Limb-specific autonomic dysfunction in complex regional pain syndrome modulated by wearing prism glasses

In unilateral upper-limb complex regional pain syndrome (CRPS), the temperature of the hands is modulated by where the arms are located relative to the body midline. We hypothesized that this effect depends on the perceived location of the hands, not on their actual location, nor on their anatomical alignment. In 2 separate cross-sectional randomized experiments, 10 (6 female) unilateral CRPS patients wore prism glasses that laterally shifted the visual field by 20 degrees. Skin temperature was measured before and after 9-minute periods in which the position of one hand was changed. Placing the affected hand on the healthy side of the body midline increased its temperature (Delta degrees C = +0.47 +/- 0.14 degrees C), but not if prism glasses made the hand appear to be on the body midline (Delta degrees C = +0.07 +/- 0.06 degrees C). Similarly, when prism glasses made the affected hand appear to be on the healthy side of the body midline, even though it was not, the affected hand warmed up (Delta degrees C = +0.28 +/- 0.14 degrees C). When prism glasses made the healthy hand appear to be on the affected side of the body midline, even though it was not, the healthy hand cooled down (Delta degrees C = 0.30 +/- 0.15 degrees C). Friedman's analysis of variance and Wilcoxon pairs tests upheld the results (P < 0.01 for all). We conclude that, in CRPS, cortical mechanisms responsible for encoding the perceived location of the limbs in space modulate the temperature of the hands. (C) 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.