What is carpal tunnel syndrome?

Carpal tunnel syndrome is possibly the most common nerve disorder experienced today. The carpal tunnel is located at the wrist on the palm side of the hand just beneath the skin surface (palmar surface). Eight small wrist bones form three sides of the tunnel, giving rise to the name carpal 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 help flex or bend the fingers.] When this median nerve in the wrist is compressed (squeezed by swollen tissues, for example), it slows or blocks nerve impulses from travelling through the nerve. Because the median nerve provides muscle function and feeling in the hand, disabling the nerve results in symptoms ranging from mild occasional numbness to hand weakness, loss of feeling and loss of hand function.

Usually carpal tunnel syndrome affects only one hand, but can affect both at the same time, causing symptoms in all or some of the fingers including thumb, index, middle and adjacent half of the ring finger but rarely the little finger (pinkie). In addition to numbness, those with the syndrome may experience tingling, pins and needle sensation or burning of the hand occasionally extending up to the forearm.

Frequently, symptoms surface in the morning upon awakening, or may cause waking during the night. Symptoms can occur with certain activities such as driving, holding a book or other repetitive activity with the hands, especially those requiring prolonged grasping or flexing (bending) of the wrist. Hand functional activities, such as buttoning, may become difficult, and sufferers may drop things more easily.

Individuals often shake their hands trying to obtain relief and may experience the sensation of swelling when, in fact, no swelling is actually present.

Because numbness and tingling may be mild and occur only as a periodic episode, many do not seek medical help. However, the disease can progress to more persistent numbness and burning. In some severe and chronic cases of carpal tunnel syndrome, loss of muscle mass (atrophy) occurs at the base of the thumb on the palm side of the hand. In these instances, especially in untreated cases, some weakness or impaired use of the hand as well as loss of sensation can occur with nerve and muscle damage that can’t be reversed by treatment.

What causes carpal tunnel syndrome?

Carpal tunnel syndrome may be found in patients who are pregnant, overweight or have various medical conditions, including thyroid disease, diabetes or arthritis, or injuries such as wrist fractures. Whether repetitive work activities cause carpal tunnel syndrome is still controversial, but it is thought that some repetitive hand activities, especially those involving vibratory motion, can worsen the symptoms. Just as frequently, the syndrome occurs on its own.

However, many other conditions also can be responsible for the same symptoms of pain, swelling, numbness or weakness in the hands including diseases of the nerves located anywhere from the neck to the wrist. The pain and swelling in the hand joints and wrists caused by arthritis can also be responsible. 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. Raynaud’s also causes fingers to change to whitish, bluish, or reddish discoloration at various times, color changes not seen in CTS.

These and other diseases need to be excluded before diagnosing carpal tunnel syndrome.