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In recent decades, repetitive stress injury (RSI) has become one of the most common workplace disabilities. The painful disorder of the hands or arms -- caused by doing the same tasks over and over -- costs billions of dollars each year in lost work time and medical expenses.
Scientists have long believed RSI arose from inflamed soft tissues pressing on nerves, resulting in pain. Treatments ranged from wearing braces to taking anti-inflammatory medicines to making ergonomic changes in posture. But new research from the University of California at San Francisco suggests this disorder is a learning "catastrophe" in certain neurons that can be best treated by basically retraining the brain.
BLURRED FEEDBACK. In research presented at the Society of Neuroscience's annual meeting in New Orleans the week of Nov. 6, Michael M. Merzenich found that "focal dystonia" of the hand, a frequently occurring form of RSI more commonly called writer's or musician's cramp, is caused by a degradation of the brain's motor control of the hand. The dysfunction is brought on by the repetitive use of fingers on a musical instrument or computer keyboard.
In both monkeys and humans, Merzenich found through brain scans that repetitive movements result in a blurring of the sensory-feedback information to the brain. The distorted information makes it difficult for the brain to control specific movements and fast-hand sequences.
Using this knowledge, a team of researchers at the University of Konstanz in Germany reported they were able to successfully treat 11 musicians with long-standing focal dystonia through the use of so-called constraint-induced movement therapy. Brain scans taken before therapy showed that the usually precise areas in the brain representing each finger overlapped or were smeared -- the probable cause of the cramping that's a hallmark of the painful condition.
NORMAL BRAIN SCANS. Using splints, the researchers immobilized one or more unaffected fingers on the dystonic hands of eight of the musicians. The other three musicians, the control group, received standard therapy. The researchers had the eight musicians do repetitive exercises with one or more of the affected fingers for one to two hours daily for eight consecutive days, under the guidance of a physical therapist. The musicians continued the exercises with the splint at home for one hour each day for a year and returned to their music practice in progressively longer sessions.
Although none of the musicians in the placebo group showed improvement, all the others had significant improvement in performance two years after the end of the treatment, the researchers said. And brain scans taken after therapy showed that representations of the fingers in the brain had normalized.
Scientists are currently debating the cause of a number of widely reported ailments without clear physiological sources, including irritable bowel syndrome and fibromyalgia, a painful condition characterized by joint inflammation, pain, and severe fatigue. These recent RSI findings could tip the medical profession further toward holding the human psyche liable for maladies that don't show up on CAT scans and X-rays. And aside from musicians, everyone from typists to journalists to tennis players might find future benefit in therapies aimed at brain cells rather than ligaments and muscles.
By Catherine Arnst in New Orleans Edited by Alex Salkever
Copyright 2000, by The McGraw-Hill Companies Inc. All rights reserved.
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