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Do you get numbness in your fingers when driving a car, talking on the telephone or using your computer? Do you awaken at night with numbness or tingling (like hitting your "funny bone") in your fingers? If so, you may have Carpal Tunnel Syndrome, a pinched nerve in your wrist. This issue of our newsletter was written by local orthopedic specialist, Jonathan E Hottenstein, MD. To learn more about this condition, read on...

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What is the carpal tunnel?
The term carpal tunnel means wrist tunnel. The carpal tunnel is a "tunnel" formed by the carpal or wrist bones arranged in a semicircle which forms the bottom and sides. A thick band of connective tissue, the transverse carpal ligament, forms the roof over them. The carpal tunnel goes from the skin creases in your wrist midway into the palm (figure 1). The tunnel is a fixed space that can't get any larger and it is pretty crowded in there. Nine tendons, one to the thumb and two to each finger, pass through the tunnel (figure 2). The tendons, which are like smooth ropes, connect the muscles to the bones so you can bend your fingers. These tendons are covered with a membrane called synovium that lubricates the tendons so they can glide easily. Also passing through the tunnel is the median nerve - a major nerve which carries messages from your brain to muscles in your hand and sensations of touch, pain, hot, and cold from your hand back to your brain. The median nerve gives sensation to the thumb, index, middle, and half of your ring finger (figure 3).

The carpal tunnel is normally quite snug. There is barely enough room for the tendons and nerve that have to pass through it. With so little room for expansion, if anything causes the synovium or other tissues to swell in the tunnel, the median nerve gets pinched against the ligament. Pinching of the nerve causes numbness and tingling characteristic of carpal tunnel syndrome. The tendons keep working so you can move your fingers, but the hand goes numb.

What are the symptoms?
Symptoms usually begin gradually with occasional episodes of burning, tingling, or itching numbness in the palm of the hand or fingers, especially the thumb and the index and middle finger. Symptoms are often worse at night and may wake the patient up. A frequent complaint is awakening and feeling the need to hang their arm out of bed or to shake the hand or wrist. As the condition progresses, symptoms may occur during the day. Some sufferers develop a decrease in grip strength making it difficult to grasp small objects or make a fist. They may become clumsy and begin to drop things. Some numbness and pain may be seen in the forearm, but not higher than that.

What causes carpal tunnel syndrome?
The cause of carpal tunnel syndrome is unknown. Symptoms can develop with diseases of the synovium such as rheumatoid arthritis or retained fluid within the tunnel that can occur with low thyroid function or pregnancy. Carpal tunnel syndrome is more common in diabetics. Although it may be aggravated by work, it frequently occurs in people who do not work with their hands. Most of the time there is no obvious reason why carpal tunnel syndrome occurs. Some authorities believe that a vitamin B6 deficiency can also cause symptoms.

How common is it?
Carpal tunnel syndrome was first diagnosed in the 1950's and now is one of the most common orthopedic problems. It affects about 1 in 100 adults at some point in their life. Both sexes are vulnerable, but women are three times more likely than men to develop carpal tunnel syndrome, perhaps because the carpal tunnel in women may be smaller than men. In 2000, there were 3.4 million office visits in the United States for carpal tunnel syndrome.

How can one prevent it?
There is no way to prevent all cases of carpal tunnel syndrome, but there are some simple things you can do to limit your risk. Some cases of carpal tunnel syndrome may be related to repetitive use of the hands and wrists. If you are beginning to develop early symptoms, you can reduce your risk of this condition by stopping or reducing activities that stress your fingers, hand, or wrist. Try switching hands and changing positions often while doing activities that require repeated motions. The use of ergonomic guidelines at work can help prevent carpal tunnel syndrome. Proper placement of your desk, keyboard, computer monitor and mouse, and chair may be helpful. Keyboarding isn't the only activity that causes carpal tunnel syndrome. Evaluate your daily routine for other activities that place stress on your wrist and try to modify them.

How does the doctor know?
Your doctor makes the diagnosis by checking the sensation in your hand. He may tap on the nerve to see if you get an "electric shock" to your fingers (Tinel test), or bend your wrist for one minute to see if the symptoms are reproduced (Phalen test). However, the most accurate test is a nerve conduction study. Electrodes are placed on the hand and wrist. Small electric shocks are applied to the nerve above the tunnel and the time it takes the impulse to reach the fingers is measured. If it is delayed, the diagnosis of carpal tunnel syndrome is made. MRI can show the anatomy of the wrist, but has not been useful in making the diagnosis of carpal tunnel syndrome.

Non-operative treatment
Carpal tunnel syndrome does not follow a predictable course and some patients get better without any treatment. For those with persistent complaints, diagnosis at an early stage and prompt treatment are important to avoid permanent damage to the median nerve. Mild cases may be treated by the use of a wrist splint. These are usually worn at night to keep the wrist straight which helps relieve pressure on the nerve. Occasionally anti-inflammatory medications taken by mouth such as aspirin, ibuprofen, or prescription non-steroidals may be prescribed to help reduce the swelling. In more severe cases, the doctor may recommend a cortisone injection directly into the carpal tunnel. Some doctors feel that harmless supplements of vitamin B6 are helpful. Workplace changes, such as wearing gloves when using vibrating tools and using wrist pads at computer keyboards, can also reduce symptoms.

Surgery
Traditionally, management of carpal tunnel syndrome has been conservative. Surgery is usually advised only after patients fail a trial of non-operative treatment. Initially developed by surgeons at the Cleveland Clinic in the 1950's, carpal tunnel surgery is now the fifth most common procedure performed among Medicare patients. Many advancements have been made over the past sixty years, but the goal of all surgical procedures is to cut the transverse carpal ligament. This allows more room in the tunnel so the nerve is able to function normally. There are currently two types of surgery - open and endoscopic.

Open release surgery is the traditional procedure used to correct carpal tunnel syndrome. This consists of a 1 to 2 inch skin incision in the wrist to expose and cut the carpal ligament.

During endoscopic carpal tunnel release, the surgeon makes two smaller incisons in the wrist and palm and inserts a thin fiber optic videocamera which shows the tissues inside the carpal tunnel on a TV monitor. Special miniaturized instruments are then used to cut the ligament. Endoscopic surgery may allow faster recovery and less discomfort than the traditional open release surgery, but may have a slightly higher risk of nerve damage. Both types of surgery are done as an outpatient under local anesthetic - meaning you can leave the surgery center or hospital and return home the same day. Most patients are given sedation which takes away memory of the procedure, but it can be done with local anesthetic only.

What to expect after surgery
The symptoms are usually better the night of surgery, but tenderness persists at the incision for several months. If the nerve is severely compressed or if the symptoms have been present for a long time, it could take several months for the numbness to resolve. The compression can be so severe that total recovery cannot occur. This is more common with older patients. The majority of patients can resume most activities within 2 weeks of the surgery. The palm is sore for several months, so returning to heavy work could take a month. A weakened grip can also take several months to recover. If the nerve compression is not severe and has not been present for a long time, recurrence of carpal tunnel syndrome following surgery is rare. The majority of patients recover completely.