One day last November, Abner Bevin awoke at 4 A.M. with an unpleasant tingling sensation and numbness in his right hand. Most people probably would have taken an aspirin and shrugged off the incident. But Bevin, a hand surgeon, instantly recognized it as an early warning sign of an ailment that increasingly affects workers today: carpal tunnel syndrome. A hand and wrist disorder that may bring debilitating pain and weakness of the thumb and fingers, carpal tunnel syndrome, or CTS, is the most common of all injuries that result from jobs requiring repetitive motion, ranging from tapping on a computer keyboard to plucking out gizzards at a meat-processing conveyor belt. According to a recent U.S. Department of Labor study, such repetitive motion injuries are soaring, from just 18 percent of all workplace maladies in 1981 to 48 percent in 1988.

As director of the Hand Rehabilitation Center at the University of North Carolina in Chapel Hill, Bevin, 54, has performed hundreds of operations for CTS in his 25-year career. Yet he blames his CTS on his avocations. Married to a homemaker, and the father of five grown children, Bevin spends his off-hours restoring furniture, tinkering with his '56 Thunderbird and moving logs in the woods around his rural home near Chapel Hill. "I do all the things that are wrong for someone who has carpal tunnel syndrome, "he admits. Bevin talked about this growing workplace hazard with correspondent Teresa Riordan.

Why is carpal tunnel syndrome so prevalent?

Advanced technology is partly to blame. New machines divide jobs into ever smaller tasks, so workers make fewer motions more frequently. Meat-packing and food-processing industries, for example, have "de-skilled" assembly lines. Butchers used to carve whole carcasses, using many different knife strokes in the course of a day. Today, the butchering is done on a high-speed conveyor system where workers make only one type of cut as many as 8,000 times a day.

Who is most at risk?

Anyone who uses his hands vigorously in the same way for prolonged periods of time. This includes mail sorters, supermarket checkout clerks, hairdressers, autoworkers, gardeners and musicians, especially pianists, violinists and drummers. At the Los Angeles Times, almost a fifth of the editorial employees have sought medical help for CTS-like symptoms.

How do computers create problems?

Today's keyboards enable secretaries to type 40 percent faster than they could on typewriters. According to one estimate, word processors can make up to 23,000 key strokes a day. And there are fewer moments of respite—waiting for the carriage return, for example. The technological revolution has outpaced human evolution, it seems. We are not biologically equipped to perform thousands of repetitive motions an hour.

Why does repetition lead to CTS?

Carpal comes from the Latin carpus, which means the wrist. Tunnel refers to the rigid space that runs through the wrist, which is bound by bone and ligament. This tunnel contains the median nerve and eight flexor tendons. Repetitive motion can cause the sheaths of these tendons to become irritated and swollen, putting pressure on the nerve.

Is repetitive motion the only cause of CTS?

No. It can be triggered by a host of disorders—thyroid problems, rheumatoid arthritis, gout, diabetes, a blow to the wrist or a sprain, anything causing an increase of swelling in the tunnel or a decrease of circulation in the median nerve.

What are the symptoms?

The chief one is numbness—some describe it as tingling or burning—usually over the thumb, index finger, long finger and half of the ring finger. Some feel discomfort radiating upward from the wrist to their shoulders. For reasons no one understands, these symptoms frequently come on in the middle of the night. Patients have to get up and shake their hand until the numbness goes away. Their hands may also feel stiff in the morning.

That doesn't sound so serious. Is it?

The pins-and-needles sensation can be very uncomfortable. The hand can feel weak, and dexterity may be reduced, making it harder to unscrew bottle caps or hold a coffeepot. CTS can also be very dangerous. Of all your pressure-sensitive nerve endings, 25 percent are in your fingertips. If you can't feel what you're touching, for instance hot objects, that's serious. If your job happens to be cutting up animal carcasses and you can't feel the difference between the handle and the blade of your knife, you're in trouble.

How is CTS treated?

The first step is to go see your personal physician. Waiting too long may result in permanent nerve damage. The initial treatment is a hand splint, which, if it works correctly, immobilizes the wrist and limits finger motion, minimizing pressure on the nerve. Often patients are given aspirin or anti-inflammatory drugs like ibuprofen. If there is a great deal of swelling, steroids might be injected to reduce it. Unfortunately, according to a I recent study of meat-packing employees, treatments like those worked only as long as the patients stayed away from work.

Most people can't do that for long. What is their recourse?

Surgery in which the transverse carpal ligament is divided to relieve pressure on the median nerve. In some cases the swollen tendon sheaths are removed. Depending on the patient's job, he can return to work in three to six weeks. I'm not about to say that every patient with the slightest symptom should have an operation. But when we can clearly demonstrate that there is a nerve conduction problem in the wrist, I believe that 95 to 97 percent of patients improve from surgery even after returning to work. Surgery is not a complicated procedure, but it's important that it be done only by a surgeon who specializes in hand surgery.

Can CTS be prevented?

Occupational therapists suggest avoiding using the wrist in a bent or twisted position for long periods, and the whole hand, not just the thumb and forefinger, should be used to grasp objects. For those who work at a computer, palms should be kept up off the keyboard. But ergonomics—adapting the workplace to the worker—is probably our best bet. Ergonomists have designed knives with bent handles so poultry workers don't have to bend their hands to cut apart chickens. Some office workers simply need to be trained how to sit correctly. Or the height of desks and chairs may need to be altered.

What role has the government played?

Health and labor agencies seem to be paying more attention to repetitive-motion traumas. Under pressure from the Labor Department, Chrysler announced in November its plans to study assembly line jobs for ways to reduce injury. In 1988 John Morrell & Co., one of the country's largest meat packers, was fined $4.3 million for conditions in its South Dakota plant. Recently the company signed an agreement with the Occupational Safety and Health Administration that calls for, among other things, the hiring of a noted neurologist to oversee medical treatment at the plant and a study of all jobs by an expert in ergonomics. These are all important steps.