- Email: [email protected]
The Dutch EEG society
124
SOCIETY PROCEEDINGS
I n order to t e s t the hypothesis t h a t a cycle of excitability exists as a characteristic phenomenon, o r as Gastaut and collaborators have said, as a measure of a time constant of a neuronal population or system, 20 normal subjects and 16 selected patients were investigated. These patients were selected irrespective of clinical diagnosis because they showed a prolonged abnormal response to photie stimulation consisting of spikes, sharp and slow waves in their EEG often associated with myoclonie jerks. I t was found that both normal and abnormal responses to flashes of light c~uld be modified bv factors other than drugs. Natural stimuli (auditory, kinesthetic, tactile, olfaetory, mental calculation) are capable of disturbing the regularity or irregularity of the EEG responses to photic stimulation at a given frequency. The effect of the a d d e d stimulus is not constant, b u t tends to diminish (rarely to increase) or disap-
pear when the stimulus is repeated more than once, even a f t e r many seconds. Changes in amplitude of the responses can be demonstrated in response to natural stimuli and changes in duration of the cycle of excitability can be suspected. However, the phenomenon of adaptation to the repetition of equivalent stimuli (apparently a general property of the brain) makes it difficult to determine the extent to which these changes can be induced by natural stimuli. I t seems, therefore, ~hat the cycle of excitability of the visual system is largely related to what is occurring and has occurred in several sensory systems, including the visual, and is not a characteristic of its neuronal population. 11. "Visual a t t e n t i o n " and the alpha r h y t h m . E. G. WAtsu, Edinburgh. Two series of experiments have been performed in an attempt to clarify the relationship that is said to exist between "visual attention '~ and 'the alpharhythm (Adrian, Trans. Opth. 8oc. U.K., 1943, 63:
190,).
.=(i) Subjects reclining in darkness and fixating a small red light have been exposed tachitoscopically to 1-10 luminous dots. The ability to recognise the patterns did not appear to depencl on the amplitude of the alpha rhythm. (ii) Subjects were exposed alternately to trains of clicks and flashes. The amplitude of the alpharhythm when t~e subject was concentrating on counting clicks did not differ significantly from the
amplitude when he was concentrating on c o u n t i n g flashes. These results do not support the " v i s u a l attention ' ' theory. 12. ( a ) A simple frequency meter. ( b ) A n autographic stimulator for diagnostic use. ~ H. W . Smt~roN, Bristol. (a) This device is used to synchronise the rotational speed of the B.N.L Toposcope with the input applied to any channel and thus to permit the effective use of this form of display in the absence of rhythmic stimuli. I t may also be used as a direct reading frequency meter. The signal to be measured is f~rst applied to a Sehmitt trigger. The resulting square wave is dif~ ferentiated and the positive going pulse selected. This pulse fires a cathode coupled multivibrstsT giving constant amplitude pulses of fixed duration. One pulse is thus produced each time the input waveform crosses its baseline and if these pulses are smoothed by a suitable C.R. network the voltage across the network is proportional to frequency. For the frequency measuring application it is not necessary to use a smoothing network as the period of a moving coil meter is sufficiently long to integrate the pulses at all frequencies above about 3 per sec. (b) The stimulator recently described before this Society, whilst of value in physiological studies, is unduly complicated for routine clinical use. The present equipment incorporates the automatic plotting facility of the earlier model but is in other respects simpler. The pulse duration is variable from 15 t~sec, to 5 msec. and output voltages exceeding 100 V. in an impedance of 100 ohms are available. Particular care has been taken to ensure that the pulse duration is stable. The circuit used incorporates a number of unusual features and is thought to be of wide application. I t may be controlled over a range of 3 deead .... by an applied D.C. potential whilst facilities for automatically expanding part of the scale are provided. A variation of 10 per cent in any of the supplies does not introduce a detectable change in pulse widths, whilst any valve may be replaced without the necessity for recalibration. Two multiar circuits are fired at times separated by the desired pulse duration. The differentiated output of these circuits is used to trip an EeclesJordan trigger circuit which is directly coupled to a power output stage.
THE DUTCH EEG SOCIETY Wilbelmina Gasth~ds, Amsterdam, Holland October 11, 1952
8eerefary: J. DROOGLEEVER FORTUYN Ne~rrologische Kliniek, Academisch Zielcenhuis, Groningen, Holland 1.
P h o d c stimulation. - - W . SVOitM VAN L~m.~V~N, UulverlitT s t Leyden. S o m e ways in which photie stimulation may be performed and the effects obtained in the EEG of various patients, are described.
The effects may be harmonic or subharmonie following, the oeeurence of slow waves not apparently related to the flash frequency or the oceurenee of sudden effects as spikes and waves or similar waveforms. The latter effects may be produced in various
SOCIETY
PROCEEDINGS
w a y s i.e. b y s h o r t b u r s t s of f l a s h e s w i t h h i g h or low f r e q u e n e e s , b y v a r y i n g t h e f l a s h f r e q u e n c e s f r o m low to h i g h a n d back, by t r i g g e r e d f l a s h i n g etc. A case is described in which slow w a v e s a n d spikes a n d waves were p r o d u c e d only w h e n t h e f l a s h f r e q u e n c y w a s slowly v a r i e d b e t w e e n 18 a n d 20 per sec. By this procedure eventually a typical "grand real" a t t a c k developped. 2.
F i l m i n g o f seizures w i t h s y n c h r o n o u s r e c o r d i n g o f t h e E E G . - - O . MAGNUS, St. U r s u l a K l i n i e k , Wassenaar.
A n electrically driven f i l m - c a m e r a is m o u n t e d in the a p p a r a t u s - r o o m above t h e e l e c t r o e n c e p h a l o g r a p h . T h r o u g h a hole in t h e p a r t i t i o n - w a N it is directed t o w a r d a m i r r o r w h i c h is m o u n t e d above t h e p a t i e n t in the p a t i e n t ' s room. A r o u n d t h e m i r r o r 6 photo floods a n d a s p o t l i g h t are fixed. A t t h e side of t h e p a t i e n t t h e r e is a clock w i t h a second h a n d which m a k e s a c o n t a c t every 5 sec. T h e c o n t a c t s s i m u l t a n eously a l i g h t 2 little l a m p s on t h e dial of t h e clock a n d move a s i g n a l p e n on t h e E E G . T h e i n s t a l l a t i o n is p u t into a c t i o n by p u l l i n g a h a n d l e , m o u n t e d in a c o n v e n i e n t p o s i t i o n above t h e e l e c t r o e n c e p h a l o g r a p h . B y p u l l i n g t h e h a n d l e down t h e l i g h t s a r e t u r n e d on a n d a t t h e s a m e t i m e t h e m o t o r of t h e c a m e r a is p u t into action. A n y seizure o c c u r r i n g d u r i n g t h e e x a m i n a t i o n , e i t h e r s p o n t a n e o u s l y or as a consequence of hyperv e n t i l a t i o n or M e t r a z o l a c t i v a t i o n m a y be f i l m e d a n d l a t e r be c o r r e l a t e d with t h e E E G . A s y n c h r o n i s a tion to a degree of 1 / 1 4 " is achieved by c o m p a r i n g in a viewer t h e m o m e n t t h e l a m p s on t h e dial f l a s h on w i t h t h e c o r r e s p o n d i n g s i g n a l on the E E G . A f i l m of a n u m b e r of seizures with the corr e s p o n d i n g E E G s h a s been shown.
125
E E G i n p a t i e n t s w i t h intracranial inflammatory p r o c e s s e s , m J. J. VAN S T a A ^ ~ N , T o w n H o s pital, Z u i d w a l , T h e H a g u e . A 31 y e a r old m a n with a n a c u t e e n c e p h a l i t i s a f t e r i n f l u e n z a showed 3-7/see. a c t i v i t y with a somew h a t p a r o x y s m a l c h a r a c t e r in t h e E E G in f r o n t a l a n d c e n t r a l leads. Two weeks l a t e r t h i s was less clear, b u t t h e n m i n o r focal c h a n g e s h a d developped in t h e r i g h t f r o n t a l area, t h e y d i s a p p e a r e d . a f t e r some t i m e a n d t h e record b e c a m e n o r m a l a g a i n . A 37 y e a r old w o m a n showed s i m i l a r 3-7/see. a c t i v i t y , she s u f f e r e d f r o m encephalitis a f t e r v i r u s hepatitis. A m a n (31) w i t h encephalitis a f t e r i n f l u e n z a h a d m i n o r a n d v a r i a b l e focal c h a n g e s in his EEG. A w o m a n (27) h a d a n a c u t e e x a c e r b a t i o n of a chronic e n c e p h a l i t i s process. Several p a t t e r n s could be recognized in her E E G : 1. V e r y r e g u l a r 7-8 sec. a c t i v i t y (witil t h e a s p e c t of a n a l p h a r h y t h m , a l t h o u g h t h e r e was no occipital b a s i c f r e q u e n c y ) in f r o n t a l a n d cent r a l leads. 2. A n o f t e n r e p e a t i n g complex in t h e l e f t temp o r a l - a v e r a g e c o m b i n a t i o n : f i r s t a slow wave ( - { - 4 / s e c . ) a n d t h e n 8-10/sec. a c t i v i t y f o r 2 sec. i m m e d i a t e l y a f t e r w a r d s . 3. R e g u l a r slow waves ( 1 - 2 / s e c . ) . A boy (9) h a d a R eerebellar abscess, E E G : R occipital delta focus. A boy (16) h a d a local encephalitis in t h e L c e n t r a l area, a f t e r a l e f t sided f r o n t a l si~tusitis, t h e r e w a s no abscess f o r m a t i o n . A m a n (39) h a d a r e c u r r e n t swollel left eye 1 m o n t h b e f o r e a d m i s s i o n . H i s condition d e t e r i o r a t e d rapidly. H i s E E G showed a f l a t t e n i n g of t h e l e f t side c o m b i n a t i o n s . T h e p a t i e n t h a d a l e f t side subd u r a l abscess. 3.
T H E DANISH E E G SOCIETY Institute of Ne~rophysiology, Copenhagen October 14th, 1952
,Secretary: B. H A R V A L D University Institute of Human Genetics. Tagensvej 14, Copenhagen, Denmark 1.
P h o t i c s t i m u l a t i o n as a provocative procedure at the electroencephalographic d i a g n o s i s of epilepsy. - - E. TaOLLE, State Hospital, N e u r o logical Department, C o p e n h a g e n .
P h o t i e s t i m u l a t i o n w i t h the flicker l a m p h a s been u s e d as a r o u t i n e p r o v o c a t i v e p r o c e d u r e in t h e E E G e x a m i n a t i o n o f 1000 p a t i e n t s a n d 487 n o r m a l a v i a t i o n a p p l i c a n t s . M o d e r a t e to severe d y s r h y t h m i a consisti n g of i r r e g u l a r slow waves, b u t no epileptic paro x y s m s , w a s t h e r e b y i n d u c e d in 2,7 p e r c e n t of n o r m a l s . Of 364 p a t i e n t s with d e f i n i t e epileptic f i t s o f v a r i o u s k i n d s 47 p e r cent h a d clear E E G abn o r m a l i t i e s in t h e r e s t i n g record or on h y p e r v e n t i l a tion, while in 17 p e r c e n t of epileptics with n o r m a l or
borderline r e s t i n g curves m o d e r a t e to severe abn o r m a l i t y w a s i n d u c e d b y photic s t i m u l a t i o n , 79 p e r c e n t of t h e a b n o r m a l i t i e s were p a r o x y s m a l . T h u s 47 per cent of t h e p a t i e n t s h a d a b n o r m a l records before photic s t i m u l a t i o n , 56 p e r c e n t with photie stimulation. 2.
Transient temporal spike-foci in EEG in children. m F. BUCHTHAL a n d G. HESS, State H o s pital, Psychiatrical Department, C o p e n h a g e n .
3.
EEG in a case of art. carotis int. thrombosis. m B. HAavAu>, Municipal Hosp., Neurological Department, Frederiksberg.
SOCIETY PROCEEDINGS
I n order to t e s t the hypothesis t h a t a cycle of excitability exists as a characteristic phenomenon, o r as Gastaut and collaborators have said, as a measure of a time constant of a neuronal population or system, 20 normal subjects and 16 selected patients were investigated. These patients were selected irrespective of clinical diagnosis because they showed a prolonged abnormal response to photie stimulation consisting of spikes, sharp and slow waves in their EEG often associated with myoclonie jerks. I t was found that both normal and abnormal responses to flashes of light c~uld be modified bv factors other than drugs. Natural stimuli (auditory, kinesthetic, tactile, olfaetory, mental calculation) are capable of disturbing the regularity or irregularity of the EEG responses to photic stimulation at a given frequency. The effect of the a d d e d stimulus is not constant, b u t tends to diminish (rarely to increase) or disap-
pear when the stimulus is repeated more than once, even a f t e r many seconds. Changes in amplitude of the responses can be demonstrated in response to natural stimuli and changes in duration of the cycle of excitability can be suspected. However, the phenomenon of adaptation to the repetition of equivalent stimuli (apparently a general property of the brain) makes it difficult to determine the extent to which these changes can be induced by natural stimuli. I t seems, therefore, ~hat the cycle of excitability of the visual system is largely related to what is occurring and has occurred in several sensory systems, including the visual, and is not a characteristic of its neuronal population. 11. "Visual a t t e n t i o n " and the alpha r h y t h m . E. G. WAtsu, Edinburgh. Two series of experiments have been performed in an attempt to clarify the relationship that is said to exist between "visual attention '~ and 'the alpharhythm (Adrian, Trans. Opth. 8oc. U.K., 1943, 63:
190,).
.=(i) Subjects reclining in darkness and fixating a small red light have been exposed tachitoscopically to 1-10 luminous dots. The ability to recognise the patterns did not appear to depencl on the amplitude of the alpha rhythm. (ii) Subjects were exposed alternately to trains of clicks and flashes. The amplitude of the alpharhythm when t~e subject was concentrating on counting clicks did not differ significantly from the
amplitude when he was concentrating on c o u n t i n g flashes. These results do not support the " v i s u a l attention ' ' theory. 12. ( a ) A simple frequency meter. ( b ) A n autographic stimulator for diagnostic use. ~ H. W . Smt~roN, Bristol. (a) This device is used to synchronise the rotational speed of the B.N.L Toposcope with the input applied to any channel and thus to permit the effective use of this form of display in the absence of rhythmic stimuli. I t may also be used as a direct reading frequency meter. The signal to be measured is f~rst applied to a Sehmitt trigger. The resulting square wave is dif~ ferentiated and the positive going pulse selected. This pulse fires a cathode coupled multivibrstsT giving constant amplitude pulses of fixed duration. One pulse is thus produced each time the input waveform crosses its baseline and if these pulses are smoothed by a suitable C.R. network the voltage across the network is proportional to frequency. For the frequency measuring application it is not necessary to use a smoothing network as the period of a moving coil meter is sufficiently long to integrate the pulses at all frequencies above about 3 per sec. (b) The stimulator recently described before this Society, whilst of value in physiological studies, is unduly complicated for routine clinical use. The present equipment incorporates the automatic plotting facility of the earlier model but is in other respects simpler. The pulse duration is variable from 15 t~sec, to 5 msec. and output voltages exceeding 100 V. in an impedance of 100 ohms are available. Particular care has been taken to ensure that the pulse duration is stable. The circuit used incorporates a number of unusual features and is thought to be of wide application. I t may be controlled over a range of 3 deead .... by an applied D.C. potential whilst facilities for automatically expanding part of the scale are provided. A variation of 10 per cent in any of the supplies does not introduce a detectable change in pulse widths, whilst any valve may be replaced without the necessity for recalibration. Two multiar circuits are fired at times separated by the desired pulse duration. The differentiated output of these circuits is used to trip an EeclesJordan trigger circuit which is directly coupled to a power output stage.
THE DUTCH EEG SOCIETY Wilbelmina Gasth~ds, Amsterdam, Holland October 11, 1952
8eerefary: J. DROOGLEEVER FORTUYN Ne~rrologische Kliniek, Academisch Zielcenhuis, Groningen, Holland 1.
P h o d c stimulation. - - W . SVOitM VAN L~m.~V~N, UulverlitT s t Leyden. S o m e ways in which photie stimulation may be performed and the effects obtained in the EEG of various patients, are described.
The effects may be harmonic or subharmonie following, the oeeurence of slow waves not apparently related to the flash frequency or the oceurenee of sudden effects as spikes and waves or similar waveforms. The latter effects may be produced in various
SOCIETY
PROCEEDINGS
w a y s i.e. b y s h o r t b u r s t s of f l a s h e s w i t h h i g h or low f r e q u e n e e s , b y v a r y i n g t h e f l a s h f r e q u e n c e s f r o m low to h i g h a n d back, by t r i g g e r e d f l a s h i n g etc. A case is described in which slow w a v e s a n d spikes a n d waves were p r o d u c e d only w h e n t h e f l a s h f r e q u e n c y w a s slowly v a r i e d b e t w e e n 18 a n d 20 per sec. By this procedure eventually a typical "grand real" a t t a c k developped. 2.
F i l m i n g o f seizures w i t h s y n c h r o n o u s r e c o r d i n g o f t h e E E G . - - O . MAGNUS, St. U r s u l a K l i n i e k , Wassenaar.
A n electrically driven f i l m - c a m e r a is m o u n t e d in the a p p a r a t u s - r o o m above t h e e l e c t r o e n c e p h a l o g r a p h . T h r o u g h a hole in t h e p a r t i t i o n - w a N it is directed t o w a r d a m i r r o r w h i c h is m o u n t e d above t h e p a t i e n t in the p a t i e n t ' s room. A r o u n d t h e m i r r o r 6 photo floods a n d a s p o t l i g h t are fixed. A t t h e side of t h e p a t i e n t t h e r e is a clock w i t h a second h a n d which m a k e s a c o n t a c t every 5 sec. T h e c o n t a c t s s i m u l t a n eously a l i g h t 2 little l a m p s on t h e dial of t h e clock a n d move a s i g n a l p e n on t h e E E G . T h e i n s t a l l a t i o n is p u t into a c t i o n by p u l l i n g a h a n d l e , m o u n t e d in a c o n v e n i e n t p o s i t i o n above t h e e l e c t r o e n c e p h a l o g r a p h . B y p u l l i n g t h e h a n d l e down t h e l i g h t s a r e t u r n e d on a n d a t t h e s a m e t i m e t h e m o t o r of t h e c a m e r a is p u t into action. A n y seizure o c c u r r i n g d u r i n g t h e e x a m i n a t i o n , e i t h e r s p o n t a n e o u s l y or as a consequence of hyperv e n t i l a t i o n or M e t r a z o l a c t i v a t i o n m a y be f i l m e d a n d l a t e r be c o r r e l a t e d with t h e E E G . A s y n c h r o n i s a tion to a degree of 1 / 1 4 " is achieved by c o m p a r i n g in a viewer t h e m o m e n t t h e l a m p s on t h e dial f l a s h on w i t h t h e c o r r e s p o n d i n g s i g n a l on the E E G . A f i l m of a n u m b e r of seizures with the corr e s p o n d i n g E E G s h a s been shown.
125
E E G i n p a t i e n t s w i t h intracranial inflammatory p r o c e s s e s , m J. J. VAN S T a A ^ ~ N , T o w n H o s pital, Z u i d w a l , T h e H a g u e . A 31 y e a r old m a n with a n a c u t e e n c e p h a l i t i s a f t e r i n f l u e n z a showed 3-7/see. a c t i v i t y with a somew h a t p a r o x y s m a l c h a r a c t e r in t h e E E G in f r o n t a l a n d c e n t r a l leads. Two weeks l a t e r t h i s was less clear, b u t t h e n m i n o r focal c h a n g e s h a d developped in t h e r i g h t f r o n t a l area, t h e y d i s a p p e a r e d . a f t e r some t i m e a n d t h e record b e c a m e n o r m a l a g a i n . A 37 y e a r old w o m a n showed s i m i l a r 3-7/see. a c t i v i t y , she s u f f e r e d f r o m encephalitis a f t e r v i r u s hepatitis. A m a n (31) w i t h encephalitis a f t e r i n f l u e n z a h a d m i n o r a n d v a r i a b l e focal c h a n g e s in his EEG. A w o m a n (27) h a d a n a c u t e e x a c e r b a t i o n of a chronic e n c e p h a l i t i s process. Several p a t t e r n s could be recognized in her E E G : 1. V e r y r e g u l a r 7-8 sec. a c t i v i t y (witil t h e a s p e c t of a n a l p h a r h y t h m , a l t h o u g h t h e r e was no occipital b a s i c f r e q u e n c y ) in f r o n t a l a n d cent r a l leads. 2. A n o f t e n r e p e a t i n g complex in t h e l e f t temp o r a l - a v e r a g e c o m b i n a t i o n : f i r s t a slow wave ( - { - 4 / s e c . ) a n d t h e n 8-10/sec. a c t i v i t y f o r 2 sec. i m m e d i a t e l y a f t e r w a r d s . 3. R e g u l a r slow waves ( 1 - 2 / s e c . ) . A boy (9) h a d a R eerebellar abscess, E E G : R occipital delta focus. A boy (16) h a d a local encephalitis in t h e L c e n t r a l area, a f t e r a l e f t sided f r o n t a l si~tusitis, t h e r e w a s no abscess f o r m a t i o n . A m a n (39) h a d a r e c u r r e n t swollel left eye 1 m o n t h b e f o r e a d m i s s i o n . H i s condition d e t e r i o r a t e d rapidly. H i s E E G showed a f l a t t e n i n g of t h e l e f t side c o m b i n a t i o n s . T h e p a t i e n t h a d a l e f t side subd u r a l abscess. 3.
T H E DANISH E E G SOCIETY Institute of Ne~rophysiology, Copenhagen October 14th, 1952
,Secretary: B. H A R V A L D University Institute of Human Genetics. Tagensvej 14, Copenhagen, Denmark 1.
P h o t i c s t i m u l a t i o n as a provocative procedure at the electroencephalographic d i a g n o s i s of epilepsy. - - E. TaOLLE, State Hospital, N e u r o logical Department, C o p e n h a g e n .
P h o t i e s t i m u l a t i o n w i t h the flicker l a m p h a s been u s e d as a r o u t i n e p r o v o c a t i v e p r o c e d u r e in t h e E E G e x a m i n a t i o n o f 1000 p a t i e n t s a n d 487 n o r m a l a v i a t i o n a p p l i c a n t s . M o d e r a t e to severe d y s r h y t h m i a consisti n g of i r r e g u l a r slow waves, b u t no epileptic paro x y s m s , w a s t h e r e b y i n d u c e d in 2,7 p e r c e n t of n o r m a l s . Of 364 p a t i e n t s with d e f i n i t e epileptic f i t s o f v a r i o u s k i n d s 47 p e r cent h a d clear E E G abn o r m a l i t i e s in t h e r e s t i n g record or on h y p e r v e n t i l a tion, while in 17 p e r c e n t of epileptics with n o r m a l or
borderline r e s t i n g curves m o d e r a t e to severe abn o r m a l i t y w a s i n d u c e d b y photic s t i m u l a t i o n , 79 p e r c e n t of t h e a b n o r m a l i t i e s were p a r o x y s m a l . T h u s 47 per cent of t h e p a t i e n t s h a d a b n o r m a l records before photic s t i m u l a t i o n , 56 p e r c e n t with photie stimulation. 2.
Transient temporal spike-foci in EEG in children. m F. BUCHTHAL a n d G. HESS, State H o s pital, Psychiatrical Department, C o p e n h a g e n .
3.
EEG in a case of art. carotis int. thrombosis. m B. HAavAu>, Municipal Hosp., Neurological Department, Frederiksberg.