In many cases, carpal tunnel syndrome is caused by a combination of factors that increase pressure on the median nerve and tendons in the carpal tunnel. Certain factors can increase your risk of developing the condition, such as rheumatoid arthritis, injury to the wrist that causes swelling, hypothyroidism, and gout.
What Causes Carpal Tunnel Syndrome?
Carpal tunnel syndrome is caused by the median nerve becoming pressed or squeezed within the carpal tunnel. The carpal tunnel is a narrow space in your wrist. It is much like a tunnel you drive your car through, with a ceiling, floor, walls, an entrance, and exit. The "walls" and "floor" are made up of bones. The carpal ligament is the tough "ceiling" of the carpal tunnel.
Running from the forearm to the hand and through the carpal tunnel is the median nerve, which controls some of your hand muscles and allows you to feel sensations with your hand.
Several tendons also pass through the carpal tunnel. These attach specific muscles in the forearm to bones in the hand that allow you to flex your fingers and thumb. Each tendon has a special slippery covering, called the synovium, which allows the tendons to glide smoothly as you move your fingers.
In a normal wrist, there is adequate room in the carpal tunnel for both the tendons and the median nerve. However, certain conditions can cause the space to become narrow and cause problems for the median nerve. For example, the synovium may become inflamed (known medically as synovitis). This can cause the synovium to thicken, which may lead to increased pressure on the median nerve.
Carpal tunnel syndrome is often caused by a combination of factors that increase pressure on the median nerve and tendons in the carpal tunnel, rather than a problem with the nerve itself. Most likely, the disorder is due to a congenital predisposition; the carpal tunnel is simply smaller in some people than in others.
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Jupiter, J. Approach to Minor Orthopedic Problems of the Elbow, Wrist, and Hand. In: Primary Care Medicine: Office Evaluation and Management of the Adult Patient. 3rd Edition. J.B. Lippincott Company, Philadelphia, 1995.
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