Objective: Our findings have the potential to transform the clinical practice of surgeons who rely solely on indirect targeting, by raising awareness of the anatomic variation of GPi across individuals, highlighting the need for direct targeting. In an era of high resolution MR imaging, it is our view that direct targeting provides more consistent and superior clinical outcomes than indirect targeting alone, particularly with GPi DBS.

Background: DBS targeting has improved with the development of new imaging modalities, however, there remains a variety of surgical techniques employed, including indirect and direct targeting. Because of anatomical variability, if a surgeon uses strictly indirect targeting, especially for laterally located structures such as the globus pallidus interna (GPi), DBS clinical outcomes may be less consistent compared to using a direct targeting method. We aimed to investigate the anatomical variations in two representative targets for Parkinson’s disease (PD) DBS targets: the GPi and the subthalamic nucleus (STN) in an effort to highlight the importance of utilizing direct targeting.

Methods: Five years (2009-2013) of single surgeon planned GPi and STN DBS trajectories for PD at the University of Florida were reviewed. MR sequences optimized for delineating the boundaries of the basal ganglia were coupled with a modified Shaltenbrand and Bailey atlas to plan the electrode trajectory to an ideal location within the GPi or the STN. The anatomic coordinates and angles of the planned trajectories were compared between the two target groups.

Results: A total of 273 planned electrode trajectories (128 GPi, 145 STN) were evaluated. The ideal target within the GPi was found to have a significantly higher degree of variability in the anterior/posterior and dorsal/ventral axes as compared to the ideal target within the STN. The average arc angle planned for GPi trajectories was significantly less lateral to medial (4.2 degrees) than that planned for STN trajectories (16.9 degrees).

Conclusions: A review of 273 planned electrode trajectories demonstrated that the ideal target for GPi DBS has significantly greater variability than the ideal target for STN DBS. Given the extent of variability of GPi boundaries, direct targeting utilizing high-resolution images should be considered the standard of care to ensure accurate, optimal placement of DBS leads.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/variability-in-the-ideal-target-of-gpi-dbs-for-parkinsons-disease-requires-advanced-direct-targeting-for-optimal-results/