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

OBJECTIVE: Frontal 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.

METHODS: A 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).

RESULTS: We 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.

SIGNIFICANCE: A history of SGTCS is related to a specific ictal semiology and interictal EEG, and may have a role in surgical risk stratification.