Julian E Girod, MD

Carpal Tunnel Syndrome

 

What is Carpal Tunnel Syndrome?
Nine tendons needed to bend the fingers stretch from the forearm into the hand through a passageway in the wrist called the carpal tunnel. Carpal bones form three walls of the tunnel and a strong, broad transverse carpal ligament bridges the top. The median nerve, which supplies feeling to the thumb, index, and ring fingers, and the tendons that flex the fingers, also passes through this tunnel. Carpal tunnel syndrome (CTS) occurs when the protective lining of the tendons within the carpal tunnel swells, or when the ligament that forms the roof becomes thicker and broader. Eventually, the swollen tendons and ligaments press on the median nerve, a process called nerve entrapment, and can result in numbness, tingling, and pain in the wrist, hand, and fingers.

Carpal tunnel syndrome is categorized as a cumulative trauma disorder; these are problems generally associated with repetitive and forceful use of the hands that damage muscles and bones of the upper extremities. Other terms that are used to define and categorize carpal tunnel syndrome are repetitive strain injuries (RSI), overuse syndromes, chronic upper limb pain syndrome, or repetitive motion disorders.

What causes Carpal Tunnel Syndrome?
Although most often associated with occupations or tasks requiring high-force, high-repetitive hand motions, the injury can be provoked by other conditions. Some experts believe that incorrect posture may play a large role in the development of CTS, particularly in people who work at computer and other types of keyboards. The tendency to roll the shoulders forward, round the lower back, and thrust the chin forward can shorten the neck and shoulder muscles, compressing nerves in the neck. This, in turn, can affect the wrist, fingers, and hand. Bone dislocations and fractures can narrow the carpal tunnel, thereby exerting pressure on the median nerve. Fluid retention during pregnancy or due to the hormonal changes associated with menopause can cause swelling and symptoms of carpal tunnel syndrome.

Certain other medical conditions, such as rheumatoid arthritis, diabetes, and thyroid hormone deficiency, can also cause inflammation in the carpal tunnel and median nerve entrapment. In many patients with CTS, an underlying cause for the disorder cannot be discovered.

What are the symptoms?
Just as stepping on a hose slows the flow of water through a garden hose, so the compression of the median nerve fibers by the swollen tendons and thickened ligament slows down the transmission of nerve signals through the carpal tunnel and results in pain, numbness, and tingling in the wrist, hand, and fingers.

Symptoms usually progress gradually over weeks and months, and, in some cases, years. The first symptoms may be pain in the wrist and hand or numbness and tingling of the fingers. Patients may also notice a sense of weakness with a tendency to drop things. They may lose the sense of heat and cold or feel that their hands are swollen even though there is no visible swelling. Symptoms may occur not only with the use of the hand but with the hand at rest or at night after going to bed. In some cases, work-related CTS symptoms first occur outside of work, so patients may fail to associate the symptoms with work-related activity. Anyone with recurrent or persistent pain, numbness and tingling, or weakness of the hand should consult a physician for a diagnosis.

Accompanying Disorders
About 25% of patients with work-related carpal tunnel syndrome also have evidence of other cumulative trauma disorders. Even when they occur alone, many of these repetitive stress disorders may have symptoms similar to carpal tunnel syndrome. A definitive diagnosis is often difficult. Most require treatments similar to those used for CTS: rest, immobilization, steroid injections, and even surgery if conservative management is unsuccessful.

Nerve Entrapment Disorders. Repetitive work can cause pressure on the median nerve in locations other than the wrist, as well as on other nerves in the arm and hand. The branch of the median nerve that runs through the palm of the hand can be damaged by repeated pounding or by the use of certain tools requiring a strong grip using the palm, such as needle-nosed pliers. The median nerve can also be pinched in the forearm.

Like the median nerve, the ulnar nerve, which controls the ring and little fingers, can also become trapped as a result of repetitive stress, with subsequent loss of sensation in these fingers and the outer half of the palm. This condition, known as ulnar tunnel syndrome, can appear as a separate disorder or with carpal tunnel syndrome. In the latter case, release surgery for CTS usually also relieves the ulnar nerve entrapment. The ulnar nerve can also be affected at the elbow.

Tendon-Related Disorders. Tenosynovitis (swelling of the tendon sheath) in the hands and fingers is also a repetitive stress injury and can effect various parts of the hand and fingers. One or more fingers may feel painful and stiff, especially in the morning; the wrist may be swollen. Trigger finger (also called snapping finger) is a condition brought on when a tendon thickens, leaving the finger in a bent position. It is a common complication of rheumatoid arthritis; it also may occur in diabetes or for unknown causes. De Quervain's disease involves tenosynovitis at the base of the thumb. These disorders are often present with carpal tunnel syndrome.

Patients who have tendinitis (swelling of the tendon) feel pain in the involved area, which is intensified when they contract the muscles adjoining the tendon or when the physician stretches the affected finger or part of the hand.

Pinched Nerves or Blood Vessels. Pinched nerves in the neck may cause weakness in the hands. A disorder known as thoracic outlet syndrome caused by compression of nerves and blood vessels running down the neck into the arm can cause symptoms very similar to CTS. The compression occurs at the first rib in the front of the shoulder. The condition is diagnosed by a physician who detects diminished blood flow in the arm, as the patient raises the affected hand and turns his or her head towards the opposite side.

Other Diseases. Arthritic conditions, including rheumatoid arthritis, gout, and osteoarthritis, can all cause pain in the hands and fingers. Raynaud's phenomenon produces symptoms of numbness and tingling or pain in the fingers of one or both hands; it is usually brought on by cold or stress and is treated with warmth or, in severe cases, medications that may open blood vessels. These conditions should be ruled out by the physician.

Who gets Carpal Tunnel Syndrome?
Occupational Risks. In 1992, according to the Bureau of Labor statistics, an estimated one million out of 2.3 million work-related injuries were associated with cumulative trauma. This may be a low estimate of the true number of cases, since, in 1988 2.8 million people reported to their doctors symptoms that they believed were those of carpal tunnel syndrome. The wide variation in severity and the difficulty in diagnosis makes it hard to pinpoint specific figures. It is certainly true, however that the incidence of cumulative trauma disorder has increased dramatically in recent years, probably due to automation and the widespread use of the computer.

Researchers have defined six key risk factors for the development of work-related cumulative trauma disorders, most of which also apply to the development of CTS: (1) repetition, (2) high force, (3) awkward joint posture, (4) direct pressure, (5) vibration, and (6) prolonged constrained posture. At highest risk are workers whose tasks require repeating the same motion in the fingers and hand for long periods. Some workers may not even be aware of the amount of force they exert while performing their jobs. For example, the fingers of typists whose speed is 60 words per minute exert up to 25 tons of pressure each day.

Meat packers complained of pain and loss of hand function as long ago as the 1860Ős. Even today, the incidence of CTS in the meat packing industry may be as high as 15%. In addition to butchers and meat packers, CTS has been reported in assembly line workers, cake decorators, postal workers, jackhammer operators, file clerks, assembly workers, virtually any group of workers who uses their hands and wrists repetitively. The use of the computer has had a great impact on the increased incidence of this problem, with people at risk including reporters, editors, data entry clerks, graphic designers, programmers, and anyone using the computer heavily.

Activities in the home can also contribute to the development of CTS, including many hobbies and household tasks. Knitting, sewing and needlepoint, cooking and housework, playing computer games, sports, card playing, carpentry, and extensive use of power tools are among the many activities that may contribute to CTS.

Gender and Age. Women suffer CTS three times as often as do men. The explanation for this is unknown, but an increased incidence while taking oral contraceptives and during pregnancy and menopause seems to indicate that hormonal changes may make women more susceptible. The hand-intensive nature of housework and typing may also contribute to a higher incidence in women. Older people also are more likely than younger ones to complain of CTS, possibly because nerve velocity slows down as people age.

Physical Characteristics. In a recent study, obese workers were 3.5 to 4.1 times more likely to have abnormal median nerve conduction than slender people. Some studies have also suggested that CTS is more common in those with square wrists (the thickness and width are about the same) than in those with the more common rectangular wrists, although other studies have failed to confirm this finding. Some researchers also claim that poor upper back strength makes people more susceptible to injuries in the upper extremities, including CTS.

Medical Conditions. Medical conditions that cause swelling in the wrist, such as arthritis, thyroid disease, diabetes, and acromegaly may increase susceptibility to CTS. In one study, 15% to 25% of people with diabetes had carpal tunnel syndrome. In addition, cigarette smoking, poor nutrition, previous injuries, and stress can increase one's risk.

Prevention
No single mode of prevention exists for carpal tunnel syndrome. It is important, however, to use common sense and ergonomic controls to help minimize risk factors predisposing to work-related CTS or other cumulative trauma disorders. A patient can learn how to adjust the work area, handle tools, or perform tasks in ways that put less stress on the hands and wrists. Exercise programs to strengthen the fingers, hands, wrists, forearms, shoulders, and neck may help prevent CTS. If the underlying cause is a medical condition, controlling the problem can prevent CTS.

Ergonomic Controls. Ergonomics is the study and control of posture, stresses, motions, and other physical forces on the human body engaged in work. Altering the way a person performs repetitive activities may help prevent inflammation in the hand and wrist from progressing into full-blown carpal tunnel syndrome. For example, replacing old tools with ergonomically-designed new ones can be very helpful.

Repetition and Rest. Anyone who does repetitive tasks should begin with a short warm-up period, take frequent break periods, and avoid overexertion of the hand and finger muscles whenever possible. Employers should be urged to rotate the tasks of their employees and vary the work content so that workers are given a variety of tasks.

Posture. Good posture is extremely important in preventing carpal tunnel syndrome, particularly for typists and computer users. A keyboard operator should sit with the spine against the back of the chair with the shoulders relaxed, the elbows along the sides of the body, and wrists straight. The feet should be firmly on the floor or on a foot rest. Typing materials should be at eye level so that the neck does not bend over the work. Keeping the neck flexible and head upright maintains circulation and nerve function to the arms and hands. Poorly designed office furniture is a major contributor to bad posture. Chairs should be adjustable for height, with a supportive backrest. Employers should be advised that the higher cost of a custom designed chair for a worker whose body does not fit a standard chair is still far less than the medical or absentee costs of an injured employee.

Force. The force placed on the fingers, hands, and wrists by a task may contribute importantly to CTS, particularly when the task is repeated often. To alleviate the effect of force on the wrist, tools and tasks should be designed so that the wrist position is maintained the same as it would be if the arms dangled in a relaxed manner at the sides. No task should require the wrist to deviate from side to side or to remain flexed or highly extended for long periods.

Keyboard operators should adjust the tension of the keys so that depressing the keyboard does not cause fatigue. The hands and wrists should remain in a relaxed position to avoid excessive force on the keyboard. For computer users, replacing the mouse with a trackball device and the standard keyboard with a new jointed-type are helpful substitutions. Wrist rests, which fit under most keyboards, can help keep the wrists and fingers in a comfortable position.

Undue force on the palm occurs with the use of tools such as screwdrivers, scrapers, paint brushes, and buffers. The handles of such tools should be designed so that the force of the worker's grip is distributed across the muscle between the base of the thumb and the little finger, not just in the center of the palm.

In order to apply force appropriately, the ability to feel an object is extremely important. Tools with textured handles are helpful. Working at low temperature, which reduces sensation in hands and fingers, should be avoided if possible.

Vibration. Tools and machines should be designed to minimize vibrations. Protective equipment can reduce vibrations. Bicyclists who ride on rough roads should wear thick cycling gloves to lessen the shock transmitted to the hands and wrists.

Exercise. Hand and wrist exercises may help reduce the risk of developing CTS. Isometric and stretching exercises can strengthen the muscles in the wrists and hands, as well as the neck and shoulders, improving blood flow to these areas. Any exercise program should be undertaken cautiously, however, and a physician consulted to be sure it is appropriate for the patient's condition. If a patient experiences any pain or discomfort, he or she should discontinue the exercise and check with the physician. The old adage, No pain-no gain, does not apply in the case of CTS. Performing the following simple exercises for four to five minutes every hour may be helpful.

Wrists. Make a loose right fist, palm up, and use the left hand to press gently down against the clenched hand. Resist the force with the closed right hand for five seconds, but be sure to keep the wrist straight. Next, turn the right fist palm down and press against the knuckles with the left hand for five seconds. Finally, turn the right palm so the thumb-side of the fist is up and press down again for five seconds.

Repeat this series of exercises five times for each hand.

Another easy wrist exercise requires first holding one hand straight up next to the shoulder with fingers together and palm facing outward. (The position looks like a shoulder-high salute); next, bend the hand backward with the fingers still held together and hold for five seconds; and third, spread the fingers and thumb open while the hand is still bent back and hold for five seconds. Repeat five times for each hand.

A third simple exercise is called wrist circles. First hold the second and third fingers up and close the others. Draw five clockwise circles in the air with the two fingertips. Draw five more counterclockwise circles. Repeat with the other hand.

Fingers and Hand. The first exercise is the finger bend and stretch. Clench the fingers of one hand into a fist tightly, then release, fanning out the fingers. Do this five times. Repeat with the other hand.

To exercise the thumb, bend it against the palm beneath the little finger and hold for five seconds. Spread the fingers apart, palm up, and hold for five seconds. This should be repeated five to 10 times with each hand. In addition, one can stretch the thumb by gently pulling it out and back and holding for five seconds, repeating five to 10 times with each hand.

Forearms. Excessive use of the hands can cause the forearm muscles to tighten, increasing pressure on tendons as they pass through the wrist. Stretching these muscles will reduce this tension. Place the hands together in front of the chest, fingers pointed upward in a prayer-like position. Keeping the palms flat together, raise the elbows to stretch the forearm muscles. Stretch for 10 seconds. Then gently shake the hands limp for a few seconds to loosen them. Repeat frequently when the hands or arms tire from activity.

Neck and Shoulders. Sit upright and place the right hand on top of the left shoulder. Hold that shoulder down and slowly tip the head away to the right. Keep the face pointed forward, or even turned slightly toward the right. Hold this stretch gently for five seconds. Repeat on the other side.

A second exercise requires standing in a relaxed position with the arms at the side. Shrug the shoulders up, then squeeze the shoulders back, then stretch the shoulders down, then press them forward. The entire exercise should take about seven seconds.

General Exercise. A regular exercise regimen using a combination of aerobic and resistance training techniques strengthens the muscles in the shoulders, arms, and back, helps reduce weight, and improves overall health and well-being. Some experts have reported that people who are physically fit, including athletes, joggers, and swimmers, have a lower risk for cumulative trauma disorders.

Tests for CTS
Medical and Personal History. Discomfort or fatigue in the fingers, hands, wrists, or arms may be caused by simple physical exertion without injury or may signal the onset of carpal tunnel syndrome. Because carpal tunnel syndrome often affects a person's work and may also involve worker's compensation benefits, it is very important to evaluate the possible association between the disorder and the patient's job. The patient should' give the physician a detailed history of complaints, including daily work activities and whether the symptoms appear especially at night or after tasks. The physician should rule out other medical conditions, such as arthritis or diabetes, that may be precipitating CTS.

Physical Examination. During a physical examination, the doctor will perform simple maneuvers. If carpal tunnel syndrome is present, tapping over the median nerve may produce a tingling or mild shock-sensation. The patient will also be asked to try and reproduce the symptoms by holding the hands together in front of the chest in a prayer position with the wrists bent out for one minute. If these tests are positive, then the patient has the physical signs as well as the symptoms of CTS.

Laboratory Tests. If the doctor suspects that an underlying medical condition may be exacerbating the symptoms, laboratory tests will be performed. The doctor may take an x-ray, for example, to check for arthritis or fractured bones.

Electrodiagnostic Tests. The treating physician may arrange for electrodiagnostic tests to confirm the diagnosis of carpal tunnel syndrome, to determine the severity of the condition, and to rule out other causes. There are two common types of electrodiagnostic tests: nerve conduction studies and electromyographies. The tests are performed by specially trained physicians who analyze the electric wave forms of nerves and muscles to detect median nerve compression in the carpal tunnel. To perform nerve conduction studies, surface electrodes are fastened to the hand and wrist and small electric shocks are applied to the nerves in the fingers, wrist, and forearm to measure the speed of conduction of sensory and motor nerve fibers. To perform electromyography, a fine sterile, wire electrode is inserted briefly into a muscle and the electrical activity is displayed on a viewing screen. Certain conditions, such as obesity, cold, and anxiety, can slow the speed of conduction and skew the results. Women and the elderly normally have slower conduction times than adult men. Both tests are fairly accurate, however, and can detect 84% of people who have carpal tunnel syndrome, and eliminate 95% of cases that are not true carpal tunnel syndrome. They can also detect causes of symptoms that mimic CTS, but which should be attributed to other problems such as pinched nerves in the neck or elbow or thoracic outlet syndrome. Ruling out other causes is extremely important in order to avoid unnecessary surgery for CTS. Costs for these tests are between $300 and $600. Physicians who are best qualified to perform the test are those certified by the American Board of Electrodiagnostic Medicine, which uses rigorous standards in qualifying doctors.

How is CTS treated?
Early Treatment. Conservative Therapy. It is critical to begin treating early phases of carpal tunnel syndrome before the damage progresses. The affected hand and wrist should be rested for at least two weeks; this allows the swollen, inflamed tissues to shrink and relieves pressure on the median nerve. A wrist splint or brace may be worn at night or during sports to help keep the wrist from bending. The splint is used for several weeks or months depending on the severity of the problem. Except for anecdotes of improvement, no evidence exists that these supports actually help.

Some experts believe that wrist supports may actually exacerbate the problem by reducing circulation and restricting movement so that the shoulder muscles tense up. Ice can be applied to provide relief; some patients have reported that alternating warm and cold soaks have been beneficial. If hot applications relieve pain, most likely the problem is an inflammation not caused by CTS but by another condition producing similar symptoms. The patient should reduce any risk factors at work or home that may aggravate the syndrome. Conservative treatment works best in men under 40 but least well in young women.

Drug Treatment. Anti-inflammatory agents, such as ibuprofen, may reduce swelling within the carpal tunnel. If conservative treatment is unsuccessful, the doctor may inject an anesthetic or a corticosteroid into the carpal tunnel to shrink the swollen tissues and relieve pressure on the nerve. To avoid attrition of the tendon, no more than three injections of cortisone should be given. It should be noted that the pain may increase for a day or two after the injection and skin color may change.

Physical Therapy. If symptoms subside, the patient may proceed with a supervised hand and wrist strengthening exercise program usually offered by a physical or occupational therapists. One study found that most people with CTS felt improvement after two months of physical therapy that included exercises to improve balance and posture.

Laser Light Therapy. One recent study found that automobile workers with CTS who were treated with a process known as cold laser light had greater improvement in grip strength and range of wrist movement than those treated with physical therapy. The process uses low-energy laser light that penetrates, but does not cut, the skin and stimulates cells activity in the injured areas.

Release Surgical Procedures. If symptoms persist for four to six months and if muscles begin to atrophy in the base of the palm, the patient may require surgery. The procedure does not cure all patients and because it requires permanently cutting the carpal ligament, it often results in some loss of wrist strength. Although carpal tunnel surgery is one of the most common procedures in the U.S., no studies have been done to determine the long-term outcome for patients after they return to work. A number of experts believe that this surgery is performed too often and that CTS sufferers should pursue conservative treatment and physical therapy as aggressively as possible before deciding to undergo surgery. Nevertheless, surgery may be necessary in certain cases, and it can be very beneficial.

Open Surgery. Traditionally, surgery for CTS entails an open surgical procedure performed in an outpatient facility. A local anesthetic is injected either into the wrist and hand or higher up the arm. The surgeon makes a two-inch incision in the palm and cuts the carpal ligament free from the underlying median nerve. This surgery is called a "release", because cutting the ligament relieves the pressure on the median nerve. Carpal tunnel release is the most commonly performed hand surgery with more than 100,000 procedures each year. Open surgery effectively relieves symptoms in 85% to 90% of patients, who can usually return to work within two months. The risk of complications is less than one percent.

Endoscopy. In the last five years, a surgical procedure has emerged which uses an endoscope, a pencil-thin lighted tube. One or two 1/2-inch incisions are made in the wrist and palm, and one or two endoscopes are inserted. A tiny camera and a knife are inserted through the lighted tube. While observing the under surface of the carpal ligament on a screen, the surgeon cuts the ligament to free the compressed median nerve. Patients do not end up with a surgical scar and can return to work within a month, about half the time as in standard open surgery.

Endoscopy, however, is more expensive than open surgery by about $500 and studies to date have not found it to be any more effective than standard open release surgery. This is a relatively new procedure and complications, including tingling or permanent loss of sensation in the fingers, increase with surgeons who are less experienced.

Post surgery. For some patients, release surgery relieves CTS symptoms of numbness and tingling immediately, but the incision site may remain sore for as long as three months. Returning to strenuous work right after surgery may cause the symptoms to recur, and patients generally stay out of work for at least month, depending upon the type of surgery and severity of the condition.

People who have the operation on both hands are completely incapacitated for about two weeks and must have someone to help them at home. In one major study, people were out of work an average of 4 months and 8% were out for more than a year. In this study, 67% returned to the same job and 15% to a different one.

With both types of surgery, nearly 25% of patients lose some wrist strength and may not be able to perform jobs that require high amounts of force to the wrist. People involved with heavy manual labor, particularly those working with vibrating tools, have a poorer outcome than others. In some studies only slightly more than half the people who used vibrating hand-held tools were symptom-free three years after their operations. Still, surgery can be beneficial in many cases. Older patients or those with a severe case of CTS may still experience symptoms weeks or even months after surgery. Post surgery complications may include nerve damage, infection, scarring, pain, and stiffness.

To help rebuild wrist strength, physical therapy is very important. Hand exercises can help rebuild circulation, muscle strength, and joint flexibility in the hand and wrist.

Percutaneous Balloon Carpal Tunnel Plasty. Percutaneous balloon carpal tunnel-plasty is a new technique still under investigation, which alleviates CTS without cutting the carpal ligament. Through a 1/4-inch incision in the base of the palm, the doctor inserts a balloon through a catheter under the ligament and inflates the balloon with saline solution to stretch the ligament and free the nerve. In one small study, all of the patients reported relief of symptoms with no postoperative complications. Most of them were back to work within two weeks. This experimental technique, which costs about $1,500, is not yet widely available.

Alternative Therapies. Many alternative therapies are offered to sufferers of carpal tunnel syndrome and other repetitive stress disorders. Most are harmless, but the benefits are unproved. Acupuncture has helped some people relieve pain. Chiropracty has been useful for some people whose condition is produced by pinched nerves. A few years ago, many people hoped that vitamin B6 would be successful in alleviating symptoms, but it is no longer considered effective, and high amounts can cause nerve damage. Some patients have reported possible benefit from using certain herbal oils, such as arnica oil, but people should approach nontraditional methods very cautiously and should check with their physician before trying any.

Some portions copyright©1996 Health ResponsAbility Systems. Used by permission.

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