Risk of epilepsy after a single seizure in multiple sclerosis.

Abstract

The 2014 International League Against Epilepsy clinical definition of epilepsy allows diagnosis after a single unprovoked seizure if the 10-year recurrence risk exceeds 60%. Multiple sclerosis (MS) carries an increased risk of epilepsy, but the risk after a first seizure is unknown. We aimed to investigate the risk of epilepsy in patients with MS who had suffered a first seizure. We cross-referenced data from the Swedish MS register with the national patient register for 15810 patients with MS and 43635 controls and included 289 patients with MS and 222 controls with a first diagnosis of seizure or status epilepticus (SE) without prior epilepsy or presumed symptomatic aetiology. Kaplan-Meier curves were used to estimate the risk of epilepsy. The 10-year risk of epilepsy was 51.4% [95% confidence interval (CI), 44.0-58.9] for patients with MS and 41.3% (95% CI, 33.5-49.1) for controls. The risk was 46.1% (95% CI, 35.3-56.9) for patients with relapsing-remitting MS and 60.7% (95% CI, 46.6-74.8) for patients with secondary progressive MS. For patients with MS with SE, the 10-year risk of epilepsy was 85.9% (95% CI, 67.9-100). Our data indicate that patients with relapsing-remitting MS have a similar risk as controls of developing epilepsy after a single seizure. Patients with secondary progressive MS could run a greater risk of subsequent epilepsy, but our data do not indicate a risk that, with certainty, exceeds the threshold specified by the International League Against Epilepsy. Patients with SE have a high risk of epilepsy, possibly motivating diagnosis and treatment.