Carpal Tunnel Syndrome By Jonathan Cluett

Carpal Tunnel Syndrome

By Jonathan Cluett, M.D., About.com Guide

Carpal tunnel syndrome occurs when a nerve is pinched in the wrist. This nerve, called the median nerve, is the connection from the brain and spinal cord, down to the finger tips. In patients with carpal tunnel syndrome, the median nerve is pinched as it passes through the wrist. Because of the compression, the nerve does not function properly.

How does the median nerve normally work?

Nerves are structures that relay messages to and from your brain. The nerve sends a message to your muscles when you want to move, and the nerve relays messages to your brain about sensations. Nerves control specific muscles, and nerves provide sensations for your body. The median nerve (the nerve that is affected in carpal tunnel syndrome) supplies messages to specific muscles of the hand. The median nerve also sends sensory information from most of the palm side of your hand and the thumb, forefinger, middle finger, and part of the ring finger.

The median nerve travels from branches off the spinal cord, down the arm, and into the wrist and hand. In the wrist, the median nerve passes through the carpal tunnel. Carpal comes from the Greek word for 'wrist'-that's what gives the tunnel its name. The carpal tunnel is actually made up of the wrist bones on the bottom, and a tight ligament on the top. The ligament that makes up the top of the carpal tunnel is not flexible, nor are the wrist bones. Coursing through the carpal tunnel is the median nerve, as well as tendons that attach to your fingers.

What is carpal tunnel syndrome?

Carpal tunnel syndrome is caused when there is pressure in the carpal tunnel that compresses the median nerve, causing the nerve to function improperly. Because the carpal tunnel is surrounded by bone on one side, and an inflexible ligament on the other, if pressure builds, the nerve has nowhere to go. Simply put, in carpal tunnel syndrome the nerve gets squished.

When carpal tunnel syndrome occurs, the median nerve is pinched, and the normal functions (as described above) are impaired. 

Problems that can occur in carpal tunnel syndrome include:

Pain

Numbness

Tingling

Weakness

People can have a wide variety of carpal tunnel syndrome symptoms, but the condition typically causes hand and wrist pain, weakness in specific muscles of the hand, and abnormal sensations including tingling and numbness in specific areas of the hand supplied by the pinched nerve.

The most common symptoms of carpal tunnel syndrome are:

Hand and finger pain

Tingling sensations of the fingers

Numbness in the fingers

One common symptom of carpal tunnel syndrome is that people find shaking the hand often relieves these symptoms. Pain may extend up the arm, and the pain from carpal tunnel syndrome is often worst at night. Often patients find they are awakened at night, and have to shake out their hand to get the tingling in their fingers to resolve. Other activities including driving and typing can aggravate symptoms of carpal tunnel syndrome.

How is the diagnosis of carpal tunnel syndrome made?

In diagnosing carpal tunnel syndrome, your doctor will look for changes in sensation and for weakness in the muscles controlled by the median nerve. Several simple tests can be done to elicit carpal tunnel syndrome symptoms to diagnose the disorder. 

Two common tests are called Tinel's and Phalen's Test.

Tinel's Sign

Tinel's test is performed by tapping the median nerve along its course in the wrist. A positive test is found when this causes worsening of the tingling in the fingers when the nerve is tapped.

Phalen's Sign

Phalen's test is done by pushing the back of your hands together for one minute. This compresses the carpal tunnel and is also positive when it causes the same symptoms you have been experiencing with your carpal tunnel syndrome.

What other tests can be done to make a diagnosis of carpal tunnel syndrome?

Definitive analysis of nerve function can be performed with studies of how well an electric impulse conducts along the nerve. A device called an EMG can detect abnormalities in nerve impulse conduction; these nerve conduction abnormalities are the cause of carpal tunnel syndrome symptoms. The EMG does not always need to be performed, but may be done if a patient's symptoms are not typical of carpal tunnel syndrome.

What causes the carpal tunnel syndrome symptoms?

As stated previously, the symptoms of carpal tunnel syndrome are caused by compression of the median nerve as it courses through the carpal tunnel in the wrist. Some systemic conditions are associated with carpal tunnel syndrome, including diabetes, hypothyroidism, arthritis, and pregnancy.

Recently, the computer keyboard has been the target of blame for many patients with carpal tunnel syndrome. Whether or not typing causes carpal tunnel syndrome is still controversial, yet it seems appropriate that anyone who spends much time at the computer be familiar with techniques in prevention of this problem. Similarly, other activities that depend on wrist motion such as shop work, weight lifting, and racquet sports have been associated with carpal tunnel syndrome. Carpal tunnel syndrome is most common in the middle aged and elderly, with over 80% of patients over 40 years of age.

Carpal Tunnel Syndrome Treatment

Carpal tunnel syndrome treatment usually begins conservatively, and moves to more aggressive and invasive techniques if the symptoms of carpal tunnel syndrome persist.

The initial carpal tunnel syndrome treatment steps include some medications and splints.

Anti-Inflammatory Medications

Anti-inflammatory medications or NSAIDs (e.g. Motrin or Advil) can decrease inflammation in the carpal tunnel and can also decrease carpal tunnel syndrome symptoms.

Wrist Brace

The brace helps to stabilize the carpal tunnel in its neutral position. The carpal tunnel is at its widest diameter in this position and the nerve is least compressed. Wearing the splint at night is especially important, as well as during activities that tend to irritate your carpal tunnel syndrome.

What if my carpal tunnel syndrome symptoms persist?

The next step in carpal tunnel syndrome treatment can be a cortisone injection to the area to decrease inflammation around the nerve. The cortisone injection is often effective because the medication is delivered to the source of the problem; however, steroids shoulder be injected sparingly, and if the carpal tunnel syndrome returns, surgery may be considered.

Injections of cortisone into the carpal tunnel work about 80% of the time. However, this relief is often temporary, and the symptoms may return. Recent research has shown that the carpal tunnel injection is probably an effective treatment for at least one year in many patients. The injection can also be very helpful in situations where the diagnosis of carpal tunnel syndrome is unclear.

If these treatments do not work, do I need surgery?

Surgical treatments are available and effective in the treatment of carpal tunnel syndrome. The most common procedure is the carpal tunnel release. A carpal tunnel release involves making an incision in the fibrous sheath around the carpal tunnel. By releasing tension in the carpal tunnel, the pressure is removed from the nerve.

If a carpal tunnel release is done, it is most commonly performed by a "open" technique. To perform an open carpal tunnel release, your surgeon makes a 4 centimeter incision down the middle of the palm. Your surgeon carefully dissects the tissues down to the carpal tunnel. The carpal tunnel is opened up to relieve the pressure on the nerve. The surgery only takes about 15 minutes, and can be performed under local, regional, or general anesthesia.

What is an endoscopic carpal tunnel release?

A carpal tunnel release can now be done through a small incision and a camera called an endoscope. In this procedure, a small (about 1 centimeter) incision is made by the wrist. Through this incision, a small camera is inserted into the carpal tunnel. A small knife attached to the camera is then used to release the carpal tunnel.

Both procedures are effective in the treatment of carpal tunnel syndrome. Many surgeons prefer the open carpal tunnel release because it is easy to ensure there is adequate relief of tension around the nerve. Furthermore, the incision from an open carpal tunnel release tends to heal well with few problems. Some surgeons have also reported complications of the endoscopic carpal tunnel release due to inadvertent cutting of a nerve.

What are the complications of a carpal tunnel release?

The most common complications of surgical release of the carpal tunnel are injury to the nerve and incision pain. Injury to the nerve usually results in a permanent area of numbness around the base of the thumb; this occurs in about 5-8% of surgeries. Prolonged pain at the site of the incision is uncommon, but can occur in about 1-2% of cases.

Prevention of Carpal Tunnel Syndrome

Carpal tunnel syndrome is best managed in its early stages of the condition. If you feel the onset of symptoms that seem consistent with carpal tunnel syndrome, you should seek medical attention as soon as possible, and begin conservative therapy.

To prevent these symptoms there are a few simple exercises that can easily be done at home. By routinely performing these exercises to warm up the wrist joint, people often avoid the symptoms of carpal tunnel syndrome.

If you are going to be working with your hands for an extended period of time, whether it be at the computer, in the shop, or in the gym, you should always stretch and warm-up the joint. Furthermore, the are ways to maintain the joint in a 'wrist-neutral' position; this decreases the pressure in the carpal tunnel. A wrist brace can help keep the wrist in this position.

At the keyboard you can use a cushioned "wrist rest;" also, specially modified keyboards and computer mice are being developed and tested as alternatives to traditional equipment. Sports-related carpal tunnel syndrome can be prevented with proper technique and braces that support the wrist during activities.

Sources:

Adams, BD. "Endoscopic Carpal Tunnel Release" J. Am. Acad. Ortho. Surg., May 1994; 2: 179 - 184.

Osterman AL, Whitman M, Porta LD. "Nonoperative carpal tunnel syndrome treatment" Hand Clin. 2002 May;18(2):279-89.