Objectives: To report the characteristics of a population of patients with idiopathic generalised epilepsy (IGE) with age of onset over 20 years, and compare them with patients with "classical" IGE.
Methods: Data were collected from a computerised database of all patients with IGE attending a regional adult epilepsy clinic. Demographic data, epilepsy characteristics, and treatment outcomes were recorded.
Results: 72 patients with IGE of a total population of 844 had an age of onset over 20 years (8.5%). There was similar incidence of family history of epilepsy, EEG findings, and remission rates between those with a younger and older age of onset of IGE. There was a lower incidence of previous febrile convulsions in patients with adult onset. There were fewer patients with absence seizures in the adult onset group (15.3% v 46.4% in the "classical" group).
Conclusions: IGE with onset later than the third decade was rare in the population studied. Prolonged EEG in selected patients may be helpful in diagnosing adult onset IGE, but the diagnosis of epilepsy remains clinical. Adult onset IGE shares many features with "classical" IGE, including EEG findings and prognosis, and is likely to represent a genetic epilepsy.