Background & Aims

Complex regional pain syndrome (CRPS) is a chronic primary pain disorder that occurs following trauma to a limb. It is accompanied by sudomotor, vascular and motor abnormalities, and is of unknown etiology with poor treatment outcomes. Patients with CRPS often report a perception that their affected limb is distorted—i.e., body perception disturbances (BPD). Multisensory illusions that modify conscious body perception can reduce pain in clinical populations such as knee osteoarthritis and CRPS, but the mechanisms underlying these analgesic responses are poorly understood. Here, we investigated differences in brain connectivity between patients with CRPS and pain-free individuals during a visual hand morph illusion using functional magnetic resonance imaging (fMRI).

Methods

47 participants (23 upper limb CRPS, 24 healthy; 9 males, 38 females) aged (mean ± SD) 52.1 ± 13.4 years consented to procedures approved by NIHR and UWE ethics. Participants underwent a visual hand morph illusion using the MIRAGE setup while undergoing an fMRI scan. Participants underwent 4 runs of the task, with 10 trials each (5 active morphs, 5 sham morphs). The illusion had a morph phase where the hand appearance changed, lasting 3 seconds, followed by a hold phase where participants viewed their new hand shape for 3 seconds. We conflated the morph and hold phase of the illusion and investigated psychophysiological interactions between the extrastriate body area (EBA) and the rest of the brain in patients with CRPS and healthy controls. Analysis was carried out using FEAT (FMRI Expert Analysis Tool) Version 6.00, part of FSL (FMRIB’S Software Library). Given the exploratory nature of the study, significance was set to an uncorrected Z>3.1.

Results

We discovered that the left and right EBA both had increased functional connectivity with the left dorsolateral prefrontal cortex (dlPFC) during the illusion task. The left EBA also had increased functional connectivity with the caudate during the illusion task.

Conclusions

Whilst experiencing illusions that modulate bodily perception, individuals with CRPS show increased connectivity of the EBA with the left dlPFC and caudate compared to healthy individuals. The dlPFC has been implicated in the cognitive dimension of the pain experience, so its functional coupling with a brain region involved in processing body image in patients with CRPS is logical. The caudate has also been implicated in pain processing, more specifically in pain avoidance behaviour. Further research is required to identify the role these brain regions have in the mechanisms of body perception and pain interactions. This will allow for better treatments that alleviate BPD and pain symptoms in individuals with CRPS.

References

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Presenting Author

Matthew Mockford

Poster Authors

Matthew Mockford

BSc

University of Toronto

Lead Author

Massieh Moayedi; PhD

Centre for Multimodal Sensorimotor and Pain Research, Faculty of Dentistry, University of Toronto

Lead Author

Jenny Lewis

Royal United Hospitals Bath NHS Foundation Trust

Lead Author

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Complex Regional Pain Syndrome (CRPS)