THE ELECTROENCEPHALOGRAM DURING SPONTANEOUS NIGHT
SLEEP IN EPILEPTIC PATIENTS
RUBENS MOURA RIBEIRO*; MICHEL P . L I S O N * ; J. ARMBRUST-FIGUEIREDO**
Recent advances in the electroencephalographic studies of normal sleep have modified the older hypothesis of the sleep mechanisms by newer inter-pretations, which explain sleep as the result of an inhibitory activity origi-nating from specific hypnogenic c e n t e r s7
-1 4
. The great importance of the
sleep was stressed by Gibbs and Gibbs 6
'20 years ago, when these authors stated that epileptic patients show more than twice seizure discharges in their EEG recorded during sleep than in the waking state. The five well known fundamental stages of sleep with especific electroencephalographic findings
were established by Dement and Kleitman2
in 1957.
These reports have presently focused the attention of the electroencepha-lographers upon the value of the sleep record as a useful tool for studying the electroencephalographic patterns of epileptic patients.
Our study was carried out in order to investigate the brain function of epileptic patients on the basis of electroencephalographic information during spontaneous night sleep.
M A T E R I A L A N D METHODS
F o r t h e p u r p o s e s of t h e present study, 5 p a t i e n t s w i t h t h e chief c o m p l a i n t of c o n v u l s i v e disorders w e r e i n v e s t i g a t e d . The EEGs w e r e t a k e n first a t day t i m e a s a r o u t i n e procedure and h a v e s h o w sharp w a v e s in t h e t e m p o r a l l e a d s in 4 cases, and b i l a t e r a l s p i k e and s l o w w a v e s a n d s y n c h r o n i c d i s c h a r g e s in o n e case. A second record w a s t a k e n d u r i n g s p o n t a n e o u s n i g h t s l e e p .
T h e EEGs w e r e recorded on an 8 c h a n n e l m o d e l VI Grass i n s t r u m e n t , the e l e c t r o d e s b e i n g placed a s u s u a l l y in t h e 1Q/20 s y s t e m ; m o n o p o l a r and bipolar t e c h n i q u e s w e r e u s e d1 5
. Eye m o v e m e n t s , s n o r i n g a n d r e a c t i v i t y t o a u d i t o r y s t i m u l i w e r e a l s o recorded.
R E S U L T S
T h e EEG findings in t h e 5 e x p e r i m e n t s i n d i c a t e t h a t t h e f o c a l sharp w a v e s , w h e n recorded d u r i n g t h e 1st and 2nd s t a g e s of s p o n t a n e o u s n i g h t sleep, are c h a r a c t e r i z e d by a s l i g h t e l e v a t i o n of t h e f r e q u e n c y of t h e d i s c h a r g e s . On t h e s a m e w a y , the q u a l i t a t i v e a s p e c t s of the b i o e l e c t r i c a l a c t i v i t y of subcortical
s t r u c t u r e s , s h o w s o m e d e g r e e of c h a n g e s in t h e i r m o r p h o l o g y ( F i g . 1 ) . O t h e r w i s e , t h e p a t i e n t w i t h c o n t i n u o u s b i l a t e r a l spike a n d w a v e d i s c h a r g e s o c c u r r i n g d u r i n g t h e w a k i n g s t a t e a n d s t a g e s I and II of s p o n t a n e o u s sleep, s h o w e d a c o m p l e t e a b s e n c e of t h e d i s c h a r g e s d u r i n g t h e 5 t h s t a g e or p a r a d o x i c a l p h a s e of t h e sleep ( F i g . 2) T h e s c h e m a t i c r e p r e s e n t a t i o n of t h e w h o l e n i g h t s l e e p i s s h o w n in F i g . 3 w h e r e o n e c a n n o t i c e t h e differents e v e n t s o c c u r r i n g d u r i n g t h e record.
COMMENTS
The qualitative study of EEGs obtained during the all night spontaneous sleep has established that there are actually a stage of light sleep characte-rized by slow waves activity and spindles burst, and the stage of deep sleep characterized by fast activity, also known as paradoxical phase of the sleep.
The experimental studies of French and Magoun5
, carried out in monkeys, have demonstrated that in the first stage, also named of cortical synchro-nization, occurs a moderate decrease of the muscular tone in the neck muscles and a slight reduction of the blood presure. From the electroence-phalographic point of view, this stage of the sleep is a very useful method of "sensibilization", mainly because it activates certain epileptic patterns, and shows some degree of reactivity for external stimulation. The second stage or deep sleep with desynchronized EEG, is characterized by vegetative disturbances, such as increase of pupil diameter and retraction of the nictante membrance of the cat. The above mentioned results suggest that the deep sleep system is related to an autonomic activity, probably of humoral nature, activating an autonomic neuro effector system elicits beha-vioral signs of deep sleep with desynchronized EEG patterns and eye movements 9
, as one can see in Fig. 3. Many a u t h o r s3
.4
-1 3
have used the terms activated sleep and rapid eye movement phase when refering to the paradoxical phase of sleep. In this stage of sleep the EEG records show fast activity and low voltage patterns as in awaked tracings. There is a moderate decrease in paroxysmal discharges either focal or centroencephalic in origen (Fig. 1), while electroencephalographic evoked reactivity to the sensorial stimulation is still absent.
The study of both normal and pathological patterns elicited during the all night spontaneous sleep can be explained on the basis of a sleep system with localization in different levels of midbrain, which may be considered the origen of these parameters. At the present time, neuro-physiological experiments related to study of all night sleep patterns suggest that the sleep system is made up of a multisynaptic pathway extending from spinal cord to the medial pontomesencephalic tegmentum. This ascending traject of hypnogenic circuit lends support to the idea that sleep is the result of an inhibitory activity exerted on subcortical l e v e l8
center maintain correlations with the neocortex and hippocampal structures through the limbicmidbrain circuit described by Nauta. In 1960 and 1961, Jouvet et al. " -1 2
reported that the neocortex is responsible for signs of sleep with a synchronized EEG pattern, while the rhomboencephalic region and interpenduncular nuclei seems likely to induce the deep stage of sleep with the typical desynchronized EEG patterns. In accordance to this expe-riments, either the light sleep or the deep sleep in cats does not need the neocortex for their manifestation.
In spite of the neocortex being not essential for the production of sleep, experiments concerned with the effect of reticular stimulation have suggested the existence of a corticoreticular projection, which would tend to inhibit the vigilance s y s t e m1 0
. The synchronized stage of sleep represents an inhibitory phenomenon since the stimulation of reticular formation increases the level of the vigilance system.
SUMMARY
The sleep sistem results of the activity of two components: a descending component originated in the limbic structures, and an ascending system invol-ving the bulbopontine structures which receives projections from the spinal cord components. Although the neocortex is not necessary for sleep mecha-nisms, it plays a very important role in sleep. Therefore, during the sleep state there is no significant quantitative difference in brain activity, but qualitative changes are recorded in EEG of epileptics patients during all night sleep.
RESUMO
O eletrencefalograma durante o sono noturno espontâneo em pacientes epilépticos
Foram estudados os traçados eletrencefalográficos obtidos durante o sono noturno de 5 pacientes epilépticos. Os resultados demonstram que a atividade paroxística focal evidencia modificações tanto qualitativas como quantitativas quando registrada no l.° e 2.° estágios do sono. Por outro lado, o EEG com descargas difusas e bilaterais intensas na fase inicial do sono, apresenta ausência de paroxismo na fase paradoxal. Assim, a análise dos diversos estágios do sono evidencia diferenças qualitativas e quantitativas na ativi-dade elétrica cerebral de pacientes epilépticos durante o sono noturno.
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