Individuals with complex regional pain syndrome (CRPS) and fibromyalgia may have extensive sensory dysfunction, including heat and cold hypoesthesia and pressure hyperalgesia, according to a study published in the Clinical Journal of Pain.
Patients with CRPS (n=36), fibromyalgia (n=36), arthritis (n=34), and healthy controls (n=37) were recruited and underwent hot and cold sensitivity, light touch threshold, 2-point discrimination, and pressure pain threshold assessments. Pragmatic quantitative sensory testing was conducted on both arms. The outcomes of these tests were assessed in the index arm (“affected” or right arm) and contralateral arm. Researchers also assessed participant responses to the Brief Pain Inventory and McGill Pain Questionnaire.
Patients with fibromyalgia were found to be more likely to have heat hyperesthesia in the index arm (P =.001) and contralateral arm (P =.005) as well as cold hyperesthesia in the contralateral arm (P =.004) than healthy participants. No changes in thermal sensitivity were detected in participants with CRPS, but this patient population, as well as patients with FMS had significant differences in pressure pain thresholds in the index and contralateral arm compared with patients with arthritis and healthy controls (P <.001 for both).
The light touch threshold values in the index and contralateral arms were higher in patients with CRPS and those with CRPS and fibromyalgia, respectively, compared with healthy controls (index arm: P =.002; contralateral arm: P =.004 for both). No differences were observed between healthy participants and patients with arthritis for any quantitative sensory testing outcome. In patients with CRPS, correlations were found between pain intensity and light touch threshold in the index arm (P <.001) and contralateral arm (P =.001) as well as pain intensity and pain interference in the index arm (P =.003) and the contralateral arm (P =.027).
Study limitations include small sample sizes and the use of a thermal sensation and pain numeric rating scale that have not been previously validated.
”[Light touch thresholds] were found to correlate with patient-reported outcome measures in CRPS and may therefore provide a clinically relevant and accessible assessment for CRPS,” noted the study authors.
Palmer S, Bailey J, Brown C, Jones A, McCabe CS. Sensory function and pain experience in arthritis, complex regional pain syndrome, fibromyalgia syndrome and healthy volunteers: a cross-sectional study [published online August 12, 2019]. Clin J Pain. doi:10.1097/AJP.0000000000000751