Retrospective comparison of 79 dystonia patients found pallidothalamic tractotomy produced substantially greater postoperative weight gain than GPi pallidotomy, with lesion mapping implicating Forel's field H1/caudal subthalamic region as a weight‑gain hotspot.

This highlights that ablative target selection can alter body‑weight regulation and helps localize circuits near the caudal subthalamic area relevant to metabolic effects of neurosurgical interventions, informing surgical planning and circuit-level hypotheses though it offers limited direct…

BACKGROUND: Postoperative weight gain is a recognized complication of deep brain stimulation, but whether ablative surgery produces target-dependent weight effects remains unknown. We investigated whether pallidothalamic tractotomy (PTT) causes greater weight gain than pallidotomy and explored spatial associations. METHODS: We retrospectively analyzed 79 patients with focal, segmental, or generalized dystonia who underwent unilateral PTT (n = 41) or globus pallidus internus (GPi) lesioning (n = 38). Multivariable linear regression quantified the effect of target on weight and body mass index (BMI) changes, adjusting for age, sex, side, preoperative BMI, follow-up duration, and Burke-Fahn-Marsden dystonia rating scale (BFMDRS) improvement. In a subset with postoperative magnetic resonance imaging (MRI), lesion overlap (N) maps and voxel-wise mean BMI-change maps were generated to explore anatomical associations. RESULTS: PTT resulted in greater postoperative weight gain than GPi lesioning (+6.7 ± 7.5 kg vs. +1.1 ± 4.7 kg), with ≥10 kg gain in 29.3% versus 5.3% of patients. After covariate adjustment, PTT remained independently associated with greater weight gain (adjusted difference + 5.18 kg; 95% confidence interval [CI] +13 to +8.23) and BMI increase (+1.92 kg/m2; 95% CI +0.85 to +2.99). Lesion mapping localized PTT lesions to Forel's field H1. Weight-gain hotspots mapped medial to the inferior border of the subthalamic nucleus, whereas GPi maps showed no consistent intranuclear hotspot. CONCLUSIONS: PTT was associated with greater postoperative weight gain than pallidotomy, independent of covariates. These findings suggest that lesion target influences postoperative body-weight regulation, highlighting the potential risk of lesions extending into the caudal subthalamic region. © 2026 International Parkinson and Movement Disorder Society.