Ambulatory EEG Recordings in Children with Infrequent Seizures Richard G. Curless, MD, R. E u g e n e Ramsay, MD, Debra A. Katz, MD, Carlos A. Gadia, MD, and Katherine A. Sheehan, RN
Twenty-one children, ages 1-15 years, were selected for outpatient ambulatory electroencephalographic (AEEG) monitoring on the basis of infrequent seizures without therapy, normal routine EEGs, and normal neurologic/developmental examinations. Technically satisfactory recordings were obtained in all patients; recording time consisted of 24, 22, and 6 hours for 15, 4, and 2 patients, respectively. Eighteen patients were not receiving antiepileptic drug therapy at AEEG. The follow-up intervals after the AEEG ranged from 4-20 months. Only 2 patients had epileptiform AEEGs. Of the remaining 19 with nonepileptiform records, 10 were seizure free without antiepileptic drug therapy, but 9 developed additional seizures which required treatment. Curless RG, R a m s a y RE, Katz D A , Gadia CA, Sheehan KA. A m b u l a t o r y E E G recordings in children with infrequent seizures. Pediatr Neurol 1990;6:184-5.
Introduction S i n c e the initial p u b l i c a t i o n o f h u m a n a m b u l a t o r y e l e c t r o e n c e p h a l o g r a p h i e s ( A E E G s ) by Ives and Woods in 1975 [1] there h a v e been m a n y attempts to demonstrate the value o f this technique in patients w h o s e histories d o c u m e n t clinical seizures requiring antiepileptic drug therapy [2-4]. Reports o f studies e v a l u a t i n g A E E G in children h a v e fostered debate about the scope o f its value [5-9]. We hypothesized that A E E G s w o u l d be justified to identify patients at risk for further seizures w h e n infrequent seizures, normal routine E E G s , and normal neurologic e x a m i n a t i o n s existed. In our experience, A E E G demonstrated an e p i l e p t i f o r m pattern in o v e r 50% o f adults m e e t i n g these criteria w h e n the seizure type i n c l u d e d only patients with partial, c o m p l e x partial, or m y o c l o n i c seizures. The A E E G yield in generalized seizures, other than in c h i l d h o o d absence epilepsy, is u n k n o w n for adults or children. B e c a u s e recent studies suggested that m a n y children
From the Department of Neurology; University of Miami School of Medicine; Miami, Florida.
184 PEDIATRIC NEUROLOGY Vol. 6 No. 3
do not have a second unprovoked seizure [10,11], we d e c i d e d to evaluate the y o u n g e r age group first. To accomplish this evaluation, patients were selected who fulfilled the above criteria and whose parents agreed to withhold antiepileptic drug therapy when the A E E G s were normal.
Methods The 21 patients ranged in age from 12 months to 15 years: ~ were 4 years of age or younger; 9. 4-9 years: and 4, 9-15 years. Parental agreement was obtained to withhold antiepileptic drug therapy unless an epileptiform discharge was found on the AEEG or additional seizures developed. Fifteen patients had experienced generalized clonic. tonic, or clonic/tonic seizures. In 3, the clinical pattern was absence, 2 had atonic episodes, and 1 had absence and a generalized tonic seizure. Twelve had experienced a single motor seizure, 3 had 2 seizures, and 6 had more than 2. All patients had normal routine EEG and neurologic examinations and normal milestones. Four were followed for longer than 18 months, 4 others for 12-17 months, and 13 for 6-11 months. The follow-up was not extended for those patients requiring antiepileptic drug therapy because of an abnormal AEEG or the developmenl of additional seizures. Twenty-four-hour EEGs were recorded using an 8-channel Oxford system. The montage used consisted of F3-F7, FT-T~, T3-Ts, P:~-C3, F~Fs, T4-T6, and P4-C4 in the International 10/20 System. A timing signal was stored on the ninth channel. At the beginning of each recording, activation with intermittent photic stimulation and 3 min of hyperventilation were performed. The tape was scanned and a hard copy was made on an 8-channel Grass Instrument of: (1) Portions in which definite or questionable abnormalities were identified on the CRT screen; and, (2) At least 20 min of representative waking and sleeping background activity. Final interpretation was made from the hard copy EEG. All recordings were technically satisfactory. Infrequently, 1 or 2 channels were lost, but even in these instances it was believed that interpretation was satisfactory. All of the studies were obtained on an outpatient basis. Equipment damage was minimized in the youngesl patients by extensive padding of the recorder. Recording times consisted of 24, 22, and 6 hours in 15.4, and 2 patients, respectively.
Results Two patients had epileptiform A E E G s . O n e was an 8year-old with a single, g e n e r a l i z e d tonic seizure, and the other was an 81/2-year-old with 3 generalized tonic seizures prior to A E E G . B o t h were placed on c a r b a m a z e p i n e
Communications should be addressed to: Dr. Curless; Department of Neurology; University of Miami School of Medicine; EO. Box 016820; Miami, FL 33101. Received December 12, 1989; accepted February 14, 1990,
with no subsequent seizures after 18 and 12 months of observation, respectively. Ten had normal AEEGs and remained seizure free without antiepileptic drug therapy; subsequent examinations were conducted over 18-, 12-, and 6-month periods in 2, 1, and 7 patients, respectively. The seizure type was distributed with 2 patients in each of the following 5 types: generalized clonic, tonic, clonic/tonic, absence, and atonic. Seven of these patients had a single seizure, 2 had 2 events, and 1 had more than 6. Nine developed seizures in spite of normal AEEGs. Two patients had either generalized tonic, generalized clonic, or absence seizures; 3 patients had generalized clonic/ tonic episodes. Prior to AEEG, 3 of these children had more than 6 episodes. All were successfully treated with antiepileptic drugs and all continued to have normal development and neurologic examinations.
quent discharges suggests more aggressive antiepileptic drug management. In our study, a normal AEEG provided considerably less prognostic information than anticipated. Although the number of patients is small, and 12 of 21 children each had a single generalized seizure upon entry into the study, we were hopeful that the AEEG might assist in making a decision about the initiation of antiepileptic drug therapy. Some authors believe that younger patients with mild epilepsy have normal EEGs more frequently than older children; however, if the false-negative routine studies were a result of brevity, the AEEG should have been helpful. It is suggested that the clinical problem be carefully reviewed prior to utilizing AEEG because the technique appears to add relatively little to the diagnosis and management of children with infrequent seizures. References
Discussion
Our results suggest the need for larger studies and add a note of caution concerning the value of AEEG monitoring in children. In 12 patients (57%), AEEG correctly differentiated patients with epilepsy by demonstrating epileptiform discharges in 2 of them, from the remaining 10 with normal AEEGs who remained seizure free without the problems of antiepileptic drug therapy [12]. Unfortunately, AEEG monitoring was unsuccessful in determining the seizure-risk category for the other 9 patients (43%). Although the recordings were normal, each patient had at least 1 additional seizure. In 8 of these patients, the seizure appeared 1-7 months after the normal AEEG and in 1 the interval was 12 months. The type and number of seizures did not explain the difference between the successful and unsuccessful AEEG groups. Although a clearly epileptiform discharge detected by routine EEG or AEEG may be an appropriate indicator for daily antiepileptic drug therapy following 1-2 motor seizures, the risk/benefit ratio may still not be in the child's best interest [12]. In children with unprovoked seizures, Camfield et al. demonstrated a surprisingly similar incidence of recurrence (40%) in compliant, treated patients compared to untreated ones [13]. They included some with and without epileptiform EEGs who had 2 or more seizures. Other reports of AEEGs in children suggested that the technique can be of value in childhood absence epilepsy [7,8]. When parents indicate a cessation of clinical seizures but continued school failure, an AEEG with fre-
[1] lves JR, WoodsJF. 4-Channel 24 hour cassette recorder for long term EEG monitoring of ambulatory patients. Electroencephalogr Clin Neurophysiol 1975;39:88-92. [2] Ebersole JS, Leroy RE An evaluation of ambulatory, cassette EEG monitoring: II. Detection of interictal abnormalities. Neurology 1983;33:8-18. [3] Bridgers SL, Ebersole JS. The clinical utility of ambulatory EEG. Neurology 1985;35:166-73. [4] Bridgers SL, Ebersole JS. Ambulatory cassette EEG in clinical practice. Neurology 1985;35:1767-8. [5] Aminnfl'MJ, Goodin DS, Berg BO, Compton MN. Ambulatory EEG recordings in epileptic and nonepileptic children. Neurology 1988;38:558-61. [6] Duchowny MS, Bonis I. Longterm cassette EEG monitoring of childhood seizures. Pediatr Neurol 1985;1:36-41. [71 KeUson MJ, Hauser WA, Magrill JP, Tepperberg J. Ambulatory cassette EEG in absence seizures. Pediatr Neurol 1987;3:273-6. [8] Blomqnist HK, Zetterlund B. Evaluation of treatment in typical absence seizures, the roles of long-term EEG monitoring and ethosuximide. Acta Paediatr Scand 1985;74:409-15. [9] Bachman DS. 24 Hour ambulatory electroencephalographic monitoring in pediatrics. Clin Electroencephalogr 1984;15:164-6. [10] Camfield PR, Camfield CS, Dooley JM, Tibbles JAR, Fung T, Garner B. Epilepsy after a first unprovoked seizure in childhood. Neurology 1985;35:1657-60. [11] Shinnar S, Zeitlin-Gross L, Moshe SL, Berg AT, Goldensohn E, Hauser WA. The low risk of seizure recurrence following a first unprovoked seizure in children and adolescence. A prospective study. Ann Neurol 1986;20:388. [12] Freeman JM, Tibbles JAR, Camfield CS, Camfield PR. Benign epilepsy of childhood: A speculation and its ramifications. Pediatrics 1987;79:864-8. [13] Camfield PR, Camfield CS, Smith EC, Tibbles JAR. Newly treated childhood epilepsy: A prospective study of recurrences and side effects. Neurology 1985;35:722-5.
Curless et al: AmbulatoryEEG 185
Twenty-one children, ages 1-15 years, were selected for outpatient ambulatory electroencephalographic (AEEG) monitoring on the basis of infrequent seizures without therapy, normal routine EEGs, and normal neurologic/developmental examinations. Technically satisfactory recordings were obtained in all patients; recording time consisted of 24, 22, and 6 hours for 15, 4, and 2 patients, respectively. Eighteen patients were not receiving antiepileptic drug therapy at AEEG. The follow-up intervals after the AEEG ranged from 4-20 months. Only 2 patients had epileptiform AEEGs. Of the remaining 19 with nonepileptiform records, 10 were seizure free without antiepileptic drug therapy, but 9 developed additional seizures which required treatment. Curless RG, R a m s a y RE, Katz D A , Gadia CA, Sheehan KA. A m b u l a t o r y E E G recordings in children with infrequent seizures. Pediatr Neurol 1990;6:184-5.
Introduction S i n c e the initial p u b l i c a t i o n o f h u m a n a m b u l a t o r y e l e c t r o e n c e p h a l o g r a p h i e s ( A E E G s ) by Ives and Woods in 1975 [1] there h a v e been m a n y attempts to demonstrate the value o f this technique in patients w h o s e histories d o c u m e n t clinical seizures requiring antiepileptic drug therapy [2-4]. Reports o f studies e v a l u a t i n g A E E G in children h a v e fostered debate about the scope o f its value [5-9]. We hypothesized that A E E G s w o u l d be justified to identify patients at risk for further seizures w h e n infrequent seizures, normal routine E E G s , and normal neurologic e x a m i n a t i o n s existed. In our experience, A E E G demonstrated an e p i l e p t i f o r m pattern in o v e r 50% o f adults m e e t i n g these criteria w h e n the seizure type i n c l u d e d only patients with partial, c o m p l e x partial, or m y o c l o n i c seizures. The A E E G yield in generalized seizures, other than in c h i l d h o o d absence epilepsy, is u n k n o w n for adults or children. B e c a u s e recent studies suggested that m a n y children
From the Department of Neurology; University of Miami School of Medicine; Miami, Florida.
184 PEDIATRIC NEUROLOGY Vol. 6 No. 3
do not have a second unprovoked seizure [10,11], we d e c i d e d to evaluate the y o u n g e r age group first. To accomplish this evaluation, patients were selected who fulfilled the above criteria and whose parents agreed to withhold antiepileptic drug therapy when the A E E G s were normal.
Methods The 21 patients ranged in age from 12 months to 15 years: ~ were 4 years of age or younger; 9. 4-9 years: and 4, 9-15 years. Parental agreement was obtained to withhold antiepileptic drug therapy unless an epileptiform discharge was found on the AEEG or additional seizures developed. Fifteen patients had experienced generalized clonic. tonic, or clonic/tonic seizures. In 3, the clinical pattern was absence, 2 had atonic episodes, and 1 had absence and a generalized tonic seizure. Twelve had experienced a single motor seizure, 3 had 2 seizures, and 6 had more than 2. All patients had normal routine EEG and neurologic examinations and normal milestones. Four were followed for longer than 18 months, 4 others for 12-17 months, and 13 for 6-11 months. The follow-up was not extended for those patients requiring antiepileptic drug therapy because of an abnormal AEEG or the developmenl of additional seizures. Twenty-four-hour EEGs were recorded using an 8-channel Oxford system. The montage used consisted of F3-F7, FT-T~, T3-Ts, P:~-C3, F~Fs, T4-T6, and P4-C4 in the International 10/20 System. A timing signal was stored on the ninth channel. At the beginning of each recording, activation with intermittent photic stimulation and 3 min of hyperventilation were performed. The tape was scanned and a hard copy was made on an 8-channel Grass Instrument of: (1) Portions in which definite or questionable abnormalities were identified on the CRT screen; and, (2) At least 20 min of representative waking and sleeping background activity. Final interpretation was made from the hard copy EEG. All recordings were technically satisfactory. Infrequently, 1 or 2 channels were lost, but even in these instances it was believed that interpretation was satisfactory. All of the studies were obtained on an outpatient basis. Equipment damage was minimized in the youngesl patients by extensive padding of the recorder. Recording times consisted of 24, 22, and 6 hours in 15.4, and 2 patients, respectively.
Results Two patients had epileptiform A E E G s . O n e was an 8year-old with a single, g e n e r a l i z e d tonic seizure, and the other was an 81/2-year-old with 3 generalized tonic seizures prior to A E E G . B o t h were placed on c a r b a m a z e p i n e
Communications should be addressed to: Dr. Curless; Department of Neurology; University of Miami School of Medicine; EO. Box 016820; Miami, FL 33101. Received December 12, 1989; accepted February 14, 1990,
with no subsequent seizures after 18 and 12 months of observation, respectively. Ten had normal AEEGs and remained seizure free without antiepileptic drug therapy; subsequent examinations were conducted over 18-, 12-, and 6-month periods in 2, 1, and 7 patients, respectively. The seizure type was distributed with 2 patients in each of the following 5 types: generalized clonic, tonic, clonic/tonic, absence, and atonic. Seven of these patients had a single seizure, 2 had 2 events, and 1 had more than 6. Nine developed seizures in spite of normal AEEGs. Two patients had either generalized tonic, generalized clonic, or absence seizures; 3 patients had generalized clonic/ tonic episodes. Prior to AEEG, 3 of these children had more than 6 episodes. All were successfully treated with antiepileptic drugs and all continued to have normal development and neurologic examinations.
quent discharges suggests more aggressive antiepileptic drug management. In our study, a normal AEEG provided considerably less prognostic information than anticipated. Although the number of patients is small, and 12 of 21 children each had a single generalized seizure upon entry into the study, we were hopeful that the AEEG might assist in making a decision about the initiation of antiepileptic drug therapy. Some authors believe that younger patients with mild epilepsy have normal EEGs more frequently than older children; however, if the false-negative routine studies were a result of brevity, the AEEG should have been helpful. It is suggested that the clinical problem be carefully reviewed prior to utilizing AEEG because the technique appears to add relatively little to the diagnosis and management of children with infrequent seizures. References
Discussion
Our results suggest the need for larger studies and add a note of caution concerning the value of AEEG monitoring in children. In 12 patients (57%), AEEG correctly differentiated patients with epilepsy by demonstrating epileptiform discharges in 2 of them, from the remaining 10 with normal AEEGs who remained seizure free without the problems of antiepileptic drug therapy [12]. Unfortunately, AEEG monitoring was unsuccessful in determining the seizure-risk category for the other 9 patients (43%). Although the recordings were normal, each patient had at least 1 additional seizure. In 8 of these patients, the seizure appeared 1-7 months after the normal AEEG and in 1 the interval was 12 months. The type and number of seizures did not explain the difference between the successful and unsuccessful AEEG groups. Although a clearly epileptiform discharge detected by routine EEG or AEEG may be an appropriate indicator for daily antiepileptic drug therapy following 1-2 motor seizures, the risk/benefit ratio may still not be in the child's best interest [12]. In children with unprovoked seizures, Camfield et al. demonstrated a surprisingly similar incidence of recurrence (40%) in compliant, treated patients compared to untreated ones [13]. They included some with and without epileptiform EEGs who had 2 or more seizures. Other reports of AEEGs in children suggested that the technique can be of value in childhood absence epilepsy [7,8]. When parents indicate a cessation of clinical seizures but continued school failure, an AEEG with fre-
[1] lves JR, WoodsJF. 4-Channel 24 hour cassette recorder for long term EEG monitoring of ambulatory patients. Electroencephalogr Clin Neurophysiol 1975;39:88-92. [2] Ebersole JS, Leroy RE An evaluation of ambulatory, cassette EEG monitoring: II. Detection of interictal abnormalities. Neurology 1983;33:8-18. [3] Bridgers SL, Ebersole JS. The clinical utility of ambulatory EEG. Neurology 1985;35:166-73. [4] Bridgers SL, Ebersole JS. Ambulatory cassette EEG in clinical practice. Neurology 1985;35:1767-8. [5] Aminnfl'MJ, Goodin DS, Berg BO, Compton MN. Ambulatory EEG recordings in epileptic and nonepileptic children. Neurology 1988;38:558-61. [6] Duchowny MS, Bonis I. Longterm cassette EEG monitoring of childhood seizures. Pediatr Neurol 1985;1:36-41. [71 KeUson MJ, Hauser WA, Magrill JP, Tepperberg J. Ambulatory cassette EEG in absence seizures. Pediatr Neurol 1987;3:273-6. [8] Blomqnist HK, Zetterlund B. Evaluation of treatment in typical absence seizures, the roles of long-term EEG monitoring and ethosuximide. Acta Paediatr Scand 1985;74:409-15. [9] Bachman DS. 24 Hour ambulatory electroencephalographic monitoring in pediatrics. Clin Electroencephalogr 1984;15:164-6. [10] Camfield PR, Camfield CS, Dooley JM, Tibbles JAR, Fung T, Garner B. Epilepsy after a first unprovoked seizure in childhood. Neurology 1985;35:1657-60. [11] Shinnar S, Zeitlin-Gross L, Moshe SL, Berg AT, Goldensohn E, Hauser WA. The low risk of seizure recurrence following a first unprovoked seizure in children and adolescence. A prospective study. Ann Neurol 1986;20:388. [12] Freeman JM, Tibbles JAR, Camfield CS, Camfield PR. Benign epilepsy of childhood: A speculation and its ramifications. Pediatrics 1987;79:864-8. [13] Camfield PR, Camfield CS, Smith EC, Tibbles JAR. Newly treated childhood epilepsy: A prospective study of recurrences and side effects. Neurology 1985;35:722-5.
Curless et al: AmbulatoryEEG 185
