Multimodal MRI Reveals Structural and Functional Alterations in Isolated Cervical Dystonia: Associations with Motor Severity and Affective Symptoms

Abstract

Isolated cervical dystonia (ICD) is the most common focal dystonia, characterized by involuntary neck muscle contractions leading to abnormal head postures and nonmotor symptoms such as anxiety. Although structural and functional brain alterations have been reported, findings remain inconsistent, and the neurobiological mechanisms underlying this motor and nonmotor symptoms are incompletely understood. In this study, thirty-five ICD patients and twenty-eight matched healthy controls underwent structural MRI and resting-state fMRI. Voxel-based morphometry assessed gray matter volume (GMV) differences, and seed-based resting-state functional connectivity (rsFC) analyses were performed using regions showing significant structural alterations. Partial correlation and mediation analyses examined associations among brain measures, motor severity, and mood symptoms. ICD patients showed reduced GMV in the left paracentral lobule (PCL) and right middle temporal gyrus (MTG). The left PCL exhibited altered connectivity with prefrontal, temporal, and thalamic regions, suggesting disruption of cerebello-thalamo-cortical pathways. The right MTG showed decreased connectivity with the left temporal pole and increased connectivity with the right middle frontal gyrus, potentially reflecting compensatory mechanisms for cognitive processing. Notably, GMV reduction in the left PCL mediated the relationship between ICD status and anxiety symptoms. These findings support ICD as a network disorder involving both motor and cognitive-affective circuits. Structural alterations in the PCL and MTG and their connectivity