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Carpal tunnel - a syndrome name so well known that nearly everyone has heard of it. Unfortunately, given this widespread familiarity, people often attribute any discomfort or pain in the hand or wrist to carpal tunnel syndrome. Carpal tunnel syndrome is quite common, affecting 4 to 10 million Americans, and usually very treatable. However, there are many other conditions which can cause similar complaints. It is important to know the difference.

The main symptom of carpal tunnel syndrome is numbness of the fingers.

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

Carpal tunnel syndrome can be effectively treated with medications, splinting, steroid injections in the wrist and/or surgery.

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.

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.

Middle aged to older individuals are more likely to develop the syndrome than younger persons, and females three times more frequently than males.

The diagnosis of carpal tunnel syndrome is often made by the physician based on an accurate description of the symptoms. During physical examination, testing may identify weakness of the muscles supplied by the median nerve in the hand including some thumb muscles affected by the syndrome. There may be decreased sensation in the hand to pin prick or light touch. Bending the wrist to 90 degrees for one minute may cause symptoms to appear in the hand (Phalen test) or tapping on the wrist with a reflex hammer may cause an electric shock-like sensation (Tinel Sign). Late in the disease, there may be thinning of the muscles or muscle atrophy at the base of the thumb.   The diagnosis of carpal tunnel syndrome can be confirmed and severity determined by a two-part electrical test:   The nerve conduction test is the strongest evidence for carpal tunnel syndrome. The nerve is stimulated with a mild electrical current generated by a small electrode placed on the skin, proximal to the tunnel (elbow side of the tunnel). The impulse travels in the nerve through the tunnel to the hand where the impulse is measured. If the median nerve is affected, the impulse will take a longer time than would be expected to get to the hand. The longer the delay in the nerve impulse, the worse the nerve damage will be. The second part of the test, electromyography, measures the degree of abnormal function of the muscles. A small needle is placed in various muscles supplied by the median nerve, and the electrical impulse of the muscle is measured at rest and upon contraction (tightening with use) of the muscle. If the nerve has been severely compressed, these muscles can be affected and will not perform normally on the electrical test.   In recent years, diagnostic ultrasonography and MRI scans have been used to help diagnose CTS and exclude other causes of hand and wrist symptoms. These technologies can identify swelling of the median nerve and abnormalities of the tunnel wall, its contents and surrounding area. This can include the source of median nerve compression including inflammation of structures in the tunnel such as inflamed tendons, which can occur in rheumatoid arthritis. Other tendon abnormalities, including a ganglion, or excessive fat in the tunnel, also can be seen on MRI.

Carpal tunnel syndrome disables a key nerve, resulting in symptoms ranging from mild occasional numbness to hand weakness, loss of feeling and loss of hand function.

Medication such as acetaminophen and nonsteroidal anti-inflammatory drugs can be used for symptom relief. Splinting the wrist, especially at night, helps keep the wrist straight during the night and thus decreases the pressure on the median nerve. These splints, which are available in most drug stores, may relieve symptoms, especially in milder cases.

A cortisone injection into the carpal tunnel area is often helpful in relieving symptoms for weeks to months and can be repeated. If there is an underlying disease, such as hypothyroidism (under active thyroid) or rheumatoid arthritis, causing the carpal tunnel syndrome, then treatment of the specific disease may also relieve symptoms.

When the above measures fail to relieve symptoms, surgical opening of the tunnel to relieve the pressure on the median nerve, known as a carpal tunnel release, is appropriate. In severe cases, early surgery may be considered. The surgery may be an open surgical procedure or an endoscopic procedure, and can be often done on an outpatient basis.

Other conditions, such as arthritis, tendonitis and other nerve involvement, need to be excluded before diagnosing carpal tunnel syndrome.

Carpal tunnel syndrome can be diagnosed by history of the symptoms, physical examination and electrical testing, and in some cases by use of ultrasound or MRI.

The syndrome is treated with analgesics (pain medicines), anti-inflammatory medications, splinting and cortisone injections. However, any underlying disease causing or contributing to the carpal tunnel syndrome, if present, also should be treated.

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