PHOTOPAROXYSMAL RESPONSES
MAURO MUSZKAT * — ROSANA M. GUIMARÃES * — ADEMIR B. DA SILVA * CARLOS J. REIS DE CAMPOS *
S U M M A R Y — S i x t y - f i v e outpatients w i t h p h o t o p a r o x y s m a l response ( P P R ) d u r i n g routine E E G w e r e studied. T h e P P R showed prevalence in w o m e n (75.4%). Seizures w e r e found in 66.1% of cases. T h e r e s t r e c o r d i n g s w e r e abnormal in 41.8% w i t h p r e v a l e n c e of g e n e -ralized p a r o x y s m . E i g h t patterns of P P R w e r e observed, b e i n g p o l y s p i k e m i x e d t o s l o w w a v e the most frequent ( 5 3 % ) . T h e epileptic g r o u p s h o w e d a b i m o d a l distribution in the several bands of photic stimulation, near 8 and 20-24 H z . A sustained p a r o x y s m a l a b n o r m a l i t y persisting after the photic stimulation w a s present in 6 epileptic patients.
Resposta iotoparoxística.
F o r a m estudados 65 pacientes d e ambulatório que apresentaram resposta f o t o p a r o x í s t i c a ( R F ) no E E G intercrítico. H o u v e p r e d o m í n i o da R F no sexo feminino (75,4%) e 61,1% d o s casos tinham história d e crises epilépticas. D o s 8 padrões d e R F observados, o padrão poliponta-onda lenta f o i o mais freqüente ( 5 3 % ) . E m relação às f a i x a s d e fotostimulação, o g r u p o epiléptico apresentou d i s t r i b u i ç ã o b i m o d a l (8 e 20-24 H z ) . Os autores discutem seus achados e m relação aos descritos na literatura.
T h e relationship between epilepsy and visual stimulation has been reported since the end of last century. T h e first reference to photosensitive epilepsy w a s made by G o w e r s ( 1 8 8 3 ) , w h o described t w o patients presenting seizures when exposed to bright l i g h t s . T h e r e followed references by Radovicci ( 1 9 3 2 ) « Cobb (1947)2, Bickford et al. ( 1 9 5 2 ) 1 . M o r e recently the papers from Jeavons & Harding 10 and Gastaut et a U described the most important clinical and electroencephalographic aspects of the photosensitive epilepsy. T w o concepts encompass the relationship between light and epilepsy: ( 1 ) protosensitivity — abnormal response to the visual stimulation observed in laboratory, not necessarily associated to seizures; it probably represents a suscepti-bility pattern, genetically determined 9.20; the photosensitivity can be found in roughly 3 % of patients w h o underwent a routine E E G recording H . 1 5 ; ( 2 ) photosensitive epilepsy — it includes the cases of patients with seizures and photosensitivity. According to Jeavons 9 and Jeavons & H a r d i n g 10 the photosensitive epilepsy can be distinguished in t w o forms; a. pure photosensitive epilepsy — it is a relative common form of reflex epilepsy, where the seizures are t r i g g e r e d only by visual stimulation of the retina 3; its most common type is the so-called «television e p i l e p s y » 6,18; b. epilepsy with photosensitivity — it includes the cases of patients with seizures not related to light stimulation, but with photosensitivity in electroencephalographic studies 9.20. T h e diagnosis of photosensitivity is made by the presence of «photopa-roxysmal response» ( P P R ) in intermittent photic stimulation on the E E G recordings. T h e P P R consists of generalized discharge recorded in all regions of the scalp during intermittent photic stimulation. Usually, it consists of spike and w a v e and polyspike and w a v e complexes. T h e localized response in anterior ( p h o t o m y o c l o n i c response) and posterior regions (photic d r i v i n g ) are considered « p h y s i o l o g i c a l » and are excluded
* Setor d e I n v e s t i g a ç ã o e T r a t a m e n t o das E p i l e p s i a s e Setor d e Eletrencefalografia, D e p a r t a m e n t o d e N e u r o l o g i a e N e u r o c i r u r g i a , Escola P a u l i s t a d e Medicina. T h i s paper w a s supported in p a r t b y g r a n t s f r o m C N P q .
from the concept of P P R 12,19. T h e photosensitivity is genetically determined, fre-quently related to familiar trait, with clear prevalence in w o m e n 6,10,15. D o o s e et a l .3
and D o o s e & G e r k e n * reported that the P P R can be linked t o susceptibility t o develop «centrencephalic seizures». Oastaut et a l .6
considered that the P P R is frequently limited to patients with «subcortical primary e p i l e p s y » , observing this response patterns, in 40% of « p e t i t m a l » cases and 2 0 % of « g r a n d m a l » cases. W i l k i n s et al.20.21 found P P R frequently associated to « g e n e r a l i z e d primary e p i l e p s y » . Although uncommon, the P P R can be found in patients without epilepsy, in cases of migraine, hysteria, anxiety, toxic and metabolic states 12,13,19.
T h e purpose of this paper is to report the study on graphic-elements that compose the P P R , as well as analyzing them in epileptic and non-epileptic groups.
M A T E R I A L A N D M E T H O D
S i x t y - f i v e outpatients seen at t h e N e u r o l o g y D e p a r t m e n t , Escola P a u l i s t a de M e d i c i n a , w e r e selected w h e n p h o t i c stimulation induced P P R during1
routine E E G . A l l the patients had standard E E G r e c o r d i n g s d o n e using a 8-channel Grass M o d e l E E G M a c h i n e . E l e c t r o d e s w e r e attached to t h e scalp a c c o r d i n g t o t h e 10-20 s y s t e m of t h e I n t e r n a t i o n a l F e d e r a t i o n . P h o t i c s t i m u l a t i o n w a s a p p l i e d t o a l l the patients in t h e f r e q u e n c y of 6, 8, 16, 20, 24 H z in addition t o m i x e d f r e q u e n c y . Clinical a n d E E G data w e r e c o l l e c t e d . T h e E E G d a t a i n c l u d e : ( a ) b a c k g r o u n d a c t i v i t y ; ( b ) r e s t i n g p a r o x y s m a l c h a n g e s ; ( c ) m o r p h o l o g i c analysis of P P R .
R E S U L T S
A . Clinical d a t a : T h e P P R s h o w e d c l e a r prevalence in w o m e n ( 7 5 . 4 % ) . T h e a v e r a g e a g e w a s 13.5 ^ 11 y e a r , r a n g i n g from 1 t o 69 y e a r s . Seizures w e r e found in 66.1% of cases (n—-43) and t h e r e m a i n i n g 22 w e r e d i s t r i b u t e d i n t o the p a r o x y s m a l non-epileptic disturbance ( n = 1 0 ) i n c l u d i n g m i g r a i n e , dizziness, s y n c o p e ; and o t h e r d i s t u r b a n c e s ( n = 1 2 ) including stroke, b e h a v i o r a l d i s o r d e r s and m e t a b o l i c states. T h e d i s t r i b u t i o n of seizure t y p e found in 43 p a t i e n t s is s h o w n in table 1. I t can b e easily seen a clear p r e v a l e n c e of the tonic-clonic t y p e ( 6 2 . 8 % ) . T h e pure photosensitive e p i l e p s y w a s found in j u s t one case, in w h i c h the s e i z u r e s w e r e t r i g g e r e d w h e n t h e patient w a s w a t c h i n g t e l e v i s i o n .
B . E l e c t r o e n c e p h a l o g r a p h ^ d a t a :
1. B a c k g r o u n d a c t i v i t y —• I n 54 cases the b a c k g r o u n d a c t i v i t y w a s normal. I n 11 cases it w a s not p o s s i b l e t o r e c o r d the b a c k g r o u n d a c t i v i t y , because r e c o r d i n g s w e r e carried-out d u r i n g sleep. N o c h a n g e w a s o b s e r v e d in b a c k g r o u n d a c t i v i t y after i n t e r m i t t e n t photic stimulation ( b e f o r e : 9.83±1.10 H z ; a f t e r : 9.56±1.60 H z ) .
3. M o r p h o l o g i c analysis of P P R — E i g h t p a t t e r n s of P P R w e r e o b s e r v e d ( i n f r e q u e n c y o r d e r ) : ( 1 ) p o l y s p i k e m i x e d to s l o w w a v e , 55.3%; ( 2 ) p o l y s p i k e , 26.1%; ( 3 ) s p i k e - w a v e c o m p l e x , 20%; ( 4 ) spike, 20%; ( 5 ) s p i k e and s l o w w a v e , 16%; ( 6 ) i r r e g u l a r s p i k e -- w a v e , 12.3%; ( 7 ) p o l y s p i k e -- w a v e c o m p l e x , 13.8%; ( 8 ) r h y t h m i c s l o w -- w a v e , 9%. In 50 cases (76.9%) association of p a t t e r n s w a s o b s e r v e d . T h e m o s t f r e q u e n t association w a s the « 1 » w i t h «2i> p a t t e r n s ( n = 4 4 ) . T h e « 2 » p a t t e r n p r e v a i l e d in 8 H z band of photic stimulation, w h e r e a s o t h e r p a t t e r n s w e r e m o r e f r e q u e n t in 16 to 24 H z . T h e « 2 » p a t t e r n s h o w e d in a v e r a g e 4 to 6 spikes f o r each c o m p l e x .
4. E p i l e p t i c x n o n - e p i l e p t i c g r o u p — A c o m p a r i s o n b e t w e e n e p i l e p t i c and non-epileptic g r o u p s h o w e d a closer h o m o g e n e i t y in the several b a n d s of p h o t i c s t i m u l a t i o n in non-epileptic patients, w h e r e a s in e p i l e p t i c g r o u p a b i m o d a l n e a r 8 and 20-24 H z w a s o b s e r v e d ( F i g . 1 ) . B o t h g r o u p s s h o w e d s i m i l a r d i s t r i b u t i o n in r e l a t i o n to E E G patterns, w i t h p r e v a i l i n g o f 1 p a t t e r n . N e v e r t h e l e s s , t h e p o l y s p i k e - w a v e c o m p l e x p a t t e r n w a s o b s e r v e d o n l y in e p i l e p t i c patients. A sustained p a r o x y s m a l a b n o r m a l i t y p e r s i s t i n g a f t e r the i n t e r m i t t e n t photic s t i m u l a t i o n ( « a f t e r - d i s c h a r g e » ) w a s p r e s e n t in 6 cases ( 9 . 2 % ) , all of t h e m f r o m e p i l e p t i c g r o u p .
C O M M E N T S
T h e prevalence of P P R in women and the average age of patients found in our paper is similar to literature data, although their causes are still unknown 9-n. One factor probably related is the oscilating level of estrogen 9. Jeavons & H a r d i n g1 0
reported cases where the P P R w a s associated to menstrual cycle phases.
W e have found a larger frequency of P P R ( 3 3 . 4 % ) in non-epileptic group than the reported in literature ( 3 % ) . W e ascribed this finding to our sample selection, w h e r e the E E G w a s performed in patients showing signs of central nervous system abnormalities, whereas in the literature the data are generally obtained from routine E E G recordings with a general population sample. G a s t a u t s found P P R in 40% of patients with absence seizures and in 20% of patients with tonic clonic seizures, ü o o s e & Jerkin 4 and Jeavons & Harding io found clear trend to photosensitive epilepsy in nomozygotic twins, and N e w m a r k & Penryi5 reported familial history of epilepsy in 25 to 3 9 % of protosensitive patients. Takahashi 19 points out the prevailing of P P R in generalized primary epilepsy.
since the authors found it in 9 0 % of photosensitive epileptic patients. In our series, the after-discharge w a s found in only 6 epileptic cases ( 9 . 2 % ) .
T h e polyspike^wave complex found only in epileptics can suggest that in photo-sensitive epileptic patients there is a prevalence of the excitatory component of the complex (the p o l y s p i k e ) o v e r the inhibitory ( s l o w w a v e ) . H o w e v e r , for its better comprehension such supposition demand further prospective study of neurophysiological nature.
R E F E R E N C E S
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