sWhat is Carpal Tunnel Syndrome?
Carpal Tunnel Syndrome (CTS) refers to the compression of the median nerve at the wrist in a structure called the carpal tunnel. The median nerve carries sensation from the palmar surface of the thumb and fingers (except the little finger). It also controls the muscles that move the thumb. The carpal tunnel is formed by wrist bones and a ligament called flexor retinaculum that runs across the wrist. This “tunnel” is a narrow passageway for the median nerve as well as the many tendons that control finger movements. Swelling or thickening of any of the structures in or around the carpal tunnel may compress the median nerve, leading to pain, numbness and weakness of the hand and thumb.
The symptoms are often gradual in onset and often more severe in the dominant hand, presumably because it is used more often. Intermittent numbness or tingling is felt on the thumb, index, middle and ring fingers. This commonly occurs at night during sleep and improves by “shaking it off”. Occasionally, the whole hand may feel as if it has “fallen asleep” or is “swollen”.
Symptoms can occur when holding objects, driving or reading. Patients also complain of intermittent weakness of the grip. In some individuals, the compression of the median nerve may worsen with time, resulting in permanent weakness and wasting of the thumb muscles.
Causes and Risk Factors
Many factors act to increase the pressure on the median nerve and tendons in the carpal tunnel. Some people may be born with narrower carpal tunnels, predisposing them to develop CTS. It is three times more common in women. Repetitive wrist movement, e.g. flexing of the wrist when using a computer mouse, may aggravate CTS. People with diabetes, obesity, hypothyroidism, rheumatoid arthritis and injury to the wrist are more likely to develop CTS. It is also more common in pregnant women.
CTS can be confirmed by nerve conduction tests. It involves giving very small electric shocks to the median nerve and recording its electrical signals across the wrist. The test usually takes about half an hour. It is a safe procedure that does not require any sedation or anaesthesia.
Most patients with mild to moderate CTS can be treated without surgery. Wearing a splint that keeps the wrist in a neutral position during sleep is recommended. Losing weight and repetitive movements of the hand and wrist (e.g. prolonged typing, knitting, SMS-ing or writing short messages on the handphone) should be avoided. Steroid injection into the carpal tunnel provides immediate but temporary relief in some people.
If the symptoms are severe or if there is significant nerve damage, surgical decompression should be considered. This involves cutting the flexor retinaculum and increasing the space in the carpal tunnel. This is a simple, effective, outpatient procedure that is performed under local anaesthesia. Complications of surgery are uncommon and include wound infection, nerve damage, stiffness and a painful scar. Most patients report improvement of symptoms after surgery.
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