Secondarily generalized seizures in temporal lobe epilepsy

Secondarily generalized tonic-clonic seizure (SGTCS) may occur rarely in temporal lobe epilepsy (TLE), but SGTCS is the major risk factor for sudden death and for seizure-related fatal injuries. Our aim was to investigate clinical factors associated with the occurrence of SGTCS in TLE by addressing two questions: (1) What clinical features differentiate patients with TLE who regularly had SGTCS from those who did not? (2) Is there an association of secondarily generalized seizures with preceding seizure elements and clinical data?

We included 171 patients with TLE (mean age 34.4 ± 10) who participated in our presurgical evaluation program, which included continuous video-electroencephalography (EEG) and magnetic resonance imaging (MRI). Patients had a temporal lobectomy as a result of mesial or neocortical TLE. To reevaluate the archived seizures, we selected the consecutively recorded seizures of each patient. If the patient had more than three recorded seizures, then we reevaluated only the first three. Altogether video-recorded seizures of 402 patients were reanalyzed.

A positive association between the presence of hippocampal sclerosis on the MRI and SGTCS in the patient history was found, whereas ictal speech and pedal automatism showed a negative association with a SGTCS history. The age of patients showed a positive association, whereas patient's reactivity before and during the seizure, oral/pedal automatisms, and vocalizations showed a negative association with secondary generalization of a focal-onset seizure during video-EEG monitoring.

Clinical features associated with SGTCS may help clinicians during presurgical monitoring identify high-risk patients for SGTCS. Our study may help in understanding the pathophysiology of secondary generalization.