Probabilistic Lesion Mapping to Optimize Thalamotomy Targets for Focal Hand Dystonia

Focal hand dystonia (FHD) severely impairs task-specific motor control, yet the optimal surgical target for stereotactic intervention remains uncertain. This study aimed to identify the precise thalamic lesion site associated with symptomatic improvement and to clarify its network connectivity.

We retrospectively analyzed 164 patients with FHD (mean age = 42.0 years, 26.2% women) who underwent stereotactic thalamotomy of the ventral lateral thalamus. Voxel-wise probabilistic lesion mapping was applied to relate lesion locations to clinical outcomes. Structural connectivity analyses assessed fiber tracts linked to the optimal lesion site. Model performance was evaluated by 10-fold cross-validation, validation in an out-of-sample cohort, and testing in reoperation cases.

We identified that lesioning the border zone between the ventralis oralis posterior (Vop) and ventralis intermedius (Vim) nuclei was associated with improvement of FHD. The predictive model achieved high accuracy in cross-validation (area under the curve [AUC] = 0.836) and performed robustly in independent validation. Connectivity analyses showed that the Vop-Vim border zone was linked to cerebellothalamic and pallidothalamic afferents as well as thalamocortical projections to the supplementary motor area and premotor cortex. In contrast, lesions extending into the ventralis oralis anterior nucleus were associated with an increased risk of motor complications.

Precise targeting of the Vop-Vim border maximizes clinical benefit while minimizing adverse effects in FHD thalamotomy. These findings establish the first evidence-based thalamic target for FHD, offering practical guidance for stereotactic interventions and advancing understanding of dystonia pathophysiology. ANN NEUROL 2026;99:1227-1238.