Visual illusions modulate body perception disturbance and pain in Complex Regional Pain Syndrome: a randomized trial

Background

Effective treatment of longstanding Complex Regional Pain Syndrome (CRPS) is a challenge, as causal mechanisms remain elusive. People with CRPS frequently report distorted subjective perceptions of their affected limb. Evidence of pain reduction when the affected limb is visually altered in size, suggests that visual illusions used to target central processing could restore coherence of this disrupted limb representation. We hypothesised that using virtual reality that alters hand image to match the patient’s desired hand appearance, would improve body perception disturbance and pain. Also, repeated exposure would maintain any therapeutic effect.

Methods

A blinded randomised controlled trial of 45 participants with refractory upper‐limb CRPS and body perception disturbance (BPD) viewed a digital image of their affected hand for one minute. The image was digitally altered according to the patient’s description of how they desired their hand to look in the experimental group and unaltered in the control group. BPD and pain were measured pre and post‐intervention. A subgroup was followed up two weeks after a course of repeated interventions.

Results

BPD (mean‐6, ±SD 7.9, p=0.036, effect size (ES)=0.6) and pain intensity (mean‐0.43, ±SD 1.3, p=0.047, ES=0.5) reduced in 23 participants after single exposure compared to controls (n=22). At follow‐up, the subgroup (experimental n=21; control n=18) showed sustained pain reduction only (p=0.037, ±SD 1.9, ES=0.7), with an overall 1.2 decrease on an 11‐point scale.

Conclusions

Visually changing the CRPS hand to a desired appearance modulates BPD and pain suggesting therapeutic potential for those with refractory CRPS. Further research to optimise this therapeutic effect is required.