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Reuters Tuesday July 21, 1998 News Bulletin -- RSD Successfully Treated with Ritalin

Tuesday July 21, 1998   1:17 PM EDT

Tissue changes linked to pain disorder

NEW YORK, Jul 21 (Reuters) -- Researchers have found evidence of damage to muscle cells and small blood vessels in patients with a rare and painful disorder called reflex sympathetic dystrophy (RSD).

"The study shows that there is indeed a real, objective abnormality in some of these patients, and the disorder is not primarily psychological, as some physicians may think," said Dr. Michael Rowbotham of the University of California, San Francisco.

His commentary, along with the results of a study by researchers at the University Hospital Nijmegen in Nijmegen, the Netherlands, is published in the July issue of the journal Neurology.

In RSD, patients recovering from injury or surgery begin to complain of a localized, chronic pain well out of proportion to the extent of the injury itself. The pain can affect any part of the body, but is most commonly found in a limb. The pain can be severe in nature, and often does not respond to traditional analgesics.

Until recently, most experts have speculated that RSD is caused by the nervous system's inability to "switch off" an exaggerated pain response to an otherwise innocuous injury.

However, new research points to other possible causes of the disease.

The Dutch investigators describe how they conducted detailed examinations of nerve and muscle tissues taken from the amputated legs of eight RSD patients.

Contrary to what might have been expected, nerve cells taken from these legs "showed no consistent abnormalities" the authors report.

However, their examination of muscle tissue revealed a variety of serious abnormalities. These abnormalities seem to "point to a microangiopathy" -- a disorder of the small blood vessels that supply oxygen to muscle cells. The authors note that, in RSD-affected limbs, "(cellular) oxygen consumption is diminished as compared to the other (arm or leg)."

In his accompanying commentary, Rowbotham points out that the Dutch findings still do not explain "the weakness, tremor... and severe pain that often accompanies" RSD. But he believes that the results will help counter arguments that the condition "may be dismissed as being of psychological origin."

In another related study, Dr. Gary Mellick of the American Pain Specialist and American Sleep Disorders Center in Elyria, Ohio, and Dr. Larry Mellick of the Medical College of Georgia, Augusta, report that treatment with Ritalin (a drug usually prescribed to treat attention-deficit/hyperactivity disorder) has effectively ended the RSD symptoms of one 46-year-old patient.

The patient had developed severe RSD after knee replacement surgery. Her RSD-related discomfort had proven unresponsive to a number of medications, and "she complained that she could not touch the left knee without provoking intense pain," the researchers explained.

However, "within 20 minutes of taking (Ritalin)... she reported the onset of complete pain relief in her left knee and leg," the authors say. Furthermore, they report that the woman "has remained pain-free for the past 2 years."

The two investigators, who published their findings in the current issue of the American Journal of Pain Management, say the exact mechanisms behind the woman's recovery remain "unknown." They believe, however, that more extensive, placebo-controlled trials are necessary to determine if her positive outcome can be duplicated in other RSD sufferers.

SOURCES: Neurology 1998;51:4-5, 20-25, American Journal of Pain Management 1998;8:78-82.

 

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