Fine-grained mapping of cortical somatotopies in chronic Complex Regional Pain Syndrome

Abstract

Chronic pain can be associated with functional and morphological changes in the brain. It has long been thought that some severe chronic pain conditions, such as Complex Regional Pain Syndrome (CRPS), are not only associated with, but even maintained by a reorganisation of the somatotopic representation of the affected limb in the primary somatosensory cortex (S1). This notion has driven treatments that aim to restore S1 representations, such as sensory discrimination training and mirror therapy. However, this notion is based on both indirect and incomplete evidence obtained with imaging methods with low spatial resolution. Here, we used functional MRI to characterize the S1 representation of the affected and unaffected hand in patients with unilateral CRPS of one hand. Our study demonstrates that the cortical area, location, and geometry of the S1 representation of the CRPS hand are comparable to those of the healthy hand, as well as to those of controls. Given that S1 representations are largely preserved in CPRS patients, it is compelling to reconsider not only the cortical mechanisms that underlie the disorder, but also the rationale for interventions that aim to \"restore\" somatotopic representations.