• Johanna C M Schilder, Marnix J Sigtermans, Alfred C Schouten, Hein Putter, Albert Dahan, Lucas P J J Noldus, Johan Marinus, and Jacobus J van Hilten.
• Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: j.c.m.schilder@lumc.nl.
• J Pain. 2013 Nov 1;14(11):1514-21.

UnlabelledThere are indications of motor circuit changes in patients with complex regional pain syndrome (CRPS). Nevertheless, although several studies have analyzed motor behavior in CRPS, a relation with pain could not be detected. This might be explained by the use of cross-sectional designs in these studies, in which pain is considered as a trait- rather than a state-dependent variable. We therefore studied the time-dependent relation between pain and motor function in affected arms of 29 CRPS patients during their participation in a placebo-controlled ketamine study. Movement parameters (velocity, frequency, amplitude, and number of arrests) were assessed during a finger tapping task. Linear mixed model analysis of the effects of pain (numerical rating scale score), treatment (ketamine/placebo), and week (1, 3, 6, and 12 weeks after treatment) on the movement parameters revealed that pain intensity was significantly (inversely) related to motor function, irrespective of whether patients had received ketamine or placebo. Movement parameters changed 3-12% per point numerical rating scale change. Because patients were unaware of possible effects of ketamine on motor function, these findings suggest that motor function changes were mediated by, or occurred simultaneously with, changes in pain intensity. By improving motor function, pain relief may offer a window of opportunity for rehabilitation programs in CRPS.PerspectiveThis article provides evidence for a direct relation between pain and motor function in CRPS, which indicates that pain relief may be an important factor in the treatment of motor disturbances in this condition. These findings may help to advance our understanding of the pathways underlying motor disturbances in CRPS.Copyright © 2013 American Pain Society. Published by Elsevier Inc. All rights reserved.

This article appears in the collection: Ketamine infusions.

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