Structural and Functional Brain Network Alterations in Psychogenic Dystonia (P1.042)

Objective: To explore the brain structural and functional MRI abnormalities in psychogenic dystonia patients (pDYT). Background: Psychogenic movement disorders (PMD) are a diagnostic and therapeutic challenge for clinicians. The pathophysiology is not well understood but traditional view has suggested the contribution of an underlying psychological or physical stress to the development of abnormal movements. Methods: This study included a large series of 31 pDYT (mean age 46 years; mean disease duration: 5 years; mean Fahn-Marsden rating scale score: 11.6; mean Unified Dystonia Rating Scale score: 11.2; mean PMD scale total score: 18.6) and 36 age- and sex-matched healthy controls. Subjects underwent 3D T1 weighted, diffusion tensor (DT) MRI and resting state functional MRI (fMRI). Cortical thickness measures and subcortical grey matter nuclei volumes were analyzed using surface-based morphometry. Tract-based spatial statistics was applied to compare DT MRI metrics between groups. Resting state fMRI was analyzed using a model free approach investigating the main sensorimotor and cognitive brain networks. Results: Compared to controls, pDYT showed reduced volume of the right thalamus and caudate bilaterally, and thinning of precentral and frontoparietal cortices, bilaterally. They also showed a distributed pattern of decreased fractional anisotropy and increased mean diffusivity including the main motor and cognitive white matter tracts. Compared to controls, pDYT showed a decreased functional connectivity of the right basal ganglia, insula and dorsolateral prefrontal cortex in the striatal-frontal network and of the precuneus in the default mode network. Conclusions: This study shows that pDYT is characterized by a structural and functional breakdown of motor and extramotor brain networks. Neuroimaging may improve our understanding of the functional and anatomical substrates of this condition and ultimately help developing new therapeutic strategies. Future studies comparing pDYT with genetic dystonia patients may help to elucidate the primary or secondary nature of these abnormalities.