The risk of seizure recurrence after a first unprovoked seizure is influenced by certain risk factors. To understand their effect in people with early diagnosed new epilepsy, we assessed the risk of recurrence of focal to bilateral tonic-clonic or generalized tonic-clonic seizures and the associated factors in a clinically well-characterized cohort of adults with a first unprovoked tonic-clonic seizure. We prospectively studied 150 consecutive adults with a first unprovoked tonic-clonic seizure and full clinical, EEG, and brain imaging assessment within the first four weeks. New epilepsy was diagnosed and classified according to the International League Against Epilepsy criteria. Time to second focal to bilateral tonic-clonic or generalized tonic-clonic seizure was analysed using the Kaplan-Meier method. Early diagnosis of new epilepsy, including type or syndrome and aetiology, was possible in 109 patients (72.7%). The diagnostic yield of sleep-deprived EEG was high in both genetic and non-genetic localized focal epilepsies. A second focal to bilateral tonic-clonic or generalized tonic-clonic seizure occurred in 100 patients (66.7%) during a three-year mean observation period. The risk was higher in non-genetic focal epilepsies and lower in genetic epilepsies. Concurrent absences or myoclonic seizures and a first occurrence after awakening were predictors of a second generalized tonic-clonic seizure in patients with genetic generalized epilepsy, while diagnosis of temporal or frontal lobe epilepsy, focal EEG discharges, and focal changes on brain imaging were related to an increased risk of focal to bilateral tonic-clonic seizure recurrence, showing additive effects. Identifiable modulators or triggers for the first tonic-clonic seizure, early treatment, and older age showed inverse association. The risk of a second generalized or focal to bilateral tonic-clonic seizure and the factors involved vary across epilepsy aetiologies and syndromes. Early diagnosis and classification of new epilepsy is possible in most patients and may enable important adjustments to their management and treatment.
Keywords: epilepsy classification; incident epilepsy; risk factors; sleep EEG; sleep deprivation.