Carpal tunnel syndrome is a painful compression (pinching) of the median nerve as it passes through the carpal tunnel in the wrist.
- The cause of most cases of carpal tunnel syndrome is unknown.
- The fingers and palm near the thumb can be painful and tingle and become numb.
- Doctors base the diagnosis on an examination and, if needed, the results of nerve function tests.
- Symptoms can usually be relieved by pain relievers, a splint, or sometimes injection of a corticosteroid or surgery.
(See also Overview of Hand Disorders.)
The carpal tunnel is called a tunnel because it is the narrow passageway through which nerves and tendons pass through the wrist to the hand. The tunnel is made of the surrounding tendons, ligaments, and bones. The median nerve is located at the palm side of the wrist and passes through the carpal tunnel. This nerve provides sensation to the thumb, index finger, middle finger, and the thumb side of the ring finger.
Carpal tunnel syndrome is very common, especially among women aged 30 to 50 years. It may affect one or both hands.
Causes of Carpal Tunnel Syndrome
Carpal tunnel syndrome results from compression (pinching) of the median nerve. The compression can be caused by swelling of tissue around or in the tunnel or by bands of fibrous tissue that form on the palm side of the wrist.
Pregnant women and people who have diabetes, an underactive thyroid gland, certain forms of amyloidosis, or rheumatoid arthritis are at increased risk of developing carpal tunnel syndrome. Also at risk are people whose work requires repeated forceful movements with the wrist extended, such as using a screwdriver. Another potential (but controversial) factor is use of a computer keyboard that is not positioned properly. Prolonged exposure to vibrations (for example, by using certain power tools) has also been claimed to cause carpal tunnel syndrome. However, most cases develop for unknown reasons.
Symptoms of Carpal Tunnel Syndrome
The symptoms of carpal tunnel syndrome are odd sensations, numbness, tingling, and pain in the first three fingers and half of the fourth finger on the thumb side of the hand. Sometimes the entire hand may be affected. Occasionally, there is also pain and a burning or tingling sensation in the forearm. Burning or aching pain with numbness and tingling often wake people at night because of the way the hand is positioned. The person may shake the hand to try to restore normal feeling. With time, the muscles in the hand on the thumb side can weaken and shrink through lack of use (atrophy).
Diagnosis of Carpal Tunnel Syndrome
- A doctor's examination
- Sometimes nerve conduction testing
The diagnosis of carpal tunnel syndrome is made largely by examining the affected hand and wrist. A doctor may do nerve conduction studies to be certain that the problem is carpal tunnel syndrome, particularly if surgery is being considered.
Proper Keyboard Position
Using a computer keyboard that is positioned improperly may cause or contribute to carpal tunnel syndrome. To prevent injury, the user should keep the wrist in a neutral position. That is, the line from the hand to the forearm should be straight. The hand may be slightly lower than the forearm. But the hand should never be higher, and the wrist should not be cocked. The keyboard should be positioned relatively low, keeping the hand slightly lower than the elbow. A wrist pad can be used to support the wrist.
Treatment of Carpal Tunnel Syndrome
- A splint
- Treatment of underlying disorders
- Sometimes injections of a corticosteroid
- Sometimes surgery
Avoiding positions that overextend the wrist or put extra pressure on the median nerve and adjusting the angle of a computer keyboard sometimes provide some relief. Wearing wrist splints that hold the hand in a neutral position (especially at night) and taking mild pain relievers often help.
Wrist splints can help reduce the pain caused by carpal tunnel syndrome because they keep the hand in a neutral position.
Injections of a corticosteroid into the carpal tunnel occasionally bring long-lasting relief.
If pain is severe or if the muscle atrophies or weakens, surgery is the best way to relieve pressure on the median nerve. A surgeon can cut away the bands of fibrous tissue that place pressure on the nerve.