880
Electroencephalography and Clinical Neurophysiology, 1977, 4 3 : 8 8 0 - - 8 8 4 © Elsevier/North-Holland Scientific Publishers, Ltd.
Technical contribution AUTOMATIC NOCTURAL SLEEP SAMPLING: A USEFUL METHOD IN CLINICAL ELECTROENCEPHALOGRAPHY J.R. IVES and P. GLOOR
Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Quebec H3A 2B4 (Canada) (Accepted for publication: April 14, 1977)
Recording a patient's EEG during sleep is regarded as a helpful procedure by electroencephalographers, neurologists and neurosurgeons because it frequently enhances epileptiform discharges (Gibbs and Gibbs 1947; Passouant 1950; Gloor et al. 1958; Klass 1975; Gloor 1975; Rasmussen 1975). All candidates considered for surgical removal of epileptic foci at the Montreal Neurological Institute routinely undergo one or more examinations during sleep (Gloor 1975; Rasmussen 1975). Nightime sleep records are not routinely obtainable because of the heavy demands they make on laboratory personnel. Therefore, the patients are usually brought to the EEG laboratory during the day and encouraged to fall asleep. If sleep does not occur spontaneously, they are given hypnotic drugs such as sodium secobarbital (Seconal), often associated with chlorpromazine (Largactil) (Stewart 1957). The disadvantages of this procedure include the following: (1) The patients may fail to sleep in spite of the medication; (2) the drugs administered could conceivably alter the interictal epileptic activity; (3) the induced sleep primarily consists of stages I--II while other stages in which useful diagnostic information could be obtained are poorly represented (Klass 1975; Hess ]974; Kuijer and Buit-Gutter 1974). (4) The recordings are time consuming as they may tie up an EEG machine and an EEG technician for several hours. To overcome these difficulties, the 16 channel cable-telemetry EEG system (Ives et al. 1974; Ires and Gloor 1975; Ives et al. 1976) has been used as a basis for the development of a method which provides automatic sampling of the EEG throughout the night while the patient sleeps naturally in his hospital room.
Basic s y s t e m
The system (Fig. 1) consists of a cable telemetry unit (Ives et al. 1974; Ives et al. 1976) directly connected via a multistation intra-hospital wiring system
to the demultiplexer located on the EEG machine. Because this ystem is completely independent of the seizure monitoring system described earlier (Ives et al. 1976), noctural sleep sampling or specific seizure monitoring can be performed either independently or simultaneously. In the latter situation, a second EEG machine is required.
Patient's Room
i 3
4
T
EEGDepartme
.......
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Fig. 1. Block diagram (A) and actual components (B) of the sleep sampling system. (1) EEG electrodes on the patient's head (either scalp or sphenoidal); (2) small package containing 16 EEG preamplifiers and a 16 channel multiplexer; (3) cable to connect battery p o w e r to head mounted unit and to bring multiplexed signal to battery pack; (4) waist-worn belt containing batteries and anchor point for patient's 25-foot co-axial cable; (5) patient's 25-foot co-axial cable carrying multiplexed EEG to wall box; (6) wall box for relaying multiplexed EEG directly to EEG department; (7) cable connecting wall box to EEG department; (8) demultiplexer to reconstruct original EEG signals; (9) EEG machine for writing out reconstructed EEG; (10) control unit to (a) turn the EEG machine on and off at set times, (b) obtain samples of EEG at predetermined intervals and durations and (c) write o u t the t i m e of day on the top of the EEG paper every 10 sec during the sampling.
AUTOMATIC N O C T U R A L SLEEP SAMPLING
881
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Fig. 2. End of an EEG sample (at 22 : 17 : 32) and beginning of following one 10 min later. EEG displays patterns of stage II and IV, respectively. A gap (flat EEG) can be seen between the two samples which is created by the sampler to help the reader recognize the end of one sample and the beginning of the next.
Electrodes, preamplifier, multiplexer, demultiplexer The same sub-assemblies used for sleep monitoring are also employed for seizure monitoring (Ives et al. 1967). A special sleep montage may be used in some patients to aid in sleep-staging, if desired. However, generally, only three montages are used for the clinical workup patients suffering from epileptic seizures. One consists of antero-posterior temporal and parasagittal scalp derivations (Fig. 2). The others combine coronal derivations from scalp and chronically inserted spbenoidal electrodes (Ives and Gloor 1976; Ives and Gloor 1977) with derivations providing either antero-posterior temporal or parasagittal coverage. The montage for use with the cable-telemetry system must be selected prior to installation o f the electrodes because the montage is permanently wired into the electrode set. Hence, the montage can only be changed by removing one set and installing another. The preamplifier-multiplexer unit that is placed on the head is small (2.5 × 3.5 X 10 ram) and light (80
g). Thus, it is easily tolerated by patients of all ages who generally have as comfortable and as restful a night as can be expected in a hospital environment.
Patient preparation The electrodes are applied in the late afternoon along with the preamplifier-multiplexer and battery pack. While still in the EEG laboratory, the patient is connected to the EEG machine to ensure that the equipment is functioning properly and any problems are immediately corrected. The overnight procedure can be performed in one of two ways: (1) Immediately upon returning to the ward, the patient can be connected to a wall box which relays the multiplexed EEG to the EEG department. The sampling can then be started as soon as the EEG machine is free at the end o f the day. This approach provides samples of waking EEG to be followed later by samples of noctural sleep record and then again of waking EEG in the morning. (2) If only
882
I.R, IVES, P. G L O O R
sleep samples are desired, t h e p a t i e n t is q u e s t i o n e d as to w h a t time he goes to bed in t h e evening a n d w h e n he wakes up in t h e m o r n i n g (for i n s t a n c e 1 1 : 0 0 p.m. and 7 : 0 0 a.m.). He is t h e n i n s t r u c t e d to keep t h e cable carrying t h e m u l t i p l e x e d E E G in his dressing gown p o c k e t until he retires. At this t i m e h e is required to plug tire p h o n e jack at t h e e n d of this cable into t h e ' P a t i e n t I n p u t ' o f t h e wall b o x close to his bed. Because all wards a n d m o s t semi-private a n d private r o o m s (20 l o c a t i o n s t o d a t e ) have b e e n conn e t t e d t o t h e E E G d e p a r t m e n t via a twisted pair wire (Ives et al. 1976), it is easy to m o n i t o r any p a t i e n t at a m o m e n t ' s n o t i c e from a n y l o c a t i o n within the hospital.
Preparation schedules
of
the
EEG
machine
and
sampling
F o r n i g h t i m e sampling, t h e E E G m a c h i n e is readied by setting a c l o c k - c o n t r o l l e d m a s t e r o n - o f f switch, a readily available h o u s e h o l d light c o n t r o l l e r , to the c u s t o m a r y retiring a n d a w a k e n i n g t i m e s o f t h e p a t i e n t , for i n s t a n c e 1 1 : 0 0 p.m. a n d 7 : 0 0 a.m. In tiffs case, t h e s w i t c h will t h e n t u r n o n t h e E E G m a c h i n e at 1 1 : 0 0 p.m. to start t h e E E G s a m p l i n g a n d t h e n it will t u r n it o f f at 7 : 0 0 a.m. to s t o p the p r o c e d u r e . T h e actual sampling is c o n t r o l l e d by a s e c o n d specially b u i l t t i m i n g m o d u l e w h i c h can be p r o g r a m m e d by t w o 10-position switches. This allows selection o f the desired interval b e t w e e n E E G samples a n d duration of the samples. The s c h e d u l e s m o s t c o m m o n l y used are: 2- or 4-rain s a m p l e s every 20 rain, 1- or 2-min samples every 10 m i n , or 20- or 40-sec samples every 5 min, b u t o t h e r c o m b i n a t i o n s can be o b t a i n e d . T h e E E G m a c h i n e used in these studies (ElemaS c h o n a n d e r M i n g o g r a f Model 16) is e q u i p p e d w i t h a n ink r o l l e r - b l o t t e r w h i c h a b s o r b s t h e excess ink o f f t h e p a p e r from t h e ink jets. This b l o t t e r b e c o m e s saturated with ink a f t e r a b o u t 2 h o f c o n t i n u o u s usage, t h u s s m e a r i n g a n y f u r t h e r E E G w r i t e o u t . Because o f this, t h e t o t a l r e c o r d i n g t i m e c a n n o t exceed 2 h. W h e n t h e a b o v e s c h e d u l e s are used over an 8-h period, n o m o r e t h a n 1 h a n d 36 m i n o f t o t a l recording t i m e is o b t a i n e d . T h e q u a n t i t y o f E E G p a p e r w r i t e o u t so g e n e r a t e d is a d e q u a t e for i n t e r p r e t a t i o n b y t h e e l e c t r o e n c e p h a l o g r a p h e r , n o t excessive for storage a n d n o t t o o costly, especially w h e n a p a p e r speed o f 15 m m / s e c is used.
t o p o f t h e EEG page every t0 sec (Fig. 2). At t h e b e g i n n i n g of each sample t h e p a p e r is a d v a n c e d to g e n e r a t e straight lines for o n e second. This provides a gap for t h e r e a d e r ' s c o n v e n i e n c e b e t w e e n the c u r r e n t a n d the previous E E G sample (Fig. 2).
Precautions Since the s y s t e m runs u n a t t e n d e d overnight, several p r e c a u t i o n s m u s t be taken. S h o u l d t h e m a c h i n e r u n o u t o f ink, air w o u l d be p u m p e d t h r o u g h t h e ink jets, t h u s d r y i n g t h e m out. To avoid this, the 'low ink' sensor b u i l t into t h e i n s t r u m e n t is used to t e r m i n a t e t h e sampling. R u n n i n g o u t of paper, or j a m m i n g o f the paper, while t h e ink c o n t i n u e s to flow m a y d a m a g e t h e i n s t r u m e n t besides causing a c o n s i d e r a b l e mess; thus, a p a p e r m o v e m e n t dei:ector ( p h o t o d i o d e and sensor) has been built. W h e n e v e r a p a p e r fold is n o t d e t e c t e d w i t h i n a 25-sec period, t h e E E G m a c h i n e is s h u t off'. Because o f t h e r e m o t e l o c a t i o n of t h e EEG laborat o r y in | h e hospital, a c o m m e r c i a l h e a t d e t e c t o r installed a b o v e t h e EEG m a c h i n e will activate t h e existing h o s p i t a l ' s fire alarm s y s t e m in case o f fire.
Results
To date, over 3 0 0 n o c t u r n a l sleep s a m p l i n g sessions (in c o n j u n c t i o n with, or i n d e p e n d e n t of, seizure m o n i t o r i n g ) including stages III and IV, have b e e n c o n d u c t e d o n 150 p a t i e n t s w i t h o u t t h e use o f drugs. T h e E E G s a m p l e s are i n d i s t i n g u i s h a b l e f r o m t h o s e obtained by c o n v e n t i o n a l m e a n s . T h e overall q u a l i t y o f t h e E E G s f r o m t h e c a b l e - t e l e m e t r y is s u p e r i o r to t h a t o f c o n v e n t i o n a l recordings ( u n d e r t h e same e n v i r o n ment conditions) because telemetry techniques greatly r e d u c e m o v e m e n t a r t e f a c t ( P o r t e r et al. 1 9 7 1 ; Ires et al. 1976). In this g r o u p o f p a t i e n t s , t h e samples have b e e n t a k e n over an average o f t w o nights ( 1 6 h) as o p p o s e d to 3 0 - m i n periods o n w h i c h previ()us studies were based ( G l o o r et al. 1958). We believe t h a t this s a m p l i n g over a m u c h longer p e r i o d o f t i m e a n d u n d e r m o r e n a t u r a l c o n d i t i o n s is likely t o p r o v i d e i n f o r m a t i o n o f special i n t e r e s t especially w h e n t h e p a t i e n t s are c o n s i d e r e d for surgical t r e a t m e n t (Rasm u s s e n 1 9 7 5 ) . In t h e s e same subjects, failures producing premature termination of the recording o c c u r r e d in less t h a n 1% o f cases.
Discussion Writeout format
The t i m e o f d a y p r o v i d e d b y a 24-h clock is written via t h e a l p h a - n u m e r i c c h a r a c t e r g e n e r a t o r at t h e
The m a j o r i t y o f p a t i e n t s p r e s e n t l y e x a m i n e d w i t h this t e c h n i q u e are epileptic p a t i e n t s in w h o m t h e purposes o f t h e o v e r n i g h t sleep s a m p l i n g are: ( 1 ) t o
AUTOMATIC NOCTURAL SLEEP SAMPLING investigate interictal abnormalities occurring during sleep and (2) to allow long-term, although intermittent, m o n i t o r i n g as o p p o s e d to brief c o n v e n t i o n a l recordings. Also, (3) to provide localization of the abnormality, and, since localization is the primary purpose, sleep staging is n o t routinely a t t e m p t e d . We have n o t e d t h a t some patients either do not sleep well or exhibit only the early sleep stages. This is probably due to (1) the 'first night' effect n o t e d by sleep investigators, (2) the effect o f the relatively 'noisy' hospital e n v i r o n m e n t and (3) the possible alteration of ' n o r m a l ' sleep stages in epileptic patients. If the patient develops a seizure while his noctural EEG is being o n l y periodically sampled, this episode m a y n o t be recorded or m a y be recorded o n l y in part; therefore, the patients are carefully screened to d e t e r m i n e if t h e y w o u l d benefit m o r e from seizure m o n i t o r i n g (Ives et al. 1976), sleep sampling, or from both. A n o t h e r advantage of overnight sleep sampling is that it decreases the demands made on the EEG laboratory during daytime and increases the utilization o f expensive EEG e q u i p m e n t . The sleep sampling is automatic, requiring no human intervention during the night. Thus, only the installation and removal o f the t e l e m e t r y package and EEG electrodes are required which are d o n e during normal working hours. A disadvantage of the system is the possibility o f early failure which m a y go u n d e t e c t e d until morning. However, with p r o p e r c o n t r o l o f the e q u i p m e n t and careful maintenance, this has o c c u r r e d very rarely.
Summary The clinical usefulness o f obtaining a sleep record in epileptic patients is well established. However, in m a n y clinical EEG laboratories, it is difficult to obtain records at night during the p a t i e n t ' s natural sleep. Thus, most sleep E E G s are recorded in the E E G l a b o r a t o r y during d a y t i m e and are induced by drugs. A 16 channel cable-telemetry system is described which a u t o m a t i c a l l y samples t h r o u g h o u t the night the EEG o f patients while sleeping in their r o o m or ward w i t h o u t the aid o f any medication. The electrodes and the cable-telemetry unit are applied to the patient in the a f t e r n o o n and the syst e m is checked. The patient is t h e n instructed to plug the system into a wall b o x upon retiring and to disc o n n e c t it w h e n he wakes up in the morning. The E E G samples are a u t o m a t i c a l l y written o u t during the night on one o f the E E G machines located in the E E G l a b o r a t o r y to which the system is connected via spectral intra-hospital wiring. The duration o f the samples and o f the intervals separating
883 t h e m can be varied according to the circumstances. We have found this m e t h o d to be very helpful in the investigation of epileptic patients, especially those considered for surgical t r e a t m e n t .
R~sum~ Echantillonnage automatique du sommeil nocturne: methode utile en electroencephalographie clinique L'utilit~ d ' o b t e n t i o n d ' u n enregistrement de somm~il chez les malades ~pileptiques est bien ~tablie en clinique. C e p e n d a n t , dans de n o m b r e u x laboratoires d ' E E G clinique, il est difficile d ' o b t e n i r des enregistrements du sommeil naturel de nuit du malade. Ainsi, la plupart des EEG de sommeil sont enregistr4s au cours de la journ~e dans les laboratories EEG et le sommeil est induit par drogue. Les auteurs d~crivent un syst~me t~l~m~trique ~ 16 cannaux qui ~chantillonne a u t o m a t i q u e m e n t t o u t au long de la nuit I'EEG de malades en train de dormir dans leur chambre ou dans leur service, sans l'aide d ' a u c u n e m~dication. Des 61ectrodes et l'unit~ cabl~e de t~l~m~trie sont adapt~es au sujet au cours de l'apr~s-midi et le syst~me est contrSl~. La malade est requis de brancher ce syst~me dans une b o i t e murale lorsqu'il va se coucher et de le d~connecter lorsqu'il se r~veille le matin. Les ~chantillons EEG s'inscrivent a u t o m a t i q u e m e n t au cours de la nuit sur l ' u n e des machines EEG situ~e dans le laboratoire auquel le syst~me est connect~ au m o y e n de cables sp~ciaux intra-hSpital. La dur~e de ces ~chantillons et des intervalles qui les s~parent peut varlet suivant les circonstances. Les auteurs o n t trouv~ cette m ~ t h o d e tr~s utile pour l'~tude de malades ~pileptiques sp~cialement ceux pour lesquels se pose une indication de t r a i t e m e n t chirurgical. References Gibbs, E.L. and Gibbs, F.A. Diagnostic and localizing value of electroencephalographic studies in sleep. Res. Publ. Ass. Nerv. Ment. Dis., 1947, 26: 3 6 6 - 376. Gloor, P., Tsai, C. and Haddad, F. An assessment o f the value of sleep-electroencephalography for the diagnosis of t e m p o r a l lobe epilepsy. Eleetroenceph. clin. Neurophysiol., 1958, 10: 633--648. Gloor, P. C o n t r i b u t i o n s o f e l e c t r o e n c e p h a l o g r a p h y and e l e c t r o c o r t i c o g r a p h y to the neurosurgical t r e a t m e n t of epilepsy. In D.P. Purpura, J.K. Penry and R.P. Walter (Eds.), Advances in Neurology, Vol. 8. Raven Press, New York, 1975: 59--105. Hess, R. Sleep activation of the EEG in patients with partial seizures. In H.M. van Praag and H. Meinardi (Eds.), Brain and Sleep. De Erven Bohn BV, Amsterdam, 1974 : 140--153.
884 Ives, J.R., Thompson, C.J., Gloor, P., Olivier, A. and Woods, J.F. Multi-channel EEG tlemetry - - c o m puter monitoring of epileptic patients. In P.A. Neukomm (Ed.), Biotelemetry II. Karger, Basel, 1974: 216--218. Ives, J.R. and Gloor, P. Automatic sampling of patients's nocturnal sleep EEG. Electroenceph. clin. Neurophysiol., 1975, 39: 295. Ives, J.R., Thompson, C.J. and Gloor, P. Seizure monitoring: a new tool in electroencephalography. Electroenceph. clin. Neurophysiol., 1976, 41: 422--427. Ives, J.R. and Gloor, P. New sphenoidal electrode assembly to permit long*term monitoring of the patient's ictal or interictal EEG. Electroenceph. clin. Neurophysiol., 1977, 42: 575--580. Klass, D.W. Electroencephalographic manifestations of complex partial seizures. In J.K. Penry and D.D. Daly (Eds.), Advances in Neurology, Vol. 11, Raven Press, New York, 1975: 113--140.
I.R. IVES, P. GLOOR Krujer, A. and Buit-Gutter, Th. Provoked sleep versus spontaneous sleep as a diagonostic tool in epilepsy. In H.M. van Praag and H. Meinardi (Eds.), Brain and Sleep. De Erven Bohn BV, Amsterdam, t974 : 167--176. Passouant, P. S6m~iologie 61ectroenc6phalographic du sommeil normal et pathologique. Rev. Neurol., 1950, 83: 545--559. Porter, R.J., Wolf, A.A. Jr. and Penry, J.K. Human electroencephalographic telemetry. Amer. J. EEG. Technol., 1971, 11: 145--159. Rasmussen, T. Surgical treatment of patients with complex partial seizures. In J.K. Penry and D.D. Daly (Eds.), Advances in Neurology, Vol. 11. Raven Press, New York, 1975: 415--449. Stewart, T. Chlorpromazine: use to activate electroencephalographic seizure patterns. Electroenceph. clin. Neurophysiol., 1957, 9: 427--440.
Electroencephalography and Clinical Neurophysiology, 1977, 4 3 : 8 8 0 - - 8 8 4 © Elsevier/North-Holland Scientific Publishers, Ltd.
Technical contribution AUTOMATIC NOCTURAL SLEEP SAMPLING: A USEFUL METHOD IN CLINICAL ELECTROENCEPHALOGRAPHY J.R. IVES and P. GLOOR
Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Quebec H3A 2B4 (Canada) (Accepted for publication: April 14, 1977)
Recording a patient's EEG during sleep is regarded as a helpful procedure by electroencephalographers, neurologists and neurosurgeons because it frequently enhances epileptiform discharges (Gibbs and Gibbs 1947; Passouant 1950; Gloor et al. 1958; Klass 1975; Gloor 1975; Rasmussen 1975). All candidates considered for surgical removal of epileptic foci at the Montreal Neurological Institute routinely undergo one or more examinations during sleep (Gloor 1975; Rasmussen 1975). Nightime sleep records are not routinely obtainable because of the heavy demands they make on laboratory personnel. Therefore, the patients are usually brought to the EEG laboratory during the day and encouraged to fall asleep. If sleep does not occur spontaneously, they are given hypnotic drugs such as sodium secobarbital (Seconal), often associated with chlorpromazine (Largactil) (Stewart 1957). The disadvantages of this procedure include the following: (1) The patients may fail to sleep in spite of the medication; (2) the drugs administered could conceivably alter the interictal epileptic activity; (3) the induced sleep primarily consists of stages I--II while other stages in which useful diagnostic information could be obtained are poorly represented (Klass 1975; Hess ]974; Kuijer and Buit-Gutter 1974). (4) The recordings are time consuming as they may tie up an EEG machine and an EEG technician for several hours. To overcome these difficulties, the 16 channel cable-telemetry EEG system (Ives et al. 1974; Ires and Gloor 1975; Ives et al. 1976) has been used as a basis for the development of a method which provides automatic sampling of the EEG throughout the night while the patient sleeps naturally in his hospital room.
Basic s y s t e m
The system (Fig. 1) consists of a cable telemetry unit (Ives et al. 1974; Ives et al. 1976) directly connected via a multistation intra-hospital wiring system
to the demultiplexer located on the EEG machine. Because this ystem is completely independent of the seizure monitoring system described earlier (Ives et al. 1976), noctural sleep sampling or specific seizure monitoring can be performed either independently or simultaneously. In the latter situation, a second EEG machine is required.
Patient's Room
i 3
4
T
EEGDepartme
.......
J~
Fig. 1. Block diagram (A) and actual components (B) of the sleep sampling system. (1) EEG electrodes on the patient's head (either scalp or sphenoidal); (2) small package containing 16 EEG preamplifiers and a 16 channel multiplexer; (3) cable to connect battery p o w e r to head mounted unit and to bring multiplexed signal to battery pack; (4) waist-worn belt containing batteries and anchor point for patient's 25-foot co-axial cable; (5) patient's 25-foot co-axial cable carrying multiplexed EEG to wall box; (6) wall box for relaying multiplexed EEG directly to EEG department; (7) cable connecting wall box to EEG department; (8) demultiplexer to reconstruct original EEG signals; (9) EEG machine for writing out reconstructed EEG; (10) control unit to (a) turn the EEG machine on and off at set times, (b) obtain samples of EEG at predetermined intervals and durations and (c) write o u t the t i m e of day on the top of the EEG paper every 10 sec during the sampling.
AUTOMATIC N O C T U R A L SLEEP SAMPLING
881
I
Fp2-F8 ~
~
'
V
V
~
'
~
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,
~
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~
~
~
/
~
,
~
~
&
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.
~
F7-T3 ~ ' ~ . , ~ . ~ , - - - ~ , - v ~ ~
~
.
.
,
~
,
~
,
~
1f.~ .~1 ~uupv
~
~
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Fig. 2. End of an EEG sample (at 22 : 17 : 32) and beginning of following one 10 min later. EEG displays patterns of stage II and IV, respectively. A gap (flat EEG) can be seen between the two samples which is created by the sampler to help the reader recognize the end of one sample and the beginning of the next.
Electrodes, preamplifier, multiplexer, demultiplexer The same sub-assemblies used for sleep monitoring are also employed for seizure monitoring (Ives et al. 1967). A special sleep montage may be used in some patients to aid in sleep-staging, if desired. However, generally, only three montages are used for the clinical workup patients suffering from epileptic seizures. One consists of antero-posterior temporal and parasagittal scalp derivations (Fig. 2). The others combine coronal derivations from scalp and chronically inserted spbenoidal electrodes (Ives and Gloor 1976; Ives and Gloor 1977) with derivations providing either antero-posterior temporal or parasagittal coverage. The montage for use with the cable-telemetry system must be selected prior to installation o f the electrodes because the montage is permanently wired into the electrode set. Hence, the montage can only be changed by removing one set and installing another. The preamplifier-multiplexer unit that is placed on the head is small (2.5 × 3.5 X 10 ram) and light (80
g). Thus, it is easily tolerated by patients of all ages who generally have as comfortable and as restful a night as can be expected in a hospital environment.
Patient preparation The electrodes are applied in the late afternoon along with the preamplifier-multiplexer and battery pack. While still in the EEG laboratory, the patient is connected to the EEG machine to ensure that the equipment is functioning properly and any problems are immediately corrected. The overnight procedure can be performed in one of two ways: (1) Immediately upon returning to the ward, the patient can be connected to a wall box which relays the multiplexed EEG to the EEG department. The sampling can then be started as soon as the EEG machine is free at the end o f the day. This approach provides samples of waking EEG to be followed later by samples of noctural sleep record and then again of waking EEG in the morning. (2) If only
882
I.R, IVES, P. G L O O R
sleep samples are desired, t h e p a t i e n t is q u e s t i o n e d as to w h a t time he goes to bed in t h e evening a n d w h e n he wakes up in t h e m o r n i n g (for i n s t a n c e 1 1 : 0 0 p.m. and 7 : 0 0 a.m.). He is t h e n i n s t r u c t e d to keep t h e cable carrying t h e m u l t i p l e x e d E E G in his dressing gown p o c k e t until he retires. At this t i m e h e is required to plug tire p h o n e jack at t h e e n d of this cable into t h e ' P a t i e n t I n p u t ' o f t h e wall b o x close to his bed. Because all wards a n d m o s t semi-private a n d private r o o m s (20 l o c a t i o n s t o d a t e ) have b e e n conn e t t e d t o t h e E E G d e p a r t m e n t via a twisted pair wire (Ives et al. 1976), it is easy to m o n i t o r any p a t i e n t at a m o m e n t ' s n o t i c e from a n y l o c a t i o n within the hospital.
Preparation schedules
of
the
EEG
machine
and
sampling
F o r n i g h t i m e sampling, t h e E E G m a c h i n e is readied by setting a c l o c k - c o n t r o l l e d m a s t e r o n - o f f switch, a readily available h o u s e h o l d light c o n t r o l l e r , to the c u s t o m a r y retiring a n d a w a k e n i n g t i m e s o f t h e p a t i e n t , for i n s t a n c e 1 1 : 0 0 p.m. a n d 7 : 0 0 a.m. In tiffs case, t h e s w i t c h will t h e n t u r n o n t h e E E G m a c h i n e at 1 1 : 0 0 p.m. to start t h e E E G s a m p l i n g a n d t h e n it will t u r n it o f f at 7 : 0 0 a.m. to s t o p the p r o c e d u r e . T h e actual sampling is c o n t r o l l e d by a s e c o n d specially b u i l t t i m i n g m o d u l e w h i c h can be p r o g r a m m e d by t w o 10-position switches. This allows selection o f the desired interval b e t w e e n E E G samples a n d duration of the samples. The s c h e d u l e s m o s t c o m m o n l y used are: 2- or 4-rain s a m p l e s every 20 rain, 1- or 2-min samples every 10 m i n , or 20- or 40-sec samples every 5 min, b u t o t h e r c o m b i n a t i o n s can be o b t a i n e d . T h e E E G m a c h i n e used in these studies (ElemaS c h o n a n d e r M i n g o g r a f Model 16) is e q u i p p e d w i t h a n ink r o l l e r - b l o t t e r w h i c h a b s o r b s t h e excess ink o f f t h e p a p e r from t h e ink jets. This b l o t t e r b e c o m e s saturated with ink a f t e r a b o u t 2 h o f c o n t i n u o u s usage, t h u s s m e a r i n g a n y f u r t h e r E E G w r i t e o u t . Because o f this, t h e t o t a l r e c o r d i n g t i m e c a n n o t exceed 2 h. W h e n t h e a b o v e s c h e d u l e s are used over an 8-h period, n o m o r e t h a n 1 h a n d 36 m i n o f t o t a l recording t i m e is o b t a i n e d . T h e q u a n t i t y o f E E G p a p e r w r i t e o u t so g e n e r a t e d is a d e q u a t e for i n t e r p r e t a t i o n b y t h e e l e c t r o e n c e p h a l o g r a p h e r , n o t excessive for storage a n d n o t t o o costly, especially w h e n a p a p e r speed o f 15 m m / s e c is used.
t o p o f t h e EEG page every t0 sec (Fig. 2). At t h e b e g i n n i n g of each sample t h e p a p e r is a d v a n c e d to g e n e r a t e straight lines for o n e second. This provides a gap for t h e r e a d e r ' s c o n v e n i e n c e b e t w e e n the c u r r e n t a n d the previous E E G sample (Fig. 2).
Precautions Since the s y s t e m runs u n a t t e n d e d overnight, several p r e c a u t i o n s m u s t be taken. S h o u l d t h e m a c h i n e r u n o u t o f ink, air w o u l d be p u m p e d t h r o u g h t h e ink jets, t h u s d r y i n g t h e m out. To avoid this, the 'low ink' sensor b u i l t into t h e i n s t r u m e n t is used to t e r m i n a t e t h e sampling. R u n n i n g o u t of paper, or j a m m i n g o f the paper, while t h e ink c o n t i n u e s to flow m a y d a m a g e t h e i n s t r u m e n t besides causing a c o n s i d e r a b l e mess; thus, a p a p e r m o v e m e n t dei:ector ( p h o t o d i o d e and sensor) has been built. W h e n e v e r a p a p e r fold is n o t d e t e c t e d w i t h i n a 25-sec period, t h e E E G m a c h i n e is s h u t off'. Because o f t h e r e m o t e l o c a t i o n of t h e EEG laborat o r y in | h e hospital, a c o m m e r c i a l h e a t d e t e c t o r installed a b o v e t h e EEG m a c h i n e will activate t h e existing h o s p i t a l ' s fire alarm s y s t e m in case o f fire.
Results
To date, over 3 0 0 n o c t u r n a l sleep s a m p l i n g sessions (in c o n j u n c t i o n with, or i n d e p e n d e n t of, seizure m o n i t o r i n g ) including stages III and IV, have b e e n c o n d u c t e d o n 150 p a t i e n t s w i t h o u t t h e use o f drugs. T h e E E G s a m p l e s are i n d i s t i n g u i s h a b l e f r o m t h o s e obtained by c o n v e n t i o n a l m e a n s . T h e overall q u a l i t y o f t h e E E G s f r o m t h e c a b l e - t e l e m e t r y is s u p e r i o r to t h a t o f c o n v e n t i o n a l recordings ( u n d e r t h e same e n v i r o n ment conditions) because telemetry techniques greatly r e d u c e m o v e m e n t a r t e f a c t ( P o r t e r et al. 1 9 7 1 ; Ires et al. 1976). In this g r o u p o f p a t i e n t s , t h e samples have b e e n t a k e n over an average o f t w o nights ( 1 6 h) as o p p o s e d to 3 0 - m i n periods o n w h i c h previ()us studies were based ( G l o o r et al. 1958). We believe t h a t this s a m p l i n g over a m u c h longer p e r i o d o f t i m e a n d u n d e r m o r e n a t u r a l c o n d i t i o n s is likely t o p r o v i d e i n f o r m a t i o n o f special i n t e r e s t especially w h e n t h e p a t i e n t s are c o n s i d e r e d for surgical t r e a t m e n t (Rasm u s s e n 1 9 7 5 ) . In t h e s e same subjects, failures producing premature termination of the recording o c c u r r e d in less t h a n 1% o f cases.
Discussion Writeout format
The t i m e o f d a y p r o v i d e d b y a 24-h clock is written via t h e a l p h a - n u m e r i c c h a r a c t e r g e n e r a t o r at t h e
The m a j o r i t y o f p a t i e n t s p r e s e n t l y e x a m i n e d w i t h this t e c h n i q u e are epileptic p a t i e n t s in w h o m t h e purposes o f t h e o v e r n i g h t sleep s a m p l i n g are: ( 1 ) t o
AUTOMATIC NOCTURAL SLEEP SAMPLING investigate interictal abnormalities occurring during sleep and (2) to allow long-term, although intermittent, m o n i t o r i n g as o p p o s e d to brief c o n v e n t i o n a l recordings. Also, (3) to provide localization of the abnormality, and, since localization is the primary purpose, sleep staging is n o t routinely a t t e m p t e d . We have n o t e d t h a t some patients either do not sleep well or exhibit only the early sleep stages. This is probably due to (1) the 'first night' effect n o t e d by sleep investigators, (2) the effect o f the relatively 'noisy' hospital e n v i r o n m e n t and (3) the possible alteration of ' n o r m a l ' sleep stages in epileptic patients. If the patient develops a seizure while his noctural EEG is being o n l y periodically sampled, this episode m a y n o t be recorded or m a y be recorded o n l y in part; therefore, the patients are carefully screened to d e t e r m i n e if t h e y w o u l d benefit m o r e from seizure m o n i t o r i n g (Ives et al. 1976), sleep sampling, or from both. A n o t h e r advantage of overnight sleep sampling is that it decreases the demands made on the EEG laboratory during daytime and increases the utilization o f expensive EEG e q u i p m e n t . The sleep sampling is automatic, requiring no human intervention during the night. Thus, only the installation and removal o f the t e l e m e t r y package and EEG electrodes are required which are d o n e during normal working hours. A disadvantage of the system is the possibility o f early failure which m a y go u n d e t e c t e d until morning. However, with p r o p e r c o n t r o l o f the e q u i p m e n t and careful maintenance, this has o c c u r r e d very rarely.
Summary The clinical usefulness o f obtaining a sleep record in epileptic patients is well established. However, in m a n y clinical EEG laboratories, it is difficult to obtain records at night during the p a t i e n t ' s natural sleep. Thus, most sleep E E G s are recorded in the E E G l a b o r a t o r y during d a y t i m e and are induced by drugs. A 16 channel cable-telemetry system is described which a u t o m a t i c a l l y samples t h r o u g h o u t the night the EEG o f patients while sleeping in their r o o m or ward w i t h o u t the aid o f any medication. The electrodes and the cable-telemetry unit are applied to the patient in the a f t e r n o o n and the syst e m is checked. The patient is t h e n instructed to plug the system into a wall b o x upon retiring and to disc o n n e c t it w h e n he wakes up in the morning. The E E G samples are a u t o m a t i c a l l y written o u t during the night on one o f the E E G machines located in the E E G l a b o r a t o r y to which the system is connected via spectral intra-hospital wiring. The duration o f the samples and o f the intervals separating
883 t h e m can be varied according to the circumstances. We have found this m e t h o d to be very helpful in the investigation of epileptic patients, especially those considered for surgical t r e a t m e n t .
R~sum~ Echantillonnage automatique du sommeil nocturne: methode utile en electroencephalographie clinique L'utilit~ d ' o b t e n t i o n d ' u n enregistrement de somm~il chez les malades ~pileptiques est bien ~tablie en clinique. C e p e n d a n t , dans de n o m b r e u x laboratoires d ' E E G clinique, il est difficile d ' o b t e n i r des enregistrements du sommeil naturel de nuit du malade. Ainsi, la plupart des EEG de sommeil sont enregistr4s au cours de la journ~e dans les laboratories EEG et le sommeil est induit par drogue. Les auteurs d~crivent un syst~me t~l~m~trique ~ 16 cannaux qui ~chantillonne a u t o m a t i q u e m e n t t o u t au long de la nuit I'EEG de malades en train de dormir dans leur chambre ou dans leur service, sans l'aide d ' a u c u n e m~dication. Des 61ectrodes et l'unit~ cabl~e de t~l~m~trie sont adapt~es au sujet au cours de l'apr~s-midi et le syst~me est contrSl~. La malade est requis de brancher ce syst~me dans une b o i t e murale lorsqu'il va se coucher et de le d~connecter lorsqu'il se r~veille le matin. Les ~chantillons EEG s'inscrivent a u t o m a t i q u e m e n t au cours de la nuit sur l ' u n e des machines EEG situ~e dans le laboratoire auquel le syst~me est connect~ au m o y e n de cables sp~ciaux intra-hSpital. La dur~e de ces ~chantillons et des intervalles qui les s~parent peut varlet suivant les circonstances. Les auteurs o n t trouv~ cette m ~ t h o d e tr~s utile pour l'~tude de malades ~pileptiques sp~cialement ceux pour lesquels se pose une indication de t r a i t e m e n t chirurgical. References Gibbs, E.L. and Gibbs, F.A. Diagnostic and localizing value of electroencephalographic studies in sleep. Res. Publ. Ass. Nerv. Ment. Dis., 1947, 26: 3 6 6 - 376. Gloor, P., Tsai, C. and Haddad, F. An assessment o f the value of sleep-electroencephalography for the diagnosis of t e m p o r a l lobe epilepsy. Eleetroenceph. clin. Neurophysiol., 1958, 10: 633--648. Gloor, P. C o n t r i b u t i o n s o f e l e c t r o e n c e p h a l o g r a p h y and e l e c t r o c o r t i c o g r a p h y to the neurosurgical t r e a t m e n t of epilepsy. In D.P. Purpura, J.K. Penry and R.P. Walter (Eds.), Advances in Neurology, Vol. 8. Raven Press, New York, 1975: 59--105. Hess, R. Sleep activation of the EEG in patients with partial seizures. In H.M. van Praag and H. Meinardi (Eds.), Brain and Sleep. De Erven Bohn BV, Amsterdam, 1974 : 140--153.
884 Ives, J.R., Thompson, C.J., Gloor, P., Olivier, A. and Woods, J.F. Multi-channel EEG tlemetry - - c o m puter monitoring of epileptic patients. In P.A. Neukomm (Ed.), Biotelemetry II. Karger, Basel, 1974: 216--218. Ives, J.R. and Gloor, P. Automatic sampling of patients's nocturnal sleep EEG. Electroenceph. clin. Neurophysiol., 1975, 39: 295. Ives, J.R., Thompson, C.J. and Gloor, P. Seizure monitoring: a new tool in electroencephalography. Electroenceph. clin. Neurophysiol., 1976, 41: 422--427. Ives, J.R. and Gloor, P. New sphenoidal electrode assembly to permit long*term monitoring of the patient's ictal or interictal EEG. Electroenceph. clin. Neurophysiol., 1977, 42: 575--580. Klass, D.W. Electroencephalographic manifestations of complex partial seizures. In J.K. Penry and D.D. Daly (Eds.), Advances in Neurology, Vol. 11, Raven Press, New York, 1975: 113--140.
I.R. IVES, P. GLOOR Krujer, A. and Buit-Gutter, Th. Provoked sleep versus spontaneous sleep as a diagonostic tool in epilepsy. In H.M. van Praag and H. Meinardi (Eds.), Brain and Sleep. De Erven Bohn BV, Amsterdam, t974 : 167--176. Passouant, P. S6m~iologie 61ectroenc6phalographic du sommeil normal et pathologique. Rev. Neurol., 1950, 83: 545--559. Porter, R.J., Wolf, A.A. Jr. and Penry, J.K. Human electroencephalographic telemetry. Amer. J. EEG. Technol., 1971, 11: 145--159. Rasmussen, T. Surgical treatment of patients with complex partial seizures. In J.K. Penry and D.D. Daly (Eds.), Advances in Neurology, Vol. 11. Raven Press, New York, 1975: 415--449. Stewart, T. Chlorpromazine: use to activate electroencephalographic seizure patterns. Electroenceph. clin. Neurophysiol., 1957, 9: 427--440.
