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pianomap: Carpal Tunnel Syndrome

The carpal tunnel is a narrow space formed by the small bones of the wrist and the ligament called the flexor retinaculum. You can locate it this way: Place your left index finger in the center of your right palm, then move the finger about two inches down your palm toward your arm, stopping when your finger approaches the edge of the fleshy part of your hand. Your finger now lies directly over the carpal tunnel. The carpal tunnel is formed by the small bones of the wrist which combine to make a U-shaped depression with bones on the bottom and sides. The flexor retinaculum ligament stretches over the top of the U to create a tunnel. The space in the tunnel is small--about as big as the end of your thumb.

Nine flexor tendons, two to each finger and one to the thumb, pass through the carpal tunnel. The space is so narrow that some of the tendons have to stack on top of each other instead of running side by side the way they do outside the tunnel. The tendons in the tunnel are enclosed in sheaths.

The median nerve also passes through the carpal tunnel. The median nerve supplies most of the palm, the thumb, fingers 2 and 3 and part of finger 4.

The carpal tunnel is a nifty structure, well-designed to do its job of providing a space for the tendons. It is vulnerable because it is small. Like a tightly-packed suitcase, it has no space for any additional items. If the tendons or their sheaths are subject to stressful movement they may become inflamed and swollen. This is a problem because any swelling within the tunnel by the tendons or their sheaths puts pressure on the other tendons, and also on the median nerve. The nerve may become compressed. The result is carpal tunnel syndrome: pain in the wrist, and pain or tingling or numbness in the hand, particularly on the thumb side of the hand. Sometimes the hand feels weak or clumsy. The symptoms may be worst at night.

Carpal tunnel syndrome is usually caused by movements that put repetitive stress on the tendons in the carpal tunnel. Examples of dangerous movements include repetitive forceful flexing of the wrist, as in "wrist octaves." "Dropping the wrist" is also dangerous (think of the wrist supports that are increasingly common among computer users).

Surgical treatment for carpal tunnel syndrome involves cutting the flexor retinaculum tendon to create more space for the tendons and the median nerve. Often this surgery produces immediate relief. Unfortunately, the relief is often temporary. If the person continues to move in a stressful manner, symptoms are likely to return. The best permanent cure is movement retraining, which makes surgery unnecessary.

Sometimes symptoms of carpal tunnel syndrome do not come from mis-use of the hand and forearm but from mis-use of the upper arm. If a person habitually holds the upper arm a way that causes the collar bone to put pressure on the median nerve where it passes under the collar bone, the symptoms may be the same as if pressure were placed on the median nerve in the carpal tunnel. It is, after all, the same nerve. When the problem originates in the upper arm it is called "thoracic outlet syndrome."

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