carpal tunnel syndrome

What is carpal tunnel syndrome?

Carpus is a word derived from the Greek word karpos, which means "wrist." The wrist is surrounded by a band of fibrous tissue that normally functions as a support for the joint. The tight space between this fibrous band and the wrist bone is called the carpal tunnel. The median nerve passes through the carpal tunnel to receive sensations from the thumb, index, and middle fingers of the hand. Any condition that causes swelling or a change in position of the tissue within the carpal tunnel can squeeze and irritate the median nerve. Irritation of the median nerve in this manner causes tingling and numbness of the thumb, index, and the middle fingers -- a condition known as "carpal tunnel syndrome."

Causes

Carpal tunnel syndrome occurs as a result of compression of the median nerve. The median nerve runs from your forearm through a passageway in your wrist (carpal tunnel) to your hand. It provides sensation to the palm side of your thumb and fingers, with the exception of your little finger. It also provides nerve signals to move the muscles around the base of your thumb (motor function).

In general, anything that crowds, irritates or compresses the median nerve in the carpal tunnel space can lead to carpal tunnel syndrome. For example, a wrist fracture can narrow the carpal tunnel and irritate the nerve, as can the swelling and inflammation resulting from rheumatoid arthritis.

In many cases, no single cause can be identified. It may be that a combination of risk factors contributes to the development of the condition.

Tests and diagnosis

Your doctor may conduct one or more of the following tests to determine whether you have carpal tunnel syndrome:

• History of symptoms. The pattern of your signs and symptoms may offer clues to their cause. For example, since the median nerve doesn't provide sensation to your little finger, symptoms in that finger may indicate a problem other than carpal tunnel syndrome. Another clue is the timing of the symptoms. Typical times when you might experience symptoms due to carpal tunnel syndrome include while holding a phone or a newspaper, gripping a steering wheel, or waking up during the night.
• Physical exam. Your doctor will want to test the feeling in your fingers and the strength of the muscles in your hand, because these can be affected by carpal tunnel syndrome. Pressure on the median nerve at the wrist, produced by bending the wrist, tapping on the nerve or simply pressing on the nerve, can bring on the symptoms in many people.
• X-ray. Some doctors may recommend an X-ray of the affected wrist to exclude other causes of wrist pain, such as arthritis or a fracture.
• Electromyogram. Electromyography measures the tiny electrical discharges produced in muscles. A thin-needle electrode is inserted into the muscles your doctor wants to study. An instrument records the electrical activity in your muscle at rest and as you contract the muscle. This test can help determine if muscle damage has occurred.
• Nerve conduction study. In a variation of electromyography, two electrodes are taped to your skin. A small shock is passed through the median nerve to see if electrical impulses are slowed in the carpal tunnel.

The electromyogram and nerve conduction study tests are also useful in checking for other conditions that might mimic carpal tunnel syndrome, such as a pinched nerve in your neck.

Your doctor may recommend that you see a rheumatologist, neurologist, hand surgeon or neurosurgeon if your signs or symptoms indicate other medical disorders or a need for specialized treatment.

Treatments and drugs

Some people with mild symptoms of carpal tunnel syndrome can ease their discomfort by taking more-frequent breaks to rest their hands and applying cold packs to reduce occasional swelling. If these techniques don't offer relief within a few weeks, additional treatment options include wrist splinting, medications and surgery. Splinting and other conservative treatments are more likely to help you if you've had only mild to moderate symptoms for less than 10 months.

Nonsurgical therapy
If the condition is diagnosed early, nonsurgical methods may help improve carpal tunnel syndrome. Methods may include:

• Wrist splinting. A splint that holds your wrist still while you sleep can help relieve nighttime symptoms of tingling and numbness. Nocturnal splinting may be a good option if you are pregnant and have carpal tunnel syndrome.
• Nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs may help relieve pain from carpal tunnel syndrome in the short term. There's no evidence, though, that these drugs can actually improve the carpal tunnel syndrome itself.
• Corticosteroids. Your doctor may inject your carpal tunnel with a corticosteroid, such as cortisone, to relieve your pain. Corticosteroids decrease inflammation and swelling, which relieves pressure on the median nerve. Oral corticosteroids aren't considered as effective as corticosteroid injections for treating carpal tunnel syndrome.

If carpal tunnel syndrome results from an inflammatory arthritis, such as rheumatoid arthritis, then treating the underlying condition may reduce symptoms of carpal tunnel syndrome, but this hasn't been proved.

Surgery
If your symptoms are severe or persist after trying nonsurgical therapy, surgery may be the best option.

The goal of carpal tunnel surgery is to relieve pressure on your median nerve by cutting the ligament pressing on the nerve. During the healing process after the surgery, the ligament tissues gradually grow back together while allowing more room for the nerve than existed before. The surgery may be done a couple of different ways. Either technique has risks and benefits that are important to discuss with your surgeon before surgery.

• Endoscopic surgery. Carpal tunnel surgery can be done using an endoscope, a telescope-like device with a tiny camera attached to it that allows your doctor to see inside your carpal tunnel and perform the surgery through small incisions in your hand or wrist.
• Open surgery. In other cases, surgery involves making a larger incision in the palm of your hand over the carpal tunnel and cutting through the ligament to free the nerve.

In general, your doctor will encourage you to use your hand after surgery, gradually working back to normal use of your hand while avoiding forceful hand motions or extreme positions of your wrist. Soreness or weakness may take from several weeks to as long as a few months to resolve after surgery. If your symptoms were very severe before surgery, symptoms may not go away completely after surgery.

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