Introduction

Carpal tunnel syndrome is a common problem that affects the hand and wrist. This condition, or syndrome, has become the focus of much attention in the last few years due to suggestions that it may be linked to occupations that require repetitive use of the hands, such as typing. In reality, there are many people who develop this condition, regardless of the type of work they do.

The Median Nerve

Carpal tunnel syndrome (CTS) occurs when the median nerve does not work properly. This improper function in the nerve is usually due to too much pressure being placed on the nerve as it runs into the wrist through an opening called the carpal tunnel.

The median nerve runs into the hand to supply sensation to the thumb, index finger, middle finger, and half of the ring finger. The nerve also supplies a branch to the muscles of the thumb, the thenar muscles. These muscles help move the thumb and enable it to touch each of the other fingers. This motion is called opposition.

The carpal tunnel is an opening into the hand that is made up of the bones of the wrist on the bottom and the transverse carpal ligament on the top. This cross section of the wrist illustrates the anatomy of the carpal tunnel.

The median nerve and the flexor tendons run into the hand through the carpal tunnel opening. The median nerve lies just under the transverse carpal ligament.

The flexor tendons help to create the movement of the fingers and the hand that occurs when we grasp objects. These tendons are covered by a material called tenosynovium. Tenosynovium is a slippery substance that allows the tendons to glide against each other as the hand grasps objects.

Any condition that causes irritation or inflammation of these tendons can result in swelling and thickening of the tenosynovium. As the tenosynovium covering the tendons swells and thickens, the pressure begins to increase in the carpal tunnel because the bones and ligaments that make up the tunnel are not able to stretch in response to the swelling. Increased pressure in the carpal tunnel begins to squeeze the median nerve against the transverse carpal ligament. Eventually, the pressure reaches a critical point, and the nerve can no longer function normally, resulting in pain and numbness in the hand.

Symptoms

One of the first symptoms of carpal tunnel syndrome is numbness in the branches of the median nerve. This is quickly followed by pain in the same areas. The pain may also radiate up the arm to the shoulder and, sometimes, the neck.

If the condition is allowed to progress, weakness of the thenar muscles can occur. This results in an inability to bring the thumb into opposition with the other fingers, hindering the ability to grasp.

Many conditions can cause irritation and inflammation of the tenosynovium and lead to carpal tunnel syndrome. Different types of arthritis can cause inflammation of the tenosynovium directly, while a fracture of the wrist bones may later cause carpal tunnel syndrome if the healed fragments result in abnormal irritation on the flexor tendons. Ultimately, anything that causes abnormal pressure on the median nerve will result in the symptoms of pain, numbness and weakness associated with carpal tunnel syndrome.

Recently, physicians have begun to recognize that activities involving highly repetitive use of the hands can result in carpal tunnel syndrome. This is thought to be caused by inflammation and swelling of the tenosynovium due to overuse.

Diagnosis

Evaluating this condition begins when your doctor obtains a history of the problem, followed by a thorough physical examination. Your description of the symptoms and the physical examination are important when diagnosing carpal tunnel syndrome. Commonly, patients will complain first of waking in the middle of the night with pain and a feeling that the whole hand is asleep.

Careful investigation usually shows that the little finger is unaffected. This can be a key piece of information used to make the diagnosis. If you awaken with your hand asleep, pinch your little finger to see if it is also numb and be sure to tell your doctor if it is or isn't. Other complaints include numbness while using the hand for gripping activities, such as sweeping, hammering, or driving. These physical findings reflect that pressure is increased in the carpal tunnel.

If more information is needed to make the diagnosis, your doctor may request electrical studies of the nerves in the wrist. Several tests are available to see how well the median nerve is functioning, including the nerve conduction velocity (NCV) test. This test measures how fast nerve impulses are conducted through the nerve.

Treatment

Non-Operative Treatment

In the early stages of carpal tunnel syndrome, a simple brace will sometimes decrease the symptoms, especially the numbness and pain occurring at night. These braces keep the wrist in a neutral position (not bent back or down too far). When the wrist is in this position, the carpal tunnel is maximized, so the nerve has as much room as possible. The brace must be worn while you sleep to prevent the numbness and pain from occurring at night. The brace may help to reduce daytime symptoms as well.

Anti-inflammatory medications may also help control the swelling of the tenosynovium and reduce the symptoms of carpal tunnel syndrome. These medications include common over-the-counter medications such as ibuprofen and aspirin. In some studies, high doses of vitamin B-6 have also shown some ability to decrease the symptoms of carpal tunnel syndrome.

There is some evidence that exercises may prevent or control the symptoms of carpal tunnel syndrome. Some studies have shown that wrist position may contribute to carpal tunnel syndrome.

Workplace ergonomics have long been thought to be a contributing factor and alteration of the worksite, along with maintaining good wrist position, is essential for reducing the risks of carpal tunnel syndrome and is a must for patients doing any type of repetitive work.

If these simple measures fail to control your symptoms, an injection of cortisone into the carpal tunnel may be suggested. This medication will decrease the swelling of the tenosynovium and may give temporary relief of symptoms. It is not only used to treat the problem, but also aids in diagnosis. If the injection doesn't provide even temporary relief, other problems may be causing the carpal tunnel symptoms.

A newer way to get cortisone medications into the carpal tunnel, called Iontophresis, uses an electrical current to move the molecules of the medication through the skin and into the carpal tunnel. It is less painful than an injection, but may not be as effective.

Surgical Treatment

If all of the previous treatments fail to control the symptoms of carpal tunnel syndrome, surgery may be required to reduce the pressure on the median nerve. Several surgical procedures are designed to relieve pressure on the median nerve. The most common are the traditional open incision technique (described below) and the newer endoscopic carpal tunnel release using a smaller incision and a fiber optic TV camera to help see inside the carpal tunnel.

Basic Steps in Open Carpal Tunnel Release

Step 1: A small incision, usually less than 2 inches, is made in the palm of the hand. In some severe cases, the incision needs to be extended into the forearm half of an inch or so.

Step 2: After the incision is made through the skin, a structure called the palmar fascia is visible. An incision is made through this material as well to expose the constricting element, the transverse carpal ligament.

Step 3: Once the transverse carpal ligament is visible, it is cut with either a scalpel or scissors, while making sure that the median nerve is out of the way and protected.

Step 4: Once the transverse carpal ligament is cut, the pressure is relieved on the median nerve.

Step 5: Finally, the skin incision is sutured. At the end of the procedure, only the skin incision is repaired. The transverse carpal ligament remains open and the gap is slowly filled by scar tissue.

A bulky dressing is applied to the hand following surgery. The pain and numbness will begin to improve after surgery, but tenderness in the area of the incision may remain for several months.