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Carpal tunnel
syndrome is a painful compression of the median nerve as it passes
through the wrist.
Carpal tunnel syndrome results from compression of the median nerve, which is located at the palm side of the wrist (an area called the carpal tunnel). The median nerve serves the thumb side of the hand. The compression results when swelling or bands of fibrous tissue form for a variety of reasons on the palm side of the wrist.
Carpal tunnel syndrome is common—especially in women—and may affect one or both hands. Particularly at risk are people whose work requires repeated forceful movements with the wrist extended, such as using a screwdriver. Another cause is use of a computer keyboard that is not positioned properly. Prolonged exposure to vibrations (for example, by using certain tools) has also been claimed to cause carpal tunnel syndrome. Pregnant women and people who have diabetes, an underactive thyroid gland, gout, or rheumatoid arthritis are at increased risk of developing carpal tunnel syndrome.
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Proper Keyboard Position
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Using a computer keyboard that is positioned improperly can result in 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.
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The symptoms, due to the nerve compression, are odd sensations, numbness, tingling, and pain in the first three fingers on the thumb side of the hand. Occasionally, there is also pain and a burning or tingling sensation in the arm and shoulder. The pain may be more severe while the person is sleeping because of the way the hand is positioned. With time, the muscles in the hand on the thumb side can weaken and shrink through lack of use (atrophy).
Diagnosis is made largely by examining the affected hand and wrist. Before surgery, a doctor may first perform nerve conduction studies (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electromyography and Nerve Conduction Studies) to be certain that the problem is carpal tunnel syndrome.
The disorder is best treated by avoiding positions that overextend the wrist or put extra pressure on the median nerve. Wrist splints that hold the hand in a neutral position (especially at night) and such measures as adjusting the angle of a computer keyboard may help. Treating underlying disorders (such as rheumatoid arthritis or an underactive thyroid gland) can help to relieve symptoms.
Injections of a corticosteroid suspension 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.
Last full review/revision February 2003
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