To investigate the impact of clinical and demographic parameters on the duration of focal onset seizures with and without secondary generalization using precise duration measurements from intracranial electroencephalographic (iEEG) recordings.
Patients with unifocal epilepsy syndromes and iEEG recording were retrospectively identified from the database of the local epilepsy center (2006‐2016). Seizure duration was defined as time difference of iEEG seizure pattern onset and cessation. The seizure semiology was classified based on video recordings. Clinical and demographic data were extracted from patient reports.
In total, 69 adults were included, and 654 focal onset seizures were analyzed. Focal to bilateral tonic‐clonic seizures (FBTCSs; 98/654) were significantly longer than focal seizures (FSs) without generalization (FS‐BTCs; 556/654, P < .001), and most FSs (545/654, 83.3%) terminated within 2 minutes. The duration of FSs was prolonged with increasing age of the patients (P = .003) and was significantly shortened (P < .001) by evolution into an FBTCS. FBTCSs with lateralizing semiologies like version (P = .015) and sign of four (P = .043) were associated with longer bilateral tonic‐clonic manifestations. Furthermore, FBTCSs with preceding aura, frontal origin, or onset during sleep were by trend shorter. Age (P < .001) and disease duration (P = .028) were essential for prediction of FS‐BTC duration, whereas the vigilance state (P = .085) was the main prediction factor for the duration of FBTCSs.
The identified modifiers of seizure duration are of great relevance for clinical risk evaluation, especially in the aging epilepsy patient suffering from temporal lobe epilepsy with secondary generalized seizures.