[Paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome associated with anti P/Q-type voltage-gated calcium channel antibody in a patient with primary double lung cancer].

We report the case of a 50-year-old man with paraneoplastic cerebellar degeneration (PCD) and Lambert-Eaton myasthenic syndrome (LEMS) associated with primary double lung cancer. He developed acute progressive double vision, slurred speech, and gait disturbance. Neurological examination revealed diplopia, mild ptosis, bilateral horizontal gaze-evoked nystagmus, and cerebellar limb and truncal ataxia. The diffusion image of brain magnetic resonance imaging (MRI) revealed no abnormal findings in the cerebellum. On the basis of the diagnosis of acute cerebelitis, he was given methylprednisolone pulse therapy followed by oral prednisolone, which gradually improved his neurological signs and symptoms. The analysis of the possible etiology suggested that the PCD was induced by lung cancer, which led to ataxia. A chest computed tomography scan revealed mass lesions of irregular shape and unclear margins in the upper lobe of the right lung and a small nodule tumor in the upper lobe of the left lung. We performed transbronchial needle aspiration and detected the bronchioloalveolar carcinoma of the right lung. An electromyogram showed waxing phenomenon in the ulnar nerve at high-frequency (50Hz) stimulation. The serum levels of anti-P/Q-type voltage-gated calcium channel (VGCC) antibody were elavated in the patient. These findings confirmed that the pathogenesis of the condition of this patient to be associated with LEMS. His cerebellar symptoms were considered to be caused by the PCD, and the diplopia, ptosis, and hyporeflexia were attributed to LEMS. We performed upper left lobectomy with mediastinal lymphnode dissection via video-assisted thoracoscopic surgery. A histological study detected small cell carcinoma. A diagnosis of double primary lung cancer was made. Physicians need to be aware that patients may develop PCD and LEMS associated with anti-VGCC antibody caused by small cell lung cancer, and a mass survey should be conducted and careful examinations performed.