Conditioned pain modulation is affected by occlusion cuff conditioning stimulus intensity, but not duration.

BACKGROUND: Various conditioned pain modulation (CPM) methodologies have been used to investigate diffuse noxious inhibitory control pain mechanisms in healthy and clinical populations. Occlusion cuff parameters have been poorly studied. We aimed to investigate whether occlusion cuff intensity and/or duration influenced CPM magnitudes. We also investigated the role of physical activity levels on CPM magnitude. METHODS: Two studies were performed to investigate the role of intensity and duration of occlusion cuff conditioning stimulus on test stimulus (tibialis anterior pressure pain thresholds). In Study 1, conditioning stimulus intensity of 2/10 or 5/10 (duration <20 s) was evaluated using a paired-samples t-test. In Study 2, duration of 2/10 conditioning stimulus was 3 min. One-way repeated-measures ANOVA was used to investigate the effect of time (0, 1, 2 and 3 min) on CPM magnitude. RESULTS: In Study 1, 27 healthy volunteers (mean ± SD: 24.9 years (±4.5); eight female) demonstrated that an occlusion cuff applied to the upper arm eliciting 5/10 local pain resulted in a significant (mean ± SD: 17% ± 46%) increase in CPM magnitude, when compared to 2/10 intensity (-3% ± 38%, p = 0.026), whereas in Study 2, 25 healthy volunteers (22.5 years (±2.7); 13 female) demonstrated that 3 min of 2/10 CS intensity did not result in a significant change in CPM (p = 0.21). There was no significant relationship between physical activity levels and CPM in either study (p > 0.22). CONCLUSIONS: This study demonstrated that an occlusion cuff of 5/10 conditioning stimulus intensity, when compared to 2/10, significantly increased CPM magnitude. Maintaining 2/10 conditioning stimulus for 3 min did not increase CPM magnitude. SIGNIFICANCE: Dysfunctional conditioned pain modulation (CPM) has been associated with poor health outcomes. Various factors can influence CPM outcomes. The role of occlusion cuff conditioning stimulus intensity and duration has not been previously investigated. Intensity (5/10), but not duration of lower intensity (2/10) conditioning stimulus, affects CPM magnitude.

Laypersons' expectations of recovery and beliefs about whiplash injury: a cross-cultural comparison between Australians and Singaporeans.

BACKGROUND: Beliefs and expectations are thought to influence outcome following whiplash injury. Studies have proposed a link between rates of chronic whiplash and laypersons' expectations about outcome following a motor vehicle accident. The prevalence of chronic whiplash is relatively high in Australia and apparently low in Singapore. This study's objectives were to compare laypersons' beliefs and expectations of recovery of whiplash injury in Brisbane and Singapore and to assess the effect of demographic factors on whiplash beliefs. METHODS: A cross-sectional study using online surveys was conducted on adult Internet users in Brisbane (Australia) and Singapore. The 14-item whiplash beliefs questionnaire (WBQ) was used to evaluate whiplash beliefs. Two additional items assessed expectations of recovery. Individual items of WBQ, WBQ score and expectations of recovery were analysed. Stratified analysis was performed to adjust for sampling bias due to quota sampling. RESULTS: A total of 402 participants from Singapore and 411 participants from Brisbane, Australia, completed the survey. While participants from Singapore demonstrated slightly more negative whiplash beliefs than participants from Brisbane [t(811) = -5.72; p < 0.0001], participants from both samples were similar in their expectations of quick recovery and return to normal activities following whiplash injury. Only gender had a significant effect on whiplash beliefs [estimated marginal means of WBQ score for men = 21.5; standard error (SE) = 0.20; women = 22.5; SE = 0.20; F(1,810) = 11.2; p = 0.001]. CONCLUSIONS: Laypersons' expectations of recovery and beliefs about whiplash injury in Brisbane and Singapore were generally similar and mostly positive. Our results demonstrate that cultural differences reflected by laypersons' beliefs may not reflect the differences in prevalence of chronic whiplash between countries.

Spinal cord metabolism and muscle water diffusion in whiplash.

STUDY DESIGN: Case series. OBJECTIVES: To quantify spinal cord metabolites and neck muscle fast and slow water diffusion in a small sample of patients with chronic whiplash and healthy controls. SETTING: Brisbane, Queensland, Australia. METHODS: In five subjects with chronic whiplash and seven controls, we performed magnetic resonance spectroscopy (MRS) of the cervical spinal cord and diffusion-weighted imaging (DWI) of the cervical multifidus muscle. RESULTS: Significant reductions in N-acetylaspartate/creatine ratios were found in subjects with chronic whiplash when compared with healthy controls (P = 0.02). Significantly higher fast apparent diffusion coefficients (ADCs) were found in chronic whiplash when compared with the healthy controls (P = 0.01). There was no difference in slow ADCs between the two groups (P = 0.3). CONCLUSION: The potential value of MRS and DWI to quantify the presence of neuromuscular degeneration as a potential mechanism underlying chronic whiplash is recognized. Larger-scaled prospective studies are warranted and required.