Carpal Tunnel Syndrome

Carpal tunnel syndrome is a painful progressive condition caused by compression of a key nerve in the wrist. Women are more likely than men to develop the syndrome. The symptoms of carpal tunnel syndrome can be treated with rest and medications. Sometimes the syndrome resolves itself or symptoms are not severe enough to warrant further interventions. Serious cases however may require surgery.

Transverse section across the wrist and fingers, showing the median nerve. Source:Gray's Anatomy ^[1]

Other Names

Carpal tunnel syndrome is sometimes called median neuropathy at the wrist.

Symptoms

Symptoms of carpal tunnel syndrome (CTS) usually start with pain, numbness or tingling, often worse at night. Often patients fear they have carpal tunnel syndrome when they have pain or numbness to any area of the hand. However, the pain and numbness of CTS are confined to the sensory distribution of the median nerve; that is, the palmar surface of the hand over the thumb, index finger and the lateral half of the middle finger. The pain is often described as burning and many patients report some relief by "flicking" their hand (positive flick sign).

As symptoms worsen, people might develop symptoms during the day and difficulty manipulating or grasping small objects. At very advanced stages the thenar eminence of the hand (just proximal to the thumb) may atrophy.

Causes

Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm into the hand, becomes compressed or squeezed at the wrist or carpal tunnel. As pictured above, the median nerve travels through the carpal tunnel along with tendons to the fingers. Inflammation in the tendons may increase pressure in the carpal tunnel, compressing the median nerve. In some cases no direct cause of the syndrome can be identified. A number of hand surgeons believe that there is a congenital predisposition – the carpal tunnel is simply smaller in some people than in others.

The relationship between carpal tunnel syndrome and repetitive motions, such as typing on a keyboard or manipulation of objects on an assembly line, is controversial. However, these movements have repeatedly been shown to worsen symptoms. ^[2]

Trauma to the wrist or arm has also been linked to carpal tunnel syndrome. This trauma can include fractures, breaks, or deformities.

Less common causes of carpal tunnel syndrome include ganglion cyst within the carpal tunnel or aberrant muscle belly.

Some diseases have been linked to the development of the syndrome:

• hypothyroidism
• obesity
• diabetes
• arthritis

Diagnosis

A physical exam can often detect carpal tunnel syndrome. A Phalen's maneuver may be used: where the wrist is flexed and held in the position until symptoms appear. The syndrome is diagnosed if numbness occurs within one minute of bending the wrist. Other diagnostic test's include a Tinel's test where the wrist is tapped as well as Direct Compression over the carpal canal.

Nerve conduction velocity tests are also used to confirm carpal tunnel syndrome. These tests measure the ability of the median nerve to conduct electrical impulses over the wrist. The motor nerve conduction velocity test involves stimulation of the median nerve and measuring the response in a muscle. Both the time elapsed from stimulation to response and the degree of the response in the muscle are measured. In the sensory nerve conduction velocity test, the median nerve is electrically-stimulated and measurements are made at another part of the nerve, usually in the fingertip. Again, the time elapsed and degree of response are measured. Carpal tunnel syndrome can reduce response times and/or degree of response. ^[3]

Chances of Developing Carpal Tunnel Syndrome

The risk of developing carpal tunnel syndrome is especially common in those performing assembly line work. Carpal tunnel syndrome commonly develops when the computer keyboard is improperly placed or poorly located for use. A major reduction in carpal tunnel syndrome among computer users has occurred because there have been advancements in the field of human-computer interaction (HCI), the use of wrist guards and ergonomically designed keyboards.

Treatment

Initial treatment generally involves resting the affected hand and wrist for at least two weeks, avoiding activities that may worsen symptoms, and immobilizing the wrist in a splint to avoid further damage from twisting or bending. This is specially useful in an intermitent basis, at night, in the initial phase of sensory disturbances.

Medications

Non-steroidal anti-inflammatory drugs, such as aspirin, ibuprofen, and other nonprescription pain relievers, may ease pain. Cool (ice) packs and prednisone (taken by mouth) or lidocaine (injected directly into the wrist) can relieve swelling and pressure on the median nerve and provide immediate, temporary relief.

Surgery

Severe cases of carpal tunnel syndrome may require surgery. The syndrome is treated by a procedure called carpal tunnel release. Carpal Tunnel Release can be performed either via a direct incision over the transverse carpal ligament or with an endoscope. In both procedures, a surgeon cuts the transverse carpal ligament at the base of the palm. The transverse carpal ligament runs from the base of the thumb to the base of the fifth finger. The cut ligament no longer applies pressure to the median nerve and relieves the numbness and pain. ^[4]

Recurrence

Recurrence of carpal tunnel syndrome following treatment is rare. The majority of patients recover completely.

Prevention

To prevent workplace-related carpal tunnel syndrome, 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. For computer users, the placement of wrist guards or specially designed pads next to keyboards and ergonomically designed keyboards has prevented the development of carpal tunnel syndrome.

Research

The National Institute of Neurological Disorders and Stroke (NINDS) conducts research on nerve-related conditions such as carpal tunnel syndrome in its laboratories at the National Institutes of Health (NIH) and also supports research through grants to major medical institutions across the country.

Scientists are also investigating the use of alternative therapies, such as acupuncture, to prevent and treat this disorder.

Clinical Trials

Current studies include several randomized clinical trials to evaluate the effectiveness of educational interventions in reducing the incidence of carpal tunnel syndrome. Another clinical study is collecting data about carpal tunnel syndrome among construction apprentices to better understand specific work factors associated with the disorder and develop strategies to prevent its occurrence among construction and other workers.

References

1. ↑ http://www.bartleby.com/107/126.html
2. ↑ Silverstein, Fein and Armstrong; "Occupational factors and carpal tunnel syndrome" American Journal of Industrial Medicine, Volume 11 Issue 3, Pages 343 - 358 Published Online: 11 Jan 2007 Abstract
3. ↑ Jablecki et al, "Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. AAEM Quality Assurance Committee." Muscle Nerve. 1994 Dec;17(12):1490-1. Abstract
4. ↑ Agee et al; "Endoscopic release of the carpal tunnel: a randomized prospective multicenter study." J Hand Surg [Am]. 1992 Nov;17(6):987-95. Abstract