Distinct thalamic volumetric profiles in cervical and upper limb dystonia

Abstract Dystonia is a large-scale motor network disorder involving the basal ganglia, cerebellum, and thalamus. This study investigated the volumetric characteristics of thalamic subnuclei in patients with isolated cervical (CD) and upper limb (ULD) dystonias, and their relationship with disease severity. We analyzed high-resolution T1-weighted MR-images from the OpenNeuro database. The sample included 37 healthy controls, 25 CD, and 29 ULD patients. Thalamic nuclei were automatically segmented using the DeepThalamus pipeline. Group differences were analyzed using analysis of covariance (ANCOVA), controlling for age, sex, and total intracranial volume (TIV). Relationships between disease severity and volumetry were assessed using Spearmans correlation. A volumetric reduction trend was observed in the CD group compared with controls, particularly in the left lateral geniculate, right ventral lateral posterior, and right intermediate nuclei. Although statistical significance remained borderline after FDR correction (p = 0.078), high Cohens values (d > 1.4) were detected. In contrast, thalamic volumes were largely preserved in the ULD group. Correlation analyses showed that increased disease severity was associated with decreased volumes of the mammillothalamic tract in the CD group and the anterior ventral nuclei in the ULD group. Observed volumetric trends may provide preliminary insights into the role of specific thalamic substructures in cervical dystonia pathophysiology. Further studies in larger cohorts, supported by functional and diffusion imaging, are needed to clarify these findings.