Carpal Tunnel Syndrome

Carpal tunnel syndrome refers to a combination of symptoms in the hand due to compression on the median nerve as it passes through the base of the palm.

The carpal tunnel is formed by a U-shaped row of bones in the wrist, and the transverse carpal ligament, a fairly rigid structure with little "give." The nine major flexor tendons of the thumb and fingers pass through the carpal tunnel, along with the median nerve. The median nerve sends branches to the thumb, index, and middle fingers, and usually half of the ring finger. Some of the smaller muscles within the hand also receive their nerve supply from the median nerve, including the majority of the muscles that make up the prominent base of the thumb referred to as the thenar eminence. Pressure can increase in the carpal tunnel for a variety of reasons, including trauma, infection, body fluid retention, and repetitive stress to the area. When this occurs, pressure is applied to the nerve, bringing on symptoms.

Classic symptoms generally begin with intermittent numbness and tingling in the thumb, index, and middle fingers and the half of the ring finger. With time these can become more frequent, constant, and even permanent. As the symptoms become more severe, weakness and a visible loss of musculature ("thenar wasting") can occur. Some patients will have a shock-like sensation in the wrist and palm, and the discomfort can sometimes radiate into the forearm. Symptoms frequently occur at night, or during daytime activity such as repetitive hand use and activities such as reading and driving in which the wrist is in a fixed flexed position.

The diagnosis of carpal tunnel syndrome is usually made by history and tests done on physical examination. Nerve studies (nerve conduction tests, and electromyelograms) can help confirm the diagnosis, and are especially helpful to rule out compression of other nerves or a second level of compression of the median nerve.

Treatment for carpal tunnel syndrome is aimed at reducing the inflammation around the nerve within the carpal tunnel. Avoidance of an inciting activity and use of anti-inflammatory medication and wrist splints are most effective. Stretching exercises that fully extend the wrist and fingers can also help, as can hand therapy treatments. Vitamin B6 has been shown to help pregnant women with carpal tunnel syndrome and has become a popular over-the-counter remedy, but has been shown only anecdotally to help in other patients. The benefit of steroid injections is debated; they are most often used to give temporary improvement and confirm the diagnosis in unclear cases.

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