Carpal tunnel syndrome is compression of the median nerve at the wrist, which may result in numbness, tingling, weakness, or muscle damage in the hand and fingers.
Median nerve dysfunction
Causes, incidence, and risk factors:
Carpal tunnel syndrome is caused by pressure on the median nerve at the point where it passes through the wrist. The median nerve supplies sensation to the thumb side of the palm, and to the thumb, index finger, middle finger, and the thumb side of the ring finger. It also helps with movement to part of the hand.
The area where the nerve enters the hand is called the carpal tunnel. Since the passageway is stiff, any swelling in this area can put pressure on the nerve. This may also be called entrapment of the nerve.
Injury to the wrist area can cause swelling of the tissues and carpal tunnel syndrome. This type of injury may be caused by sports such as racquetball and handball, or occur during sewing, typing, driving, assembly-line work, painting, writing, use of tools (especially hand tools or tools that vibrate), or similar activities.
Carpal tunnel syndrome is common in people who perform repetitive motions of the hand and wrist, such as typing. The condition occurs most often in people 30 to 60 years old, and is more common in women than men.
Some of the conditions associated with carpal tunnel syndrome include:
- Numbness or tingling in the thumb and next two or three fingers of one or both hands
- Numbness or tingling of the palm of the hand
- Pain extending to the elbow
- Pain in wrist or hand in one or both hands
- Problems with fine finger movements (coordination) in one or both hands
- Wasting away of the muscle under the thumb (in advanced or long-term cases)
- Weak grip or difficulty carrying bags (a common complaint)
- Weakness in one or both hands
Signs and tests:
During a physical examination, the doctor may identify numbness in the palm, thumb, index finger, middle finger, and thumb side of the ring finger. Hand grip may be weak.
Tapping over the median nerve at the wrist may cause pain to shoot from the wrist to the hand. This is called Tinel's sign. Bending the wrist forward all the way for 60 seconds will usually result in numbness, tingling, or weakness. This is called Phalen's test.
Electromyography and nerve conduction velocity will show decreased conduction across the wrist. Wrist x-rays should be done to rule out other problems (such as wrist arthritis).
The first line of treatment often involves a splint to stabilize the wrist. The splint is worn at night for several weeks. If this does not help, you may need to wear the splint during the day. Hot and cold compresses may also be recommended.
There are many ergonomic devices that can be used in the workplace to reduce the stress placed on the wrist. These include special keyboards, cushioned mouse pads, and keyboard drawers. Make sure the keyboard is low enough so that the wrists aren't bent upward during typing. You may also need to make changes in your work duties or recreational activities. Some of the jobs associated with carpal tunnel syndrome include those that involve typing and vibrating tools. Carpal tunnel syndrome has also been linked to professional musicians.
Medications used in the treatment of carpal tunnel syndrome include nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen. Corticosteroid injections, given into the carpal tunnel area, may provide relief of symptoms.
Carpal tunnel release is a surgical procedure that cuts into the ligament that is pressing on the nerve. Surgery is successful most of the time, but depends on severity and duration of nerve compression.
After surgery, the damaged nerve must heal for the symptoms to improve. This can take months. In severe cases, the nerve may not be able to fully heal. Certain types of damage (such as muscular atrophy) may not be reversible.
In severe cases, electromyography or nerve conduction studies may be used to check how well the nerve is recovering.
Symptoms often improve with treatment, but more than 50% of cases eventually require surgery. Surgery is often successful, but full healing can take months.
If the condition is treated properly, there are usually no complications. If untreated, the nerve can be damaged, causing permanent weakness, numbness, and tingling.
Calling your health care provider:
Call for an appointment with your health care provider if you have symptoms of carpal tunnel syndrome.
Call your health care provider if symptoms of carpal tunnel syndrome do not respond to treatment, or if there seems to be a loss of muscle mass in the fingers.
Avoid or reduce the number of repetitive wrist movements whenever possible. Use tools and equipment that are properly designed to reduce the risk of wrist injury.
Ergonomic aids, such as split keyboards, keyboard trays, typing pads, and wrist braces, may be used to improve wrist posture during typing. Take frequent breaks when typing and always stop if there is tingling or pain.
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Piazzini DB, Aprile I, Ferrara PE, et al. A systematic review of conservative treatment of carpal tunnel syndrome. Clin Rehabil. 2007;21(4):299-314.