• Gilles Caty, Li Hu, Valéry Legrain, Léon Plaghki, and André Mouraux.
• Institute of Neuroscience (IoNS), Université Catholique de Louvain, Avenue Mounier 53, Bte B1.53.04, B-1200 Brussels, Belgium.
• Pain. 2013 Nov 1;154(11):2521-8.

AbstractThe aim of this study was to assess the function of the thermo-nociceptive system in 25 patients with long-lasting, medium-to-severe refractory complex regional pain syndrome (CRPS)-1 using behavioral (detection rates and reaction times) and electrophysiological (event-related brain potentials) responses to brief (50 milliseconds) and intense (suprathreshold for Aδ-nociceptors) carbon dioxide laser stimuli delivered to the affected and contralateral limbs, and by comparing these responses to the responses obtained in the left and right limbs of age- and sex-matched healthy controls. Compared with healthy controls and compared with the contralateral limb, the detection rate of pricking pain related to the activation of Aδ-fibers was markedly reduced at the affected limb. Furthermore, reaction times were substantially prolonged (>100 milliseconds in 84% of patients and >300milliseconds in 50% of patients). Finally, the N2 and P2 waves of laser-evoked brain potentials were significantly reduced in amplitude, and their latencies were significantly increased. Taken together, our results show that in the majority of patients with chronic CRPS-1, thermo-nociceptive pathways are dysfunctional. A number of pathological mechanisms involving the peripheral nervous system and/or the central nervous system could explain our results. However, the primary or secondary nature of these observed changes remains an open question.Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

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