Prevalence and immunological spectrum of temporal lobe epilepsy with glutamic acid decarboxylase antibodies

Abstract

Background and purpose: High levels of glutamic acid decarboxylase (GAD)-ab were initially described in patients with stiff person syndrome, and have since also been observed in patients with other neurological diseases. Temporal lobe epilepsy (TLE) seems to be specially associated. Our purpose is to describe the prevalence of GAD-ab in patients with TLE, and to characterize the clinical-immunological profile of TLE patients with high levels of GAD-ab.

Methods: An immunological profile including GAD-ab and antinuclear, anti-DNA, anti-cardiolipin, anti-transglutaminase and antithyroid antibodies was determined in a consecutive series of patients with TLE. As adulthood onset is the least common onset in TLE + hipocampal sclerosis and febrile seizures, we selected patients whose onset was after 30 years of age, to expand the spectrum of aetiologies. Patients were divided into two groups: known aetiology, 19 patients (45%) and unknown aetiology, 23 (55%). The clinical-immunological study included TLE patients with high GAD-ab levels (>1000 IU).

Results: Amongst 42 patients, serum GAD-ab levels were positive in 5 (152-11, 963 IU/ml), all from the unknown aetiology group. Thus, GAD-ab levels were positive in 21.7% and high in 8.7% of the unknown aetiology group. The immunological profile study included nine patients (seven pharmacoresistant), of whom six were women (66%) with mean age 41 years. Three patients reported acute debut, four (44%) insulin-dependent diabetes mellitus, five (55%) other concomitant autoimmune diseases, four (44%) memory impairment and four moderate-to-severe mood disturbance. Intrathecal synthesis of GAD-ab was observed in seven patients (77%).

Conclusions: Temporal lobe epilepsy with GAD-ab is not a rare condition. In the subgroup of patients with high titres, this epilepsy is often pharmacoresistant and associated with memory impairment, depression and other autoimmune diseases.