[Paraneoplastic Cerebellar Degeneration with Lambert-Eaton Myasthenic Syndrome: A Report of an Effectively Treated Case and Systematic Review of Japanese Cases].

A 63-year-old female who developed dizziness, diplopia and subsequent gait disturbance from September X-1 year was analyzed. The first neurological findings in May X year revealed cerebellar ataxia, weakness in the proximal limbs, decreased tendon reflexes, and autonomic symptoms (ADL:mRS 3). Furthermore, an incremental phenomenon was observed in the repetitive nerve stimulation test, and she was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) based on the serum P/Q-type calcium channel (VGCC) antibody positivity. In addition, small cell lung cancer was detected by chest CT and bronchoscopy, and her cerebellar ataxia was diagnosed as paraneoplastic cerebellar degeneration (PCD). Therefore, the patient underwent chemotherapy and radiotherapy from June in X year. Six months after initiation of treatment, her cerebellar ataxia had almost disappeared and she could walk without assistance (ADL:mRS 1). The P/Q-type VGCC antibodies were also negative at that time. Cases wherein cerebellar ataxia resolved almost completely in parallel with disappearance of the serum P/Q-type VGCC antibodies are of great interest. We conducted a systematic literature review of PCD-LEMS cases in Japan reported since P/Q-type calcium channel antibody measurement was reported in 1995. As a result, 13 cases (including our study) that concurrently displayed cerebellar ataxia and LEMS were selected. The average age of the 13 patients (10 males and 3 females) was 61.5 years. Small cell carcinoma was complicated in 11 patients (10 in the lung and 1 in the oropharynx); in the other 2 patients, cancer was not found at the time of reporting (the observation period was as short as 1-2 months). The time from onset to treatment ranged between 1 week and 10 months. While 1 of the 13 patients developed cerebellar ataxia during the subsequent course of the treatment, the remaining 12 had already developed cerebellar ataxia and LEMS symptoms, although their main neurologic finding was cerebellar ataxia and they were subsequently diagnosed with LEMS after electrophysiological testing and autoantibody detection. Small cell carcinoma was found in 11 patients. We define the pathology following such a certain clinical course as PCD-LEMS. The P/Q-type VGCC antibodies were positive in 11 of the 13 cases, although their antibody titers were not necessarily very high. Treatment for the associated small cell carcinoma might have improved the neurological findings in 9 of the 11 PCD-LEMS patients. The P/Q-type VGCC antibodies were measured before and after the treatment. The PCD-LEMS symptoms improved in all patients and their antibody titers decreased. These findings indicate that P/Q-type VGCC antibodies are involved in the pathology of PCD-LEMS. Appropriate and timely treatment, at least in PCD-LEMS patients in Japan, that actively treats any associated cancer can be expected to improve not only life prognosis but also cerebellar ataxia. (Received October 15, 2018; Accepted November 5, 2018; Published January 1, 2019).