Altering visual feedback during reaching: no mitigating effect on pain for individuals with Complex Regional Pain Syndrome, but visuomotor adaptation is preserved

Marion Dagenais^1,2Chloe Sutter^1,2Clémentine Brun^1,2Anne Marie Pinard^1,2,3Jean-Sebastien Roy^1,2Catherine Mercier^1,2*

• ¹Center for Interdisciplinary Research in Rehabilitation and Social Integration (CIRRIS), Quebec, Canada
• ²Universite Laval Faculte de Medecine, Québec City, Canada
• ³Centre Hospitalier Universitaire de Quebec-Universite Laval, Québec City, Canada

Introduction: Complex regional pain syndrome (CRPS) is often associated with pain-related fear of movement, and virtual reality has been proposed as a potential rehabilitation intervention to overcome this issue. Therefore, this cross-sectional study aimed to test whether altering the visual feedback (VF) on movement could mitigate pain and promote movement. Methods: Fifteen participants with upper-limb CRPS and 15 age-and gender-matched pain-free participants undertook a target reaching task in the Kinarm exoskeleton, with two VF conditions being tested (Per Exposure: GREATER or SMALLER VF; two separate sessions), preceded and followed by reaching movements without VF (Pre-/Post-Exposure). Proprioception was assessed with a Limb Position Sense task, and a Movement Accuracy outcome was derived from the Pre-Exposure reaching movements. Results: Contrary to our hypothesis, pain intensity was not influenced by VF conditions but increased over Time (p<0.001). Analyses performed on kinematics data showed that participants displayed visuomotor adaptation both Per Exposure, and Pre-/Post-Exposure to altered VF (VF condition*Time: p<0.001). Per Exposure analyses revealed that CRPS participants tended to adapt their Movement Length to a lesser extent than pain-free participants (Group*VF condition: p=0.048). Pre-/Post-Exposure analyses revealed that CRPS participants consistently performed larger movements than pain-free participants (p=0.002). Both groups performed similarly for the Limb Position Sense task, but CRPS participants displayed significantly larger errors for Movement Accuracy, suggesting impaired proprioceptive integration in the CRPS group. Discussion: These findings support the idea that visuomotor adaptation is preserved in CRPS and can be used to promote movement.