Background Fibromyalgia (FM) may be considered part of a clinical continuum with chronic widespread pain, which is its cardinal symptom . These conditions are associated with abnormal nociceptive system processing, which is characterised by central sensitisation and signs of allodynia and hyperalgesia [2, 3]. Deficient endogenous pain inhibition has been implicated in the aetiology of FM , which may be measured by assessing conditioned pain modulation (CPM). Psychological factors such as pain catastrophising may also play a role in the heightened pain experience in FM. There is evidence that pain catastrophising may be associated with reduced CPM efficacy . However, it is not yet known whether the CPM dysfunction in FM occurs at a spinal or supraspinal level and if this is related to pain catastrophising.
Objectives The aims of the present study were to: (1) compare the function of the CPM response in healthy controls and individuals with chronic widespread pain; (2) to explore the relationship between pain catastrophizing and CPM efficacy; and (3) to examine the level of the nervous system where CPM dysfunction may occur in individuals with chronic widespread pain.
Methods Twenty-three people with chronic widespread pain (19 of which met the criteria for FM) and 22 age- and gender-matched healthy control participants took part. Pain beliefs and depression were assessed using the Pain Catastrophising Scale (PCS) and the Depression, Anxiety, and Stress Scale (DASS), respectively. CPM efficacy was assessed by comparing the nociceptive flexion reflex (NFR) area and pain ratings elicited by electrostimulation of the dominant foot (the test stimulus) before and during a cold pressor test applied to the contralateral hand (the conditioning stimulus).
Results The chronic widespread pain group had significantly higher scores in the PCS and DASS (P<0.05). In the chronic widespread pain group, test and conditioned reflex areas (P=0.06) and verbal pain ratings (P=0.09) were not significantly different. In contrast, the control group had a significantly smaller reflex area (P=0.001) and a lower verbal pain rating (P=0.02) during conditioning compared to the test stimulus alone. There were no significant correlations between catastrophising and CPM efficacy using either VAS or nociceptive NFR measures in either the widespread pain or control group (P>0.05).
Conclusions This study suggests that, compared to healthy controls, people with chronic widespread pain have a dysfunctional CPM response and therefore, impaired endogenous pain inhibition. However, there was no evidence of a relationship between pain catastrophising and CPM efficacy at either spinal or supraspinal levels.
Toda K. J Musculoskelet Pain. 2011;19:52–5.
Clauw D, et al. Mayo Clinic Proceedings. 2011;86:907–11.
Petersel D, et al. J Neurosci Res. 2011;89:29–34.
Julien N, et al. Pain. 2005;114:295–302.
Piché M, et al. Neuroscience. 2011;195:166–75.
Disclosure of Interest None declared