Dynamic cortical gray matter volume changes after botulinum toxin in cervical dystonia

Previous electrophysiological and functional imaging studies in focal dystonia have reported on cerebral reorganization after botulinum toxin (BoNT) injections. With the exception of microstructural changes, alterations in gray matter volume after BoNT have not been explored. In this study, we sought to determine whether BoNT influences gray matter volume in a group of cervical dystonia (CD) patients. We analyzed whole brain gray matter volume in a sample of CD patients with VBM analysis. In patients, scans were repeated immediately before and some weeks after BoNT injections; controls were only scanned once. We analyzed 1) BoNT-related gray matter volume changes within patients; 2) gray matter volume differences between patients and controls; and 3) correlations between gray matter volume and disease duration and disease severity. The pre- and post-BoNT treatment analysis revealed an increase of gray matter volume within the right precentral sulcus, at the lateral border of the premotor cortex. In comparison to healthy controls, CD patients had reduced gray matter volume in area 45 functionally corresponding to the left ventral premotor cortex. No gray matter volume increase was found for CD patients in comparison to controls. Gray matter volume of the left supramarginal gyrus and left premotor cortex correlated positively with disease duration, and that of the right inferior parietal lobule correlated negatively with disease severity. We have identified structural, yet dynamic gray matter volume changes in CD. There were specific gray matter volume changes related to BoNT injections, illustrating indirect central consequences of modified peripheral sensory input. As differences were exclusively seen in higher order motor areas relevant to motor planning and spatial cognition, these observations support the hypothesis that deficits in these cognitive processes are crucial in the pathophysiology of CD.