Abstracts

Rationale: Postictal generalized EEG suppression (PGES) has been proposed as a neurophysiological marker for sudden unexpected death in epilepsy (SUDEP). If PGES is a marker of potentially fatal seizures, it is critical to identify clinical features that distinguish people with epilepsy that are prone to PGES. We analyzed the clinical features of pediatric patients with PGES undergoing video EEG (vEEG).Methods: A retrospective review of vEEG at the Hospital for Sick Children (2009-2011) was performed, to identify episodes of PGES. PGES was defined as generalized voltage attenuation <10 V by A-P bipolar montage, within 30 seconds of cessation of the ictal discharges and >1 second in length. Sex, age, duration of epilepsy, epilepsy syndrome, seizure types, antiepileptic medications (AEDs) used, MRI findings, past medical history, family history and presence of developmental disability were analyzed at the time of PGES recording. The E-Chess score was used as an outcome measure for epilepsy severity.Results: A total of 977 vEEG reports (<18 years old) were reviewed including 399 (41%) with electroclinical seizures. 26 children (62%; 16 male) demonstrated 49 seizures with PGES (37%) from a total of 134 seizures. Mean age of epilepsy onset was 5.9 years and mean duration of epilepsy was 7.2 year at the time of PGES recording. Mean number of seizures types was 3 with a range 1 6. Mean lifetime use of AEDs was 5 with a range of 2 11. Duration of PGES ranged 2-54 sec (mean 30 sec). 42 of 48 (88%) seizures associated with PGES were generalized tonic clonic seizures (GTCS). Duration of 42 PGES with GTCS (mean 35 sec) was significantly longer than that of 6 PGES without GTCS (mean 9.6 sec; p <0.005). Longer PGES duration significantly correlated with lower E-Chess score, a marker of epilepsy severity in children (R = 0.63; p < 0.001) and with less lifetime use of AEDs (R = 0.40; p < 0.05). 8 children had global developmental delay (31%) and had a shorter PGES duration (mean 17.7 sec) compared to those children with normal development or with attention-deficit hyperactivity disorder (ADHD) and/or mild cognitive impairment (mean 37.7 sec; p<0.005).Conclusions: Longer duration of PGES in children significantly correlates with GTCS, lower E-Chess score, less lifetime use of AEDs and normal development. The latter three findings suggest that PGES is more common in those pediatric patients with less severe epilepsy.