Abstracts

Rationale: To determine the peri-ictal electrophysiological characteristics of nocturnal and diurnal generalized convulsive seizures (GCS) and to further understand the implications of sleep in sudden unexpected death in epilepsy (SUDEP). Methods: We retrospectively reviewed the video-EEG of 109 consecutive patients with 150 GCS during long-term video-EEG monitoring. We determined the heart rate (HR), respiratory rate (RR), total seizure duration, total convulsive phase, tonic phase, and clonic phase, as well as the presence and duration of postictal generalized EEG suppression (PGES) in patients with nocturnal GCS and diurnal GCS. Results: Forty patients had 67 nocturnal GCS, 61 patients had 83 diurnal GCS, and 8 patients with both nocturnal and diurnal GCS. Pre-ictal HR was significantly lower in patients with nocturnal GCS than in those with diurnal GCS (p=0.0016). However, there was no significant difference in total seizure duration, total convulsive phase, tonic phase and clonic phase as well as postictal HR and RR in the two patient groups. Forty-five of 67 (67.2%) nocturnal GCS were associated with PGES, whereas 49 of 83 (59%) diurnal GCS were associated with PGES. The duration of PGES was prolonged in patients with nocturnal GCS (46.7 ± 21.7 s) than in those with diurnal GCS (38.5 ± 15.6 s), however, it was not statistically significant (p=0.63). Conclusions: Nocturnal GCS is associated with a higher pre-ictal parasympathetic tone comparing to diurnal GCS. However, postictal autonomic dysfunction as reflected by postictal HR and RR, and the duration of PGES were comparable in two patient groups. Future studies involving factors such as sleep environment and position may be necessary to further understand the implications of sleep in the pathogenesis of SUDEP.