Less Efficacious Conditioned Pain Modulation and Sensory Hypersensitivity in Chronic Whiplash-associated Disorders in Singapore

Abstract

OBJECTIVES: Cultural differences in pain perception exist. Although chronic whiplash-associated disorder (WAD) is well investigated in western countries, little is known about its presentation in Singapore. We studied the neck motion and pain sensitivity in people with chronic WAD in Singapore. MATERIALS AND METHODS: Thirty chronic WAD participants (>3 mo, Neck Disability Index: 40% [SD 17%]) were age, sex, and ethnicity matched with 30 pain-free controls. All 60 participants underwent the following tests: active neck motion, pain thresholds (pressure, brachial plexus provocation test [BPPT], cold), cold pain tolerance, and conditioned pain modulation (CPM). The test stimulus of contact heat and conditioning stimulus of cold water immersion was used to assess CPM. Data were evaluated to determine differences between WAD and control groups. RESULTS: Active neck motion (F1,29=80.02), pain thresholds of blunt pressure (F1,29=20.84), BPPT (F1,29=54.56), and cold (Z=-4.31) were significantly lower in participants with WAD (P<0.0001). Cold pressor pain tolerance was significantly lower in participants with WAD (Z=-2.89, P=0.02). A less efficacious CPM was also demonstrated in participants with WAD (F1,29=9.20, P=0.03). A combination of BPPT and cold hyperalgesia best predicted the WAD group (sensitivity=96.7%, specificity=96.7%). DISCUSSION: These findings of sensory hypersensitivity and decreased neck motion in Singaporeans with chronic WAD are consistent with physical impairments reported in western populations.