Median nerve dysfunction
Carpal tunnel syndrome is compression of the median nerve at the wrist, which may result in numbness, tingling, weakness, or muscle atrophy in the hand and fingers.
Causes, incidence, and risk factors
Carpal tunnel syndrome is common in people who perform repetitive motions of the hand and wrist, such as typing. When the wrist is poorly positioned, there isn’t enough space for the median nerve to travel to the hand.
Carpal tunnel syndrome is caused by pressure exerted 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 supplies movement to part of the hand.
The nerve enters the hand between the wrist bones (called the carpal bones) and the tough membrane that holds the bones together (the transverse carpal ligament). This space is called the carpal tunnel. Since the passageway is rigid, any swelling in this area can cause compression of the nerve (this is also called entrapment of the nerve).
The condition occurs most often in people 30 to 60 years old, and is five times more common in women than men. Some of the conditions associated with carpal tunnel syndrome include pregnancy, premenstrual syndrome (PMS), and menopause. This is probably because of hormone changes that cause fluid retention and swelling of the tissues.
Other conditions associated with carpal tunnel syndrome include rheumatoid arthritis, renal failure, diabetes, acromegaly, hypothyroidism, multiple myeloma, obesity, recent tuberculosis, fungal infection, and high blood pressure.
Injury or trauma to the area, including (but not limited to) repetitive movement of the wrists, 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.
- weakness in one or both hands
- 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
- wrist or hand pain in one or both hands
- pain extending to the elbow
- impaired fine finger movements (coordination) in one or both hands
- weak grip or difficulty carrying bags (a common complaint)
- atrophy of the muscular bulge under the thumb (in advanced or chronic cases)
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 (Tinel’s sign). Bending the wrist forward all the way (Phalen’s test) for 60 seconds will usually result in numbness, tingling, or weakness.
Electromyography and nerve conduction velocity may be performed, showing decreased conduction across the wrist. Wrist X-rays should be obtained to ensure that other problems (such as wrist arthritis) are not the cause of the patient’s pain.
The first line of treatment may be wearing night splints for the wrist for several weeks. If unsuccessful, the splints are worn during the day and heat or cold compresses may be added.
Modifications in the work area (particularly ensuring that the keyboard is low enough so that the wrists aren’t bent upward during typing), work duties, or recreational activities may be necessary. Some of the jobs associated with carpal tunnel syndrome include those that involve typing or use of vibrating tools; mining; and professional musicians.
There are many specialized devices designed to be used in the workplace to reduce the stress placed on the wrist and improve carpal tunnel syndrome and these should be used when possible.
Medications used in the treatment of carpal tunnel syndrome include anti-inflammatory analgesics (NSAIDs such as ibuprofen or naproxen). The carpal tunnel may also be injected with corticosteroids. This may provide dramatic relief of symptoms. (Note: It is the carpal tunnel space that is injected, not the nerve.)
Carpal tunnel release is a surgical procedure that cuts into the ligament to relieve pressure on the median nerve. Surgery is successful about 85% of the time, depending on the severity of the problem. Surgery reduces the pressure on the nerve, but the damaged nerve must heal for the symptoms to improve. This can take months and in severe cases the nerve may be incapable of fully healing.
In severe cases, electromyography or nerve conduction studies may be used to follow the recovery of the nerve.
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.
by David A. Scott, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.