Carpal Tunnel Syndrome Caused by Parosteal Lipoma of Carpal Bones: A Case Report

The aetiology of carpal tunnel syndrome is often idiopathic, and it is seldom caused by a space-occupying lesion. Herein, we report our experience with a case of parosteal lipoma causing carpal tunnel syndrome. A 66-year-old woman with a history of hyperthyroidism and hypertension presented with numbness and pain on the ulnar side of the left index finger without any triggers. A positive Tinel sign in the left carpal tunnel and presence of a space-occupying lesion with fat concentration extending from the carpal tunnel to the central subcutaneous palmar region on computed tomography led to the diagnosis of carpal tunnel syndrome due to lipoma. Subsequently, carpal tunnel release, tumour resection and median nerve dissection were performed. At 1 year and 3 months postoperatively, the disease course was good, without recurrence or sensory disturbance. Although rare, carpal tunnel syndrome may be caused by a space-occupying parosteal lipoma. <b>Level of Evidence:</b> Level V (Therapeutic).