GAD65 Antibody-Associated Epilepsy

Autoimmune processes are an increasingly recognized cause of seizures. Antibodies against neuronal surface antigens are implicated in the development of acute symptomatic seizures secondary to autoimmune encephalitis, whereas antibodies against intracellular antigens (anti-glutamic acid decarboxylase (GAD) and onconeural antibodies) are found in cases of autoimmune-associated epilepsy (AAE). AAE is described as isolated drug-resistant epilepsy without any specific magnetic resonance imaging (MRI) or cerebrospinal fluid changes and with a very limited response to immunotherapy. We present a clinical case and a literature review on autoimmune-associated epilepsy to increase awareness of this disease and illustrate its complexity. This is a clinical case of a female with a history of refractory focal epilepsy. The patient had been given several trials of multiple antiepileptic drugs and their combinations without any clear effect. Multiple evaluations including brain MRI, PET, and interictal and ictal electroencephalograms were performed. An APE2 score was calculated with a result of 4 and, in the presence of anti-GAD65 antibodies in the serum, the diagnosis of AAE was confirmed. There was no effect after five sessions of plasma exchange; however, after a course of intravenous immunoglobulin, a positive but temporary clinical effect was noticed: anti-GAD65 levels initially decreased but rebounded to previous levels 6 months later.