P.050 Autoimmune encephalitis associated with GAD65 antibodies: brief review of the relevant literature

Abstract

Background: Recently, many cases of autoimmune encephalitis with positive GAD65 (Glutamic acid decarboxylase) antibodies have been described in the literature. However, it remains an understudied topic. Methods: We conducted a search on reported cases of anti-GAD65 encephalitis. Specific variables were identified as general characteristics, clinical manifestations, MRI and EEG findings, concomitant systemic autoimmune disorders and cancer, and outcome and autoantibodies findings. Results: We identified a total of 58 cases, from one to 70 years old. It most frequently presented with seizures (97%) and memory impairment (59%). It commonly occurred in association with systemic autoimmune disease, particularly diabetes (28%). Brain MRI was usually abnormal (78%); involvement of temporal lobes was more frequent than multifocal abnormalities (59% vs 16%). GAD65 antibodies were reported positive in CSF and/or serum (31% in serum only). Other antibodies such as GABA_BR, GABA_AR and VGKC were concurrently reported positive in some cases (19%). However, we found that the vast majority of cases were not tested for all those cell-surface antibodies. Overall, no distinctive pattern of clinical and paraclinical findings was found. Persistent impairments were common. Optimal treatment remained undefined. Conclusions: Prospective studies recruiting patients with autoimmune encephalitis are needed to better elucidate the contributions of GAD65 autoantibodies, and to evaluate treatment and outcomes in this population.