Abstracts

Rationale: Postictal generalized EEG suppression (PGES) may be associated with sudden unexpected death in patients with epilepsy. Generalized tonic-clonic seizure (GTCS) is one of the well-known risk factors for PGES. GTCS associated with PGES has various characteristics, including semiological features such as longer tonic phase or typical generalized tonic clonic type. However, the factors predictive of PGES remain unclear. The present study investigated the epilepsy classification and semiological features in patients suffering GTCS with PGES. Methods: We retrospectively reviewed 80 consecutive patients (37 men and 43 women) with epilepsy aged 13 to 50 years, who manifested a total of 116 GTCSs during long-term video EEG monitoring. Eighteen patients with generalized epilepsy suffered 22 primary GTCSs (pGTCSs) and 62 patients with focal epilepsy had 94 secondary GTCSs (sGTCSs). PGES was determined using the previously published criterion of generalized absence of EEG activity of amplitude >10 V. First, we compared PGES occurrence between pGTCSs in generalized epilepsy and sGTCSs in focal epilepsy. Then, we reviewed the semiological features of sGTCSs in focal epilepsy. Forty-three sGTCSs occurring with PGES were classified as the PGES (+) group. Semiological features including lateralizing signs were compared between the PGES (+) and (-) groups to determine the predictive factors for the occurrence of PGES in focal epilepsy. Results: Eighteen (82%) of 22 pGTCSs in generalized epilepsy showed PGES, whereas 43 (46%) of 94 sGTCSs in focal epilepsy showed PGES. In particular, all 8 pGTCSs in idiopathic generalized epilepsy showed PGES. Right hemispheric seizures were significantly (p < 0.01) less common in the PGES (+) group (7 of 43, 16%) than in the PGES (-) group (32 of 51, 63%). Preceding "bilateral asymmetric tonic posturing" was significantly (p < 0.0001) less common in the PGES (+) group (18 of 43, 42%) than in the PGES (-) group (42 of 51, 82%). However, preceding "version" occurred in similar numbers in the PGES (+) (26 of 43, 60%) and PGES (-) groups (29 of 51, 57%). Conclusions: Idiopathic generalized epilepsy, left hemispheric or nonlateralizable seizure onset, and absence of "bilateral asymmetric tonic posturing" may be potential predictive factors for PGES. Epilepsy classification, lateralization of the ictal onset zone, and propagation pathways leading to sGTCSs are important characteristics of PGES. Funding: None