The present study sought to understand whether targeted questioning in the Emergency Department (ED) about focal features at onset of focal to bilateral generalized tonic-clonic seizures (FBTCS) can unveil underlying epilepsy and alter treatment management.

FBTCS are typically the presenting seizure type in patients with focal epilepsy in the ED. These seizures are frequently preceded by unrecognized focal seizures, which should prompt the diagnosis of epilepsy and initiation of treatment. For busy ED physicians, identifying key historical features is essential for timely management. We aimed to determine whether patients with prior focal seizures can typically describe a focal onset at the time of their FBTCS.

Patients in the Human Epilepsy Project (HEP), a multi-center prospective observational study of newly diagnosed focal epilepsy, who presented to the ED with a first lifetime GTCS visits were identified. Structured interviews were performed to characterize the semiology of their initial seizures. We identified the proportion of patients who 1) experienced prior focal seizures and 2) reported similar symptoms at FBTCS onset.

Of the 248 patients who presented to the emergency room with a first lifetime FBTCS, 185 patients (74%) reported a history of prior spells; 142 patients (57%) reporting that their FBTCS began with a similar prodrome, 24 patients (13%) reporting a distinctly different or uncertain onset and 19 (10%) patients were unsure about their prodrome. 61 patients (25%) reported no prior spells or prodrome, and 2 patients (<1%) reported a prodrome before their FBTCS but without any prior spells. 

Fifty-seven percent of patients with focal epilepsy presenting to the ED with first lifetime FBTCS could be diagnosed with underlying epilepsy based on the seizure onset history. A single structured questionnaire at presentation may facilitate earlier treatment initiation and safer disposition decisions, potentially improving outcomes in this population.