Abstracts

RATIONALE: Postictal slowing is a well-known phenomenon occurring after both generalized and focal onset seizures. There is limited information in the medical literature regarding the length of postictal changes following seizures. The objective of this study was to determine how long after a seizure slowing can be attributed to that seizure, and what characteristics of a seizure influence the postictal changes.
METHODS: Thirty seizures recorded from 15 patients admitted during the past 12 months to the epilepsy monitoring unit at Children[ssquote]s Hospital, Boston were reviewed. Electroencephalogram (EEG) and video were recorded and stored digitally. Seizures were classified based on EEG characteristics as having either a focal or generalized onset. The location, spread and length of each seizure was recorded. The postictal period, including the location and length of the slowing, was assessed utilizing visual inspection. Quantitative analysis of the postictal slowing was performed to confirm the length of time it took for the EEG to return to baseline. For patients who fell asleep postictally, the EEG was analyzed after they awoke spontaneously. Exclusion criteria included an abnormal background with extensive slowing present interictally and benzodiazepine administration due to prolonged seizures.
RESULTS: The mean duration of all seizures was 0:02:01 with a range of 0:00:06-0:07:55. For seizures after which the patient remained awake, the mean duration of the postictal slowing was 0:20:02 with a range of 0:00:05-2:41:00 (n=19). For seizures followed by sleep, the mean duration of the postictal slowing was 2:32:56 with a range of 1:00:03-7:28:00 (n=11). No slowing was present in any instance upon awakening. The mean postictal slowing duration was 2:49:18 for seizures with a generalized onset and 0:38:02 for seizures with a focal onset. The duration of postictal slowing was a function of the seizure duration: 0:01:24 for seizures less than 1 minute, 0:21:05 for seizures lasting 1-2 minutes, 0:57:39 for seizures lasting 2-3 minutes, and 1:20:37 for seizures longer than 3 minutes.
CONCLUSIONS: Based on the review of thirty seizures recorded in patients with epilepsy the average duration of the postictal EEG slowing was sixty-five minutes. Focal onset seizures not followed by sleep caused substantially shorter periods of postictal slowing than generalized seizures followed by sleep. The longer the seizure lasted, the longer the duration of postictal slowing. This study reveals that postictal EEG slowing resolves rapidly following typical seizures in patients with epilepsy.