Guyon's Canal Syndrome
Guyon's Canal Syndrome is a common nerve compression affecting the ulnar nerve as it passes through a tunnel in the wrist called Guyon's Canal. Though less common than carpal tunnel syndrome, it is the same type of compression that results in the carpal tunnel, which affects the median nerve.
The ulnar nerve, which runs from the neck and down the arm to the hand and fingers, crosses the wrist with the median and radial nerves. The ulnar nerve and ulnar artery run through the Guyon's canal - a tunnel formed by two bones, the pisiform and hamate and the connecting ligaments. Once it passes through the canal, it branches out to supply feeling to the little finger and half of the ring finger. Other branches of this nerve supply the small muscles in the palm, as well as the muscle that pulls the thumb toward the palm.
Those at Risk
There are a number of causes for this condition including: strenuous tasks involving the wrist, such as heavy gripping or twisting; constant pressure placed on the palm such as in cycling and weightlifting; and uncommon or unnatural activities placing great pressure on the wrist such as using a jackhammer or crutches.
A traumatic injury to the wrist may cause swelling and place pressure on the ulnar nerve within the canal. And arthritis in the wrist bones and joint may also irritate and compress the nerve.
Those suffering from Guyon's Canal Syndrome experience numbness in the little finger and half of the ring finger. Gradual weakening of the muscles controlled by the ulnar nerve eventually makes it hard to spread the fingers out and pinch the thumb.
A physical examination and possible nerve conduction velocity (NCV) test are performed to determine the type of compression and its exact location. The NCV is a test that measures how fast nerve impulses travel along the nerve. Occasionally this test is combined with an electromyogram (EMG). The EMG can determine if the forearm muscles controlled by the ulnar nerve are functioning properly. And if the symptoms were the result of a traumatic wrist injury, an X-ray may be taken to check for a fracture or dislocation.
Often times the symptoms can be eliminated if the activity that caused it is changed or eliminated - such as repetitive hand motions or positions. Physical therapy may help to facilitate this process. A wrist brace may also be used to alleviate the symptoms by keeping the wrist in "resting position" and decreasing the pressure placed on the nerve.
If nonsurgical treatment is unsuccessful, a surgical procedure to release the ligament above the canal and reduce the pressure on the ulnar nerve is performed.