Abstracts

Rationale: The postictal effects of generalized seizures are disabling and potentially life-threatening, yet the origins of these clinical features are a mystery, and their electrophysiological correlates have not been systematically documented. In particular, the assumption that seizure termination can be defined as cessation of visible, large amplitude EEG discharges and/or whole body clonic jerking has never been critically assessed. Methods: We examined retrospective video EEG recordings from intracranially implanted patients with recorded seizures who subsequently underwent cortical resection. Analysis focused on the first 10 minutes after seizure termination, which was defined by clinical consensus. We determined whether widespread postictal attenuation was present, and characterized the time course of the return to a continuous background pattern, and its correlation with the clinical semiology. Results: There were 26 secondarily generalized seizures in 12 patients (7 men, 5 women). Postictal immobility was observed after 20 seizures (77%). Positive clinical semiologies were observed after 12 seizures (46%), including oral/manual automatisms (7), bilateral limb posturing (4), myoclonic jerking (11), and complex behaviors such as bicycling (1). Widespread attenuation of all frequencies was noted immediately after seizure termination in 18 seizures (69%), with an average duration of 36 seconds. Reemergence of background activity followed a stuttering course in 15 seizures (58%). The time from seizure termination to resumption of a continuous background was on average 89 seconds (range 8 seconds to 3 minutes). Focal runs of epileptiform activity were noted after 6 seizures (23%). Conclusions: These findings raise the possibility that seizure-related activity continues after putative seizure termination in brain regions not sampled by the implanted electrodes and distant from the site of seizure origin. Such activity could have indirect effects on cortical EEG, and explain some postictal behavioral manifestations.