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 the median nerve in the wrist is 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, this causes 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 the thumb and the index, middle and ring fingers. In addition to numbness, patients with carpal tunnel syndrome may experience tingling, a pins and needle sensation or burning of the hand occasionally extending up to the forearm.

Frequently, symptoms appear in the morning after a person wakes up, but they can also happen during the night and interrupt their sleep. Symptoms can occur with certain activities such as driving, holding a book or other repetitive activity with the hands, especially activities that require a person to grasp something for long periods of time or bend their wrist. Activities that require use of the hands, such as buttoning a shirt, may become difficult, and carpal tunnel sufferers may drop things more easily. Individuals will often shake their hands trying to obtain relief and may feel that their hand is swollen when no swelling is present.

Because numbness and tingling may be mild and occur only periodically, 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 occurs at the base of the thumb on the palm side of the hand. In these instances, especially when untreated, individuals can experience hand weakness, impaired use of the hand, and loss of sensation in their hand due to permanent nerve and muscle damage.

Carpal tunnel syndrome may occur in patients who are pregnant, overweight or have various medical conditions, including thyroid disease, diabetes or arthritis, or injuries such as wrist fractures. It is still debated whether repetitive work activities cause carpal tunnel syndrome, but it is thought that some repetitive hand activities, especially motions that can produce vibrations, can worsen the symptoms. Just as frequently, the syndrome occurs on its own.

However, many other conditions also can be responsible for symptoms of pain, swelling, numbness or weakness in the hands, such as 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 also can be responsible. For example, pain at the base of the thumb is commonly caused by osteoarthritis. Tendonitis – an inflammation of the tendons that connect muscles to bones – 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 have a whitish, bluish or reddish color at various times; color changes are not seen in carpal tunnel syndrome. Health care professionals should exclude these and other diseases before diagnosing carpal tunnel syndrome.

Diagnosis of carpal tunnel syndrome based on an accurate description of the symptoms a patient is experiencing. 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 when pricked with a pin or lightly touched. Bending the wrist at a 90-degree angle 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, the muscles might be thinning or declining at the base of the thumb.

Health care professionals can confirm the diagnosis of carpal tunnel syndrome and determine its severity with a two-part electrical test called the nerve conduction test. The nerve conduction test is the strongest evidence for carpal tunnel syndrome.

During the first part of the test, a small electrode that generates a mild electrical current is placed on the skin on the elbow side of the tunnel. This current stimulates the median nerve. The impulse from the stimulation travels down the nerve, through the tunnel, and to the hand – where the doctor will measure how long it took for the impulse to get there. If the median nerve is damaged, the impulse will take longer than expected to get to the hand. The worse the nerve damage is, the longer it will take for the impulse to get to the hand.

The second part of the test is called electromyography. It measures how badly the muscle is functioning. A small needle is placed in various muscles that receive impulses from the median nerve. The electrical impulses in the muscle are measured when the muscle is not being used and when the muscle is being used. If the median nerve is severely squeezed, these muscles can be affected and will not perform normally during the test.

Diagnostic ultrasonography and MRI have been used to help diagnose carpal tunnel syndrome 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. They can also help determine why the median nerve is being squeezed, or compressed. For example, inflammation of structures in the tunnel like inflamed tendons might be causing the median nerve to be compressed. This can occur in rheumatoid arthritis. Other tendon abnormalities, such as excessive fat in the tunnel (also called a ganglion) also can be seen using MRI.

Pain medications such as acetaminophen and nonsteroidal anti-inflammatory drugs can be used for symptom relief. Placing a splint on the affected wrist, especially at night, can help keep the wrist straight during the night and decrease the pressure on the median nerve. These splints are available in most drug stores and may relieve symptoms, especially in milder cases.

A cortisone injection into the carpal tunnel area often is helpful in relieving symptoms for weeks to months at a time and can be repeated. If an underlying disease like hypothyroidism (an underactive thyroid) or rheumatoid arthritis is causing the carpal tunnel syndrome, then treatment of the disease also may relieve symptoms.

When the above measures fail to relieve symptoms, surgery may be needed to open the carpal tunnel and relieve the pressure on the median nerve. This is known as a carpal tunnel release. In severe cases, physicians may consider surgery early on before trying other methods. The surgery may be an open surgical procedure or an endoscopic procedure and often can be done on an outpatient basis.