Planned Surgical Trajectory Affects Clinical Motor Outcome in Deep Brain Stimulation Targeted at Subthalamic Nucleus for Parkinson's Disease

Background and objectives: Surgical planning is critical to achieve optimal outcome in deep brain stimulation (DBS). The relationship between clinical outcomes and DBS electrode position relative to subthalamic nucleus (STN) is well investigated, but the role of surgical trajectory remains unclear. We sought to determine whether preoperatively planned DBS lead trajectory relates to adequate motor outcome in STN-DBS for Parkinson's disease (PD).

Methods: In 49 participants who underwent bilateral STN-DBS for PD using a Leksell® frame, we coregistered the frame and participant MRI images to obtain participant-specific anatomical planes. We evaluated relationships between clinical data and planned trajectories relative to their midsagittal and axial planes. We computed percent change in Unified PD Rating Scale subsection 3 (Unified Parkinson's Disease Rating Scale, part III) scores before and after DBS, and performed binary logistic regression to determine whether planned trajectories affect adequate (>30% Unified Parkinson's Disease Rating Scale, part III improvement) motor outcome.

Results: Preoperatively planned left lead trajectory relative to midsagittal plane predicted likelihood of adequate right body motor outcomes (odds ratio = 0.69, P = .024), even when controlling for ventricular width through Evans index. This effect reflects that increasingly lateral angle of approach reduced odds of adequate motor outcome. Right lead trajectory lacked a similar trend.

Conclusion: Left DBS lead trajectory predicts adequate right-body motor outcome after bilateral STN-DBS. Greater planned trajectory angle relative to midsagittal plane reduces motor outcomes, independent of patients' ventricular width. These data may guide patient selection, inform risk/benefit discussions, optimize surgical planning, or support evidence-based evaluation of the methodologies used to select the approach trajectory, with careful consideration of the angle of approach relative to target.