Functional imaging of deep brain stimulation in dystonia: a review

Much remains to be learned about the mechanism of benefit of deep brain stimulation in movement disorders in general and dystonia specifically. A full accounting of the pathophysiology of dystonia additionally remains unclear. Given its ability to evaluate whole-brain network changes, functional neuroimaging is an important tool to advance understanding of the effects of deep brain stimulation, which in turn could offer insight into the pathophysiology of dystonia and suggest novel deep brain stimulation targets for the disorder. This review surveys the published literature of functional neuroimaging studies evaluating deep brain stimulation effects in dystonia, including PET, SPECT, and functional MRI studies. To date, study cohorts have been relatively small, though several general patterns emerge when studies are viewed collectively, including reduced functional activation patterns with stimulation turned on during motor tasks, particularly in frontal cortical regions. During rest with stimulation on, several studies showed areas of relatively decreased perfusion only in those participants who experienced clinical benefit from deep brain stimulation. Future research may benefit from larger cohorts with more homogeneous forms of dystonia, potentially enabled by multi-center initiatives. Additional benefits may result from more detailed longitudinal assessments and greater use of functional MRI, with study designs that take into account the technical limitations of this modality in the context of movement disorders and deep brain stimulation.