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carpal tunnel syndrome

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Median nerve

Alternative Names
median nerve compression or entrapment

Carpal tunnel syndrome (CTS) refers to numbness, tingling, weakness, and discomfort in the wrist and hand. It is caused by compression of the median nerve at the wrist.

What is going on in the body?
A ligament and the bones at the base of the palm of the hand, just beyond the wrist, form the carpal tunnel. Through this tunnel passes the median nerve and tendons going to the fingers and thumb. The median nerve conducts sensation from the palm side of the thumb and fingers, except for the little finger. It also carries impulses to small muscles in the hand, particularly at the palm side of the base of the thumb. If the pressure in the carpal tunnel increases enough, the median nerve is compressed. The result is abnormal sensations and weakness.

What are the signs and symptoms of the condition?
CTS usually starts gradually, with a vague aching in the wrist, extending into the hand or forearm. Acute onset occurs when the compression of the nerve happens suddenly. This sudden onset is more likely to cause pain. The numbness and tingling is felt in the thumb, index finger, long finger, and half of the ring finger on the palm side. Often a person will wake up at night with pain or numbness, needing to shake or massage the wrist in order to "improve the circulation." Similar symptoms can occur during the day, particularly when performing repetitive activities with the wrist bent. Eventually the nerve trouble can result in weakness of the thumb muscles, and a tendency to drop things.

What are the causes and risks of the condition?
CTS can be caused by anything that increases pressure on the nerve in the carpal tunnel. The cause is often swelling due to repetitive motion or overuse of the wrist and fingers, called repetitive strain injury syndrome. Diseases such as diabetes, rheumatoid arthritis, hypothyroidism, and sarcoidosis can also cause increased pressure on the nerve. Other causes include having a cyst on the tendon, and using birth control pills. Pregnant women often have CTS that disappears several months after delivery.

What can be done to prevent the condition?
Overuse of the wrist and fingers should be avoided. Other underlying causes should be treated. Computer workstations should be designed so that the wrists are well supported.

How is the condition diagnosed?
CTS is diagnosed based on a combination of symptoms and physical signs. Often electrical testing of the median nerve is performed. These tests and studies of nerve conduction are done by a neurologist and show abnormalities in 95% of people with CTS.

Tinel's sign is positive for CTS when tapping on the wrist causes tingling of the fingers affected by the median nerve. Phalen's test involves holding the wrist bent or extended as far as it will go. If numbness or aching results within 45 seconds, the test is positive for CTS. Another test consists of placing a thumb over the carpal tunnel for 30 seconds. Discomfort or tingling in the fingers indicate CTS.

Later in the course of CTS, the muscles at the base of the thumb may become smaller, or atrophy. The thenar muscles, which allow touching of the thumb to the little fingertip, may also weaken. X-rays are usually normal, except when the pressure is caused by arthritis of the wrist or hand, or a broken or dislocated bone.

What are the long-term effects of the condition?
Progressive or permanent numbness and weakness in the hand are possible long-term effects.

What are the treatments for the condition?
Underlying diseases, such as diabetes, underactive thyroid, and rheumatoid arthritis should be treated. Weight loss or reduced salt intake may be helpful.

Repetitive use of the hand with the wrist bent must be avoided. Frequent changes of activity, with breaks for 5 minutes every hour, can help prevent overuse. Certain exercises can be done to increase flexibility in the wrist and fingers. People with CTS should not sleep on their hands. It is very important to sit properly at the computer, with good support for the wrists. Yoga-based exercises may be effective.

For mild cases, the first treatment is to splint the wrist at night, and during the day if possible. Non-steroidal anti-inflammatory drugs (NSAIDs), can be used for a short time although they are minimally effective for this condition. If these do not help, a corticosteroid can be injected into the carpal tunnel. This may help permanently or only temporarily. Surgery, called carpal tunnel release, is reserved for people with unrelieved pain, atrophy and decreased sensation. This surgery is usually considered when the symptoms are no better after several months of treatment.

What are the side effects of the treatments?
NSAIDs can effect the stomach, kidneys, blood, or liver. Injecting corticosteroids rarely can accidentally injure the nerve. Surgical complications can include injury to the nerve or its branches, infection, and stiffness of the wrist or fingers.

What happens after treatment for the condition?
After the surgery, the wrist is immobilised for a short time. Exercises help to regain mobility of the wrist and fingers. It is important to practice proper use of the wrist.

How is the condition monitored?
People with CTS are monitored for the recurrence of symptoms, or pressure on other nerves affecting the arm, such as can occur with neck arthritis or a lumbar disc problem.

Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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