MULTIMETHOD ASSESSMENT OF EXPERIMENTAL AND CLINICAL PAIN IN PATIENTS WITH FIBROMYALGIA

Experimental measures of responsiveness to painful and non-painful stimuli as well as measures of typical and present clinical pain were assessed in 26 female patients with fibromyalgia and in an equal number of age-matched healthy women. Pressure pain thresholds, determined by means of a dolorimeter, were lower in the patients compared to the control subjects both at a tender point (trapezius) and at a non-tender control point (inner forearm). The same was true for the heat pain thresholds, measured using a contact thermode. In contrast, the pain thresholds for electrocutaneous stimuli were decreased only at the tender point. The detection thresholds for non-painful stimuli (warmth, cold and electrical stimuli) seemed to be less affected in the fibromyalgia patients, with only the detection threshold for cold being lower at both sites. Tender points were more sensitive than control points for mechanical pressure. The reverse was found for the other modalities which were tested. Although the 3 experimental pain thresholds showed patterns of either generalized or site-specific pain hyperresponsiveness, the between-methods correlations were not very high. While the correlations between the experimental pain thresholds and the various measures of clinical pain (Localized Pain Rating, McGill Pain Questionnaire) in the patients were generally low, there were significant negative correlations between pressure pain thresholds at the two sites and the level of present pain assessed by the Localized Pain Rating. We conclude that a pattern of pain hyperresponsiveness, generalized across the site of noxious stimulation and across the physical nature of the stressor, is associated with fibromyalgia. The pattern of hyperresponsiveness appears to involve both peripheral factors (e.g., sensitization of muscle nociceptors) and central ones (e.g., hypervigilance or a lack of nociceptive inhibition).