Abstract
A 46-year-old woman was admitted with tonic-clonic seizures. She was noticed to be withdrawn and low in mood for few months. She had reduced level of consciousness with hyper-reflexia and myoclonus. Metabolic, vasculitic, autoimmune, paraneoplastic and septic screen were normal. Lumbar puncture showed raised protein in the cerebrospinal fluid but the cytology, bacterial and viral screens were negative. A CT of the head revealed global brain swelling consistent with encephalitis which was empirically treated with antibiotics and antiviral therapy. Despite this she continued to have altered sensorium. She had moderately raised titres of antithyroid peroxidise antibodies suggestive of an underlying diagnosis of Hashimoto's encephalitis. She displayed a significant improvement in her cognitive functions with high-dose steroids which was further in keeping with this rare diagnosis.