prognostic value of the neonatal EEG also depends upon the pathological EEG criteria and the time of the first recording, since inactive and paroxysmal EEGs disappear in general during the 2nd week.
4. EEG findings in acute intermittent porphyria and a Schwartz--Bartter syndrome ( S I A D H ) . - - H . P . Ackermann and G. Scollo-Lavizzari (Basle) A 24-year-old female with gastrointestinal disturbances, nausea and vomiting, had a convulsion with loss of urine and bitten lips on the 5th day of hospitalization. A significant decrease of sodium and
0013-4649/81/0000--0000/$02.50 © 1981 Elsevier/North-Holland Scientific Publishers, Ltd.
SWISS E E G S O C I E T Y p o t a s s i u m levels a n d l o w e r e d o s m o l a l i t y o f t h e s e r u m as well as u r i n a r y h y p e r o s m o l a l i t y p e r m i t t e d t h e diagnosis o f t h e so~called s y n d r o m e o f i n a p p r o p r i a t e antid i u r e t i c h o r m o n e release ( S I A D H , d e s c r i b e d b y S c h w a r t z - - B a r t t e r ) , o f u n k n o w n aetiology. Twice s h o r t tests for p o r p h y r i a were negative; t h e n t h e elevated p o r p h y r i n p r e c u r s o r s c o l l e c t e d in 24 h u r i n e i n d i c a t e d t h e e x i s t e n c e of a n a c u t e i n t e r m i t t e n t porphyria. A clinical f o l l o w - u p a n d i m p r o v e m e n t were d e m o n s t r a t e d b y t h e E E G findings. Since a n i m a l exp e r i m e n t s a n d p a t h o h i s t o l o g i c a l findings i n d i c a t e t h a t p o r p h y r i n m e t a b o l i t e s s u c h as d e l t a - a m i n o laevulinic acid a n d p o r p h o b i l i n o g e n m a y i n f l u e n c e i n h i b i t o r y a n d n e u r o s e c r e t o r y s t r u c t u r e s in c e n t r a l n e r v o u s tissue a n d i n t e r f e r e w i t h G A B A , c e r e b r a l h y p e r e x c i t a b i l ity as well as d i s t u r b a n c e o f e l e c t r o l y t e s m a y be explained. F i n a l l y , t h e q u e s t i o n o f w h e t h e r t h e E E G c h a n g e s are d u e t o t h e significant e l e c t r o l y t e disturb a n c e s or are typical signs o f a c u t e i n t e r m i t t e n t porp h y r i a ( A I P ) is discussed.
5. T o p o g r a p h y o f m o n o - and binocularly evoked potential fields using upper and lower hemiretinal stimuli. -- E. Adachi-Usami, F. Zafiridis and D. Lehmann ( Z u r i c h ) Monocularly and binocularly evoked potentials (using 56 m i n or 14 rain checks, 16 ° target, 2/sec reversal) were r e c o r d e d f r o m 4 m i d l i n e e l e c t r o d e s ( f r o m i n i o n to 7.5 c m a b o v e ) vs. a c o m m o n a n t e r i o r r e f e r e n c e in 14 n o r m a l s u b j e c t s . A m p l i t u d e profiles of t h e e v o k e d p o t e n t i a l fields were c o n s t r u c t e d at t h e latency of maximal potential difference between any 2 o f t h e e l e c t r o d e s , b e t w e e n 85 a n d 1 3 0 msec. M e a n profiles were c o m p u t e d over subjects. F o r u p p e r h e m i r e t i n a l s t i m u l i ( 5 6 a n d 14 m i n c h e c k s ) t h e maximal m e a n profile a m p l i t u d e for b i n o c u l a r r e s p o n s e s was significantly m o r e a n t e r i o r t h a n for m o n o c u l a r responses, w h e r e a s an i n v e r t e d l o c a t i o n d i f f e r e n c e was o b s e r v e d for l o w e r h e m i r e t i n a l s t i m u l i (i.e. b i n o c ular m a x i m a m o r e p o s t e r i o r t h a n m o n o c u l a r ) . We c o n c l u d e t h a t b i n o c u l a r i n p u t is p r o c e s s e d b y a cortical n e u r a l p o p u l a t i o n at least partially d i f f e r e n t f r o m t h a t for m o n o c u l a r i n p u t . T h e o b s e r v e d localizat i o n s agree w i t h t h e a s s u m p t i o n t h a t n e u r o n s w h i c h r e s p o n d exclusively t o b i n o c u l a r s t i m u l i are m o r e f r e q u e n t in h i g h e r t h a n l o w e r o r d e r visual areas, a n d / or t h a t these exclusively b i n o c u l a r n e u r o n s m o r e o f t e n have p e r i p h e r a l t h a n c e n t r a l r e c e p t i v e fields.
6. Displacement o f scalp field maxima evoked by upper and lower hemiretinal stimuli: digital bandpass f i l t e r i n g . - D. Lehmann, R. Miiller and E. Adachi-Usami (Zurich)
97P C h e c k e r b o a r d reversal e v o k e d average field distrib u t i o n s s i m u l t a n e o u s l y s a m p l e d w i t h 4 5 c h a n n e l s exh i b i t an o c c i p i t a l field p e a k s h o w i n g m a x i m a l slope s t e e p n e s s at a b o u t 1 0 0 msec l a t e n c y for u p p e r , a n d at a b o u t 1 1 0 msec for l o w e r h e m i r e t i n a l s t i m u l i . Typically, t h e s e field peaks d e v e l o p a n d fade a w a y b e t w e e n 80 a n d 130 msec l a t e n c y in t h e m i d l i n e w i t h o u t c h a n g e o f l o c a t i o n , at a m o r e a n t e r i o r posit i o n for u p p e r t h a n l o w e r h e m i r e t i n a l stimuli. Occasionally, h o w e v e r , c h a n g e s of p e a k l o c a t i o n over t i m e are o b s e r v e d . F o r e x a m p l e , in s o m e s u b j e c t s t h e u p p e r h e m i retinal r e s p o n s e s s h o w e d p e a k d i s p l a c e m e n t s between 80 a n d 1 2 0 msec over a 6 c m d i s t a n c e in an a n t e r o posterior direction, whereas the lower hemiretinal r e s p o n s e s s h o w e d d i s p l a c e m e n t in t h e o p p o s i t e direct i o n b e t w e e n 90 a n d 130 msec. Band-pass filtering a n d s u b s e q u e n t m a p p i n g o f t h e m u l t i c h a n n e l field d a t a i n t o low ( 2 - - 8 Hz) a n d h i g h e r ( 8 - - 2 6 Hz) freq u e n c y c o m p o n e n t s revealed d i f f e r e n t p e a k o r b i t s for t h e d i f f e r e n t f r e q u e n c y b a n d s , suggesting several n e u r a l g e n e r a t o r m e c h a n i s m s for t h e e v o k e d fields. Differing peak latencies s o m e t i m e s also are observed in c o n v e n t i o n a l l y r e c o r d e d averaged p o t e n t i a l s f r o m few e l e c t r o d e s against a c o m m o n r e f e r e n c e . Baseline-to-peak m e a s u r e m e n t s d e t e r m i n e t h e c h a n n e l which detects the potential of maximal amplitude, a n d w h i c h t h e r e f o r e m u s t b e used for t h e m e a s u r e m e n t o f l a t e n c y a n d l o c a t i o n o f t h e c o m p o n e n t . If there were c h a n g e s o f p e a k l o c a t i o n over t i m e , a n d if p o t e n t i a l s f r o m o n l y 1 c h a n n e l were m e a s u r e d , latencies of the component might erroneously be j u d g e d as t o o s h o r t or t o o long.
7. Intracortical events during epileptic seizures and c o r t i c a l s t r u c t u r e . - - H. P e t s c h e ( V i e n n a , A u s t r i a ) E p i l e p t i c seizures, elicited b y t h e local a p p l i c a t i o n of penicillin t o t h e visual area o f t h e r a b b i t , h a v e b e e n r e c o r d e d b y i n t r a c o r t i c a l 16-fold semi-microelect r o d e s ( c o n t a c t size: 1 0 × 10 p m 2 ; d i s t a n c e s : 150 p m ) . Spikes a n d seizures have b e e n r e c o r d e d o n a 16c h a n n e l tape r e c o r d e r a n d e v a l u a t e d off-line. S p e c t r a l analyses as well as t h e i n t r a c o r t i c a l d i s t r i b u t i o n o f c u r r e n t s o u r c e s a n d sinks h a v e b e e n c a l c u l a t e d c o n t i n u o u s l y a n d r e p r e s e n t e d t o p o g r a p h i c a l l y as c o n t o u r line d i a g r a m s (X axis: t i m e ; Y axis: cortical d i a m eter). S p o n t a n e o u s activities c o r r e s p o n d largely t o a dipole b e t w e e n layers II a n d V w i t h a z o n e o f minimal activity at t h e u p p e r b o r d e r of layer IV. In c o n t r a s t t o this, seizure p a t t e r n s e x h i b i t a v a r y i n g spectral b e h a v i o u r , m o s t l y w i t h a p o w e r m a x i m u m in layer V w i t h m o r e or less steep g r a d i e n t s t o w a r d s t h e cortical surface a n d t h e w h i t e m a t t e r . P h a s e e s t i m a t e s d e m o n s t r a t e in m o s t cases t h a t t h e d e e p e s t activities are t h e leading ones.
98P
SOCIETY PROCEEDINGS
This finding is due to an interaction of 2 or more current sinks and sources in different cortical layers, with different strengths and latencies. There are preferred locations for sinks and sources; the frequency of the seizure pattern at the m o m e n t depends on their number, intensity, position and latency. During tonic patterns, these parameters remain almost equal whereas, in clonic patterns, they undergo considerable changes.
8. Stereo-electroencephalographic
correlates
of
m o t o r seizures. - - H.G. Wieser (Zurich)
It is generally agreed that surface EEG findings in focal motor seizures are often ambiguous. With the aid of combined surface and depth recording (SEEG exploration), which we perform on drug-resistant epileptics with a view to surgical intervention, we find a substantially increased correlation between clinical ictal phenomena and the bioelectric seizure discharges or epileptic paroxysms, provided that a systematic exploration of the m o t o r cortex can be done. Selected examples of SEEG-explored patients with focal m o t o r seizures illustrate this improved correlation with respect to chronotopographical and formal aspects. The presented cases also illustrate specific features of the bioelectric activity of the Rolandic and supplementary motor areas, especially the changes of Rolandic EEG activity produced by voluntary movements. Results of intracerebral stimulation of the Rolandic and supplementary m o to r areas are discussed with respect to the somatotopic organization.
9. Changes of correlation of intracerebral activity of different brain areas during epileptic s e i z u r e s . H.P. Meles, T.M. Darcey and H.G. Wieser (Zurich) From simultaneous measurements of intracortical activity at 32 sites we calculated the correlation coef-
ficients of all observation pairs. We compared these similarities with the anatomical distances to detect coupling of distant, and independence of adjacent, activities. We interpret the dynamic changes of the correlation matrix before, during and after partial seizures with complex symptomatology as varying conductivity of the neural pathways. At the onset and at the end of seizures we observed a 3-fold stepwise change of the correlation matrix. Brain regions exhibiting rather independent activity were preictally located frontally, during the transition period centrally and temporally, and predominantly mediobasaltemporal during the seizure.
10. Posttraumatic spike-wave-variant status. A case r e p o r t . - E. Pavlincova, R. Gugger and K. Karbowski (Berne) A 10.5-year-old boy showed a clinical picture of somnolence, headache and vomiting 1 day after a head injury. The EEG pattern was one of a continuous generalized slow spike-wave activity, accentuated in the frontal region. After an i.v. injection of diazepare this pattern disappeared and a delta focus in the left temporal region was seen. The CT scan showed a left temporal basic epidural hematoma, which was surgically drained. The boy was treated with valproate and had no seizures half a year later although, at that time, irregular 3 c/sec spike-wave activity and repetitive slow waves, asynchronous in the frontal and posterior regions of the right side, were found. The EEG of the boy's parents, brothers and sisters showed no epileptic pattern. Because of the personal and familial history of the boy (twin B, breech delivery, one unclear syncope, seizures and debility of the relatives of the father) there existed a suspicion of cerebral hyperexcitability prior to the head injury. The latter may have been sufficient to trigger such a phenomenon.
Electroencephalography and Clinical Neurophysiology, 1981, 52: 96P--98P Elsevier/North-Holland Scientific Publishers, Ltd.
Society proceedings SCHWEIZERISCHE VEREINIGUNG KLINISCHE NEUROPHYSIOLOGIE
F()R ELEKTROENZEPHALOGRAPHIE
UND
Interlaken, May 1--2, 1981
President: Prof. G. DUMERMUTH University Children's Hospital, 8032 Zurich (Switzerland) (Accepted for publication: July 24, 1981)
1. EEG changes before and after cranioplasty.-A. Hecker, D. Stula and G. Scollo-Lavizzari (Basle) Yamaura et al. reported that patients with decompressive craniectomy who developed the 'syndrome of the sinking skin flap', showed significant improvement of the neurological deficits and EEG changes following cranioplasty. In our study on 20 patients we could confirm that there was clinical improvement in 60%, an EEG improvement in 55%, an EEG deterioration in 25% and an unchanged EEG in 20%. The physiopathological basis for these improvements is the normalization of the cerebral structures, which can be demonstrated with computerized tomography.
2. Transient EEG patterns during sleep in healthy newborns. -- A. Statz and G. Dumermuth (Zurich) Twenty-four healthy full-term newborns underwent polygraphic recording of EEG, EMG, EOG, ECG and abdominal and thoracic respiration during day-time sleep. The alpha and beta activity patterns, spikes and sharp waves and 'frontal sharp transients' were visually evaluated and quantified. They showed a high degree of variability in terms of frequency and morphology. Apart from individual differences these depended on the state of sleep. Rhythmic alpha and beta activity are not very prominent. They are found in all states of sleep. Rhythmic alpha activity appears only as scattered waves and interrupted sequences. Their duration varies from 1 to 5 sec. Beta activity is found in spindle-like formations. In a few cases it appears in the form of the 'delta brush' pattern. Spikes/sharp waves are sporadic in appearance, non-repetitive in nature and mostly multifocal, with
parietal predominance. They are more frequent in quiet sleep (1/2--3 min on average) than in REM sleep (1/18 min) and are rare in transitional states of sleep (2/h). 'Frontal sharp transients' occur most frequently in quiet sleep. Often they appear only unilaterally. Their voltage maximum is frontal, frontotemporal or precentral. They are more frequent in REM sleep after wakefulness than after quiet sleep.
3. Prognostic value of the inactive and paroxysmal EEG in prematures and full-term b a b i e s . - P.A. Despland (Lausanne) In premature or full-term babies, EEGs recorded during the first 24 h of life may give useful information for predicting a severely unfavourable outcome. If the favourable prognostic significance of a normal EEG is clear, criteria of normality are still difficult for prematures. The present study is a follow-up among 1525 babies during 1971 and 1980 for some specific tracings with an unfavourable prognostic significance for both newborns and prematures, such as inactive and paroxysmal tracings. Among 82 inactive and paroxysmal EEGs, only 15 were alive and 3 with no sequelae. The prognostic value of the neonatal EEG also depends upon the pathological EEG criteria and the time of the first recording, since inactive and paroxysmal EEGs disappear in general during the 2nd week.
4. EEG findings in acute intermittent porphyria and a Schwartz--Bartter syndrome ( S I A D H ) . - - H . P . Ackermann and G. Scollo-Lavizzari (Basle) A 24-year-old female with gastrointestinal disturbances, nausea and vomiting, had a convulsion with loss of urine and bitten lips on the 5th day of hospitalization. A significant decrease of sodium and
0013-4649/81/0000--0000/$02.50 © 1981 Elsevier/North-Holland Scientific Publishers, Ltd.
SWISS E E G S O C I E T Y p o t a s s i u m levels a n d l o w e r e d o s m o l a l i t y o f t h e s e r u m as well as u r i n a r y h y p e r o s m o l a l i t y p e r m i t t e d t h e diagnosis o f t h e so~called s y n d r o m e o f i n a p p r o p r i a t e antid i u r e t i c h o r m o n e release ( S I A D H , d e s c r i b e d b y S c h w a r t z - - B a r t t e r ) , o f u n k n o w n aetiology. Twice s h o r t tests for p o r p h y r i a were negative; t h e n t h e elevated p o r p h y r i n p r e c u r s o r s c o l l e c t e d in 24 h u r i n e i n d i c a t e d t h e e x i s t e n c e of a n a c u t e i n t e r m i t t e n t porphyria. A clinical f o l l o w - u p a n d i m p r o v e m e n t were d e m o n s t r a t e d b y t h e E E G findings. Since a n i m a l exp e r i m e n t s a n d p a t h o h i s t o l o g i c a l findings i n d i c a t e t h a t p o r p h y r i n m e t a b o l i t e s s u c h as d e l t a - a m i n o laevulinic acid a n d p o r p h o b i l i n o g e n m a y i n f l u e n c e i n h i b i t o r y a n d n e u r o s e c r e t o r y s t r u c t u r e s in c e n t r a l n e r v o u s tissue a n d i n t e r f e r e w i t h G A B A , c e r e b r a l h y p e r e x c i t a b i l ity as well as d i s t u r b a n c e o f e l e c t r o l y t e s m a y be explained. F i n a l l y , t h e q u e s t i o n o f w h e t h e r t h e E E G c h a n g e s are d u e t o t h e significant e l e c t r o l y t e disturb a n c e s or are typical signs o f a c u t e i n t e r m i t t e n t porp h y r i a ( A I P ) is discussed.
5. T o p o g r a p h y o f m o n o - and binocularly evoked potential fields using upper and lower hemiretinal stimuli. -- E. Adachi-Usami, F. Zafiridis and D. Lehmann ( Z u r i c h ) Monocularly and binocularly evoked potentials (using 56 m i n or 14 rain checks, 16 ° target, 2/sec reversal) were r e c o r d e d f r o m 4 m i d l i n e e l e c t r o d e s ( f r o m i n i o n to 7.5 c m a b o v e ) vs. a c o m m o n a n t e r i o r r e f e r e n c e in 14 n o r m a l s u b j e c t s . A m p l i t u d e profiles of t h e e v o k e d p o t e n t i a l fields were c o n s t r u c t e d at t h e latency of maximal potential difference between any 2 o f t h e e l e c t r o d e s , b e t w e e n 85 a n d 1 3 0 msec. M e a n profiles were c o m p u t e d over subjects. F o r u p p e r h e m i r e t i n a l s t i m u l i ( 5 6 a n d 14 m i n c h e c k s ) t h e maximal m e a n profile a m p l i t u d e for b i n o c u l a r r e s p o n s e s was significantly m o r e a n t e r i o r t h a n for m o n o c u l a r responses, w h e r e a s an i n v e r t e d l o c a t i o n d i f f e r e n c e was o b s e r v e d for l o w e r h e m i r e t i n a l s t i m u l i (i.e. b i n o c ular m a x i m a m o r e p o s t e r i o r t h a n m o n o c u l a r ) . We c o n c l u d e t h a t b i n o c u l a r i n p u t is p r o c e s s e d b y a cortical n e u r a l p o p u l a t i o n at least partially d i f f e r e n t f r o m t h a t for m o n o c u l a r i n p u t . T h e o b s e r v e d localizat i o n s agree w i t h t h e a s s u m p t i o n t h a t n e u r o n s w h i c h r e s p o n d exclusively t o b i n o c u l a r s t i m u l i are m o r e f r e q u e n t in h i g h e r t h a n l o w e r o r d e r visual areas, a n d / or t h a t these exclusively b i n o c u l a r n e u r o n s m o r e o f t e n have p e r i p h e r a l t h a n c e n t r a l r e c e p t i v e fields.
6. Displacement o f scalp field maxima evoked by upper and lower hemiretinal stimuli: digital bandpass f i l t e r i n g . - D. Lehmann, R. Miiller and E. Adachi-Usami (Zurich)
97P C h e c k e r b o a r d reversal e v o k e d average field distrib u t i o n s s i m u l t a n e o u s l y s a m p l e d w i t h 4 5 c h a n n e l s exh i b i t an o c c i p i t a l field p e a k s h o w i n g m a x i m a l slope s t e e p n e s s at a b o u t 1 0 0 msec l a t e n c y for u p p e r , a n d at a b o u t 1 1 0 msec for l o w e r h e m i r e t i n a l s t i m u l i . Typically, t h e s e field peaks d e v e l o p a n d fade a w a y b e t w e e n 80 a n d 130 msec l a t e n c y in t h e m i d l i n e w i t h o u t c h a n g e o f l o c a t i o n , at a m o r e a n t e r i o r posit i o n for u p p e r t h a n l o w e r h e m i r e t i n a l stimuli. Occasionally, h o w e v e r , c h a n g e s of p e a k l o c a t i o n over t i m e are o b s e r v e d . F o r e x a m p l e , in s o m e s u b j e c t s t h e u p p e r h e m i retinal r e s p o n s e s s h o w e d p e a k d i s p l a c e m e n t s between 80 a n d 1 2 0 msec over a 6 c m d i s t a n c e in an a n t e r o posterior direction, whereas the lower hemiretinal r e s p o n s e s s h o w e d d i s p l a c e m e n t in t h e o p p o s i t e direct i o n b e t w e e n 90 a n d 130 msec. Band-pass filtering a n d s u b s e q u e n t m a p p i n g o f t h e m u l t i c h a n n e l field d a t a i n t o low ( 2 - - 8 Hz) a n d h i g h e r ( 8 - - 2 6 Hz) freq u e n c y c o m p o n e n t s revealed d i f f e r e n t p e a k o r b i t s for t h e d i f f e r e n t f r e q u e n c y b a n d s , suggesting several n e u r a l g e n e r a t o r m e c h a n i s m s for t h e e v o k e d fields. Differing peak latencies s o m e t i m e s also are observed in c o n v e n t i o n a l l y r e c o r d e d averaged p o t e n t i a l s f r o m few e l e c t r o d e s against a c o m m o n r e f e r e n c e . Baseline-to-peak m e a s u r e m e n t s d e t e r m i n e t h e c h a n n e l which detects the potential of maximal amplitude, a n d w h i c h t h e r e f o r e m u s t b e used for t h e m e a s u r e m e n t o f l a t e n c y a n d l o c a t i o n o f t h e c o m p o n e n t . If there were c h a n g e s o f p e a k l o c a t i o n over t i m e , a n d if p o t e n t i a l s f r o m o n l y 1 c h a n n e l were m e a s u r e d , latencies of the component might erroneously be j u d g e d as t o o s h o r t or t o o long.
7. Intracortical events during epileptic seizures and c o r t i c a l s t r u c t u r e . - - H. P e t s c h e ( V i e n n a , A u s t r i a ) E p i l e p t i c seizures, elicited b y t h e local a p p l i c a t i o n of penicillin t o t h e visual area o f t h e r a b b i t , h a v e b e e n r e c o r d e d b y i n t r a c o r t i c a l 16-fold semi-microelect r o d e s ( c o n t a c t size: 1 0 × 10 p m 2 ; d i s t a n c e s : 150 p m ) . Spikes a n d seizures have b e e n r e c o r d e d o n a 16c h a n n e l tape r e c o r d e r a n d e v a l u a t e d off-line. S p e c t r a l analyses as well as t h e i n t r a c o r t i c a l d i s t r i b u t i o n o f c u r r e n t s o u r c e s a n d sinks h a v e b e e n c a l c u l a t e d c o n t i n u o u s l y a n d r e p r e s e n t e d t o p o g r a p h i c a l l y as c o n t o u r line d i a g r a m s (X axis: t i m e ; Y axis: cortical d i a m eter). S p o n t a n e o u s activities c o r r e s p o n d largely t o a dipole b e t w e e n layers II a n d V w i t h a z o n e o f minimal activity at t h e u p p e r b o r d e r of layer IV. In c o n t r a s t t o this, seizure p a t t e r n s e x h i b i t a v a r y i n g spectral b e h a v i o u r , m o s t l y w i t h a p o w e r m a x i m u m in layer V w i t h m o r e or less steep g r a d i e n t s t o w a r d s t h e cortical surface a n d t h e w h i t e m a t t e r . P h a s e e s t i m a t e s d e m o n s t r a t e in m o s t cases t h a t t h e d e e p e s t activities are t h e leading ones.
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SOCIETY PROCEEDINGS
This finding is due to an interaction of 2 or more current sinks and sources in different cortical layers, with different strengths and latencies. There are preferred locations for sinks and sources; the frequency of the seizure pattern at the m o m e n t depends on their number, intensity, position and latency. During tonic patterns, these parameters remain almost equal whereas, in clonic patterns, they undergo considerable changes.
8. Stereo-electroencephalographic
correlates
of
m o t o r seizures. - - H.G. Wieser (Zurich)
It is generally agreed that surface EEG findings in focal motor seizures are often ambiguous. With the aid of combined surface and depth recording (SEEG exploration), which we perform on drug-resistant epileptics with a view to surgical intervention, we find a substantially increased correlation between clinical ictal phenomena and the bioelectric seizure discharges or epileptic paroxysms, provided that a systematic exploration of the m o t o r cortex can be done. Selected examples of SEEG-explored patients with focal m o t o r seizures illustrate this improved correlation with respect to chronotopographical and formal aspects. The presented cases also illustrate specific features of the bioelectric activity of the Rolandic and supplementary motor areas, especially the changes of Rolandic EEG activity produced by voluntary movements. Results of intracerebral stimulation of the Rolandic and supplementary m o to r areas are discussed with respect to the somatotopic organization.
9. Changes of correlation of intracerebral activity of different brain areas during epileptic s e i z u r e s . H.P. Meles, T.M. Darcey and H.G. Wieser (Zurich) From simultaneous measurements of intracortical activity at 32 sites we calculated the correlation coef-
ficients of all observation pairs. We compared these similarities with the anatomical distances to detect coupling of distant, and independence of adjacent, activities. We interpret the dynamic changes of the correlation matrix before, during and after partial seizures with complex symptomatology as varying conductivity of the neural pathways. At the onset and at the end of seizures we observed a 3-fold stepwise change of the correlation matrix. Brain regions exhibiting rather independent activity were preictally located frontally, during the transition period centrally and temporally, and predominantly mediobasaltemporal during the seizure.
10. Posttraumatic spike-wave-variant status. A case r e p o r t . - E. Pavlincova, R. Gugger and K. Karbowski (Berne) A 10.5-year-old boy showed a clinical picture of somnolence, headache and vomiting 1 day after a head injury. The EEG pattern was one of a continuous generalized slow spike-wave activity, accentuated in the frontal region. After an i.v. injection of diazepare this pattern disappeared and a delta focus in the left temporal region was seen. The CT scan showed a left temporal basic epidural hematoma, which was surgically drained. The boy was treated with valproate and had no seizures half a year later although, at that time, irregular 3 c/sec spike-wave activity and repetitive slow waves, asynchronous in the frontal and posterior regions of the right side, were found. The EEG of the boy's parents, brothers and sisters showed no epileptic pattern. Because of the personal and familial history of the boy (twin B, breech delivery, one unclear syncope, seizures and debility of the relatives of the father) there existed a suspicion of cerebral hyperexcitability prior to the head injury. The latter may have been sufficient to trigger such a phenomenon.