Evidence of qualitatively altered nociception in patients with fibromyalgia

OBJECTIVE: To investigate the perception of pain in tender muscles of patients with fibromyalgia.

METHODS: Twenty-five women with fibromyalgia and 25 healthy women were examined. Seven different pressure intensities were used to palpate a highly tender muscle and a largely normal muscle. Subjects then recorded their response to induced pain on a visual analog scale. The examiner was blinded to each subject's response.

RESULTS: The stimulus-response function for pressure versus pain recorded for normal muscle was well described by a power function. For highly tender muscle, the stimulus-response function was displaced toward lower pressures and, more importantly, it was linear, i.e., qualitatively different from that of normal muscle.

CONCLUSION: This study demonstrates that nociception is qualitatively altered in patients with fibromyalgia, which is consistent with recent findings in other patients with tender muscles. The data strongly indicate that fibromyalgic pain, at least in part, is due to aberrant central pain mechanisms.