Prisms to shift pain away: Physiopathological and therapeutic exploration of CRPS with prism adaptation

Objective Complex regional pain syndrome (CRPS) is an invalidating chronic condition subsequent to peripheral lesions, with frequent therapeutic failure. There is growing consensus for a central contribution to CRPS. However, the nature of this central body representation disorder is increasingly debated. Although it has been repeatedly argued that CRPS results in motor neglect of the affected side, visual egocentric reference frame was found to be deviated towards the pain, i.e. neglect of the healthy side. Accordingly, prism adaptation has been successfully used to normalize this deviation by some teams, leading to clinical improvement. This study aimed at exploring a CRPS groupu0027s spatial references modifications as well as investigating the pathophysiological mechanisms of this manifestation and of the therapeutic effects of prism adaptation. Material/Patients and methods On a CRPS patients group ( n  = 7), pain and quality of life, egocentric reference frames (visual and proprioceptive straight-ahead), and neglect-tests (line-bisection, kinematic analyses of motor neglect and motor extinction) were repeatedly assessed prior to, during and following a week of prism adaptation (twice a day for five days). Results First, our results provide no support for visual and motor neglect in CRPS. Second, reference frames for body representations were not systematically deviated. Third, prism adaptation intervention durably ameliorated pain and quality of life (effect was maintained 2 weeks after intervention). Discussion/Conclusion Prism adaptation, which is inexpensive and non-invasive, seems to be a promising tool to use in addition to usual methods to alleviate pain in therapeutic failure situations for CRPS patients. Indeed, our results suggest a sustainable improvement of pain and quality of life. Moreover, these results overturn the neglect-like theory and provide wide physiopathological data on spatial references’ modifications. As for spatial neglect, understanding the therapeutic effects of prism adaptation deserves further investigations.