Factors influencing the duration of generalized tonic–clonic seizure

PURPOSE This study investigated the duration of generalized tonic-clonic seizure (GTCS) and the factors that prolong GTCS duration. METHOD We retrospectively analyzed clinical data collected from a consecutive group of patients who underwent video-electroencephalography (EEG) and experienced at least one GTCS during monitoring. Each seizure was divided into seven phases. The duration of GTCS was defined as the comprehensive duration of each GTCS phase, particularly those of Phase 3 to Phase 7. RESULTS The mean GTCS duration per patient was 74.6s. The results indicated that patients with an age of seizure onset <2 years exhibited a significantly longer duration than those with an age of seizure onset >2 years (p=0.033). A significant difference was also observed in the duration of GTCS between wakefulness and sleep (wakefulness 76.2 ± 38.5, sleep 66.3 ± 27.8, p=0.017). Our data suggest no significant differences between primary and secondary GTCS. The correlations between the duration of GTCS and many risk factors were also analyzed, including gender, age, neurological examination, cognitive status, family history of epilepsy, location of MRI brain abnormalities, reported seizure frequency at time of admission, number of current AEDs, history of SE, and duration of epilepsy. CONCLUSIONS The mean duration of GTCS was<2 min. The age of seizure onset and the circadian pattern of seizure are the major factors influencing the duration of GTCS.