Prevalence of neurologic autoantibodies in cohorts of patients with new and established epilepsy.

PURPOSE: Autoantibodies to specific neurologic proteins are associated with subacute onset encephalopathies, which often present with seizures that are poorly controlled by conventional antiepileptic drugs (AEDs). Previous cross-sectional studies have found specific neurologic antibodies in a small proportion of people with established epilepsy, but these investigations have seldom included patients with recent diagnosis. METHODS: We screened two large epilepsy cohorts to investigate the prevalence of multiple autoantibodies in adult patients with either established or newly diagnosed, untreated epilepsy. KEY FINDINGS: Eleven percent of patients had antibodies to one or more antigen: voltage-gated potassium channel (VGKC) complex proteins (5%), glycine receptors (3%), and glutamic acid decarboxylase (GAD) and N-methyl-D-aspartate (NMDA) receptors (1.7% each). There was no difference in the prevalence of antibodies, individually or collectively, between patients with established and newly diagnosed epilepsy or with generalized or focal epilepsy. There was, however, a significantly higher prevalence of positive antibody titers in patients with focal epilepsy of unknown cause than in those with structural/metabolic focal epilepsy (14.8% vs. 6.3%; p < 0.02). Newly diagnosed antibody-positive patients were less likely to achieve adequate seizure control with initial treatment than antibody-negative patients, but this difference failed to reach statistical significance. SIGNIFICANCE: The presence of autoantibodies is equally common in newly diagnosed and established epilepsy, it is therefore unlikely to be an epiphenomenon of long-standing refractory seizures.