# Structure–function association of the cerebellar motor network is altered in isolated cervical dystonia

## TL;DR

This study shows that the connection between the cerebellum and motor areas is altered in people with cervical dystonia, affecting how brain stimulation impacts motor learning.

## Contribution

The study identifies a disrupted structure–function relationship in the cerebellar motor network in cervical dystonia patients.

## Key findings

- FA of the DRTT was not different between CD patients and healthy controls.
- In healthy controls, DRTT FA correlated with the effect of ctDCS on sensorimotor plasticity.
- This correlation was absent in CD patients, indicating disrupted cerebellar network function.

## Abstract

Cervical dystonia (CD) has been recognized as a disorder of the brain’s sensorimotor network. Within this malfunctioning network, the cerebellum plays an important role that needs to be further characterized.

To investigate the structural connectivity of the dentato-rubro-thalamic tract (DRTT), probabilistic tractography was performed in 18 CD patients and 18 matched healthy control (HC) subjects. Connectivity was quantified with fractional anisotropy (FA). Thirteen subjects in each group also participated in a neurophysiological double-blind experiment to investigate the effect of cathodal and sham cerebellar transcranial direct current stimulation (ctDCS) on sensorimotor associative plasticity, as evoked by paired associative stimulation (PAS). The association of FA of the DRTT and neurophysiological parameters was studied with linear models.

The FA of the DRTT was not different between the groups and not related to motor symptom severity in CD patients. In the HC group, there was a significant association between the structural connectivity of the DRTT and the effect that cathodal ctDCS had on the PAS effect. This association was not found in CD patients.

The microstructural state of the DRTT is a potential biomarker for the efficacy of ctDCS in HC. The lack of this structure–function association in patients is further evidence of abnormal properties of the cerebellar motor network in CD.

The online version contains supplementary material available at 10.1007/s00415-025-13186-x.