Sensory Function and Pain Experience in Arthritis, Complex Regional Pain Syndrome, Fibromyalgia Syndrome, and Pain-Free Volunteers: A Cross-Sectional Study.

OBJECTIVES: This study aimed to identify relationships between sensory function and pain in 3 common pain conditions (arthritis, Complex Regional Pain Syndrome [CRPS] and fibromyalgia syndrome [FMS]) and pain-free participants. Sensory abnormalities are known to be concomitant with some types of chronic pain but comparison across pain conditions using existing research is difficult due to methodological differences. Pragmatic Quantitative Sensory Testing (QST) methods were used.
MATERIALS AND METHODS: Hot and cold sensitivity, light touch threshold (LTT), two-point discrimination and pain threshold were assessed in 143 participants (n=37 pain-free, n=34 arthritis, n=36 CRPS, n=36 FMS). Outcomes were assessed in the index ("affected" or right) and contralateral arm. Participants also completed the Brief Pain Inventory and the McGill Pain Questionnaire.
RESULTS: There were statistically significant differences between groups for all QST outcomes except two-point discrimination. Relative to pain-free participants, FMS displayed heat hyperesthesia in both arms and cold hyperesthesia in the contralateral arm. CRPS demonstrated no changes in thermal sensitivity. Both CRPS and FMS exhibited bilateral pressure hyperalgesia. LTT hypoesthesia was observed bilaterally for CRPS but only in the contralateral arm for FMS. CRPS and FMS had pressure hyperalgesia in the index arm relative to arthritis patients. There were no differences between arthritis and pain-free participants for any QST outcome. In CRPS, there were significant correlations between LTT and pain outcomes bilaterally. DISCUSSION: People with FMS and CRPS demonstrate extensive sensory dysfunction. Arthritis patients had sensory profiles closer to pain-free participants. LTT may provide a clinically relevant and accessible assessment for CRPS.