Abstracts

Rationale: Interictal spiking is frequently potentiated by sleep, but occurrence of seizures in children with epilepsy during wakefulness and sleep, as well as during the day and nighttime, has not been well characterized. We hypothesized that diurnal patterns of seizures and occurrence out of wakefulness and sleep vary based on the localization of the epileptogenic focus. Methods: Charts of 332 children (aged 0-18) with refractory epilepsy undergoing Video EEG monitoring (VEM) were reviewed. Patients with lesional focal epilepsy as evidenced by concordant ictal and interictal EEG as well as a single lobar epileptogenic lesion on MRI were included. Seizure patterns recorded during the VEM were analyzed based on occurrence during the day (7 am to 10 pm) or night and their relationship to wakefulness and sleep. Appropriate statistical analysis was performed using SPSS (version 16.0). Results: Sixty-six children (59% females), median age 12 years (range 2-18) were included in the study. The median age of seizure onset was 2.5 years and the median duration of epilepsy was 6.3 years. Seizure frequency was 1-2/month in 25%, 1-2/week in 25%, 3-6/week in 10% and > 1/day in 40% of patients. Neuroimaging findings included malformation of cortical development (41%), hippocampal atrophy/mesial temporal hyperintensity suggestive of hippocampal sclerosis (25.8%), tumors (12.1%), focal leucomalacia (7.6%), tuberous sclerosis (4.3%), schizencephaly (3%), Rasmussen’s chronic focal encephalitis (1.5%) and perinatal infarct (1.5%). The median duration of monitoring was 5 days (range 3-10) and the median number of seizures recorded was 6 (range 1-77). The distribution of the lesions were mesial temporal (MT) 29%, neocortical temporal (NT) 18%, frontal (F) 17.5%, parietal (P) 13.5% and occipital (O) 12%. Two hundred-fifty nine seizures were analyzed: 77 (29%) were MT, 48 (18%) NT 79(31%) F, 23 (9%) P and 32 (13%) O. The median duration of seizures was 82 seconds (10-558). EEG duration of seizures occurring out of wakefulness was 96 ± 9.3 seconds, longer when compared to seizures occurring out of sleep, 66± 5 seconds (p=0.015, Mann Whitney U test). However, there was no difference with respect to duration of seizures which occur during day- or nighttime (p=0.23). Overall, 62% of seizures occurred during the daytime (48% out of wakefulness and 14% out of sleep) and 38% during the nighttime (32% out of sleep and 6% out of wakefulness). F seizures occurred mostly out of sleep (62%) while MT in 36%, NT in 29%, O in 34% and P in 39% (p=0.001, Kruskall-Wallis test). Sixty-five percent of MT, 67% of NT, 51% of F, 81% of O and 61% of P seizures occurred at night (p=0.23, Kruskall-Wallis test). Conclusions: Sleep, not time of day or night, provides a more robust stimulus for seizure onset, maximally seen in frontal lobe epilepsy, but duration of EEG seizures is longer when onset occurs out of wakefulness. This observation may be used to further understand the mechanisms of seizure expression, and provide the basis for novel intervention strategies.