Abstracts

We determined how sleep with spindles altered the spatial pattern of interictal spike activity on ECoG in children with focal seizures being evaluated for epilepsy surgery., We studied a series of 26 children with focal seizures (age: 0.5-17y) who underwent subdural electrode placement involving the fronto-central region for extraoperative ECoG monitoring. Sleep spindles were visually identified and described by a Board-certified clinical neurophysiologist. Interictal spike frequency was determined for each channel during wakefulness and sleep. The mean spike frequency across the whole subdural electrode arrays was compared between wakefulness and sleep (paired t-test). Spearman[apos]s rank correlation was applied to each patient[apos]s dataset, and determined whether the spatial pattern of spike frequency was similar between wakefulness and sleep. Subsequently, we determined whether sleep differentially increased spike frequency in the medial temporal region or the ictal onset zone. Finally, we determined whether the ictal onset zones were predicted by frequent spike activity on both awake and sleep recordings., Spindles were noted in the frontal-central region during sleep in 21/26 children, who were included into further analyses. Independently from such spindles, another type of spindles (Malow et al, 1999) was noted in the medial temporal region in 18 children, whose subdural electrodes were placed on the medial temporal region. Conversely, 5/21 children were excluded from further analyses, since no clear spindles were noted due to frequent spikes in 3 children with spasms, and no sufficient interictal sleep segments were available due to frequent seizures in another 2 children. The mean spike frequency was higher on sleep compared to awake recordings (p=0.04). Three children showed no spike on awake recordings but had spikes [gt] 1 /min on sleep recordings. In all children showing at least 1 spike/min in an electrode, both during wakefulness and sleep, the spatial pattern of spike frequency was quite similar between wakefulness and sleep (mean rho=0.72; p[lt]0.0001). There was no significant difference in the fractional rank of spike frequency of the ictal onset zone (p=0.2) or the medial temporal region (p=0.4) between wakefulness and sleep. Spike frequency was higher in the ictal onset zones (mean fractional rank: 0.85 on awake and 0.83 on sleep recording) compared to the non-onset areas (mean fractional rank: 0.57 on awake and 0.53 on sleep recording) (p[lt]0.0001) in 15 children showing at least 1 spike/min in an electrode., The present study of children with focal seizures failed to demonstrate differential activation of interictal spike activity associated with sleep. Instead, the overall spatial pattern of interictal spike activity was similar between wakefulness and sleep, and both awake and sleep ECoG recordings were good predictors of the ictal onset zones.,