The limbic and extra-limbic encephalitis associated with glutamic acid decarboxylase (GAD)-65 antibodies: an observational study

We aimed to define the clinical features and outcomes of encephalitis associated with anti-GAD65 Abs. In addition, we reviewed cases published in the literature with GAD65 encephalitis. We retrospectively studied 482 consecutive patients attending a tertiary care center for evaluation of an autoimmune neurological disorder. Nineteen patients were enrolled (3.94% of the cohort). Twelve (63.16%) patients were females, and the mean age at onset of the cohort was 31.68 ± 13.88 years. The following clinical-neuroimaging syndromes were identified: limbic encephalitis (n = 10), limbic plus extra-limbic encephalitis (n = 6), meningoencephalitis (n = 1), extralimbic encephalitis (n = 1), and unclassified (n = 1). The mesial temporal lobes were the most frequently affected (n = 13, 68.42%) in the brain magnetic resonance imaging (MRI), followed by frontal lobes (21%), and insular lobes (21%). Epileptiform discharges (94.4%), mostly from temporal lobes, were the most common electroencephalogram (EEG) finding. Most patients received immunotherapy and were followed for a mean duration of 21 months. A total of 73 patients, including 54 from the literature and 19 presented from the current series, were analyzed. Limbic encephalitis was the predominant presentation, and most patients received immunotherapy. Outcomes varied considerably. Considering patients from the literature and this series (n = 70), mortality was 5.7%. Also, 82.8% of patients had persistent neurologic manifestations, including seizures and cognitive impairment following immunotherapy. Limbic encephalitis is the most common form of GAD65 encephalitis, while a smaller proportion of patients may have signs of extra-limbic involvement. Most patients have persistent manifestations following combined immunotherapy with a relatively low mortality rate.