White Matter Structure in Complex Regional Pain Syndrome: A High Angular Resolution and Fixel-Based Study

Treatment of chronic pain conditions such as complex regional pain syndrome (CRPS) has been underpinned by the concept of the condition being driven or maintained by disorganisation of the sensory system. Previously reported differences in brain structure and function between individuals with CRPS and healthy controls have supported this concept, although results have been mixed.

In a cross-sectional study, we examined white matter structure in the brains of people with CRPS and healthy controls (n = 42) using high angular resolution diffusion imaging at 3 Tesla and analysed the data using a fixel-based approach.

We found no significant differences in any diffusion measures between participants with CRPS and controls. Linear regression analyses and equivalence tests demonstrated that fibre density cross-section measures were indistinguishable between the two groups; neither CRPS symptomology nor opioid use could be explained by any white matter structural differences detected by diffusion imaging.

A relatively large sample size and fine-grained methods add confidence to our findings. These results argue against permanent brain changes that prevent recovery in CRPS.

In one of the largest studies of white matter structure in complex regional pain syndrome, fixel-based high angular resolution diffusion scans showed no significant difference to controls and were statistically equivalent. This indicates that white matter structural change is unlikely to be of clinical significance in CRPS. This points to functional changes underpinning the deficits associated with the condition and highlights improving neural function through movement-based approaches such as graded motor imagery, graded exposure, desensitisation and functional movement rehabilitation approaches.