Correlation Between Lead Location and Motor Improvement in STN DBS for Parkinson’s Disease

Introduction: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) treats motor symptoms in Parkinson’s disease, yet outcomes vary. This study analyzed lead placement relative to motor improvement, using a probabilistic map to identify optimal stimulation regions and examine why some ideal placements fail to yield best results.

Methods: We analyzed data from 275 PD patients with bilateral DBS leads (550 VTAs) and measured motor improvements by percent change in UPDRS III scores. Each patient’s pre-operative levodopa challenge improvement score was compared to their post-op on-stimulation best improvement. Patients with at least a 35% post-op improvement, matching or exceeding their pre-op score, were classified as the "best optimal group" (230 VTAs). A probabilistic map identified the "hottest spot" as the likely optimal stimulation site. VTAs were categorized into "optimal" (post-op improvement within 10% of or better than pre-op) and suboptimal groups. Distances from each VTA to the hotspot were calculated, and both groups’ VTAs were analyzed in 3D, assessing spatial distribution by quartiles based on hotspot distance.

Results: The study included 133 patients in the suboptimal group (266 VTAs) and 142 in the optimal group (284 VTAs). VTAs in the optimal group were significantly closer to the "hottest spot" on the probabilistic map than those in the suboptimal group (p = 0.0057). Initial spatial distribution of all VTA centers showed no significant group difference. However, when divided into quartiles by VTA-to-hotspot distance, a pattern emerged: suboptimal group VTAs in the bottom quartile clustered in octant 5, superior, posterior, and medial to the hotspot, while the optimal group’s farthest quartile included VTAs in superior, anterior, medial, or lateral positions, often extending into white matter dorsally to the STN.

Conclusion : Our findings suggest favorable outcomes may extend beyond lead placements solely within the STN, with nearby white matter playing a key role. Further tractography studies are needed to confirm its impact on prognosis.