Catherine M. Foley

Cerebral edema causing death in children with maple syrup urine disease

Four children with the classic form of maple syrup urine disease (MSUD) died of cerebral edema during an intercurrent infection that caused severe dehydration and acidosis. The diagnosis of MSUD had been established during the neonatal period in all four patients, on day 1 of life in three of them. All were in satisfactory control before the intercurrent illness. Two patients underwent peritoneal dialysis. Signs of brain-stem compression occurred after treatment, when biochemical abnormalities were improving. Computed tomography of the head, which was done in two patients, revealed cerebral edema; one of these patients also had subarachnoid hemorrhage. Autopsy in one case revealed cerebral edema with herniation. Our experience documents that cerebral edema may occur in the older child with MSUD as well as in the neonate. The pathogenesis of cerebral edema in MSUD remains unclear. Early treatment of dehydration and acidosis may prevent the catastrophic consequences that we have observed.

Diagnostic Value of Pediatric Outpatient Video-EEG

Outpatient video-electroencephalography (OVEEG) was performed in 100 infants, children, and adolescents with diagnosed (group I, n = 64) or suspected (group II, n = 36) epilepsy. Median monitoring duration was 4 hours. Indications for OVEEG in group I were classification of seizures, reported seizure exacerbation, or onset of new signs. OVEEG indications in group II were repetitive paroxysmal and stereotyped signs of myoclonic movements, fixed gaze, abnormal behavior, or nonmyoclonic motor activity. In group I patients, symptomatic events were recorded in 89%, half of which were seizures. Among group II patients, events were recorded in 67% and were seizures in 22%. Overall, OVEEG was successful in 83% of patients. Compared to a 24-hour inpatient admission for video-EEG monitoring, OVEEG represented cost reductions of 55-80% per patient. We conclude that OVEEG is a cost-effective, useful alternative to continuous inpatient video-EEG monitoring in the investigation of selected infants, children, and adolescents with diagnosed or suspected epilepsy.

Long-Term Computer-Assisted Outpatient Electroencephalogram Monitoring in Children and Adolescents

The aims of this study were (1) to define the role of long-term computer-assisted outpatient electroencephalographic monitoring (COEEG) in children and adolescents with known or suspected epilepsy, and (2) to compare COEEG data with routine interictal electroencephalograms (EEG). We performed 18-channel COEEG in 84 children and adolescents with diagnosed (group 1, n = 49) or suspected (group 2, n = 35) epilepsy. Mean recording time was 1.4 days. Overall, COEEG was useful in 87% of patients. In group 1, events were recorded in 73% of patients and were electrographic seizures in 45%. In group 2, events were detected in 86% of patients and were electrographic seizures in 17%. Nocturnal and partial seizures predominated. Seizure diagnosis and classification by COEEG was concordant with interictal EEG findings in 19% and discordant in 63% of patients. COEEG is a useful technique for the diagnosis of epileptic and nonepileptic events among selected children and adolescents. When compared to routine interictal EEG, COEEG could offer additional accuracy in the classification of seizures in pediatric patients. (J Child Neurol 2000;15:49-55).

The Epileptiform Significance of Intermittent Rhythmic Delta Activity in Childhood

Intermittent rhythmic delta activity is reported in various disorders and is classified as a nonspecific abnormal electroencephalographic pattern. We have investigated its clinical and electroencephalographic features in childhood. Intermittent rhythmic delta activity was identified in 54 children over a period of 48 months. Epilepsy was present in 81%, 4% had only a single generalized tonic-clonic seizure, and 15% had no seizures. Generalized seizures were more common than partial seizures (83% versus 13%; 4% were mixed). The largest group of patients had idiopathic epilepsy. Epileptiform features were present in 70%. No patient identified prospectively has had a space-occupying lesion. Intermittent rhythmic delta activity should be considered an epileptiform pattern in children, most commonly occurring as an interictal pattern in primary generalized epilepsy. (J Child Neurol 1992; 7:156-160).

West syndrome in tuberous sclerosis complex

West syndrome occurs commonly in children with tuberous sclerosis complex and is associated with a grave prognosis for cognitive and seizure outcomes. We sought to determine the epilepsy outcome of children with tuberous sclerosis complex and West syndrome and whether EEG, MRI, or steroid therapy duration were different in those whose epilepsy improved compared with those with intractable seizures. Seventeen patients with tuberous sclerosis complex and West syndrome were identified. For each patient, two sets of clinical evaluations, EEG and MRI data, and treatment information separated by at least 12 months were obtained. The patients were divided into two seizure outcome groups. EEG, MRI, and treatment data were compared between the groups. The intellectual deficiency was either severe (76%) or moderate (24%). Seizure control improved in 10 and worsened in seven, without mortality (follow-up range = 12-216 months). No significant differences in EEG background, MRI findings, or steroid treatment duration were evident between the groups. The difference in EEG-sleep approached statistical significance (P = 0.06). Our findings did not confirm reports of high mortality and poor epilepsy outcome in intellectually deficient children with West syndrome and tuberous sclerosis complex. EEG sleep was the best indicator of seizure control and approached statistical significance. The duration of steroid therapy had no influence on seizure control.

Steady-state auditory evoked responses to pulsed frequency modulations in children

This study investigated steady-state auditory evoked responses to pulsed frequency modulations (FM) of a continuous tone in normal children ranging in age from 6 to 12 years. We examined variations in response amplitude and phase as a function of age, recording site, and FM pulse duration. The surface topography of these evoked potentials suggested a relatively broad distribution with maximal responses observed at frontal electrode sites, smaller responses from parietal leads and the smallest responses were evident at the temporal lobe placements. Response parameters varied significantly as a function of pulse duration. Fifty milliseconds pulses elicited responses that were on average 20% larger than 100 ms FM pulses. Mean phase differences suggested that responses to the 100 ms pulses also lagged behind responses to the 50 ms pulses by the equivalent of 20 ms. There were no significant age-related variations in response amplitude. Phase varied with age only in response to the 50 ms FM pulses. The findings indicated that steady-state responses are sensitive to temporal parameters of frequency change present in pulsed modulations. The possibility is raised that this paradigm may be clinically useful in detecting dysfunction of specialized auditory mechanisms involved in frequency modulation analysis.

Value of plasmapheresis in hepatic encephalopathy

Plasmapheresis is used for treating the complications of liver failure. We performed plasmapheresis on 6 children with hepatic encephalopathy resulting from acute hepatic failure and prospectively assessed its effects on neurologic and electrophysiologic (electroencephalography and evoked potentials) function. Clinical improvement was observed in 3 of 6 patients; changes in the serum ammonia value or the results of initial electrophysiologic tests did not predict the patient response. Two patients underwent transplantation after neurologic improvement was produced by plasmapheresis; however, despite plasmapheresis, 4 patients progressed to brain death. Our data demonstrate that plasmapheresis may transiently improve the encephalopathy of acute hepatic failure but is not curative alone. Therefore, plasmapheresis may be a useful adjunct in the treatment of liver failure, potentially improving the pretransplantation status of the patient.

Technetium 99mTc-HMPAO SPECT in Children and Adolescents With Neurologic Disorders:

We evaluated regional cerebral blood flow with technetium 99mTc hexamethylpropyleneamineoxime single photon emission computed tomography (SPECT) in 20 children and adolescents with neurologic dysfunction of varied etiology and abnormal electroencephalograms (EEGs). All patients were also examined with computed tomography (CT) and magnetic resonance imaging (MRI). Abnormal perfusion was found in 17 (85%) of 20 SPECT scans. Abnormal CT or MRI scans were noted in nine (45%) and in 10 (50%) of 20 cases, respectively. In eight (73%) of 11 cases with normal CT scans and in seven (70%) of 10 with normal MRI scans, the SPECT scan was abnormal. Abnormal regional cerebral blood flow on SPECT scans correlated better with EEG abnormalities than with neurologic examination or CT or MRI scan findings. We conclude that in children and adolescents with a spectrum of neurologic diseases and abnormal EEGS, abnormalities of brain structure or function are more likely to be documented by SPECT than by CT or MRI scans. SPECT findings correlate well with the location and type of EEG abnormality. (J Child Neurol 1993;8:227-234).

Tuberous Sclerosis Complex and Epilepsy: Prognostic Significance of Electroencephalography and Magnetic Resonance Imaging

Tuberous sclerosis complex is a disease that affects many organs, including the central nervous system. Nervous system involvement in the form of hamartomas often results in seizures. In this study we wanted to determine the outcome of epilepsy in tuberous sclerosis complex and determine whether interictal electroencephalograms (EEGs) and hamartoma burden as seen with magnetic resonance imaging (MRI) are predictive of degree of seizure control. The study population consisted of 30 patients. For each patient two sets of EEG and MRI data, separated by at least 12 months, and information on seizure frequency at time of data collection were obtained. Sensitivity, specificity, and positive and negative predictive values of various EEG and MRI findings were determined. Seizure control improved in 20 and worsened in 10 patients. In relation to seizure control, the specificity of an abnormal sleep EEG and the positive predictive value of normal sleep EEG were 100%. MRI and EEG background were neither sensitive nor specific for predicting seizure control. A majority of children with tuberous sclerosis complex can achieve good seizure control. The sleep EEG is helpful in predicting eventual seizure control. (J Child Neurol 2000;15:81-83).