The clinical profile of adult-onset idiopathic generalised epilepsy

Idiopathic generalised epilepsies (IGE) tend to begin in childhood or adolescence, whereas adult-onset presentations are less frequently observed. In this study, we describe the disease course of a cohort of patients with adult-onset IGE.

In this retrospective observational study, we evaluated clinical features, seizure outcomes, and antiseizure medication (ASM) prescribing trends in a cohort of IGE patients with seizure onset aged 18 years or older.

In a cohort of 425 IGE patients, we identified 55 with adult-onset IGE (12.9 %). Forty-nine patients (89.1 %) experienced seizure onset between ages 18 and 30 years, while the remaining six patients (10.9 %) had onset after the age of 30 years. Eleven patients were initially diagnosed with focal epilepsy (20 %). Most patients (98.2 %) initially presented with generalised tonic-clonic seizures (GTCS). Epilepsy with generalised tonic-clonic seizures alone (GTCA) was the most common syndrome (65.4 %). Thirty-five patients (63.6 %) were treated with ASM monotherapy, 17 (30.9 %) with polytherapy, and three (5.4 %) were not taking any ASM. Lamotrigine, levetiracetam (38.2 %), and valproate (27.3 %) were the most prescribed ASMs. At last clinical review, 40 patients (72.7 %) were seizure-free (no seizures for ≥12 months), including those with absence seizures and myoclonic seizures, and 46 were free of GTCS for a mean duration of 6.2 years (range 1-21 years). Eight patients (14.5 %) had drug-resistant epilepsy (DRE). Eight patients attempted ASM withdrawal, with seizure recurrence occurring in six (75 %), with the period off ASM ranging from one week to 26 years.

IGE should be considered as a possible diagnosis in people who first present with convulsive seizures in adulthood, particularly those aged between 18 and 30 years with normal neuroimaging. Adult-onset IGE has a good prognosis overall, with most people becoming seizure-free, although the risk of seizure recurrence appears to be high after ASM withdrawal. A minority develop DRE and require polytherapy with ≥2 ASMs.