Paraneoplastic cerebellar degeneration after improvement of Lambert-Eaton myasthenic syndrome

A 57-year-old man presented with progressive muscle weakness in the lower limbs, with elevated anti-P/Q-type voltage-gated calcium channel antibody levels. A repetitive stimulation test showed waxing with high-frequency stimulation. He was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) and small-cell lung cancer. After four courses of cisplatin and etoposide, computed tomography showed a decrease in tumor size and muscle weakness improved. After 3 months, the patient presented with progressive ataxic gait and dysarthria and was admitted to our hospital. Magnetic resonance imaging revealed slight cerebellar atrophy. We diagnosed the patient with paraneoplastic cerebellar degeneration (PCD)-LEMS. The patient received intravenous immunoglobulin therapy, steroid pulse therapy, and plasmapheresis. The patient's cerebellar ataxia then improved. This represents a rare case of PCD-LEMS after improvement of LEMS.