Deep Brain Stimulation of the Internal Pallidum Modulates the Mesencephalic Locomotor Pathway in Improved Cervical Dystonic Patients

BACKGROUND: Deep brain stimulation of the internal globus-pallidus (GPi-DBS) improves focal dystonia, often incompletely. GPi-DBS modulates pallido-thalamo-cortical pathways; however, involvement of descending pathways, including the mesencephalic locomotor region (MLR), has been proposed. OBJECTIVES: To investigate structural connectivity for predicting outcomes. METHODS: We retrospectively analyzed 21 focal dystonia patients with GPi-DBS. Dystonia was assessed pre- and postoperatively. Contacts were localized, volumes of tissue activated (VTA) modeled, and structural connectivity quantified using probabilistic tractography and each patient's VTA to filter a normative connectome from two healthy cohorts. RESULTS: GPi-DBS induced mean improvement of 48.2% (SD 37.4%) in TWSTRS (p = 0.0003) and 26.7% (SD 63.4%) in BFMDRS (p = 0.068) in cervical dystonia patients. The sweet-spot was within sensorimotor GPi. For the 15 cervical dystonia patients, VTA-MLR connectivity positively correlated with TWSTRS improvement (p = 0.048), with no significant VTA-thalamic connectivity association (p > 0.30). CONCLUSIONS: Cervical dystonia improvement depends on the GPi-MLR pathway, supporting tractography to optimize DBS efficacy.