What is carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) is common, affecting 3% to 7% of the population. Middle aged to older individuals are more likely than younger persons to develop carpal tunnel syndrome. Women are three times more prone to the condition than men.

Carpal tunnel syndrome may interfere with hand strength and sensation, and often leads to a decrease in hand function.

The carpal tunnel is located at the wrist on the palm side of the hand just beneath the skin surface. Eight small wrist bones form the three sides of the tunnel. The remaining side of the tunnel, the palmar surface, is composed of soft tissues, consisting mainly of a ligament called the transverse carpal ligament. This ligament stretches over the top of the tunnel.

The median nerve and nine flexor tendons to the fingers pass through the carpal tunnel. Flexor tendons are the tendons that help bend the fingers. When the median nerve in the wrist is compressed, nerve impulses are slowed as they travel through the nerve. Because the median nerve provides the ability for the muscles to function and also provides the ability to feel in the hand, pressure on the nerve results in symptoms ranging from mild numbness to hand weakness, loss of feeling and loss of hand function.

While carpal tunnel syndrome usually affects one hand, it can affect both. It causes symptoms mostly in the thumb, index, middle and the inner half of the ring finger but rarely the little finger. In addition to numbness, a patient may experience tingling, pins and needles, or burning of the hand radiating up the forearm.

Frequently, symptoms occur in the morning when a patient awakens. Symptoms also may cause the patient to wake during the night. Symptoms can occur with certain activities such as driving, holding a book or repetitive activities with the hands, especially those activities requiring prolonged grasping or flexing (bending) of the wrist. Hand activities, such as buttoning, may become difficult, and patients can lose strength in the hands. This may cause them to drop things easily.

Individuals often shake their hands trying to obtain relief. They also can experience a sensation of swelling even though no swelling is present.

The disease can progress. In severe and chronic cases of carpal tunnel syndrome, loss of muscle mass (atrophy) occurs at the base of the thumb. In these situations, weakness or impaired use of the hand as well as loss of sensation can occur with nerve and muscle damage that becomes irreversible.

Carpal tunnel syndrome is found in patients who are pregnant, obese, or who have various medical conditions such as thyroid disease, diabetes or arthritis, or injuries such as wrist fractures. Repetitive work activities also may cause carpal tunnel syndrome. In particular, repetitive hand activities, especially those involving vibratory motion, can aggravate the symptoms.

The pain and swelling in the hand joints and wrists caused by arthritis can also be responsible for similar symptoms. For instance, pain at the base of the thumb is commonly caused by osteoarthritis. Tendonitis, an inflammation of the tendons that connect muscles to bones, such as a trigger finger, can cause pain, swelling, and impaired use of the hand or wrist. Raynaud’s phenomena can cause numbness and burning of the fingers as a result of cold exposure and sometimes due to autoimmune diseases.

These diseases need to be excluded before diagnosing carpal tunnel syndrome. Diagnosis and treatment is discussed in other articles.