Abstracts

Rationale: We studied the duration of seizures arising from different lobes in focal epilepsy to better understand spread and inhibitory mechanisms involved. It has been noted that seizure duration may be different in different focal epilepsy syndromes, but actual duration has not been studied systematically. Methods: We investigated the seizure duration as measured by ictal EEG and seizure semiology in 623 seizures of 84 patients with temporal (TLE), frontal (FLE) and parieto-occipital lobe epilepsies (POLE). Seizure onset was taken from EEG or seizure semiology only in case the respective activity was sustained. Seizure end was mostly considered by the end of ictal EEG, as postictal behaviour may be difficult to differentiate from ictal semiology. Subclinical ictal EEG discharges or seizures limited clinically to auras were not included in the comparisons. Since duration was not normally distributed we report median values. Results: Seizure duration differed significantly between the syndromes. Focal seizures in FLE patients were shortest with 43 seconds, followed by seizures in POLE with 56 s and TLE with 68 s (p<0.05). Seizures that generalized secondarily also differed significantly between FLE (97s) and POLE (107s) on one hand and TLE on the other hand (130s; p<0.05). The prolongation of seizure duration through secondary generalization did not differ significantly between the syndromes. Conclusions: We conclude that exhaustion and the activation of inhibitory mechanisms differ between focal epilepsies. Reasons may be different connectivity for example to the basal ganglia and differences in the cortical structures involved.