Changing hand appearance using visual illusions modulates body perception disturbance and pain in longstanding Complex Regional Pain Syndrome: A randomised trial

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. 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. BPD (p=0.036, effect size (ES)=0.6) and pain intensity (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 ES=0.7), with an overall 1.2 decrease on an 11-point scale. Visually changing the CRPS hand to a desired appearance modulates BPD and pain suggesting therapeutic potential for those with refractory CRPS. Future detailed studies to optimise this therapeutic effect are required. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial ISRCTN64093359 ### Funding Statement J Lewis and costs of the project were funded by a National Institute for Health Research Post-Doctoral Fellowship (grant number CAT-CL-03-2012-019). ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The data is the copyright of the authors. Permission is required to use the data