A Patient With Focal Dystonia That Occurred Secondary to a Peripheral Neurogenic Tumor: A Case Report.

Dystonia is a movement disorder characterized by involuntary muscle contractions. Patients with dystonia may experience uncontrollable twisting, repetitive movements, or abnormal posture. A 55-year-old man presented with an involuntary left forearm supination, which he had experienced for five years. There was no history of antecedent trauma to the wrist or elbow. Although conventional therapeutic modalities had been performed, the symptoms persisted. When he visited our hospital, electromyography was performed. Reduced conduction velocity was evident at the elbow-axilla segment of the left median nerve. We suspected that there was a problem on the median nerve between the elbow and the axilla. For this reason, we performed an ultrasonography and magnetic resonance imaging study. A spindle-shaped soft tissue mass was observed at the left median nerve that suggested the possibility of neurofibroma. Dystonia caused by traumatic or compressive peripheral nerve injury has often been reported, but focal dystonia due to a neurogenic tumor is extremely rare. Here, we report our case with a review of the literature.