Ventral STN stimulation is associated with improved axial motor outcomes in Parkinson's disease

Subthalamic nucleus (STN) deep brain stimulation (DBS) is well-established for improving appendicular motor signs but its effect on axial motor signs is less clear. Additionally, the location of active electrode contact within the STN has been shown to differentially affect motor outcomes. We investigate the effect of STN DBS and the role of active electrode contact location on axial motor outcomes. Axial scores were assessed in 70 patients with advanced PD between 6 and 12 months after bilateral STN DBS. Repeated measures one-way ANOVA was performed to compare the mean axial motor scores between different medication and stimulation treatment conditions. Multiple linear regression was performed to determine the association between electrode contact location and axial motor score. The mean duration of follow-up was 7.37 ± 2.49 months. The mean total axial score was improved with STN DBS compared to the OFF MED-OFF STIM condition (6.36 ± 4.50 vs. 8.91 ± 5.49, p < 0.0001). A more dorsal electrode contact location on the right was associated with increased (worsened) total axial score (slope = 0.407, p = 0.0047). Total axial score was also lower (improved) in the anterior ventral STN region but not the posterior ventral STN region on the right. STN DBS improves total axial score and several axial subscores in patients with PD 6-12 months postoperatively. A more ventral electrode contact location on the right was associated with improved axial score. Additional research is warranted to determine if this is the optimal stimulation location to improve axial signs in other DBS cohorts.