Local Anesthetic Sympathectomy Restores fMRI Cortical Maps in CRPS I after Upper Extremity Stellate Blockade: A Prospective Case Study

Abstract

Background: Patients 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. Objective: Aim 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 Design: Case series analysis of prospectively collected data. Methods: We 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. Statistics: Wilcoxon-Test, paired t-test, P < 0.05. Results: Pain 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. Limitations: The interpretation of the present results is partly limited due to the small number of included patients and the missing control group with placebo injection. Conclusions: The 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. Key words: Cortical reorganization, cortical plasticity, cortical maps, complex regional pain syndrome (CRPS), sympathetically maintained pain (SMP), sympathetic block (SB)