AUTOIMMUNE LIMBIC ENCEPHALITIS (CASE REPORTS)

Limbic encephalitis (LE) is an autoimmune or paraneoplastic disease that affects the medial temporal lobes. The patient will usually present with cognitive impairment, psychiatric changes, and seizures. Autoimmune limbic encephalitis (LE) is a challenging diagnosis as it is not always included in the typical paraneoplastic/autoimmune panels. Anti-GAD antibodies are associated with various disease including type I diabetes mellitus, various autoimmune processes, some neoplastic and infectious diseases. Thus, it is not as specific as some of the antibodies causing LE. We are presenting two cases of isolated anti-GAD antibody-associated limbic encephalitis. Both patients were adults who developed status epilepticus and refractory seizures, cognitive impairment and mood instability. Patients' cerebrospinal fluid (CSF) and serum anti- GAD antibodies were elevated and after treatment returned to normal reference range. The diagnosis for both patients was delayed (by over one month following hospitalization), both patients required prolonged hospitalization and rehabilitation after discharge. Patient's condition improved only after immunotherapy, but required several antiepileptic drugs for seizure control. The diagnosis was more difficult in the first patient, who had numerous other medical problems including ESRD and moderately severe microvascular changes on brain imaging. In this particular patient, it was hard to appreciate any signal changes on MRI in the mesial temporal lobes given the underlying white matter disease. We recommend inclusion of anti- GAD antibody in the paraneoplastic/encephalopathy panels in order to decrease missed cases of this important cause of LE as well as to hasten the diagnosis. This is a treatable disease, and timely diagnosis is imperative to improve outcomes.