[Synchronous appearance and improvement with anticancer chemotherapy of paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome complicated with small cell lung cancer].

A 62-year-old man who had suffered from instability of gait and double vision for two months was admitted to our hospital because of weakness of the extremities and ataxia of the extremities and trunk. Chest X-rays and CT scans showed enlargement of the left hilar lymph nodes and a nodular shadow in the left lung. Transbronchial biopsy revealed small cell lung cancer. We diagnosed the patient with two conditions: paraneoplastic cerebellar degeneration (PCD), based on cerebellar ataxia, the presence of Hu antineuronal antibodies, and the absence of cerebellar atrophy and malignancy; and Lambert-Eaton myasthenic syndrome (LEMS), based on weakness of the extremities, the presence of P/Q-type voltage-gated calcium channel antibodies, and waxing in the evoked electromyogram. Anticancer chemoradiation therapy that was started within three months of symptom onset resulted in reductions in size of the hilar lymph nodes and the nodule. Concurrently, cerebellar ataxia, weakness of the extremities, and double vision all disappeared. Anticancer chemotherapy is effective against LEMS while usually less effective against PCD. Early commencement of anticancer chemotherapy is recommended for the treatment of PCD with LEMS.