[Compression of the ulnar nerve in Guyon's canal by a traumatic aneurysm. A case report].

A patient developed after an occupational trauma with fall on the ulnar edge of his right hand pain and swelling in the ulnar area with reduced sensation in the fourth and fifth finger. After examination performed by a neurologist, ulnar nerve-entrapment was diagnosed and operative treatment was indicated. The release of the ulnar tunnel showed a traumatic aneurysma of the ulnar artery compressing the superficial branch of the ulnar nerve. The tumor was removed and end-to-end anastomosis ensued. Four weeks after surgery, examination showed complete recovery. Various reasons of ulnar tunnel syndrome are discussed.