Comparing Central Pain Processing in Individuals With Non-Traumatic Neck Pain and Healthy Individuals: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis examined the evidence for altered central pain processing in people with nontraumatic neck pain and the relationship among central pain processing, demographics, and pain-related characteristics. Case-control studies reporting measures of altered central pain processing using quantitative sensory testing were reviewed. Standardized mean differences (SMDs) and 95% confidence intervals between people with nontraumatic neck pain and controls were calculated. Meta-analysis was performed using random-effects models when appropriate. Associations between SMDs with demographics and pain-related characteristics were explored on a study level using metaregression. Twenty-six studies were eligible with 25 included for meta-analysis. Meta-analysis demonstrated mechanical hyperalgesia at remote nonpainful sites in the full sample (sample size [n] = 1305, SMD = -0.68) and in the subgroup with moderate/severe disability (n = 165, SMD = -0.86; moderate-quality evidence). Metaregression indicated that remote mechanical hyperalgesia was negatively associated with age (R2  = 25.4%, P = 0.031). Very low- to low-quality evidence of remote cold and heat hyperalgesia and dysfunctional conditioned pain modulation were identified. This review suggests that altered central pain processing is present in people with nontraumatic neck pain and may be associated with disability levels and age. PERSPECTIVE: This review found moderate-quality evidence of mechanical hyperalgesia at remote nonpainful sites in patients with nontraumatic neck pain compared with controls, indicating altered central pain processing. However, more studies are needed to confirm findings from dynamic quantitative sensory testing.