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Central nociceptive hyperexcitability may be important in fibromyalgia (FM), according to the results of a study published in the May issue of Arthritis & Rheumatism. The nociceptive flexion reflex may be helpful in discriminating which patients would benefit from central analgesia.

"Our results strongly, although indirectly, point to a state of central hyperexcitability of the body's central pain system in patients with FM," lead author J. A. Desmeules, M.D., from Geneva University Hospital in Switzerland, says in a news release.

Of 85 outpatients with FM attending a self-management program, 89% were women, all were middle-aged, and mean disease duration was eight years.

Compared with 40 healthy controls matched for age and sex, peripheral quantitative sensory testing in FM patients showed significantly altered cold and heat pain thresholds, with tolerance to cold pain 66% lower. Threshold for the spinal nociceptive flexion reflex was 50% lower than in controls.

Using a cutoff value of less than 27.6 mA for nociceptive flexion reflex, sensitivity was 73% and specificity was 80% for detecting central allodynia.

According to Dr. Desmeules, these findings suggest the benefits of treating FM with analgesics acting on the central nervous system. Antidepressants have been shown to reduce the pain sensitivity reflex of healthy volunteers after a single dose.

"The nociceptive flexion reflex can be used to assess central allodynia in patients with FM," the authors write, while recommending additional research. "It may also help discriminate patients who may benefit from use of centrally acting analgesics."

Study Reference: Arthritis Rheum. 2003;48:1420-1429

Reviewed for WebMD by Gary D. Vogin, M.D.