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Carpal tunnel syndrome

What causes carpal tunnel syndrome?

Certain medical conditions such as wrist injury and excessive repetitive movements of the arms, wrists or hands can cause carpal tunnel syndrome. Pregnancy can also cause carpal tunnel syndrome.

The carpal tunnel is the passageway in the hand made up of the arching carpal bones (eight bones in the wrist) and the ligament connecting the pillars of the arch. The median nerve and the tendons that connect the fingers to the muscles of the forearm pass through the tightly spaced tunnel. Carpal tunnel syndrome occurs when the median nerve, which relays sensation from the palm of the hand and fingers, becomes pinched, usually by swelling of the tendons or fluid collection. This leads to numbness and sometimes pain of the fingers and hand, and sometimes the forearm.

Carpal Tunnel Syndrome

What are the symptoms of carpal tunnel syndrome?

Usually, people with carpal tunnel syndrome initially notice that their fingers "fall asleep" and become numb at night. They often wake up with numbness and tingling in their hands. A person may notice weakness of thumb movements and wasting away of thumb muscles. Burning pain is frequently associated with the feeling of numbness, and it generally runs up the centre of the person's forearm, sometimes as far as the shoulder. As carpal tunnel syndrome becomes more severe, symptoms are noticed during the day.

What happens in severe cases of carpal tunnel syndrome?

When chronic irritation occurs around the median nerve, it becomes compressed and is continually pushed against the ligament above it. When the median nerve in the hand is continually compressed, it can reach a point where it begins to deteriorate. This results in a slowed transmission of nerve impulses, which may cause a loss of feeling in the fingers and a loss of muscle function at the base of the thumb. If the condition is not treated, it could result in a deterioration of muscle tissue.

Do certain medical conditions make people more likely to develop carpal tunnel syndrome?

People with diabetes or metabolic conditions may be more likely to develop carpal tunnel syndrome. These conditions affect the nerves directly, making them more vulnerable to compression. Carpal tunnel syndrome is also common in pregnancy due to fluid build-up.

What tests can help diagnose carpal tunnel syndrome?

Often, an electromyogram, which includes nerve conduction studies, is done to document the extent of nerve damage in carpal tunnel syndrome. An electromyogram is a test that measures the electrical activity in your nerves and muscles. Nerve conduction studies measure the ability of specific nerves to transmit electrical impulses or messages.

The nerve conduction studies, however, may not become positive until there is significant nerve damage (degeneration). In addition, the severity of a person's symptoms is often not correlated with the findings of a nerve conduction study.

Two other useful tests for diagnosing carpal tunnel syndrome are the Tinel and Phalen manoeuvres. Tingling sensations in the fingers caused by tapping on the palm side of the wrist is a positive Tinel test, whereas reproduction of symptoms by flexing the wrist is a positive Phalen test.

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