Recurrent secondary generalization in frontal lobe epilepsy: Predictors and a potential link to surgical outcome?

ObjectiveFrontal lobe epilepsy (FLE) frequently leads to secondary generalized tonic-clonic seizures (SGTCS). However, little is known about the clinical, electrophysiologic, and radiologic correlates of SGTCS and whether these could influence diagnosis and treatment. MethodsA cohort of 48 patients with confirmed FLE was retrospectively identified and dichotomized into a group with and a group without SGTCS defined by history (1/year) or video-electroencephalography (vEEG). Demographics, seizure semiology, vEEG, neuroimaging data, and estimated seizure-onset zone were tabulated, and their association with the occurrence of SGTCS was evaluated with use of a chi-square test. Independent predictors of SGTCS were confirmed using a stepwise multivariate analysis. Similarly, these predictors as well as a history of SGTCS were tested as multivariate predictors of the postoperative International League Against Epilepsy (ILAE) score in the surgical subgroup (n=25). ResultsWe identified three independent predictors of a history of SGTCS in FLE, including loss of responsiveness at seizure onset (corrected p=0.04), a semiology involving early elementary motor signs (corrected p=0.01), and multifocal spikes on EEG (corrected p=0.02). A seizure-free outcome occurred in 57% of surgical cases and was more likely in the group without SGTCS (100%, p=0.001). When considering only SGTCS occurring during video-EEG monitoring, the association with semiology and surgical outcome vanished, but the association with preserved awareness and a multifocal EEG persisted. SignificanceA history of SGTCS is related to a specific ictal semiology and interictal EEG, and may have a role in surgical risk stratification.