Supplementary Material for: Effective Subthalamic Nucleus Deep Brain Stimulation Sites May Differ for Tremor, Bradykinesia and Gait Disturbances in Parkinson’s Disease

Background/Aims: Subthalamic nucleus (STN) deep brain stimulation (DBS) is an effective therapy for Parkinson’s disease (PD). This study investigates whether improvement for particular PD symptoms varies differentially with respect to stimulation location in the STN. Methods: Ten PD patients treated with bilateral STN DBS were enrolled in the study. Each electrode contact was stimulated independently to assess for changes in tremor, bradykinesia, and gait. Electrode contacts were localized via MRI. A novel iterative volumetric analysis was used to search the contact space for stimulation regions corresponding to alleviation of specific symptoms. Results: Tremor was best controlled with DBS applied to the more dorsal, anterior, and medial areas of the contact space. Improvement in bradykinesia was seen largely within the middle of the contact space. Gait improvement was observed with ventral contacts, likely bordering the ventral boundaries of the STN. Conclusion: The iterative volumetric analysis is a valuable tool in identifying anatomic regions responsive to DBS across a subject population treated for PD. In the subjects tested, overlapping efficacy for all symptoms was observed in the region of the STN, but anatomic variances in the responsiveness for tremor, bradykinesia, and gait were found.