July 20, 1999

Common but Confusing: Workers' Wrist Ailments

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By ERIC NAGOURNEY

any people feel alarmed when they begin to experience numbness and tingling in their hands and wrists, assuming that they must have carpal tunnel syndrome, the sometimes disabling nerve disorder. Now a new study -- the most comprehensive to date -- finds that they are often wrong, although the disease is more prevalent than had been expected.

	The New York Times

As many as 1 in 5 people with these symptoms -- characteristic of the family of diseases known as repetitive strain injury -- have the syndrome, in which a nerve becomes pinched in the wrist, the researchers found. An estimated 200,000 people in the United States have surgery each year to repair the condition, often paid for by workers' compensation programs.

But while the study, published in the current issue of The Journal of the American Medical Association, won praise for its scope and the precision with which it documented the prevalence of the disease, some experts said it only underscored basic disagreement among health professionals over how to diagnose carpal tunnel syndrome and even how to define it.

"This is a condition which appears to be very common and exacts a considerable toll and morbidity on a large number of people," said Dr. Alfred Franzblau, a public health specialist at the University of Michigan. Yet, he said, "We don't have well-defined criteria for who should get surgery."

The study was conducted by Swedish researchers who began by sending questionnaires to 3,000 people randomly selected in southern Sweden. The people were asked a range of questions about their health, including whether they were experiencing the classic symptoms of carpal tunnel syndrome: pain, numbness, or tingling in two or more fingers. These symptoms often occur during sleep.

About 80 percent of those surveyed replied, a rate considered extraordinary by researchers in other parts of the world. Of those responding, almost 15 percent, or 354 people, reported having the symptoms. When researchers examined that group, they found they could document carpal tunnel syndrome in as many as 3.8 percent of the people and nerve damage in about 5 percent. Although researchers looked for a link with other medical conditions, only people with weight problems appeared to be at greater risk.

People suffering from symptoms similar to those of carpal tunnel syndrome may actually have other R.S.I. conditions, like tendinitis.

The lead author of the study, Dr. Isam Atroshi, said in a telephone interview that researchers had not expected the prevalence of the disease to be so high. "I was surprised," he said.

Carpal tunnel syndrome is often found in people who perform repetitive tasks that put a strain on the tendons of the wrist. It is common among meat packers and people who use computers a great deal. It can often be prevented by taking frequent breaks to stretch and by making sure that the work station puts minimal strain on the wrists.

A person develops the syndrome when the tendons of the wrist become swollen from overuse, trapping the median nerve that carries signals to the hand. Left untreated, serious nerve damage can occur. In many cases, splints and medications can ease the problem, but when this does not work, surgeons slice open the sheath through which the nerve and tendons run, freeing the pressure on the nerve.

Vast disagreement over diagnosing and defining carpal tunnel syndrome.

Although some experts not associated with the study praised the research, saying that it helped to document the prevalence of the problem, it also highlighted the level of uncertainty about carpal tunnel syndrome even among the doctors who treat the problem.

"One would expect there to be a strong empirical foundation to explain the pathophysiology and natural history of the syndrome and to support clear diagnostic criteria," Dr. Franzblau wrote in an editorial in the medical journal. "Surprisingly, this is not the case."

In examining their subjects to see which ones had carpal tunnel syndrome, the Swedish researchers used several methods, with each yielding different results.

They first made diagnoses based on clinical examinations in which the subjects were asked to describe their symptoms and were checked for signs like sensitivity and muscle strength.

The subjects were then given nerve conduction tests in which technicians administered small jolts of electricity and measured how quickly the jolts traveled along the nerves. If the electricity moves too slowly, it can be a sign of carpal tunnel syndrome.

But the researchers found that some patients who showed nerve damage in the conduction tests experienced no symptoms, while some of those diagnosed clinically with carpal tunnel syndrome exhibited no nerve damage.

Dr. Atroshi said there was nothing unusual about the difficulty involved in defining carpal tunnel syndrome, saying that similar issues have surfaced with other diseases.

In the absence of clear-cut diagnostic tools, many physicians are taking different paths when treating patients who may have carpal tunnel syndrome.

Dr. Barry P. Simmons, chief of hand surgery at Brigham and Women's Hospital in Boston, said that most of the time he did not order conductivity tests, relying instead on a clinical examination. Even if a conductivity test suggested nerve damage, he said, he would not operate if the patient was symptom-free. And for those patients experiencing symptoms, he said, the evidence is usually clear enough without other tests.

"As a clinician," he said, "my concern is, what are the patient's symptoms?"