They can cause stiffness, swelling, tingling, weakness, numbness, and, in some cases, irreversible nerve damage. Carpal tunnel syndrome is the most frequently reported RSI, with 192 cases per 100,000 workers in 1989, according to the U.S. Public Health Service. It occurs when tissues on the palm side of the hand swell, compressing or entrapping the important median nerve, which runs through this area. Numbness and tingling usually start in the wrist, and can radiate down to the thumb and fingers, or up to the elbow. Many patients feel pins and needles when their wrist is tapped.
Weakness occurs on effort.
For example, patients may suddenly drop objects they are holding. A nerve conduction test, a recording of the electrical activity of the hand and arm muscles, is helpful in diagnosing this disorder. When nerve entrapment and the pressure caused by it occurs over a long period, the nerve can become irritated and go into spasms, stimulating muscle activity that eventually causes pain similar to severe muscle cramps. When finger tendons, fibrous bands of tissue that connect muscle to bone, get irritated, they can grow nodules, which, at the points of attachment, get caught in the lubricating sheath that surrounds them. RSIs are self-limiting conditions that result from excessive use of the muscles and tendons of the hands, wrists and forearms.