The carpal tunnel is a narrow passage in the wrist, surrounded by bones and ligaments, through which the tendons of the thumb and fingers, as well as the median nerve pass. The median nerve controls sensations to the index, middle and ring fingers and the thumb. Carpal tunnel syndrome (CTS) is a painful, progressive peripheral neuropathy, caused by compression of the median nerve, due to narrowing of the carpal tunnel. This compression is usually due to thickening from irritated tendons or ligaments. The symptoms of this condition start slowly, and may initially involve tingling, burning, or numbing sensations in the palm and fingers, usually at night, or upon waking. As the disease develops further, the tingling feeling remains throughout the day, and other symptoms including decreased grip strength, difficulty in performing manual tasks involving the hand, severe weakness in the thumb, and even muscle wasting in severe cases can be seen. Apart from genetic causes, CTS may also develop due to trauma or injury to the wrist, overwork of the hand, fluid retention due to hormonal changes, or due to an underlying cause such as hypothyroidism, rheumatoid arthritis, or diabetes. Incidentally, the condition affects women three times more often than men, and the dominant hand is the one that is affected first.
To diagnose CTS are the Tinel test, which involves tapping the patient's wrist on the median nerve, and the Phalen test or wrist-flexion test are used. A sudden, sharp, shooting pain or tingling in the fingers and thumb during this test points towards a diagnosis of CTS. For confirmation, physicians may ask for results of nerve conduction study tests, or electromyography. In most cases, treatment concentrates on wearing a splint to protect the wrist, and/or administering non-steroidal anti-inflammatory drugs, or corticosteroids. However, if CTS is evinced due to an underlying physiological cause like diabetes or arthritis, then it is important to treat that cause first. In some cases, surgery may be opted for, which involves removing the ligament that presses on the median nerve. Surgery may be performed endoscopically.
Previously, it was thought that CTS is an occupational hazard, brought about by overworking the hand. However, it is now getting clearer that CTS has a profound genetic element. Especially CTS developing in young people have been shown by studies to have a genetic influence. Some people, by birth, have a narrow carpel tunnel. Unfortunately, the exact genes involved have not yet been discovered. Some studies have implicated defects in a collagen subtype, making the wrist ligament unusually stiff. Similarly, some other studies have pointed towards abnormalities in myelin regulation.