Abnormal Connectivity of the Head Neural Integrator in Cervical Dystonia.

BACKGROUND Cervical dystonia is characterized by abnormal neck and head movements, possibly related to a dysfunction of the interstitial nucleus of Cajal (INC) and the head neural integrator, a system responsible for the control of head and eye movements. However, neuroanatomical evidence of alterations in the head neural integrator in cervical dystonia is sparse. OBJECTIVES We investigated structural and functional integrity of the INC and its connections in cervical dystonia. METHODS This cross-sectional, observational study compared 19 cervical dystonia patients and 21 healthy controls, using anatomical, diffusion-weighted, and resting-state functional images. We reconstructed tracts converging on the INC, and involved in the control of head movements. We evaluated group differences in microstructural integrity using fixel-based analysis, and effective connectivity using dynamic causal modeling. RESULTS Compared with controls, patients showed microstructural abnormalities within the INC and cerebral peduncle. Effective connectivity showed abnormal self-inhibition in the INC, substantia nigra, and vermis in patients, with decreased excitation from the substantia nigra to the INC, increased inhibition from the deep cerebellar nuclei and primary sensorimotor cortex, and decreased excitation from the INC to the cerebellar vermis. CONCLUSIONS A dysfunction of the INC might contribute to altered sensorimotor integration in cervical dystonia, and abnormal feedback from its afferent connections could alter its integrative function, resulting in a disturbed head and neck posture. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.