The motor system shows adaptive changes in complex regional pain syndrome

The complex regional pain syndrome (CRPS) is a disabling neuropathic pain condition that may develop following injuries of the extremities. In the present study we sought to characterize motor dysfunction in CRPS patients using kinematic analysis and functional imaging investigations on the cerebral representation of finger movements. Firstly, 10 patients and 12 healthy control subjects were investigated in a kinematic analysis assessing possible changes of movement patterns during target reaching and grasping. Compared to controls, CRPS patients particularly showed a significant prolongation of the target phase in this paradigm. The pattern of motor impairment was consistent with a disturbed integration of visual and proprioceptive inputs in the posterior parietal cortex. Secondly, we used functional MRI (fMRI) and investigated cortical activations during tapping movements of the CRPS-affected hand in 12 patients compared to healthy controls (n = 12). During finger tapping of the affected extremity, CRPS patients showed a significant reorganization of central motor circuits, with an increased activation of primary motor and supplementary motor cortices (SMA). Furthermore, the ipsilateral motor cortex showed a markedly increased activation. When the individual amount of motor impairment was introduced as regressor in the fMRI analysis, we were able to demonstrate that activations of the posterior parietal cortices (i.e. areas within the intraparietal sulcus), SMA and primary motor cortex were correlated with the extent of motor dysfunction. In summary, the results of this study suggest that substantial adaptive changes within the central nervous system may contribute to motor symptoms in CRPS.