Objective: To describe our methodology for directional programming in GPi-DBS for PD and report on retrospective assessment of stable programming settings, energy savings using specific programming approaches, and UPDRS III outcomes.

Background: GPi is the preferred target for many clinicians in patients with cognitive decline risk for the treatment of advanced PD. Currently, there is a lack of reporting of clinical experience with GPi directional stimulation.

Method: In our practice, a monopolar review is performed 4 weeks post-surgery. We map electrodes in monopolar full-ring mode with a step size of 0.5mA at 60µs and 130Hz in 60-90 minutes. The full-ring contact with the best symptom relief and TW is selected on each side. At the first follow-up session, the best full-ring is reassessed and the three directional segments on the best-segmented level are mapped for the more symptomatic side in 30-40 minutes. This is done with directional programming based on functional testing and smaller stimulation step sizes (usually 0.25 mA) to account for larger VTAs produced by single segment activation (SSA). If one of the segments performs better than the best full-ring, that segment is selected over the full-ring contact. The same is repeated in the second follow-up on the other side.

Results: Active contacts were on the segmented (directional) levels in 8/9 patients (14/17 leads). SSA ended up being the stable active montage in 9/17 leads (6/9 patients). Average power consumption was 37% lower in leads programmed using a directional programming software automatically recommending smaller step sizes during SSA testing and enabling means to simultaneously optimize TW and TCS. Of 13 leads programmed using this approach, 7 ended up on omnidirectional settings suggesting that the software was not biased towards directional programming but towards optimizing therapy and leveraging directionality. The average UPDRS III improvement in our patients from baseline to stable settings was 42%. 3/6 patients with pre-DBS dyskinesias had resolved or improved symptoms,  the other 3 are pending post segmentation evaluation.

Conclusion: Our data suggest that there is value in assessing directionality in GPi-DBS. Reductive approaches and use of monopolar review guidance software geared towards functional testing and leveraging directionality when needed can make this practical within clinic routines.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/directional-programming-in-gpi-dbs-for-parkinsons-disease-and-retrospective-assessment-of-updrs-iii-outcomes-first-clinical-case-series/