There have been many articles highlighting differences and similarities between complex regional pain syndrome (CRPS) and functional neurological disorders (FND) but until now the discussions have often been adversarial with an erroneous focus on malingering and a view of FND as ‘all in the mind’. However, understanding of the nature, frequency and treatment of FND has changed dramatically in the last 10–15 years. FND is no longer assumed to be only the result of ‘conversion’ of psychological conflict but is understood as a complex interplay between physiological stimulus, expectation, learning and attention mediated through a Bayesian framework, with biopsychosocial predisposing, triggering and perpetuating inputs. Building on this new ‘whole brain’ perspective of FND, we reframe the debate about the ‘psychological versus physical’ basis of CRPS. We recognise how CRPS research may inform mechanistic understanding of FND and conversely, how advances in FND, especially treatment, have implications for improving understanding and management of CRPS.
- complex regional pain syndrome
- reflex sympathetic dystrophy
- functional neurological disorder
- conversion disorder
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SP and IH contributed equally.
Contributors SP and IH contributed equally to writing the first draft of the manuscript and conducting the literature search. LC, AJC and JS were involved in literature selection, editing and writing of the manuscript. All authors approved the final version of the manuscript.
Funding SP was supported by a scholarship from the FoRUM Forschungsreferat (research office) of the Medical Faculty of the Ruhr-University Bochum, Germany. IH is supported by an Association of British Neurologists/Patrick Berthoud Charitable Trust Clinical Research Training Fellowship. JS is supported by an NHS Scotland NRS Career Fellowship.
Competing interests SP and IH declare no conflicts of interest. LC has received honoraria for speaking at educational meetings to healthcare professionals on a range of chronic pain topics (Pfizer (October 2015); is an editor on the British Journal of Anaesthesia (receives an honorarium plus a contribution towards related departmental expenses (October 2010–to date)) and chairs the Scottish Pain Research Community (SPaRC/ NHS Research Scotland Pain Research Network, which has received non-promotional funding from Pfizer, Grunenthal and QDem to support the Annual Scientific Meeting. AJC reports giving independent testimony in court on a range of topics that include functional neurologic symptoms; being a paid editor at the Journal of Neurology, Neurosurgery, and Psychiatry and receiving lecture fees from a range of firms on general neuropsychiatric topics (total income in last decade less than £1500). JS reports giving independent testimony in court on a range of topics that include functional neurological symptoms and CRPS and having received royalties from UpToDate for articles on functional neurological disorder and runs a free non-profit self-help website, www.neurosymptoms.org, which discusses these issues.
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Provenance and peer review Commissioned; externally peer reviewed.