Ulnar Tunnel Syndrome

Ulnar Nerve Entrapment at the Wrist

Ulnar tunnel syndrome occurs when the ulnar nerve gets compressed at the wrist. The small and ring fingers go numb. The symptoms are very similar to those of Cubital Tunnel Syndrome, as the same nerve is involved, but ulnar tunnel syndrome is much less common. These two nerve compression syndromes are therefore often confused. Ulnar tunnel syndrome may be caused by a mass, such as a ganglion cyst, or by a fracture of a nearby wrist bone (the hook of the hamate). Ulnar tunnel syndrome is often diagnosed on nerve conduction studies.

The ulnar tunnel, also known as Guyon’s canal, lies above the carpal tunnel. (Figures 1& 2) The floor of Guyon’s canal is the transverse carpal ligament, which is also the roof of the carpal tunnel. So if both carpal tunnel syndrome and Ulnar Tunnel Syndrome are present, and there is no mass present in the ulnar tunnel, then an Endoscopic Carpal Tunnel Release can cure both nerve compressions.

If there’s a mass in Guyon’s canal, then an open approach to Guyon’s canal is needed to remove the mass. That’s why, in cases of ulnar tunnel syndrome, an MRI is often ordered before surgery. The MRI can determine if a simple endoscopic carpal tunnel release will be enough, or if more needs to be done to cure the ulnar tunnel syndrome. If ulnar tunnel syndrome exists alone, without carpal tunnel syndrome, an open Ulnar Tunnel Release may also be more effective.

Ulnar Tunnel Release is an outpatient procedure, and the results of treatment are very good. The wound should be kept clean and dry for 24 hours, at which point showering is allowed. Don’t get the wound dirty or submerge the wound under water for 10 days. There is a piece of tape over the wound. The longer it stays on, the nicer the wound will do.

The Transverse Carpal Ligament (transverse white structure) is the roof of the carpal tunnel and the floor of the ulnar tunnel (arrow).
The Ulnar Nerve in the Ulnar Tunnel