Carpal tunnel syndrome is characterized by weakness, pain, tingling, numbness, or burning in the palm, the thumb, the index finger, the middle finger, and the ring finger caused by entrapment of the median nerve in the wrist. (This condition, like any syndrome, is not a disease in itself but rather a collection of symptoms.) The condition most often affects women in their 30s, 40s, and 50s. It may develop or become worse because of work that requires repeated grasping, twisting, or turning of the hand and wrist, especially against resistance or while using vibrating tools.

The carpal tunnel is formed by the bones of the wrist (carpal means wrist) and the tough band of connective tissue known as the transverse carpal ligament. Among the structures inside the tunnel are the median nerve and the tendons that flex the fingers and thumb. Any swelling or thickening of tissue within the tunnel can cause the median nerve to be compressed be-tween the transverse carpal ligament and the tendons and other contents of the tunnel. The squeezed nerve, which controls the thumb, index finger, and third finger, cannot work as it should, and the symptoms of carpal tunnel syndrome result.

Causes

The most common causes of carpal tunnel syndrome are repeated and forceful grasping with the hands or repeated bending of the wrists (such as while typing or playing the piano). Pregnancy and other conditions that produce generalized swelling of body tissues may also be a cause of carpal tunnel syndrome, as can localized swelling caused by a dislocation, sprain, or fracture of the wrist.

Rheumatoid arthritis can cause inflammation of the sheaths (coverings) of the tendons, causing compression. Other possible causes include an inflamed wrist joint, a benign (noncancerous) tumor, myxedema (tissue swelling due to lack of thyroid hormone), tuberculosis, amyloidosis (a disease characterized by abnormal deposits of the protein amyloid), sacromegaly (overgrowth of connective tissue), and diabetes mellitus.

Symptoms

Aching pain may travel up the forearm and even into the shoulder joint, neck, and chest. (This type of pain can usually be relieved by shaking the hand vigorously or dangling the arm loosely from its socket; occasionally, however, such pains are caused by compression of the median nerve in the forearm or upper arm.) Other signs of carpal tunnel syndrome include an inability to make a fist, deterioration of the fingernails, and dryness and shininess of the skin over the involved surfaces.

The pains may occur in both hands at the same time. They may be constant or intermittent, and they are increased by manual work or movement that flexes the wrist or palm. Weakness of the fingers occurs later than other symptoms of the condition and accompanies atrophy (wasting away) of the muscles. The symptoms of carpal tunnel syndrome are usually worse at night and in the morning.

Diagnosis

Preliminary diagnostic tests include tapping the wrist, which causes tingling in the area of pain if carpal tunnel syndrome is present, and forced flexion of the wrist, which may also reproduce the pain. Though rarely necessary, an X-ray examination may reveal abnormalities of the wrist bones. Testing of the conduction of nerve impulses is the most specific means of diagnosing the condition.

Treatment

Treatment is aimed first at relieving pressure on the median nerve. If soft-tissue swelling is a cause, elevating the hand may eliminate the symptoms. It may help to place the forearm in a splint at night, which keeps the hand turned upward, extending the wrist. If an inflammation inside the wrist is at fault, cortisone may be injected into the carpal tunnel. Anti-inflammatory medication can relieve some of the pressure. Other causes or aggravating factors associated with the disorder are treated appropriately.

If conservative forms of treatment prove ineffective, surgery to release the transverse carpal ligament may be necessary to relieve the pressure on the nerve and prevent permanent damage. Usually, muscle strength gradually returns after such surgery, but if surgery has been delayed too long and muscles have severely deteriorated, full strength does not always return.



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