Patterns of cortical reorganization in complex regional pain syndrome

Objective: To use magnetoencephalography to assess possible cortical reorganization in the primary somatosensory cortex (S1) of patients with complex regional pain syndrome (CRPS). Background: Patterns of pain and sensory symptoms in CRPS may indicate plastic changes of the CNS. Methods: Magnetic source imaging was used to explore changes in the cortical representation of digits (D) 1 and 5 in relation to the lower lip on the unaffected and affected CRPS side in 12 patients. Results: The authors found a significant shrinkage of the extension of the cortical hand representation for the CRPS affected side. The center of the hand was shifted toward the cortical representation of the lip. The cortical reorganization correlated with the amount of CRPS pain (r = 0.792), as measured by the McGill questionnaire, and the extent of mechanical hyperalgesia (r = 0.860). Using multiple regression analysis, the best predictor for the plastic changes was found to be mechanical hyperalgesia. Additionally, S1 sources following tactile stimulation were significantly increased on the CRPS side compared to the unaffected limb. Conclusions: This study showed reorganization of the S1 cortex contralateral to the CRPS affected side. The reorganization appeared to be linked to complaints of neuropathic pain.