• Philipp Stude, Elena K Enax-Krumova, Melanie Lenz, Silke Lissek, Volkmar Nicolas, Soeren Peters, Amy Westermann, Martin Tegenthoff, and Christoph Maier.
• Department of Neurology, BG University Hospital Bergmannsheil GmbH, Ruhr University Bochum, Germany; Department for Diagnostic and Interventional Radiology and Nuclear Medicine, BG University Hospital Bergmannsheil GmbH, Ruhr University Bochum, Germany; D.
• Pain Physician. 2014 Sep 1;17(5):E637-44.

BackgroundPatients with complex regional pain syndrome type I (CRPS I) show a cortical reorganization with contralateral shrinkage of cortical maps in S1. The relevance of pain and disuse for the development and the maintenance of this shrinkage is unclear.ObjectiveAim of the study was to assess whether short-term pain relief induces changes in the cortical representation of the affected hand in patients with CRPS type I.Study DesignCase series analysis of prospectively collected data.MethodsWe enrolled a case series of 5 consecutive patients with CRPS type I (disease duration 3 - 36 months) of the non-dominant upper-limb and previously diagnosed sympathetically maintained pain (SMP) by reduction of the pain intensity of more than > 30% after prior diagnostic sympathetic block. We performed fMRI for analysis of the cortical representation of the affected hand immediately before as well as one hour after isolated sympathetic block of the stellate ganglion on the affected side.StatisticsWilcoxon-Test, paired t-test, P < 0.05.ResultsPain decrease after isolated sympathetic block (pain intensity on the numerical rating scale (0 - 10) before block: 6.8 ± 1.9, afterwards: 3.8 ± 1.3) was accompanied by an increase in the blood oxygenation level dependent (BOLD) response of cortical representational maps only of the affected hand which had been reduced before the block, despite the fact that clinical and neurophysiological assessment revealed no changes in the sensorimotor function.LimitationsThe interpretation of the present results is partly limited due to the small number of included patients and the missing control group with placebo injection.ConclusionsThe association between recovery of the cortical representation and pain relief supports the hypothesis that pain could be a relevant factor for changes of somatosensory cortical maps in CRPS, and that these are rapidly reversible.

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