Abstract
BACKGROUND: The central pathology causing idiopathic focal dystonia remains unclear. The recently identified somato-cognitive action network (SCAN) has been implicated. OBJECTIVE: We tested whether the effector-agnostic SCAN may constitute a central pathology shared across dystonia subtypes, whereas the effector-specific regions in the primary sensorimotor cortex may show distinct functional changes specific to the dystonic body part. METHODS: We collected functional magnetic resonance imaging (MRI) from patients with focal dystonia (laryngeal dystonia [LD], N = 24; focal hand dystonia [FHD], N = 18) and healthy control participants (N = 21). Regions of interest were selected a priori within the basal ganglia-thalamo-cortical and cerebello-thalamo-cortical sensorimotor pathways. We investigated dystonia-dependent resting-state connectivity changes: between SCAN and related cortical regions, between cortical and noncortical regions, and among noncortical regions. Cortical network boundaries were individualized based on resting-state data. Separately, individualized hand and mouth/larynx regions were also generated from task-based MRI (finger-tapping and phonation, respectively) for comparison. RESULTS: Both focal dystonia subtypes showed significant functional changes (P = 0.048 for LD, P = 0.017 for FHD) compared to controls, driven by SCAN's higher functional connectivity to task-based mouth/larynx region and concomitantly lower connectivity to the cingulo-opercular network. No significant subcortical or cerebellar changes were observed when LD and FHD were modeled as independent groups. However, exploratory analysis combining LD and FHD suggested a dystonia-dependent asynchronization between SCAN and sensorimotor cerebellum (P = 0.010) that may indicate a pathological rather than compensatory process. CONCLUSIONS: We demonstrate that SCAN is uniquely associated with focal dystonia dysfunction beyond the dystonic effector regions, offering insights into pathophysiology and treatments. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.