Structural and Functional Abnormalities of the Primary Somatosensory Cortex in Diabetic Peripheral Neuropathy: A Multimodal MRI Study

Diabetic distal symmetrical peripheral polyneuropathy (DSP) results in decreased somatosensory cortical gray matter volume, indicating that the disease process may produce morphological changes in the brains of those affected. However, no study has examined whether changes in brain volume alters the functional organisation of the somatosensory cortex and how this relates to the different painful DSP clinical phenotypes. In this case-controlled, multimodal magnetic resonance brain imaging study of 44 carefully phenotyped subjects, we found significant anatomical and functional changes in the somatosensory cortex. Painful DSP insensate subjects have the lowest somatosensory cortical thickness with expansion of the area representing pain in the lower limb to include face and lip regions. Furthermore, there was a significant relationship between anatomical and functional changes within the somatosensory cortex and severity of the peripheral neuropathy. These data suggest a dynamic plasticity of the brain in DSP, driven by the neuropathic process. It demonstrates, for the first time, a pathophysiological relationship between a clinical painful DSP phenotype and alterations in the somatosensory cortex.