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Subclinical rhythmic EEG discharge of adults: SREDA in two children
Subclinical Rhythmic EEG Discharge of Adults: SREDA in Two Children Lakshmi Nagarajan, MD*, Pauline B. Gregory*, Ian K. Hewitt, MD†, Sasson S. Gubbay, MD*, and Trevor S. Parry, MD‡ Subclinical rhythmic electroencephalogram (EEG) discharge is an uncommon rhythmic EEG pattern that has been reported to occur in adults. It is thought to be a nonspecific finding with little clinical significance. This article reports this EEG pattern in two children and suggests it be called subclinical rhythmic EEG discharge of adults and children. © 2001 by Elsevier Science Inc. All rights reserved. Nagarajan L, Gregory PB, Hewitt IK, Gubbay SS, Pary TS. Subclinical rhythmic EEG discharge of adults: SREDA in two children. Pediatr Neurol 2001;24:313-316.
Introduction Subclinical rhythmic electroencephalogram (EEG) discharge is a distinctive EEG rhythmic pattern that has been reported to occur in adults. It is fairly uncommon with an estimated incidence of one in 1,500 [1,2]. Subclinical rhythmic EEG discharge of adults (SREDA) is reported to occur primarily in older adults, in whom cerebral vascular disease may be common. No clinical alterations are associated with the pattern, and the occurrence of SREDA does not correlate with clinical seizures. The consensus has been that it represents a benign EEG phenomenon of little clinical significance [3]. This discharge has not been reported in children [2]. This article reports SREDA in two female patients 10 and 11 years of age.
From the Departments of *Neurology and †Nephrology; Princess Margaret Hospital for Children; Perth, Western Australia; and the ‡ State Child Development Centre; Perth, Western Australia.
© 2001 by Elsevier Science Inc. All rights reserved. PII S0887-8994(01)00238-7 ● 0887-8994/01/$—see front matter
Case Reports Patient 1. The first patient was a female who presented at 11 years of age with abdominal pain, hematemesis, dysentery, hypertension, renal failure, and seizures. A diagnosis of hemolytic uremic syndrome (HUS) was made. She was treated for renal failure and was on peritoneal dialysis for 18 months. At presentation she initially was loaded with phenytoin for her generalized tonic-clonic seizures. Carbamezapine was then started but discontinued because of a rash. Vigabatrin was then introduced, along with a small dose of clobazam. Five days after starting vigabatrin her neurologic state deteriorated; she was restless, jerky, and encephalopathic. The vigabatrin was discontinued. The patient was reloaded with phenytoin. A second EEG performed 48 hours after onset of clinical deterioration was encephalopathic with the background predominantly in the delta range and significantly worse than the previous EEG (the first) performed a week earlier. Phenytoin was continued, and she was given three doses of fresh-frozen plasma over 3 consecutive days. There was remarkable improvement both clinically and on the third EEG performed 3 days later, which revealed a normal background. At follow-up, 20 months later, Patient 1 is off dialysis but continues to experience renal failure. Apart from mild hyperreflexia she is neurologically intact (has been since 1 month after initial presentation) and academically is doing well at school. Computed tomography (CT) scans at presentation were suggestive of multiple areas of cerebral ischemia. A subsequent CT scan was unremarkable apart from mild prominence of the cortical sulci. A magnetic resonance imaging (MRI) scan of the brain a few months later was normal. Patient 1 received five EEGs (27-45 minutes duration) in the first 4 months of her illness, and SREDA was evident on three of these. SREDA occurred six times on her first and fourth EEG and 10 times on her fifth EEG. Her fourth and fifth EEGs where performed while she was free of all antiepileptic drugs. The rhythmic discharge was at times bilateral and more generalized, sometimes predominantly temporal with asymmetry, and occasionally was frontally dominant. There was often asymmetry and variability in the amplitude and in the field during the 5-7 cycles per second rhythmic discharge. The rhythmic EEG pattern lasted 3-300 seconds in duration with an average duration of ⬃54 seconds. It began abruptly about 80% of the time and gradually ⬃20%. It terminated either abruptly (⬃50%) or gradually. It was 30-100 V in amplitude. There were no clinical accompaniments to the discharge. One of the episodes of SREDA occurred during intermittent photic stimulation at a flash frequency of 15, two during hyperventilation, and one just after hyperventilation. Six episodes of SREDA occurred during stages 1 and 2 of sleep. In addition, 14 and 6 positive bursts were seen frequently in the first EEG and occasionally in the fourth and fifth. Examples of SREDA in this patient are illustrated in Fig 1. Patient 2. The second patient was a 10-year-old female initially assessed because of concerns regarding learning difficulties and complaints of headaches and “pins and needles” sensations. Neurologically she was intact, and the remainder of her clinical examination was normal. On the Wechsler intelligence scale for children (WISC-IIIR) she performed with a verbal intelligence quotient (IQ) in the low-average range, a performance IQ in the high-average range, and a full-scale IQ in the average range when assessed in July 1999. This patient received two EEGs that illustrated features of SREDA. On the first EEG there were
Communications should be addressed to: Dr. Nagarajan; Neurology Department; Princess Margaret Hospital; PO Box D184; Perth, Western Australia 6840. Received July 25, 2000; accepted January 3, 2001.
Nagarajan et al: SREDA in Two Children 313
Figure 1. Epochs from Patient 1’s electroencephalogram (EEG) illustrate the rhythmic EEG discharge reported as subclinical rhythmic EEG discharge of adults (SREDA). The first epoch (Ep1) demonstrates 14 and 6 positive spikes. Ep2 demonstrates the discharge in a coronal montage. Ep4 and Ep5 reveal SREDA while Patient 1 is asleep. Ep6 illustrates the discharge continuing although cessation of intermittent photic stimulation at 30 per second.
four episodes, and on the second EEG (given 7 months later) there were seven episodes of SREDA. After the first EEG, valproate was initiated because the EEG was thought to be epileptiform, although clinically there were no seizures. This treatment did not make a significant difference to her clinical profile, and the second EEG was performed while she was on valproate. The bursts of rhythmic discharge resembling SREDA often began asymmetrically. The amplitude of the discharge was often asymmetric and varied from 30-100 V. At times the discharge was bilateral and at times unilateral. It was often posterior temporally dominant, although at times parietally dominant. Almost all the episodes appeared to terminate abruptly in this patient, although they began gradually approximately half the time and built up to the 5-7 cycles per second rhythm. Sometimes there were sharp waves at the onset. They varied in duration from 8-900
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seconds (average was ⬃146 seconds). One of the episodes began just before intermittent photic stimulation and continued to occur during stimulation. One episode occurred during stage 1 sleep, but no deeper stages were recorded. One began after 160 seconds of hyperventilation and another at the end of hyperventilation. The onset of a 300-second episode on the second EEG was after the cessation of hyperventilation. On this run of SREDA the discharge initially was generalized and then became predominantly right sided. During this prolonged discharge, Patient 2 was able to follow commands, do simple motor tasks, such as squeezing her hands and moving her arms up and down, perform mental math, and answer questions regarding name, place, age, etc. The episode terminated during a 5-second intermittent photic stimulation. The EEG was otherwise normal. Illustrations of SREDA in this patient are seen in Fig 2.
Figure 2. Epochs of the rhythmic electroencephalogram (EEG) discharge in Patient 2. The first epoch (Ep1) illustrates onset after hyperventilation. Ep2 reveals continuation of the discharge while Patient 2 is naming objects. Ep3 demonstrates the right-sided discharge while strength is tested in the patient’s upper limbs. Ep4 illustrates the discharge while CR2 is undertaking mental mathematics. Ep5 reveals termination of the discharge during IPS. Ep6 illustrates the presence of sharp waves at the onset on the left side.
Discussion Patient 1 presented at 11 years of age with HUS, a syndrome in which neurologic complications are well known [4]. In the course of her illness, a week after admission to the hospital, she became excessively encephalopathic with recurrence of seizures. Her antiepileptic drugs were changed at that stage. She was also treated with three daily infusions of fresh-frozen plasma, and an EEG performed after that demonstrated marked improvement, as did her clinical status. Pascual-Leone et al. [5]
have reported a similar response to fresh-frozen plasma in a child with HUS. A deficiency in prostacycline is postulated in HUS and, therefore, fresh-frozen plasma, as well as plasma exchange, may be useful. Three of the five EEG recordings for Patient 1 revealed prolonged runs of a subclinical rhythmic EEG discharge that had features consistent with SREDA. The discharges were of variable duration (average of ⬃54 seconds) at an amplitude of 30-100 V. There was variability in the field. There was mostly a gradual onset of the discharge, although at times it was abrupt (⬃20%), and the termina-
Nagarajan et al: SREDA in Two Children 315
tion was either abrupt or gradual. The discharge was often asymmetric. Discharge occurred when Patient 1 was awake, drowsy, and asleep. The rhythmic EEG discharge, without any clinical accompaniments, occurred during and after hyperventilation and during intermittent phobic stimulation. At times there were harmonics in association with the primary discharge at 5-7 cycles per second. We have illustrated that the features of the discharge are most consistent with SREDA as described by Westmoreland and Klass [1], although they have had some features of the midtemporal theta rhythms (psychomotor variant of paroxysmal cerebral dysrhythmia) frequently seen in children of this age and described by Gibbs and Gibbs [6]. In Westmoreland’s article [1], 15 of 65 adult patients with this discharge had cerebrovascular disease. Only four of 65 had a confirmed convulsive disorder. It is interesting to speculate that perhaps cerebral vascular insufficiency in Patient 1, who had HUS with clinical and EEG evidence of neurologic impairment, is responsible for the SREDA in this child. Although 14 and six positive bursts generally are regarded as a benign variant [3], there has been some suggestion that increased frequency (as observed in Patient 1’s first EEG) occurs in brain injury [7]. However, the SREDA was present on her fourth and fifth EEGs undertaken when she was clinically stable and neurologically intact. This evidence suggests that, similar to adults, SREDA in childhood is a benign phenomenon. Patient 2 was a young female patient with learning difficulties, headaches, and a normal neurologic examination. On her second recording the rhythmic discharge continued during several tasks: motor, mental, intermittent photic stimulation, and hyperventilation. These are features not observed with the midtemporal theta rhythms that are present predominantly in drowsiness. The de-
316
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scribed characteristics of the discharges in Patient 2 have several features distinctive of SREDA. Therefore it is illustrated that in both these children the rhythmic discharges that occurred resemble subclinical seizures, are unique, and are most consistent with those described in adults and termed subclinical rhythmic EEG discharge of adults (SREDA). We believe this discharge in the two children reported is of no clinical significance. To our knowledge SREDA has not been reported in children previously, perhaps because of under recognition, and we suggest this condition be called subclinical rhythmic EEG discharge of adults and children, or SREDAC.
Medical illustrations, compliments of Princess Margaret Hospital, are acknowledged. Jennifer Eastwell, Neurology Department, Princess Margaret Hospital, is also acknowledged.
References [1] Westmoreland B, Klass D. A distinctive rhythmic EEG discharge of adults. Electroenceph Clin Neurophysiol 1981;51:186-91. [2] Miller C, Westmoreland B, Klass D. Subclinical rhythmic EEG discharge of adults (SREDA): Further observations. Am J EEG Technol 1985;25:217-24. [3] Klass D, Westmoreland B. Nonepileptogenic epileptiform electroencephalographic activity. Ann Neurol 1985;18:627-35. [4] Hahn J, Havens P, Higgins J, O’Rourke P, Estroff J, Strand R. Neurological complications of hemolytic-uremic syndrome. J Child Neurol 1989;4:108-13. [5] Pascual-Leone A, Dhuna A, Janousek S, Talwar D. EEG correlation of improvement in hemolytic-uremic syndrome after plasma infusion. Pediatr Neurol 1990;6:269-71. [6] Gibbs E, Gibbs F. Psychomotor-variant type of paroxysmal cerebral dysrhythmia. Clin Electroenceph 1989;20:147-52. [7] Gibbs F, Gibbs E. Electroencephalographic study of head injury in childhood. Clin Electroenceph 1987;18:10.
Introduction Subclinical rhythmic electroencephalogram (EEG) discharge is a distinctive EEG rhythmic pattern that has been reported to occur in adults. It is fairly uncommon with an estimated incidence of one in 1,500 [1,2]. Subclinical rhythmic EEG discharge of adults (SREDA) is reported to occur primarily in older adults, in whom cerebral vascular disease may be common. No clinical alterations are associated with the pattern, and the occurrence of SREDA does not correlate with clinical seizures. The consensus has been that it represents a benign EEG phenomenon of little clinical significance [3]. This discharge has not been reported in children [2]. This article reports SREDA in two female patients 10 and 11 years of age.
From the Departments of *Neurology and †Nephrology; Princess Margaret Hospital for Children; Perth, Western Australia; and the ‡ State Child Development Centre; Perth, Western Australia.
© 2001 by Elsevier Science Inc. All rights reserved. PII S0887-8994(01)00238-7 ● 0887-8994/01/$—see front matter
Case Reports Patient 1. The first patient was a female who presented at 11 years of age with abdominal pain, hematemesis, dysentery, hypertension, renal failure, and seizures. A diagnosis of hemolytic uremic syndrome (HUS) was made. She was treated for renal failure and was on peritoneal dialysis for 18 months. At presentation she initially was loaded with phenytoin for her generalized tonic-clonic seizures. Carbamezapine was then started but discontinued because of a rash. Vigabatrin was then introduced, along with a small dose of clobazam. Five days after starting vigabatrin her neurologic state deteriorated; she was restless, jerky, and encephalopathic. The vigabatrin was discontinued. The patient was reloaded with phenytoin. A second EEG performed 48 hours after onset of clinical deterioration was encephalopathic with the background predominantly in the delta range and significantly worse than the previous EEG (the first) performed a week earlier. Phenytoin was continued, and she was given three doses of fresh-frozen plasma over 3 consecutive days. There was remarkable improvement both clinically and on the third EEG performed 3 days later, which revealed a normal background. At follow-up, 20 months later, Patient 1 is off dialysis but continues to experience renal failure. Apart from mild hyperreflexia she is neurologically intact (has been since 1 month after initial presentation) and academically is doing well at school. Computed tomography (CT) scans at presentation were suggestive of multiple areas of cerebral ischemia. A subsequent CT scan was unremarkable apart from mild prominence of the cortical sulci. A magnetic resonance imaging (MRI) scan of the brain a few months later was normal. Patient 1 received five EEGs (27-45 minutes duration) in the first 4 months of her illness, and SREDA was evident on three of these. SREDA occurred six times on her first and fourth EEG and 10 times on her fifth EEG. Her fourth and fifth EEGs where performed while she was free of all antiepileptic drugs. The rhythmic discharge was at times bilateral and more generalized, sometimes predominantly temporal with asymmetry, and occasionally was frontally dominant. There was often asymmetry and variability in the amplitude and in the field during the 5-7 cycles per second rhythmic discharge. The rhythmic EEG pattern lasted 3-300 seconds in duration with an average duration of ⬃54 seconds. It began abruptly about 80% of the time and gradually ⬃20%. It terminated either abruptly (⬃50%) or gradually. It was 30-100 V in amplitude. There were no clinical accompaniments to the discharge. One of the episodes of SREDA occurred during intermittent photic stimulation at a flash frequency of 15, two during hyperventilation, and one just after hyperventilation. Six episodes of SREDA occurred during stages 1 and 2 of sleep. In addition, 14 and 6 positive bursts were seen frequently in the first EEG and occasionally in the fourth and fifth. Examples of SREDA in this patient are illustrated in Fig 1. Patient 2. The second patient was a 10-year-old female initially assessed because of concerns regarding learning difficulties and complaints of headaches and “pins and needles” sensations. Neurologically she was intact, and the remainder of her clinical examination was normal. On the Wechsler intelligence scale for children (WISC-IIIR) she performed with a verbal intelligence quotient (IQ) in the low-average range, a performance IQ in the high-average range, and a full-scale IQ in the average range when assessed in July 1999. This patient received two EEGs that illustrated features of SREDA. On the first EEG there were
Communications should be addressed to: Dr. Nagarajan; Neurology Department; Princess Margaret Hospital; PO Box D184; Perth, Western Australia 6840. Received July 25, 2000; accepted January 3, 2001.
Nagarajan et al: SREDA in Two Children 313
Figure 1. Epochs from Patient 1’s electroencephalogram (EEG) illustrate the rhythmic EEG discharge reported as subclinical rhythmic EEG discharge of adults (SREDA). The first epoch (Ep1) demonstrates 14 and 6 positive spikes. Ep2 demonstrates the discharge in a coronal montage. Ep4 and Ep5 reveal SREDA while Patient 1 is asleep. Ep6 illustrates the discharge continuing although cessation of intermittent photic stimulation at 30 per second.
four episodes, and on the second EEG (given 7 months later) there were seven episodes of SREDA. After the first EEG, valproate was initiated because the EEG was thought to be epileptiform, although clinically there were no seizures. This treatment did not make a significant difference to her clinical profile, and the second EEG was performed while she was on valproate. The bursts of rhythmic discharge resembling SREDA often began asymmetrically. The amplitude of the discharge was often asymmetric and varied from 30-100 V. At times the discharge was bilateral and at times unilateral. It was often posterior temporally dominant, although at times parietally dominant. Almost all the episodes appeared to terminate abruptly in this patient, although they began gradually approximately half the time and built up to the 5-7 cycles per second rhythm. Sometimes there were sharp waves at the onset. They varied in duration from 8-900
314
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seconds (average was ⬃146 seconds). One of the episodes began just before intermittent photic stimulation and continued to occur during stimulation. One episode occurred during stage 1 sleep, but no deeper stages were recorded. One began after 160 seconds of hyperventilation and another at the end of hyperventilation. The onset of a 300-second episode on the second EEG was after the cessation of hyperventilation. On this run of SREDA the discharge initially was generalized and then became predominantly right sided. During this prolonged discharge, Patient 2 was able to follow commands, do simple motor tasks, such as squeezing her hands and moving her arms up and down, perform mental math, and answer questions regarding name, place, age, etc. The episode terminated during a 5-second intermittent photic stimulation. The EEG was otherwise normal. Illustrations of SREDA in this patient are seen in Fig 2.
Figure 2. Epochs of the rhythmic electroencephalogram (EEG) discharge in Patient 2. The first epoch (Ep1) illustrates onset after hyperventilation. Ep2 reveals continuation of the discharge while Patient 2 is naming objects. Ep3 demonstrates the right-sided discharge while strength is tested in the patient’s upper limbs. Ep4 illustrates the discharge while CR2 is undertaking mental mathematics. Ep5 reveals termination of the discharge during IPS. Ep6 illustrates the presence of sharp waves at the onset on the left side.
Discussion Patient 1 presented at 11 years of age with HUS, a syndrome in which neurologic complications are well known [4]. In the course of her illness, a week after admission to the hospital, she became excessively encephalopathic with recurrence of seizures. Her antiepileptic drugs were changed at that stage. She was also treated with three daily infusions of fresh-frozen plasma, and an EEG performed after that demonstrated marked improvement, as did her clinical status. Pascual-Leone et al. [5]
have reported a similar response to fresh-frozen plasma in a child with HUS. A deficiency in prostacycline is postulated in HUS and, therefore, fresh-frozen plasma, as well as plasma exchange, may be useful. Three of the five EEG recordings for Patient 1 revealed prolonged runs of a subclinical rhythmic EEG discharge that had features consistent with SREDA. The discharges were of variable duration (average of ⬃54 seconds) at an amplitude of 30-100 V. There was variability in the field. There was mostly a gradual onset of the discharge, although at times it was abrupt (⬃20%), and the termina-
Nagarajan et al: SREDA in Two Children 315
tion was either abrupt or gradual. The discharge was often asymmetric. Discharge occurred when Patient 1 was awake, drowsy, and asleep. The rhythmic EEG discharge, without any clinical accompaniments, occurred during and after hyperventilation and during intermittent phobic stimulation. At times there were harmonics in association with the primary discharge at 5-7 cycles per second. We have illustrated that the features of the discharge are most consistent with SREDA as described by Westmoreland and Klass [1], although they have had some features of the midtemporal theta rhythms (psychomotor variant of paroxysmal cerebral dysrhythmia) frequently seen in children of this age and described by Gibbs and Gibbs [6]. In Westmoreland’s article [1], 15 of 65 adult patients with this discharge had cerebrovascular disease. Only four of 65 had a confirmed convulsive disorder. It is interesting to speculate that perhaps cerebral vascular insufficiency in Patient 1, who had HUS with clinical and EEG evidence of neurologic impairment, is responsible for the SREDA in this child. Although 14 and six positive bursts generally are regarded as a benign variant [3], there has been some suggestion that increased frequency (as observed in Patient 1’s first EEG) occurs in brain injury [7]. However, the SREDA was present on her fourth and fifth EEGs undertaken when she was clinically stable and neurologically intact. This evidence suggests that, similar to adults, SREDA in childhood is a benign phenomenon. Patient 2 was a young female patient with learning difficulties, headaches, and a normal neurologic examination. On her second recording the rhythmic discharge continued during several tasks: motor, mental, intermittent photic stimulation, and hyperventilation. These are features not observed with the midtemporal theta rhythms that are present predominantly in drowsiness. The de-
316
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scribed characteristics of the discharges in Patient 2 have several features distinctive of SREDA. Therefore it is illustrated that in both these children the rhythmic discharges that occurred resemble subclinical seizures, are unique, and are most consistent with those described in adults and termed subclinical rhythmic EEG discharge of adults (SREDA). We believe this discharge in the two children reported is of no clinical significance. To our knowledge SREDA has not been reported in children previously, perhaps because of under recognition, and we suggest this condition be called subclinical rhythmic EEG discharge of adults and children, or SREDAC.
Medical illustrations, compliments of Princess Margaret Hospital, are acknowledged. Jennifer Eastwell, Neurology Department, Princess Margaret Hospital, is also acknowledged.
References [1] Westmoreland B, Klass D. A distinctive rhythmic EEG discharge of adults. Electroenceph Clin Neurophysiol 1981;51:186-91. [2] Miller C, Westmoreland B, Klass D. Subclinical rhythmic EEG discharge of adults (SREDA): Further observations. Am J EEG Technol 1985;25:217-24. [3] Klass D, Westmoreland B. Nonepileptogenic epileptiform electroencephalographic activity. Ann Neurol 1985;18:627-35. [4] Hahn J, Havens P, Higgins J, O’Rourke P, Estroff J, Strand R. Neurological complications of hemolytic-uremic syndrome. J Child Neurol 1989;4:108-13. [5] Pascual-Leone A, Dhuna A, Janousek S, Talwar D. EEG correlation of improvement in hemolytic-uremic syndrome after plasma infusion. Pediatr Neurol 1990;6:269-71. [6] Gibbs E, Gibbs F. Psychomotor-variant type of paroxysmal cerebral dysrhythmia. Clin Electroenceph 1989;20:147-52. [7] Gibbs F, Gibbs E. Electroencephalographic study of head injury in childhood. Clin Electroenceph 1987;18:10.