Two predictors of postictal generalized EEG suppression: Tonic phase duration and postictal immobility period

Purpose: To determine the effect of different seizure characteristics on the occurrence of postictal generalized EEG suppression (PGES). PGES is considered as a potential risk factor of sudden unexpected death in epilepsy (SUDEP) by several studies. Methods: In this retrospective cross-sectional study, episodes of generalized convulsive seizures (GCS) were reviewed in regard to state at seizure-onset, the seizure and tonic phase durations, postictal immobility (PI) duration and whether the patient received oxygen (02) mask during the post-ictal phase. Moreover, the presence and duration of PGES was determined for each seizure. Results: Among 98 episodes of GCSs, 56 (57.1%) had PGES and 42 (42.9%) did not have PGES. The mean seizure duration for attacks with and without PGES was 106.62 +/- 97.04 and 104.85 +/- 91.81 s, respectively (P > 0.05). The tonic phase duration was significantly longer in PGES positive compared to PGES negative seizures (4.25 +/- 3.17 s vs. 2.82 +/- 3.58 s, P < 0.05). Early O2 mask administration and state of wakefulness at seizure-onset did not show any significant correlation with the presence of PGES (P > 0.05). Seizures with PGES had higher PI duration than those without PGES (156.24 s vs. 124.73 s) (P < 0.05). Interestingly, in seizures with PGES, there was a positive correlation between PI and tonic phase durations (r: 0.4, P < 0.05). Conclusions: According to our findings, higher tonic phase duration and longer PI period increased the odds of PGES formation.