Background: Writer's cramp is a task-specific dystonia impairing writing and sometimes other fine motor tasks. Neuroimaging studies using manifold designs have shown varying results regarding the nature of changes in the disease.
Objective: To clarify and extend the knowledge of underlying changes by investigating functional connectivity (FC) in intrinsic connectivity networks with putative sensorimotor function at rest in an increased number of study subjects.
Methods: Resting-state functional magnetic resonance imaging with independent component analysis was performed in 26/27 writer's cramp patients/healthy controls, and FC within and between resting state networks with putative sensorimotor function was compared. Additionally, voxel-based morphometry was carried out on the subjects' structural images.
Results: Patients displayed increased left- and reduced right-hemispheric primary sensorimotor FC in the premotor-parietal network. Mostly bilaterally altered dorsal/ventral premotor FC, as well as altered parietal FC were observed within multiple sensorimotor networks and showed differing network-dependent directionality. Beyond within-network FC changes and reduced right cerebellar grey matter volume in the structural analysis, the positive between-network FC of the cerebellar network and the basal ganglia network was reduced.
Conclusions: Abnormal resting-state FC in multiple networks with putative sensorimotor function may act as basis of preexisting observations made during task-related neuroimaging. Further, altered connectivity between the cerebellar and basal ganglia network underlines the important role of these structures in the disease.
Keywords: ADDS, arm dystonia disability scale; BGN, basal ganglia network; BOLD, blood oxygen level-dependent; CN, cerebellar network; CONTR, healthy controls; Cerebellum; Dystonia; FC, functional connectivity; FHD, focal hand dystonia; FWHM, full width at half maximum; FoV, field of view; Functional connectivity; GM, grey matter; IC, independent component; ICA, independent component analysis; ICN, intrinsic connectivity network; IPS, intraparietal sulcus; M1, primary motor cortex; PAT, writer's cramp patients; PCA, principal component analysis; PMd/v, dorsal/ventral premotor cortex; PPN, premotor parietal network; Premotor cortex; ROI, region of interest; Resting state; S1, primary somatosensory cortex; S2, secondary somatosensory cortex; SM1, primary sensorimotor cortex; SMA, supplementary motor area; SMG, supramarginal gyrus; SPC, superior parietal cortex; TIV, total intracranial volume; WC, writer's cramp; WCRS, writer's cramp rating scale; rsfMRI, resting state functional magnetic resonance imaging; v/dSMN, ventral/dorsal sensorimotor network.