Hypersomnia as presenting symptom of anti-Ma2-associated encephalitis: case study.

We describe a patient who presented with excessive daytime sleepiness (EDS) and was eventually diagnosed with anti-Ma2 encephalitis. Neurological examination disclosed somnolence, left palpebral ptosis, and vertical gaze paresis. A brain MRI showed high signal intensity in the hypothalamus and each hippocampus. Ma2 antibodies were found in the patient's serum, and fiberbronchoscopy disclosed a lung carcinoma. After three months of steroid treatment, the results of the patient's neurological exam became normal. We conclude that anti-Ma2 encephalitis may present with mostly isolated EDS and that it may respond to steroids despite old age and the presence of an untreated lung cancer.