Abstracts

RATIONALE: This study seeks to examine the relationship between the amount of epileptiform activity in children with Benign Epilepsy with Centrotemporal Spikes (BECTS) and parental reports of cognitive and language difficulties. Aims: 1. To determine the incidence of EEG features-spike location, lateralization, discharge frequency, and focal slowing during wakefulness and sleep in a cohort of children with BECTS, 2. To determine by systematic telephone interview any difficulties in cognitive development (learning, problem-solving, memory, language), behaviour, and school performance, 3. To correlate this data with EEG features.
METHODS: Patients were recruited from the EEG laboratories by identification of the typical EEG feature of BECTS. Syndrome was confirmed by telephone interview. In each record, the duration of wakefulness, drowsiness, and sleep were reviewed. Spike location was defined by maximum negativity in 10-20 electrode system, [gte]2 non-homotopic regions were defined as multiple. A laterality index was computed by determining spike frequency over time in either hemisphere expressing this as a ratio.
RESULTS: Twenty children (12 males, 8 females) aged 4-14 yrs (mean 9.4 yrs) were studied. A central (eg. C4, T4, or Cz) focus was identified in 40% of the children and 60% had multiple spike foci. In 35% of children, the spike foci were lateralized to one hemisphere. The discharge frequency in wakefulness varied between 1-46 spikes/minute. There were frequent long runs of discharges in wakefulness in 12 children and in 6 these occupied [gte]10% of the recording in wakefulness. Eight children had focal slowing independent of spikes. The increase in spike frequency with sleep was 0.3 to 23 times the wakeful baseline record. In 4 children, spikes occupied [gte]85% of the sleep record. Eight children were identified as having cognitive problems by interview, of these 4 had language problems, in 2 these preceded first seizure. Seven had behaviour problems and 7 difficulties in school performance. Seven children did not have problems identified by parents. Children with reported cognitive, school difficulties, or behavioural problems had higher spike frequency in wakefulness. This was only significant (means 20/min. v. 9/min, p=0.04) for behaviour. There was no correlation between the presence of cognitive, school, or behavioural problems and the presence of multiple foci, laterality or sleep activation of spikes.
CONCLUSIONS: Multiple foci, continuous spike activity in sleep, and focal slowing were common in this cohort of BECTS with infrequent seizures. Reports of cognitive, behavioural, and school difficulties were present in more than half of the cohort. However, we did not find significant correlations between measures of discharge location, lateralisation, or frequency in wake or sleep and reports of cognitive or school problems. The clinical significance and origin of the relationship between behavioural problems and spike frequency will be tested further as recruitment continues and formal neuropsychological assessments are completed.
[Supported by: NHMRC, Australia]