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Eastern association of electroencephalographers, Laurentian SKI meeting
Electroencephalography and Clinical Neurophysiology, 1981, 52: 43P--48P Elsevier/North-Holland Scientific Publishers, Ltd.
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Society proceedings EASTERN ASSOCIATION OF ELECTROENCEPHALOGRAPHERS, LAURENTIAN SKI MEETING Le Chantecler, Ste. Adele, Que., February 26--March 1, 1981
Secretary~Treasurer: Dr. IRA SHERWIN EA EEG, 200 Springs Road (151), Bedford, Mass. 01730 (U.S.A.) (Accepted for publication: April 8, 1981)
1. Increased response to 'non-competitive' GABA antagonists in amygdala-kindled r a t s . M.W. Kalichman, K.E. Livingston and W.M. Burnham (Toronto, Canada) The convulsant potency of drugs which antagonize GABA-mediated inhibition was measured 1 m o n t h subsequent to kindling in amygdala-kindled and 'handled control' rats. The potency of the 'noncompetitive' GABA antagonists, picrotoxin, NMPP barbituric acid and pentylenetetrazol, was found to be significantly increased in kindled animals. No change was found, however, in the potencies of the specific receptor blocker bicuculline, or of the GABA synthesis inhibitors isoniazid and 3-mercaptopropionic acid. These findings suggest that kindling induces a long-lasting functional deficit in GABAmediated inhibition, and that the deficit involves changes in the later steps in GABAergic transmission -- those subsequent to the process of synaptic recognition.
2. What is the role of GABA in seizure mechanisms?. -- G.H. Fromm, A.S. Chattha and Ch.F. Terrence (Pittsburgh, Pa.) The role of GABA in seizure mechanisms remains elusive despite considerable research. We have found that anti-absence drugs selectively depress descending inhibitory pathways, such as the periventricular inhibition (PVI) of the trigeminal nucleus. Therefore, we have investigated the effect of agonists and antagonists of GABA, and also of acetylcholine, on our experimental model. Bicuculline markedly facilitated the PVI. Muscimol antagonized the effect of bicuculline, but had a variable effect when given alone. Eserine also markedly facilitated the PVI. Atropine antagonized the effect of both eserine and bicuculline, but had a variable effect when given alone.
Our results indicate that the PVI is modulated by a GABAergic inhibitory mechanism, and by a cholinergic facilitatory mechanism. This suggests that the mechanism of action of anti-absence drugs may involve both an anticholinergic and a GABAergie effect. The difficulty in identifying the role of GABA in the control of seizures is thus due to the interaction of GABA and acetylcholine mechanisms, which makes it difficult to study one of these neurotransmitters in isolation.
3. Potentiation of recruiting responses in feline generalized penicillin epilepsy. -- G. Kostopoulos and M. Avoli (Montreal, Canada) Rhythmic stimulation of nucleus centralis medialis in cats produced recruiting responses in cortex and thalamus. Stimulus intensity was adjusted so that the second or third stimulus in a train of stimuli was at threshold for producing a recruiting response (a monophasic negative wave in cortical leads). The amplitude of the responses fluctuated presumably due to subtle changes in arousal. However, consistent records were obtained through EEG averaging. Following 2--3 control averages, 350,000 IU of penicillin were injected i.m. which is known to produce generalized bilaterally synchronous spike and wave discharges in about 1--2 h. The amplitude of the averages started progressively to increase before the appearance of spike and wave discharges and often as early as 10 min after the injection of penicillin. Maximum recruitment was now produced by a shorter train of stimuli while individual recruiting waves acquired positive phases of progressively larger amplitude. Often such large biphasic recruiting waves occluded the appearance of the succeeding recruiting response. We have previously described similar features characterizing the evolution of spikes of spike and wave discharges. Along with previous studies, the present findings support the
0013-4649/81/0000--O000/$02.50 © 1981 Elscvier/North-Holland Scientific Publishers, Ltd.
44P p r o p o s a l t h a t spike a n d wave discharges are p r o d u c e d b y similar t h a l a m o c o r t i c a l volleys as t h o s e p r o d u c i n g recruiting responses.
4. D e t e c t i n g ear d o m i n a n c e using a u d i t o r y e v o k e d p o t e n t i a l s . -- F. M a r t i n , R. E f r o n a n d E.W. Y u n d (Martinez, Calif.) T h e ear d o m i n a n c e for p i t c h described b y E f r o n a n d Y u n d (J. acoust. Soc. A m e r . , 1 9 7 6 , 59: 8 8 9 ) has b e e n previously d e t e c t e d only b y p s y c h o p h y s i c a l methods. The present report uses the P 3 0 0 c o m p o n e n t of t h e a u d i t o r y e v o k e d p o t e n t i a l to i d e n t i f y t h e m a g n i t u d e and d i r e c t i o n of ear d o m i n a n c e . T h e m e t h o d entails t h e p r e s e n t a t i o n of a series of identical d i c h o t i c chords. R a n d o m l y interspersed in this series are b i n a u r a l t o n e s with a f r e q u e n c y s o m e w h e r e b e t w e e n t h e left a n d right ear t o n e s o f t h e d i c h o t i c chords. A P 3 0 0 wave is generated only when the binaural tone's pitch is p e r c e p t i b l y d i f f e r e n t f r o m t h a t o f t h e series o f d i c h o t i c chords. T h e results o f this m e t h o d correlate well with p s y c h o p h y s i c a l m e a s u r e s of ear d o m i n a n c e in t h e s a m e subjects.
5. Regional variability analysis o f e v o k e d p o t e n t i a l s . -- P.K.H. Wong, C.T. L o m b r o s o a n d Y. Mats u m i y a ( B o s t o n , Mass.) In p a t i e n t s w i t h cortical disease, e v o k e d p o t e n t i a l s ( E P S ) m a y be h e l p f u l in l o c a l i z a t i o n of lesion. One w o u l d e x p e c t a b n o r m a l i t i e s in l a t e n c y , a m p l i t u d e and l o t m o r p h o l o g y o f t h e p e a k c o m p o n e n t s r e c o r d e d over t h e a b n o r m a l c o r t e x . S u c h t r a d i t i o n a l analysis m a y s o m e t i m e s be i n a d e q u a t e as occasionally we see n o a p p a r e n t EP a b n o r m a l i t i e s in cases with clear s t r u c t u r a l lesions. We are currently investigating a d i f f e r e n t a p p r o a c h : t h a t of s t u d y i n g t h e variability of EP f r o m d i f f e r e n t regions using its signal-to-noise r a t i o ( S N R ) as an o b j e c t i v e measure. T h e u n d e r l y i n g h y p o t h e s i s is: w h e n s t i m u l a t e d , n o r m a l n e u r o n a l s t r u c t u r e s g e n e r a t e s t a b l e scalp p o t e n t i a l changes, while diseased s t r u c t u r e s m a y n o t , t h u s p r o d u c i n g EPs w h i c h vary significantly f r o m trial t o trial. This is r e f l e c t e d b y a l o w S N R (or p o o r s u p e r i m p o s i t i o n ) . T e c h n i c a l factors (artifacts, etc.) o f course s h o u l d b e c o n t r o l l e d for. T o test o u r h y p o t h e s i s , we s t u d i e d 18 cerebral palsy p a t i e n t s w i t h unilateral h e m i s p h e r i c lesion due t o p r e v i o u s b r a i n injury. P r e l i m i n a r y results are e n c o u r a g i n g . In t h e m a j o r i t y o f cases, regional variability m e a s u r e suggests a p p r o p r i a t e l y t h e side o f t h e lesion despite e q u i v o c a l results f r o m t r a d i t i o n a l peak c o m p o n e n t analysis. T h e data and m e t h o d
SOCIETY PROCEEDINGS o f calculating t h e S N R will be p r e s e n t e d a n d discussed.
6. E l e c t r o p h y s i o l o g i c a l d e v e l o p m e n t o f b r a i n s t e m a u d i t o r y f u n c t i o n in n e w b o r n s . - - L.J. Streletz, D.B. G e r s h a n d L.J. G r a z i a n i (Philadelphia, Pa.) Brain s t e m a u d i t o r y evoked p o t e n t i a l s ( B A E P s ) were s t u d i e d in 40 low risk i n f a n t s with c o n c e p t i o n a l ages b e t w e e n 26 a n d 42 weeks. T h e y were distinguished f r o m high risk i n f a n t s o n t h e basis o f neonatal medical complications. BAEPs were r e c o r d e d s i m u l t a n e o u s l y f r o m vertex-ipsilateral a n d -contralateral ear r e f e r e n c e t o aid in d i f f e r e n t i a t i o n of c o m p o n e n t s . M o n a u r a l 70 dB HL r a r e f a c t i o n clicks were p r e s e n t e d at a rate of l l / s e c . B o t h ears were r e c o r d e d a n d serial recordings at w e e k l y intervals were o b t a i n e d f r o m several infants. T h e peak a n d i n t e r p e a k latencies o f waves I, III and V were m e a s u r e d in t e r m a n d p r e t e r m infants. T h e o b s e r v e d s h o r t e n i n g o f wave I peak l a t e n c y a n d wave I V i n t e r p e a k l a t e n c y d u r i n g t h e n e w b o r n p e r i o d suggests t h a t t h e peripheral (processes b e f o r e wave I, 45%) a n d central (processes b e t w e e n waves I--V, 55%) contributions to development of the brain stem p o r t i o n o f t h e a u d i t o r y s y s t e m are n e a r l y equal. These results are c o m p a r e d t o o t h e r s investigating development of infant brain stem auditory function.
7. T h e e f f e c t o f increased i n t r a c r a n i a l pressure with o r w i t h o u t p a p i l l e d e m a o n t h e V E P . - - I. BodisWollner, M. O n o f r j a n d L. Mylin (New York, N.Y.) Visual e v o k e d p o t e n t i a l s (VEPs) were o b t a i n e d in o n e p a t i e n t w i t h unilateral p a p i l l e d e m a a n d o p t i c a t r o p h y in t h e o t h e r eye, a s e c o n d p a t i e n t w i t h bilateral p a p i l l e d e m a due t o h y d r o c e p h a l u s caused by a pineal t u m o r , a n d a t h i r d p a t i e n t with h y d r o cephalus without papilledema. Previous VEP studies in h y d r o c e p h a l u s used o n l y flash stimuli (Vikova 1 9 7 4 ; Ehle 1 9 7 9 ; Sklar 1 9 7 9 ; G a m b i 1980}. We s t u d i e d t r a n s i e n t and s t e a d y - s t a t e VEPs using c o u n t e r p h a s e gratings in each p a t i e n t b e f o r e a n d a f t e r t h e r a p y . T h e i r d a t a were c o m p a r e d with n o r m a t i v e data e s t a b l i s h e d in o u r l a b o r a t o r y using t h e same stimuli (Bodis-Wollner 1979}. T h e latency o f t h e m a j o r positive wave was d e l a y e d in b o t h p a t i e n t s w i t h h y d r o c e p h a l u s , a n d it decreased a f t e r t h e r a p y , while in t h e p a t i e n t with t h e F o s t e r - K e n n e d y s y n d r o m e t h e V E P was n o r m a l from t h e eye with p a p i l l e d e m a , a n d d e l a y e d f r o m t h e eye w i t h o p t i c a t r o p h y . T h e s t e a d y - s t a t e EPs similarly paraL leled t h e clinical r e c o v e r y following t h e r a p y , b u t t h e r e s p o n s e t o specific spatial f r e q u e n c i e s , t h e t i m e o f
EASTERN ASSOCIATION OF E L E C T R O E N C E P H A L O G R A P H E R S recovery, and the precise measurements of interocular differences revealed that the two types of EPs (recorded at slow and faster temporal rates) may tap different systems.
8. Depth electrode e x p l o r a t i o n b e f o r e surgery for e p i l e p s y : a l w a y s , s o m e t i m e s or never. - - G. Bouvier, J.-M. Saint-Hflaire, R. Maltais, R. B~ique and A. Leduc (Montreal, Canada) The present study is a review of our personal experience of the past 6 years. Out of 97 patients monitored with chronic surface electrodes (SE), 56 had a chronic monitoring with depth electrodes (DE). We found that chronic monitoring with DE was indispensable in 84% of the cases. 29 patients were classified as clear-cut cases prior to DE exploration but 83% of them were false clear-cut. The remaining 27 patients without any localizing elements, patients that otherwise would have been rejected, had a DE exploration and 90% of these had surgery with a high percentage of cure. Many conclusions may be drawn: (1) DE exploration is safe; (2) DE exploration should always be done before surgery; (3) surgical results largely favor such an apparently aggressive approach.
9. Thalamic discharge patterns. -- O.J. Andy and M. Jurko (Jackson, Miss.) Diagnostic depth EEG recordings were done in 15 patients having medically intractable seizures. Recordings were made in the resting state at each level of electrode insertion and following electrical stimulation. Bipolar recordings were made from a concentric electrode at the tip and from each of the two components referred to the scalp. Bipolar scalp recordings were also made. Thaiamic discharge frequency patterns grouped themselves as follows: 3--7/sec, 8--12/sec, 13--17/sec and 18--25/sec. The patterns varied from sinusoidal to sharp wave configurations and spike and wave patterns. Single spikes with a predominant negative or positive polarity occurred most often. Biphasic, triphasic and polyspikes were seldom present. The spikes tended to occur in bursts of 0.5--1.5 sec duration, most lasting less than 1.0 sec. Injury discharge patterns often developed with small increments of electrode insertion, 0.5--1.0 ram. The injury discharge may last a few seconds or slowly build up to a prolonged discharge. This depth discharge may or may not spread to scalp recording electrodes. Electrical stimulation in some instances also induced discharges. Behavioral changes were associated with the thalamic discharges
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in 7 patients. These consisted of eye blinking, twitching of the face, chin lip and forehead, eyeball movements, conjugate eye turning, pupil dilation, and jerking of the extremities. These various movements were most frequently associated with 4/sec to 6/sec bursts, and occasionally with 3/sec bursts in the thalamus.
10. S o m e relationships b e t w e e n spikes, seizures and sleep. - - J. G o t m a n , P. G l o o r , J.R. Ives, A. Olivier and F. Q u e s n e y (Montreal, Canada)
In 5 epileptic patients with electrodes chronically implanted in the temporal and frontal areas, we studied the interaction in time, over several days, between occurrence of seizures, inter-ictal spiking rate and activation of inter-ictal spiking by sleep. Sleep staging was impossible because no scalp electrode was available, but cyclic variations in spiking activity, present during the night and not during the day, were assumed to be caused by sleep. Spike recognition was performed automatically and continuously during several days for each patient. The following observations were made: (1) Seizures rarely occurred during nights in which there was clear cyclic sleep activation of spiking. (2) Repeated seizures during daytime or seizure occurrence at night corresponded to a relatively uniform spiking rate at night (no cyclic activation), most clearly seen in the region where seizures originated; other areas could remain subject to cyclic fluctuations. (3) Seizures were not preceded or followed (in terms of minutes or hours) by clear changes in spiking rate (except one post-ictal activation). (4) Seizures did not occur when the spiking rate was the highest. These observations are tentative, given the small number of patients. They nevertheless raise the question of the apparent lack of temporal relationship between seizure occurrence and spiking rate.
11. Myoclonic absence: presentation of a case and review of its features. - - M. McBride and M.H. Charlton (Rochester, N.Y.) A 13-year~ld male was admitted to hospital on account of a 2 h confusional state, accompanied by 2--3 c/sec rhythmic myoclonus of his upper extremities and neck. This was associated with bilaterally synchronous 2--3 c/sec spike and wave activity on EEG. The confusional state and the myoclonus disappeared 2 min after administration of i.v. diazepam. Later, single or repetitive jerks recurred concurrent with spike and wave discharge
46P on EEG, finally controlled by valproate and acetazolamide. Myoclonic absence presents points of similarity and difference from other forms of absence in regard to genetic factors, sex ratio, age of onset, alteration of consciousness, concurrence of grand real, photosensitivity, response to medication, and EEG manifestations. These are discussed with respect to the present case.
12. Differential behavioral effects of spike-wave discharge. -- M.M. Often and A.F. Mirsky (Boston, Mass. and Bethe~la, Md.) Behavioral tasks utilizing different sensory modalities were administered to a group of 7 petit mal patients with generalized spike-wave discharges in the EEG and clinical absences. The purpose was to assess the functional capabilities of patients during EEG seizure discharge. The tasks required a simple or discriminative (key press) response to spatially discrete or diffuse visual stimuli, pure tones and, in one case, shock to the median nerve. Repetitive execution of the response without the presentation of task stimuli was also tested. Performance was monitored simultaneously with 6--10 channels of EEG recorded from bilaterally placed parasagittal scalp electrodes. During tasks involving discrete visual stimuli, eye position was recorded on videotape. Changes in correct responding over successive pre-seizure, seizure, and post-seizure segments were analyzed separately for each patient. Although, as expected, correct responding was significantly reduced during spike-wave discharge, the degree of behavioral impairment and its time course in relation to the spike-wave burst depended on stimulus modality, with individual patients showing unique patterns of functional impairment and recovery. The results underline the idiosyncratic expression of seizures among patients sharing a c o m m o n diagnosis and suggest differential rather than uniform disruption of functional systems during spike-wave discharge.
13. Epileptiform EEG abnormalities and photosensitivity in relatives o f patients with focal epilepsy, -- M. Straszak and E. Andermann (Montreal, Canada) Although genetic factors are known to be important in generalized epilepsy, their role in focal epilepsy is less welt established. Andermann (1972) was able to demonstrate a significantly increased frequency of EEG abnormalities in relatives of patients operated for focal epilepsy as compared to
SOCIETY PROCEEDINGS control relatives. These abnormalities were markedly age- and sex-dependent, as in generalized epilepsy. Based on these findings, a multifactorial mode of inheritance was postulated for both focal and generalized epilepsy (Andermann, 1980). We have reanalyzed the data on epileptiform EEG abnormalities in 167 first degree relatives of focal probands, employihg stricter electroencephalographic criteria (Gloor 1978), and compared the findings in relatives according to the type of removal (temporal only, fronto-temporal, etc.), as well as the sex and age of the proband. Total epileptiform EEG abnormalities were again significantly more frequent in experimental relatives, as compared to control relatives (14.5% vs. 6.3%, P ~ 0.05). In particular, this was true for generalized epileptiform abnormalities (7.9% vs. 1.1%, P ~ 0.02), whereas focal epileptiform abnormalities were not significantly elevated. Photosensitive epileptiform EEG abnormalities were also more frequent in experimental relatives, but the differences were not significant. These abnormalities were again found to be sex- and age-dependent. All types of EEG abnormalities were more frequent in relatives of patients with temporal lobe removals alone as compared with other relatives, particularly those of patients with both frontal and temporal removals. Abnormal photosensitivity was found more frequently in relatives of temporal probands than in relatives of those with combined ['ronto-temporal removals (9.5% vs. 0.0%. P = 0.03 L The findings confirm the presence of genetic factors in focal epilepsy and suggest that generalized epileptiform EEG abnormalities and abnormal photosensitivity are indicative of a genetic predisposition to both generalized and focal epilepsy, particularly temporal lobe epilepsy.
14. 32-channel cable-telemetry: w h o needs it?. -J.R. Ives, J. Gotman, P. Gloor and A. Olivier
(Montreal, Canada) Epileptic patients who require exploration with chronic multicontact (9) stereotaxic depth electrodes (10) may have 100 recording sites available if surface/ sphenoidal contacts are also included. When 32 channels are used, this doubles the simultaneous coverage and should reduce the implantation period. Our fundamental reason necessitating depth electrodes is the failure of surface/sphenoidal recordings to resolve the epileptic focus. Thus it is logical to investigate comparative recordings between surface and depth. 32 channels permit a m o r e realistic approach to this form of investigation. The 32-channel preamplifier/multiplexor worn
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by the patient weighs less than 170 g while the 32channel multiplexed signal is completely compatible with the existing cable-telemetry system. The 32 channels of E E G are dealt with by the computer and the seizure-monitoring program which records 2 min before and 2 rain after the pushing of the patient's seizure-push-button. The computer can then play back 16 channels at a time of these 4 min sequences which are time-locked by the digital clock. By placing them above one another, the 32~channel seizure can be easily read by the electroencephalographer.
15. Antagonism between concurrently developing kindled seizure loci in the limbic system of the rat. -- J.L. Burchfiel (Boston, Mass.) Evidence from many laboratories indicates that kindling induces extensive reorganization of neural elements beyond the actual site of stimulation. Particularly striking evidence of this is the propagation of epileptic hyperexcitability demonstrated by the 'transfer effect': seizure development kindled from one brain site ('primary site') induces enhanced seizure susceptibility in other brain regions ('secondary' or 'transfer' sites). In addition to these 'positive transfer' effects, however, there is evidence that secondary site kindling can temporarily block seizures from the primary site (the so-called 'interference effect' or 'negative transfer'). In order to study in more detail positive and negative transfer during kindling we attempted to kindle concurrently two brain sites (septal area and entorhinal cortex) by alternatively stimulating them on a trial-by-trial basis. This 'alternate kindling' paradigm was characterized by a striking antagonism of seizure development. Typically, progressive seizure development occurred from only one site; kindling from the alternately stimulated site was suppressed. Which site became dominant during alternate kindling appeared to be random: in 13 animals, the septum was dominant in 8 and the entorhinal cortex in 5. Antagonism of kindling appears to be the best description of the results since kindling failed to develop even after several times the number of stimulations required for primary kindling. Moreover, stimulation of the suppressed site consistently elicited long afterdischarges and behavioral signs of limbic activation (behavioral arrest and automatisms). Thus, neuronal excitability per se was not suppressed; rather, it was the propagation of neuronal excitability to motor mechanisms (kindling) which was blocked. These results indicate that transsynaptic neural reorganization induced by kindling involves both positive and negative effects upon seizure susceptibility.
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16. The seizures of morphea. -- P. Hwang, F. Andermann, K. Metrakos and G. Watters (Montreal, Canada) In a series of 24 patients with morphea (localized scleroderma), both epileptogenic and non-epileptogenic EEG abnormalities were 3 times as common as in an age-matched control population. Twenty-five per cent (6/24) of patients had clinical seizures. Of the 6 patients studied, 4 had 'coup de sabre' lesions in the territory of the first trigeminal division, and seizures arising from the underlying brain. Seizures occurred in 66% (4/6) of patients with coup de sabre lesions. Two other patients had morphea of the leg and body respectively. Both had seizures originating in the temporal lobe. The incidence of seizures in extra-trigeminal morphea was 11% (2/18). The seizures were easily controlled and there was a strong tendency for improvement in electrographic abnormalities, suggesting that the epileptic disorder of these patients is benign.
17. A longitudinal s t u d y o f f i e l d d e f e c t s using transient and steady-state VEP stimulation. - - M. Onofrj, I. Bodis-Wollner and L. Mylin (New York, N.Y.) We studied 15 patients referred for VEP evaluation and suspected of having a field defect. VEP interpretation was 'blind', i.e., not tainted by information concerning campimetry. Stimuli were reversing checkerboard patterns with 15' checks and vertical gratings of 13', in contrast with the larger stimuli used by other researchers (Halliday and Blumhardt 1979; Agrado 1980). Nine degree full field and hemifield stimuli were used. VEPs were recorded from a horizontal array of electrodes with Oz 2.5 cm above the inion. Our data on normal subjects confirm the 'paradoxical lateralization' of the responses to hemifield stimuli (Barrett 1976; Shagass 1976). The VEP to full-field stimuli forecasted the campimetry results only in 50% of our patients, while there was diagnostic concordance in 84% of patients using hemifield stimuli. 'Crossed' alterations were found in bitemporal field defects and 'uncrossed' ones in homonymous hemianopia. Steady-state responses did not show the same lateralization as transient responses in two patients. A longitudinal study of 6 patients revealed that the classic inverted polarity EP appears only several months following the initial symptoms.
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18. EEG investigation of temporal lobe disorders: a multi-basal-electrode a p p r o a c h , - J.H. Fisher and D.L. Schomer (Boston, Mass.) E p i l e p t o g e n i c foci in deep s t r u c t u r e s (mesiobasal or o r b i t o f r o n t a l ) m a y p r o d u c e c o n f u s i n g discharges w h e n r e c o r d e d f r o m s t a n d a r d scalp electrodes. Neurophysiologic e f f o r t s t o e x a m i n e t h e area of a n a t o m i c i n t e r e s t have led to t h e i n t r o d u c t i o n o f n a s o p h a r y n geal, s p h e n o i d a l , a n d n a s o e t h m o i d a l r e c o r d i n g techniques. C o r r e l a t i o n s have b e e n r e p o r t e d b e t w e e n scalp discharge p a t t e r n s a n d t h o s e f r o m each o f t h e deeper electrode placements. A c o m b i n a t i o n of s c a l p - n a s o p h a r y n g e a l - s p h e n o i d a l and scalp-nasopharyngeal-sphenoidal-nasoethmoidal t e c h n i q u e s were used in t w o p a t i e n t s w i t h s u s p e c t e d t e m p o r a l lobe epilepsy; t h e diagnosis was c o n f i r m e d in o n e a n d altered t o o r b i t o f r o n t a l (focal) epilepsy in t h e second, The contribution of multiple recording techniques is reviewed. Its c o n t r i b u t i o n to medical t h e r a p y and surgical i n t e r v e n t i o n will be discussed.
19. I m p o r t a n c e o f dorsal and lateral decubitus in detecting and abolishing sleep-induced apneas (SIA). - - J.P. C6t~, J.P. Bernier, M. Lebel and J. Reiher (Sherbrooke, Canada) T h a t p o s t u r e can a f f e c t SIA has previously b e e n alluded to. Its i m p o r t a n c e has, h o w e v e r , n o t b e e n widely recognized, especially its relevance to the search for simpler a n d less invasive t r e a t m e n t s of this condition. This s t u d y was u n d e r t a k e n to assess h o w consistently a n d t o w h a t e x t e n t a p n e a s a n d s y m p t o m s of SIA c o u l d be effectively m o d i f i e d b y sleeping postures. O b s e r v a t i o n s were m a d e f r o m a c o n s e c u t i v e series of 20 p a t i e n t s w i t h SIA in w h o m s u f f i c i e n t d a y t i m e or all-night sleep p o l y g r a p h i c recordings were available in b o t h dorsal a n d 50 ° lateral decubitus positions, w i t h t h e f o l l o w i n g c o n c l u s i o n s :
SOCIETY PROCEEDINGS (1) R e c o r d i n g in t h e dorsal d e c u b i t u s p o s i t i o n is m a n d a t o r y for d e t e c t i o n of SIA In t h a t position, the E E G h a l l m a r k s of SIA can be r e c o g n i z e d even without the benefit of pneumographic monitoring. {2) In t h e 50 ° lateral d e c u b i t u s p o s i t i o n , i m m e d i a t e a n d c o n s i s t e n t s u b s i d e n c e o f apneas is observed in 19 o u t o f 20 p a t i e n t s w i t h n o r m a l progression t h r o u g h various stages o f sleep. (3) D a y t i m e recordings in b o t h dorsal a n d lateral d e c u b i t u s provides i n f o r m a t i o n w h i c h is equivalent to t h a t o f all-night sleep recordings, at less cost. ~4) Posture specifications in studies o n SIA o u g h t to be i n c l u d e d in the m e t h o d o l o g i c a l d e s c r i p t i o n A d d i t i o n a l investigation of sleeping in lateral d e c u b i t u s as an effective t r e a t m e n t of SIA seems warranted
20. Hypersomnia-sleep-apnea syndrome: report of 3 female cases. -- C. Guerreiro and B. Ehren. berg (Unicamp and Boston. Mass.) T w o p a t i e n t s with severe h y p e r s o m n i a - s i e e p a p n e a s y n d r o m e a n d one p a t i e n t with clinically significant s l e e p - h y p o p n e a are r e p o r t e d . Excessive daytime sleepiness, decreased daytime activity levels, a b n o r m a l b e h a v i o r (1 case), m o r n i n g headaches ( 2 c a s e s ) , excessive weight ( 2 c a s e s ) , heavy snoring, cardiac a r r h y t h m i a s (2 cases) and m u l t i p l e medical p r o b l e m s are t h e main clinical findings. T h e y were diagnosed o n Lhe basis of t h e clinical findings and nap sleep studies w i t h p o l y s o m n o g r a p h y . Tracheostomy, p e r f o r m e d in the severe cases, alleviated d r a m a t i c a l l y the clinical findings of these patients. T h e sleep h y p o p n e a p a t i e n t achieved an e x c e l l e n t result w i t h o x y g e n t h e r a p y d u r i n g t h e n i g h t in a s h o r t follow-up. T h e E E G c h a r a c t e r i s t i c s seen in such sleep disturb a n c e s will be discussed. In a d d i t i o n , t h e p a t h o p h y s iologic r e l a t i o n s h i p o f t h e clinical findings to t h e d i s t u r b a n c e o f sleep will be reviewed a n d a new hypothesis presented.
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Society proceedings EASTERN ASSOCIATION OF ELECTROENCEPHALOGRAPHERS, LAURENTIAN SKI MEETING Le Chantecler, Ste. Adele, Que., February 26--March 1, 1981
Secretary~Treasurer: Dr. IRA SHERWIN EA EEG, 200 Springs Road (151), Bedford, Mass. 01730 (U.S.A.) (Accepted for publication: April 8, 1981)
1. Increased response to 'non-competitive' GABA antagonists in amygdala-kindled r a t s . M.W. Kalichman, K.E. Livingston and W.M. Burnham (Toronto, Canada) The convulsant potency of drugs which antagonize GABA-mediated inhibition was measured 1 m o n t h subsequent to kindling in amygdala-kindled and 'handled control' rats. The potency of the 'noncompetitive' GABA antagonists, picrotoxin, NMPP barbituric acid and pentylenetetrazol, was found to be significantly increased in kindled animals. No change was found, however, in the potencies of the specific receptor blocker bicuculline, or of the GABA synthesis inhibitors isoniazid and 3-mercaptopropionic acid. These findings suggest that kindling induces a long-lasting functional deficit in GABAmediated inhibition, and that the deficit involves changes in the later steps in GABAergic transmission -- those subsequent to the process of synaptic recognition.
2. What is the role of GABA in seizure mechanisms?. -- G.H. Fromm, A.S. Chattha and Ch.F. Terrence (Pittsburgh, Pa.) The role of GABA in seizure mechanisms remains elusive despite considerable research. We have found that anti-absence drugs selectively depress descending inhibitory pathways, such as the periventricular inhibition (PVI) of the trigeminal nucleus. Therefore, we have investigated the effect of agonists and antagonists of GABA, and also of acetylcholine, on our experimental model. Bicuculline markedly facilitated the PVI. Muscimol antagonized the effect of bicuculline, but had a variable effect when given alone. Eserine also markedly facilitated the PVI. Atropine antagonized the effect of both eserine and bicuculline, but had a variable effect when given alone.
Our results indicate that the PVI is modulated by a GABAergic inhibitory mechanism, and by a cholinergic facilitatory mechanism. This suggests that the mechanism of action of anti-absence drugs may involve both an anticholinergic and a GABAergie effect. The difficulty in identifying the role of GABA in the control of seizures is thus due to the interaction of GABA and acetylcholine mechanisms, which makes it difficult to study one of these neurotransmitters in isolation.
3. Potentiation of recruiting responses in feline generalized penicillin epilepsy. -- G. Kostopoulos and M. Avoli (Montreal, Canada) Rhythmic stimulation of nucleus centralis medialis in cats produced recruiting responses in cortex and thalamus. Stimulus intensity was adjusted so that the second or third stimulus in a train of stimuli was at threshold for producing a recruiting response (a monophasic negative wave in cortical leads). The amplitude of the responses fluctuated presumably due to subtle changes in arousal. However, consistent records were obtained through EEG averaging. Following 2--3 control averages, 350,000 IU of penicillin were injected i.m. which is known to produce generalized bilaterally synchronous spike and wave discharges in about 1--2 h. The amplitude of the averages started progressively to increase before the appearance of spike and wave discharges and often as early as 10 min after the injection of penicillin. Maximum recruitment was now produced by a shorter train of stimuli while individual recruiting waves acquired positive phases of progressively larger amplitude. Often such large biphasic recruiting waves occluded the appearance of the succeeding recruiting response. We have previously described similar features characterizing the evolution of spikes of spike and wave discharges. Along with previous studies, the present findings support the
0013-4649/81/0000--O000/$02.50 © 1981 Elscvier/North-Holland Scientific Publishers, Ltd.
44P p r o p o s a l t h a t spike a n d wave discharges are p r o d u c e d b y similar t h a l a m o c o r t i c a l volleys as t h o s e p r o d u c i n g recruiting responses.
4. D e t e c t i n g ear d o m i n a n c e using a u d i t o r y e v o k e d p o t e n t i a l s . -- F. M a r t i n , R. E f r o n a n d E.W. Y u n d (Martinez, Calif.) T h e ear d o m i n a n c e for p i t c h described b y E f r o n a n d Y u n d (J. acoust. Soc. A m e r . , 1 9 7 6 , 59: 8 8 9 ) has b e e n previously d e t e c t e d only b y p s y c h o p h y s i c a l methods. The present report uses the P 3 0 0 c o m p o n e n t of t h e a u d i t o r y e v o k e d p o t e n t i a l to i d e n t i f y t h e m a g n i t u d e and d i r e c t i o n of ear d o m i n a n c e . T h e m e t h o d entails t h e p r e s e n t a t i o n of a series of identical d i c h o t i c chords. R a n d o m l y interspersed in this series are b i n a u r a l t o n e s with a f r e q u e n c y s o m e w h e r e b e t w e e n t h e left a n d right ear t o n e s o f t h e d i c h o t i c chords. A P 3 0 0 wave is generated only when the binaural tone's pitch is p e r c e p t i b l y d i f f e r e n t f r o m t h a t o f t h e series o f d i c h o t i c chords. T h e results o f this m e t h o d correlate well with p s y c h o p h y s i c a l m e a s u r e s of ear d o m i n a n c e in t h e s a m e subjects.
5. Regional variability analysis o f e v o k e d p o t e n t i a l s . -- P.K.H. Wong, C.T. L o m b r o s o a n d Y. Mats u m i y a ( B o s t o n , Mass.) In p a t i e n t s w i t h cortical disease, e v o k e d p o t e n t i a l s ( E P S ) m a y be h e l p f u l in l o c a l i z a t i o n of lesion. One w o u l d e x p e c t a b n o r m a l i t i e s in l a t e n c y , a m p l i t u d e and l o t m o r p h o l o g y o f t h e p e a k c o m p o n e n t s r e c o r d e d over t h e a b n o r m a l c o r t e x . S u c h t r a d i t i o n a l analysis m a y s o m e t i m e s be i n a d e q u a t e as occasionally we see n o a p p a r e n t EP a b n o r m a l i t i e s in cases with clear s t r u c t u r a l lesions. We are currently investigating a d i f f e r e n t a p p r o a c h : t h a t of s t u d y i n g t h e variability of EP f r o m d i f f e r e n t regions using its signal-to-noise r a t i o ( S N R ) as an o b j e c t i v e measure. T h e u n d e r l y i n g h y p o t h e s i s is: w h e n s t i m u l a t e d , n o r m a l n e u r o n a l s t r u c t u r e s g e n e r a t e s t a b l e scalp p o t e n t i a l changes, while diseased s t r u c t u r e s m a y n o t , t h u s p r o d u c i n g EPs w h i c h vary significantly f r o m trial t o trial. This is r e f l e c t e d b y a l o w S N R (or p o o r s u p e r i m p o s i t i o n ) . T e c h n i c a l factors (artifacts, etc.) o f course s h o u l d b e c o n t r o l l e d for. T o test o u r h y p o t h e s i s , we s t u d i e d 18 cerebral palsy p a t i e n t s w i t h unilateral h e m i s p h e r i c lesion due t o p r e v i o u s b r a i n injury. P r e l i m i n a r y results are e n c o u r a g i n g . In t h e m a j o r i t y o f cases, regional variability m e a s u r e suggests a p p r o p r i a t e l y t h e side o f t h e lesion despite e q u i v o c a l results f r o m t r a d i t i o n a l peak c o m p o n e n t analysis. T h e data and m e t h o d
SOCIETY PROCEEDINGS o f calculating t h e S N R will be p r e s e n t e d a n d discussed.
6. E l e c t r o p h y s i o l o g i c a l d e v e l o p m e n t o f b r a i n s t e m a u d i t o r y f u n c t i o n in n e w b o r n s . - - L.J. Streletz, D.B. G e r s h a n d L.J. G r a z i a n i (Philadelphia, Pa.) Brain s t e m a u d i t o r y evoked p o t e n t i a l s ( B A E P s ) were s t u d i e d in 40 low risk i n f a n t s with c o n c e p t i o n a l ages b e t w e e n 26 a n d 42 weeks. T h e y were distinguished f r o m high risk i n f a n t s o n t h e basis o f neonatal medical complications. BAEPs were r e c o r d e d s i m u l t a n e o u s l y f r o m vertex-ipsilateral a n d -contralateral ear r e f e r e n c e t o aid in d i f f e r e n t i a t i o n of c o m p o n e n t s . M o n a u r a l 70 dB HL r a r e f a c t i o n clicks were p r e s e n t e d at a rate of l l / s e c . B o t h ears were r e c o r d e d a n d serial recordings at w e e k l y intervals were o b t a i n e d f r o m several infants. T h e peak a n d i n t e r p e a k latencies o f waves I, III and V were m e a s u r e d in t e r m a n d p r e t e r m infants. T h e o b s e r v e d s h o r t e n i n g o f wave I peak l a t e n c y a n d wave I V i n t e r p e a k l a t e n c y d u r i n g t h e n e w b o r n p e r i o d suggests t h a t t h e peripheral (processes b e f o r e wave I, 45%) a n d central (processes b e t w e e n waves I--V, 55%) contributions to development of the brain stem p o r t i o n o f t h e a u d i t o r y s y s t e m are n e a r l y equal. These results are c o m p a r e d t o o t h e r s investigating development of infant brain stem auditory function.
7. T h e e f f e c t o f increased i n t r a c r a n i a l pressure with o r w i t h o u t p a p i l l e d e m a o n t h e V E P . - - I. BodisWollner, M. O n o f r j a n d L. Mylin (New York, N.Y.) Visual e v o k e d p o t e n t i a l s (VEPs) were o b t a i n e d in o n e p a t i e n t w i t h unilateral p a p i l l e d e m a a n d o p t i c a t r o p h y in t h e o t h e r eye, a s e c o n d p a t i e n t w i t h bilateral p a p i l l e d e m a due t o h y d r o c e p h a l u s caused by a pineal t u m o r , a n d a t h i r d p a t i e n t with h y d r o cephalus without papilledema. Previous VEP studies in h y d r o c e p h a l u s used o n l y flash stimuli (Vikova 1 9 7 4 ; Ehle 1 9 7 9 ; Sklar 1 9 7 9 ; G a m b i 1980}. We s t u d i e d t r a n s i e n t and s t e a d y - s t a t e VEPs using c o u n t e r p h a s e gratings in each p a t i e n t b e f o r e a n d a f t e r t h e r a p y . T h e i r d a t a were c o m p a r e d with n o r m a t i v e data e s t a b l i s h e d in o u r l a b o r a t o r y using t h e same stimuli (Bodis-Wollner 1979}. T h e latency o f t h e m a j o r positive wave was d e l a y e d in b o t h p a t i e n t s w i t h h y d r o c e p h a l u s , a n d it decreased a f t e r t h e r a p y , while in t h e p a t i e n t with t h e F o s t e r - K e n n e d y s y n d r o m e t h e V E P was n o r m a l from t h e eye with p a p i l l e d e m a , a n d d e l a y e d f r o m t h e eye w i t h o p t i c a t r o p h y . T h e s t e a d y - s t a t e EPs similarly paraL leled t h e clinical r e c o v e r y following t h e r a p y , b u t t h e r e s p o n s e t o specific spatial f r e q u e n c i e s , t h e t i m e o f
EASTERN ASSOCIATION OF E L E C T R O E N C E P H A L O G R A P H E R S recovery, and the precise measurements of interocular differences revealed that the two types of EPs (recorded at slow and faster temporal rates) may tap different systems.
8. Depth electrode e x p l o r a t i o n b e f o r e surgery for e p i l e p s y : a l w a y s , s o m e t i m e s or never. - - G. Bouvier, J.-M. Saint-Hflaire, R. Maltais, R. B~ique and A. Leduc (Montreal, Canada) The present study is a review of our personal experience of the past 6 years. Out of 97 patients monitored with chronic surface electrodes (SE), 56 had a chronic monitoring with depth electrodes (DE). We found that chronic monitoring with DE was indispensable in 84% of the cases. 29 patients were classified as clear-cut cases prior to DE exploration but 83% of them were false clear-cut. The remaining 27 patients without any localizing elements, patients that otherwise would have been rejected, had a DE exploration and 90% of these had surgery with a high percentage of cure. Many conclusions may be drawn: (1) DE exploration is safe; (2) DE exploration should always be done before surgery; (3) surgical results largely favor such an apparently aggressive approach.
9. Thalamic discharge patterns. -- O.J. Andy and M. Jurko (Jackson, Miss.) Diagnostic depth EEG recordings were done in 15 patients having medically intractable seizures. Recordings were made in the resting state at each level of electrode insertion and following electrical stimulation. Bipolar recordings were made from a concentric electrode at the tip and from each of the two components referred to the scalp. Bipolar scalp recordings were also made. Thaiamic discharge frequency patterns grouped themselves as follows: 3--7/sec, 8--12/sec, 13--17/sec and 18--25/sec. The patterns varied from sinusoidal to sharp wave configurations and spike and wave patterns. Single spikes with a predominant negative or positive polarity occurred most often. Biphasic, triphasic and polyspikes were seldom present. The spikes tended to occur in bursts of 0.5--1.5 sec duration, most lasting less than 1.0 sec. Injury discharge patterns often developed with small increments of electrode insertion, 0.5--1.0 ram. The injury discharge may last a few seconds or slowly build up to a prolonged discharge. This depth discharge may or may not spread to scalp recording electrodes. Electrical stimulation in some instances also induced discharges. Behavioral changes were associated with the thalamic discharges
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in 7 patients. These consisted of eye blinking, twitching of the face, chin lip and forehead, eyeball movements, conjugate eye turning, pupil dilation, and jerking of the extremities. These various movements were most frequently associated with 4/sec to 6/sec bursts, and occasionally with 3/sec bursts in the thalamus.
10. S o m e relationships b e t w e e n spikes, seizures and sleep. - - J. G o t m a n , P. G l o o r , J.R. Ives, A. Olivier and F. Q u e s n e y (Montreal, Canada)
In 5 epileptic patients with electrodes chronically implanted in the temporal and frontal areas, we studied the interaction in time, over several days, between occurrence of seizures, inter-ictal spiking rate and activation of inter-ictal spiking by sleep. Sleep staging was impossible because no scalp electrode was available, but cyclic variations in spiking activity, present during the night and not during the day, were assumed to be caused by sleep. Spike recognition was performed automatically and continuously during several days for each patient. The following observations were made: (1) Seizures rarely occurred during nights in which there was clear cyclic sleep activation of spiking. (2) Repeated seizures during daytime or seizure occurrence at night corresponded to a relatively uniform spiking rate at night (no cyclic activation), most clearly seen in the region where seizures originated; other areas could remain subject to cyclic fluctuations. (3) Seizures were not preceded or followed (in terms of minutes or hours) by clear changes in spiking rate (except one post-ictal activation). (4) Seizures did not occur when the spiking rate was the highest. These observations are tentative, given the small number of patients. They nevertheless raise the question of the apparent lack of temporal relationship between seizure occurrence and spiking rate.
11. Myoclonic absence: presentation of a case and review of its features. - - M. McBride and M.H. Charlton (Rochester, N.Y.) A 13-year~ld male was admitted to hospital on account of a 2 h confusional state, accompanied by 2--3 c/sec rhythmic myoclonus of his upper extremities and neck. This was associated with bilaterally synchronous 2--3 c/sec spike and wave activity on EEG. The confusional state and the myoclonus disappeared 2 min after administration of i.v. diazepam. Later, single or repetitive jerks recurred concurrent with spike and wave discharge
46P on EEG, finally controlled by valproate and acetazolamide. Myoclonic absence presents points of similarity and difference from other forms of absence in regard to genetic factors, sex ratio, age of onset, alteration of consciousness, concurrence of grand real, photosensitivity, response to medication, and EEG manifestations. These are discussed with respect to the present case.
12. Differential behavioral effects of spike-wave discharge. -- M.M. Often and A.F. Mirsky (Boston, Mass. and Bethe~la, Md.) Behavioral tasks utilizing different sensory modalities were administered to a group of 7 petit mal patients with generalized spike-wave discharges in the EEG and clinical absences. The purpose was to assess the functional capabilities of patients during EEG seizure discharge. The tasks required a simple or discriminative (key press) response to spatially discrete or diffuse visual stimuli, pure tones and, in one case, shock to the median nerve. Repetitive execution of the response without the presentation of task stimuli was also tested. Performance was monitored simultaneously with 6--10 channels of EEG recorded from bilaterally placed parasagittal scalp electrodes. During tasks involving discrete visual stimuli, eye position was recorded on videotape. Changes in correct responding over successive pre-seizure, seizure, and post-seizure segments were analyzed separately for each patient. Although, as expected, correct responding was significantly reduced during spike-wave discharge, the degree of behavioral impairment and its time course in relation to the spike-wave burst depended on stimulus modality, with individual patients showing unique patterns of functional impairment and recovery. The results underline the idiosyncratic expression of seizures among patients sharing a c o m m o n diagnosis and suggest differential rather than uniform disruption of functional systems during spike-wave discharge.
13. Epileptiform EEG abnormalities and photosensitivity in relatives o f patients with focal epilepsy, -- M. Straszak and E. Andermann (Montreal, Canada) Although genetic factors are known to be important in generalized epilepsy, their role in focal epilepsy is less welt established. Andermann (1972) was able to demonstrate a significantly increased frequency of EEG abnormalities in relatives of patients operated for focal epilepsy as compared to
SOCIETY PROCEEDINGS control relatives. These abnormalities were markedly age- and sex-dependent, as in generalized epilepsy. Based on these findings, a multifactorial mode of inheritance was postulated for both focal and generalized epilepsy (Andermann, 1980). We have reanalyzed the data on epileptiform EEG abnormalities in 167 first degree relatives of focal probands, employihg stricter electroencephalographic criteria (Gloor 1978), and compared the findings in relatives according to the type of removal (temporal only, fronto-temporal, etc.), as well as the sex and age of the proband. Total epileptiform EEG abnormalities were again significantly more frequent in experimental relatives, as compared to control relatives (14.5% vs. 6.3%, P ~ 0.05). In particular, this was true for generalized epileptiform abnormalities (7.9% vs. 1.1%, P ~ 0.02), whereas focal epileptiform abnormalities were not significantly elevated. Photosensitive epileptiform EEG abnormalities were also more frequent in experimental relatives, but the differences were not significant. These abnormalities were again found to be sex- and age-dependent. All types of EEG abnormalities were more frequent in relatives of patients with temporal lobe removals alone as compared with other relatives, particularly those of patients with both frontal and temporal removals. Abnormal photosensitivity was found more frequently in relatives of temporal probands than in relatives of those with combined ['ronto-temporal removals (9.5% vs. 0.0%. P = 0.03 L The findings confirm the presence of genetic factors in focal epilepsy and suggest that generalized epileptiform EEG abnormalities and abnormal photosensitivity are indicative of a genetic predisposition to both generalized and focal epilepsy, particularly temporal lobe epilepsy.
14. 32-channel cable-telemetry: w h o needs it?. -J.R. Ives, J. Gotman, P. Gloor and A. Olivier
(Montreal, Canada) Epileptic patients who require exploration with chronic multicontact (9) stereotaxic depth electrodes (10) may have 100 recording sites available if surface/ sphenoidal contacts are also included. When 32 channels are used, this doubles the simultaneous coverage and should reduce the implantation period. Our fundamental reason necessitating depth electrodes is the failure of surface/sphenoidal recordings to resolve the epileptic focus. Thus it is logical to investigate comparative recordings between surface and depth. 32 channels permit a m o r e realistic approach to this form of investigation. The 32-channel preamplifier/multiplexor worn
EASTERN
ASSOCIATION
OF ELECTROENCEPHALOGRAPHERS
by the patient weighs less than 170 g while the 32channel multiplexed signal is completely compatible with the existing cable-telemetry system. The 32 channels of E E G are dealt with by the computer and the seizure-monitoring program which records 2 min before and 2 rain after the pushing of the patient's seizure-push-button. The computer can then play back 16 channels at a time of these 4 min sequences which are time-locked by the digital clock. By placing them above one another, the 32~channel seizure can be easily read by the electroencephalographer.
15. Antagonism between concurrently developing kindled seizure loci in the limbic system of the rat. -- J.L. Burchfiel (Boston, Mass.) Evidence from many laboratories indicates that kindling induces extensive reorganization of neural elements beyond the actual site of stimulation. Particularly striking evidence of this is the propagation of epileptic hyperexcitability demonstrated by the 'transfer effect': seizure development kindled from one brain site ('primary site') induces enhanced seizure susceptibility in other brain regions ('secondary' or 'transfer' sites). In addition to these 'positive transfer' effects, however, there is evidence that secondary site kindling can temporarily block seizures from the primary site (the so-called 'interference effect' or 'negative transfer'). In order to study in more detail positive and negative transfer during kindling we attempted to kindle concurrently two brain sites (septal area and entorhinal cortex) by alternatively stimulating them on a trial-by-trial basis. This 'alternate kindling' paradigm was characterized by a striking antagonism of seizure development. Typically, progressive seizure development occurred from only one site; kindling from the alternately stimulated site was suppressed. Which site became dominant during alternate kindling appeared to be random: in 13 animals, the septum was dominant in 8 and the entorhinal cortex in 5. Antagonism of kindling appears to be the best description of the results since kindling failed to develop even after several times the number of stimulations required for primary kindling. Moreover, stimulation of the suppressed site consistently elicited long afterdischarges and behavioral signs of limbic activation (behavioral arrest and automatisms). Thus, neuronal excitability per se was not suppressed; rather, it was the propagation of neuronal excitability to motor mechanisms (kindling) which was blocked. These results indicate that transsynaptic neural reorganization induced by kindling involves both positive and negative effects upon seizure susceptibility.
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16. The seizures of morphea. -- P. Hwang, F. Andermann, K. Metrakos and G. Watters (Montreal, Canada) In a series of 24 patients with morphea (localized scleroderma), both epileptogenic and non-epileptogenic EEG abnormalities were 3 times as common as in an age-matched control population. Twenty-five per cent (6/24) of patients had clinical seizures. Of the 6 patients studied, 4 had 'coup de sabre' lesions in the territory of the first trigeminal division, and seizures arising from the underlying brain. Seizures occurred in 66% (4/6) of patients with coup de sabre lesions. Two other patients had morphea of the leg and body respectively. Both had seizures originating in the temporal lobe. The incidence of seizures in extra-trigeminal morphea was 11% (2/18). The seizures were easily controlled and there was a strong tendency for improvement in electrographic abnormalities, suggesting that the epileptic disorder of these patients is benign.
17. A longitudinal s t u d y o f f i e l d d e f e c t s using transient and steady-state VEP stimulation. - - M. Onofrj, I. Bodis-Wollner and L. Mylin (New York, N.Y.) We studied 15 patients referred for VEP evaluation and suspected of having a field defect. VEP interpretation was 'blind', i.e., not tainted by information concerning campimetry. Stimuli were reversing checkerboard patterns with 15' checks and vertical gratings of 13', in contrast with the larger stimuli used by other researchers (Halliday and Blumhardt 1979; Agrado 1980). Nine degree full field and hemifield stimuli were used. VEPs were recorded from a horizontal array of electrodes with Oz 2.5 cm above the inion. Our data on normal subjects confirm the 'paradoxical lateralization' of the responses to hemifield stimuli (Barrett 1976; Shagass 1976). The VEP to full-field stimuli forecasted the campimetry results only in 50% of our patients, while there was diagnostic concordance in 84% of patients using hemifield stimuli. 'Crossed' alterations were found in bitemporal field defects and 'uncrossed' ones in homonymous hemianopia. Steady-state responses did not show the same lateralization as transient responses in two patients. A longitudinal study of 6 patients revealed that the classic inverted polarity EP appears only several months following the initial symptoms.
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18. EEG investigation of temporal lobe disorders: a multi-basal-electrode a p p r o a c h , - J.H. Fisher and D.L. Schomer (Boston, Mass.) E p i l e p t o g e n i c foci in deep s t r u c t u r e s (mesiobasal or o r b i t o f r o n t a l ) m a y p r o d u c e c o n f u s i n g discharges w h e n r e c o r d e d f r o m s t a n d a r d scalp electrodes. Neurophysiologic e f f o r t s t o e x a m i n e t h e area of a n a t o m i c i n t e r e s t have led to t h e i n t r o d u c t i o n o f n a s o p h a r y n geal, s p h e n o i d a l , a n d n a s o e t h m o i d a l r e c o r d i n g techniques. C o r r e l a t i o n s have b e e n r e p o r t e d b e t w e e n scalp discharge p a t t e r n s a n d t h o s e f r o m each o f t h e deeper electrode placements. A c o m b i n a t i o n of s c a l p - n a s o p h a r y n g e a l - s p h e n o i d a l and scalp-nasopharyngeal-sphenoidal-nasoethmoidal t e c h n i q u e s were used in t w o p a t i e n t s w i t h s u s p e c t e d t e m p o r a l lobe epilepsy; t h e diagnosis was c o n f i r m e d in o n e a n d altered t o o r b i t o f r o n t a l (focal) epilepsy in t h e second, The contribution of multiple recording techniques is reviewed. Its c o n t r i b u t i o n to medical t h e r a p y and surgical i n t e r v e n t i o n will be discussed.
19. I m p o r t a n c e o f dorsal and lateral decubitus in detecting and abolishing sleep-induced apneas (SIA). - - J.P. C6t~, J.P. Bernier, M. Lebel and J. Reiher (Sherbrooke, Canada) T h a t p o s t u r e can a f f e c t SIA has previously b e e n alluded to. Its i m p o r t a n c e has, h o w e v e r , n o t b e e n widely recognized, especially its relevance to the search for simpler a n d less invasive t r e a t m e n t s of this condition. This s t u d y was u n d e r t a k e n to assess h o w consistently a n d t o w h a t e x t e n t a p n e a s a n d s y m p t o m s of SIA c o u l d be effectively m o d i f i e d b y sleeping postures. O b s e r v a t i o n s were m a d e f r o m a c o n s e c u t i v e series of 20 p a t i e n t s w i t h SIA in w h o m s u f f i c i e n t d a y t i m e or all-night sleep p o l y g r a p h i c recordings were available in b o t h dorsal a n d 50 ° lateral decubitus positions, w i t h t h e f o l l o w i n g c o n c l u s i o n s :
SOCIETY PROCEEDINGS (1) R e c o r d i n g in t h e dorsal d e c u b i t u s p o s i t i o n is m a n d a t o r y for d e t e c t i o n of SIA In t h a t position, the E E G h a l l m a r k s of SIA can be r e c o g n i z e d even without the benefit of pneumographic monitoring. {2) In t h e 50 ° lateral d e c u b i t u s p o s i t i o n , i m m e d i a t e a n d c o n s i s t e n t s u b s i d e n c e o f apneas is observed in 19 o u t o f 20 p a t i e n t s w i t h n o r m a l progression t h r o u g h various stages o f sleep. (3) D a y t i m e recordings in b o t h dorsal a n d lateral d e c u b i t u s provides i n f o r m a t i o n w h i c h is equivalent to t h a t o f all-night sleep recordings, at less cost. ~4) Posture specifications in studies o n SIA o u g h t to be i n c l u d e d in the m e t h o d o l o g i c a l d e s c r i p t i o n A d d i t i o n a l investigation of sleeping in lateral d e c u b i t u s as an effective t r e a t m e n t of SIA seems warranted
20. Hypersomnia-sleep-apnea syndrome: report of 3 female cases. -- C. Guerreiro and B. Ehren. berg (Unicamp and Boston. Mass.) T w o p a t i e n t s with severe h y p e r s o m n i a - s i e e p a p n e a s y n d r o m e a n d one p a t i e n t with clinically significant s l e e p - h y p o p n e a are r e p o r t e d . Excessive daytime sleepiness, decreased daytime activity levels, a b n o r m a l b e h a v i o r (1 case), m o r n i n g headaches ( 2 c a s e s ) , excessive weight ( 2 c a s e s ) , heavy snoring, cardiac a r r h y t h m i a s (2 cases) and m u l t i p l e medical p r o b l e m s are t h e main clinical findings. T h e y were diagnosed o n Lhe basis of t h e clinical findings and nap sleep studies w i t h p o l y s o m n o g r a p h y . Tracheostomy, p e r f o r m e d in the severe cases, alleviated d r a m a t i c a l l y the clinical findings of these patients. T h e sleep h y p o p n e a p a t i e n t achieved an e x c e l l e n t result w i t h o x y g e n t h e r a p y d u r i n g t h e n i g h t in a s h o r t follow-up. T h e E E G c h a r a c t e r i s t i c s seen in such sleep disturb a n c e s will be discussed. In a d d i t i o n , t h e p a t h o p h y s iologic r e l a t i o n s h i p o f t h e clinical findings to t h e d i s t u r b a n c e o f sleep will be reviewed a n d a new hypothesis presented.