Carpal tunnel syndrome can be caused by pressure on the median nerve at the wrist, which can lead to pain and weakness in the hand. The median nerve supplies feelings to the thumb, first two fingers, part of the third finger, and also to some of the muscles of the hand.

The carpal tunnel is composed of two "walls" -- the deep wall is the bones of the wrist and the superficial wall is a thick ligament located just under the skin on the palm side of the wrist. The median nerve, and the tendons that flex the fingers to form a fist, pass through this tunnel.

Certain conditions such as wrist fractures, inflammatory conditions (rheumatoid arthritis, for example) and overuse syndromes can cause swelling in the carpal tunnel. Sometimes there is no identifiable cause. Because the walls of the tunnel are rigid, the swelling increases pressure on the nerve.

Nerves are very sensitive to pressure, and when the median nerve is pressed, the muscles it supplies become weak and the skin over the thumb, index, and middle fingers becomes painful, tingly, or even numb.

Carpal tunnel surgery involves 1 or 2 small incisions over the palm of the hand. The surgery can be performed endoscopically (using a small camera attached to a monitor). The carpal ligament is directly below the incision(s), in the area of the palm just past the wrist in the direction of the fingers. This ligament is cut in line with the arm. This releases the pressure on the nerve passing through.

Some surgeons will remove tissue surrounding the nerve, especially if the tissue is swollen or irritated (as is often found in arthritis patients). The surgeon will then usually close the skin and underlying tissues over only the carpal ligament, leaving the carpal tunnel uncovered. Other surgeons reattach the carpal ligament after lengthening it.

After the surgery, the wrist is usually immobilized in a splint or heavy bandage for about a week. Then motion exercises or a physical therapy program will begin.

The results of carpal tunnel release for carpal tunnel syndrome are generally very good.

Patients who have symptoms consistent with carpal tunnel syndrome usually undergo non-surgical treatment first. This includes anti-inflammatory medications, wrist splints, occupational therapy, and workplace modification. If this fails to improve symptoms, an injection of steroids into the carpal tunnel may be helpful.

If all treatments do not help, most surgeons will use an EMG to test the electrical activity of the median nerve. If the results of the test are consistent with carpal tunnel syndrome, carpal tunnel release surgery is an option.

Risks for any anesthesia include the following:

• Allergic reactions to medications
• Problems breathing

• Bleeding
• Infection

Risks specific to carpal tunnel release include the following:

• Injury to the median nerve or its branches
• Failure of the surgery to improve symptoms
• Rarely, injury to another nerve or blood vessel (artery or vein)
• Scar sensitivity