[A patient with paraneoplastic limbic encephalitis induced by breast cancer presenting with hypersomnia].

A 50-year-old woman developed gait disturbance and hypersomnia over a period of a month. General physical examination revealed axillary lymph node swelling. On neurological examinations she was fully orientated but hypersomnic; short term memory disturbance, horizontal gaze evoked nystagmus and ataxic gait were observed. Electroencephalography disclosed a tendency for easily decreasing vigilance with delta activities but normal dominant rhythm. Cerebrospinal fluid examinations showed increased protein amounts (109 mg/dl) without either pleocytosis or atypical cells. An echogram of the breasts revealed a tiny mass in the left side. Pathological studies on a biopsied lymph node and the mass in her left breast showed a mammillary duct carcinoma. Brain MRI was normal, and no anti-neuronal antibody was detected in sera by two dimensional immunoblotting using human brain crude antigens. She was diagnosed as having paraneoplastic limbic encephalitis (PLE) associated with breast cancer. Over 42 hours polysomnography showed long total sleep time (TST) with a high ratio of sleep stage 1/TST and no REM sleep abnormalities; this resembled a thalamic-hypothalamic damaged sleep pattern. At first she was treated with plasma exchanges, but no improvement was observed. Hormonal and chemotherapies produced partial resolution of her neurologic symptoms and there were signs of reduction of the breast mass. Most reported PLE cases with hypersomnia have been associated with testicular cancer and anti-Ma antibodies. The present case is an extremely rare example manifesting hypersomnia without either testicular cancer or anti-Ma antibody. Since anti-tumor therapy successfully ameliorated her neurologic symptoms, cell-mediated immunity against a common tumor and neuronal antigens rather than hormonal immunity may have played a role in the development of her PLE.