Carpal Tunnel Syndrome

Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm into the hand, becomes pressed or squeezed at the wrist. 

The median nerve controls sensations to the palm side of the thumb and three fingers, as well as impulses to some muscles in the hand that allow the fingers and thumb to move. 

The carpal tunnel is a narrow, rigid passageway of ligament and bone at the base of the hand and houses the median nerve and tendons. 

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Sometimes, thickening from irritated tendons or other swelling narrows the tunnel and causes the median nerve to be compressed. 

The result may be pain, weakness, or numbness in the hand, wrist and occasionally the forearm. 

Although painful sensations may indicate other conditions, carpal tunnel syndrome is the most common and widely known of the entrapment neuropathies in which the body's peripheral nerves are compressed or traumatized. 

What are the symptoms of carpal tunnel syndrome?
Symptoms often begin gradually, with burning, tingling, or itching numbness in the palm of the hand and the fingers, especially the thumb and the index and middle fingers. 

Some sufferers say their fingers feel useless and swollen, even though little or no swelling is apparent. 

The symptoms often first appear in one or both hands during the night, since many people sleep with flexed wrists. 

A person with carpal tunnel syndrome may wake up feeling the need to "shake out" the hand or wrist. 

As symptoms worsen, people might feel tingling during the day. Decreased grip strength may make it difficult to form a fist, grasp small objects, or perform other manual tasks. 

In chronic and/or untreated cases, the muscles at the base of the thumb may waste away. Some people are unable to tell between hot and cold by touch.

What are the causes of carpal tunnel syndrome?
Carpal tunnel syndrome is often the result of a combination of factors that increase pressure on the median nerve and tendons in the carpal tunnel, rather than a problem with the nerve itself. 

Most likely the disorder is due to a congenital predisposition - the carpal tunnel is simply smaller in some people than in others.

Other contributing factors include trauma or injury to the wrist that cause swelling, such as sprain or fracture; overactivity of the pituitary gland; hypothyroidism; rheumatoid arthritis; mechanical problems in the wrist joint; work stress; repeated use of vibrating hand tools; fluid retention during pregnancy or menopause; or the development of a cyst or tumor in the canal. In some cases no cause can be identified.

There is little clinical data to prove whether repetitive and forceful movements of the hand and wrist during work or leisure activities can cause carpal tunnel syndrome. 

Repeated motions performed in the course of normal work or other daily activities can result in repetitive motion disorders such as bursitis and tendonitis. 

Writer's cramp - a condition in which a lack of fine motor skill coordination and ache and pressure in the fingers, wrist, or forearm is brought on by repetitive activity - is not a symptom of carpal tunnel syndrome.

Who is at risk of developing carpal tunnel syndrome?
Women are three times more likely than men to develop carpal tunnel syndrome, perhaps because the carpal tunnel itself may be smaller in women than in men.

The dominant hand is usually affected first and produces the most severe pain.

Persons with diabetes or other metabolic disorders that directly affect the body's nerves and make them more susceptible to compression are also at high risk. Carpal tunnel syndrome usually occurs only in adults.

The risk of developing carpal tunnel syndrome is not confined to people in a single industry or job, but is especially common in those performing assembly line work - manufacturing, sewing, finishing, cleaning, and meat, poultry, or fish packing. 

In fact, carpal tunnel syndrome is three times more common among assemblers than among data-entry personnel. 

A 2001 study by the Mayo Clinic found heavy computer use (up to 7 hours a day) did not increase a person's risk of developing carpal tunnel syndrome. 

During 1998, an estimated three of every 10,000 workers lost time from work because of carpal tunnel syndrome. 

Half of these workers missed more than 10 days of work.

The average lifetime cost of carpal tunnel syndrome, including medical bills and lost time from work, is estimated to be about $30,000 for each injured worker.

How is carpal tunnel syndrome diagnosed?
Early diagnosis and treatment are important to avoid permanent damage to the median nerve. 

A physical examination of the hands, arms, shoulders, and neck can help determine if the patient's complaints are related to daily activities or to an underlying disorder, and can rule out other painful conditions that mimic carpal tunnel syndrome. 

The wrist is examined for tenderness, swelling, warmth, and discoloration. 

Each finger should be tested for sensation, and the muscles at the base of the hand should be examined for strength and signs of atrophy. 

Routine laboratory tests and X-rays can reveal diabetes, arthritis, and fractures. 

Physicians can use specific tests to try to produce the symptoms of carpal tunnel syndrome. 

In the Tinel test, the doctor taps on or presses on the median nerve in the patient's wrist.

The test is positive when tingling in the fingers or a resultant shock-like sensation occurs. 

The Phalen, or wrist-flexion, test involves having the patient hold his or her forearms upright by pointing the fingers down and pressing the backs of the hands together. 

The presence of carpal tunnel syndrome is suggested if one or more symptoms, such as tingling or increasing numbness, is felt in the fingers within 1 minute. 

Doctors may also ask patients to try to make a movement that brings on symptoms.

Often it is necessary to confirm the diagnosis by use of electrodiagnostic tests. In a nerve conduction study, electrodes are placed on the hand and wrist. Small electric shocks are applied and the speed with which nerves transmit impulses is measured.

In electromyography, a fine needle is inserted into a muscle; electrical activity viewed on a screen can determine the severity of damage to the median nerve. 

Ultrasound imaging can show impaired movement of the median nerve. Magnetic resonance imaging (MRI) can show the anatomy of the wrist but to date has not been especially useful in diagnosing carpal tunnel syndrome. 

How can carpal tunnel syndrome be prevented?
At the workplace, workers can do on-the-job conditioning, perform stretching exercises, take frequent rest breaks, wear splints to keep wrists straight, and use correct posture and wrist position.

Wearing fingerless gloves can help keep hands warm and flexible. 

Workstations, tools and tool handles, and tasks can be redesigned to enable the worker's wrist to maintain a natural position during work. 

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Jobs can be rotated among workers.

Employers can develop programs in ergonomics, the process of adapting workplace conditions and job demands to the capabilities of workers.

However, research has not conclusively shown that these workplace changes prevent the occurrence of carpal tunnel syndrome.

What research is being done?
The US National Institute of Neurological Disorders and Stroke (NINDS), a part of the National Institutes of Health, is the federal government's leading supporter of biomedical research on neuropathy, including carpal tunnel syndrome. 

Scientists are studying the chronology of events that occur with carpal tunnel syndrome in order to better understand, treat, and prevent this ailment. 

By determining distinct biomechanical factors related to pain, such as specific joint angles, motions, force, and progression over time, researchers are finding new ways to limit or prevent carpal tunnel syndrome in the workplace and decrease other costly and disabling occupational illnesses. 

Percutaneous balloon carpal tunnel-plasty is an experimental technique that can ease carpal tunnel pain without cutting the carpal ligament. 

In this procedure, a ¼-inch cut is made at the base of the palm. 

The doctor then inserts a balloon through a catheter under the carpal ligament and inflates the balloon to stretch the ligament and free the nerve. 

Patients in one small study of pertucaneous balloon carpal tunnel-plasty reported relief of symptoms with no postoperative complications; most of them were back to work within two weeks. 

This experimental technique is not yet widely available. 

Randomized clinical trials are being designed to evaluate the effectiveness of educational interventions in reducing the incidence of carpal tunnel syndrome and upper extremity cumulative trauma disorders. 

Data to be collected from an NINDS-sponsored clinical study of carpal tunnel syndrome among construction apprentices will provide a better understanding of the specific work factors associated with the disorder, furnish pilot data for planning future projects to study its natural history, and assist in developing strategies to prevent its occurrence among construction and other workers. 

Other research will discern differences between the relatively new carpal compression test (in which the examiner applies moderate pressure with both thumbs directly on the carpal tunnel and underlying median nerve, at the transverse carpal ligament) and the pressure provocative test (in which a cuff placed at the anterior of the carpal tunnel is inflated, followed by direct pressure on the median nerve) in predicting carpal tunnel syndrome. Scientists are also investigating the use of alternative therapies, such as acupuncture, to prevent and treat this disorder. 

Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm into the hand, becomes pressed or squeezed at the wrist. 

The median nerve controls sensations to the palm side

...

The dominant hand is usually affected first and produces the most severe pain.

Persons with diabetes or other metabolic disorders that directly affect the body's nerves and make them more susceptible to compression are also at high risk. Carpal tunnel syndrome usually occurs only in adults.

The risk of developing carpal tunnel syndrome is not confined to people in a single industry or job, but is especially common in those performing assembly line work - manufacturing, sewing, finishing, cleaning, and meat, poultry, or fish packing. 

In fact, carpal tunnel syndrome is three times more common among assemblers than among data-entry personnel. 

A 2001 study by the Mayo Clinic found heavy computer use (up to 7 hours a day) did not increase a person's risk of developing carpal tunnel syndrome. 

During 1998, an estimated three of every 10,000 workers lost time from work because of carpal tunnel syndrome. 

Half of these workers missed more than 10 days of work.

The average lifetime cost of carpal tunnel syndrome, including medical bills and lost time from work, is estimated to be about $30,000 for each injured worker.

How is carpal tunnel syndrome diagnosed?
Early diagnosis and treatment are important to avoid permanent damage to the median nerve. 

A physical examination of the hands, arms, shoulders, and neck can help determine if the patient's complaints are related to daily activities or to an underlying disorder, and can rule out other painful conditions that mimic carpal tunnel syndrome. 

The wrist is examined for tenderness, swelling, warmth, and discoloration. 

Each finger should be tested for sensation, and the muscles at the base of the hand should be examined for strength and signs of atrophy. 

Routine laboratory tests and X-rays can reveal diabetes, arthritis, and fractures. 

Physicians can use specific tests to try to produce the symptoms of carpal tunnel syndrome. 

In the Tinel test, the doctor taps on or presses on the median nerve in the patient's wrist.

The test is positive when tingling in the fingers or a resultant shock-like sensation occurs. 

The Phalen, or wrist-flexion, test involves having the patient hold his or her forearms upright by pointing the fingers down and pressing the backs of the hands together. 

The presence of carpal tunnel syndrome is suggested if one or more symptoms, such as tingling or increasing numbness, is felt in the fingers within 1 minute. 

Doctors may also ask patients to try to make a movement that brings on symptoms.

Often it is necessary to confirm the diagnosis by use of electrodiagnostic tests. In a nerve conduction study, electrodes are placed on the hand and wrist. Small electric shocks are applied and the speed

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