Directional Deep Brain Stimulation Programming: Is the Segment Clearly Identifiable and Stable Over Time?

In our early experience programming directional deep brain stimulation (d-DBS) in PD, we found the optimal directional segment changed over time in some patients. To determine the frequency/reasons for this we examined whether (1) different programmers would identify the same segment as "optimal"; and (2) the same programmer would select the same "optimal" segment over time. We hypothesized there would be a moderately high level of agreement on optimal electrode selection between different assessors and repeated assessments by the same evaluator.

This was a prospective, double-blind investigation evaluating the reliability and stability of programming d-DBS. Each patient underwent a mono-polar survey four times (2 time points by 2 separate assessors). The primary aim was the inter-rater agreement of selecting the optimal electrode at 1 and 6 months. The secondary aim was to determine the intra-rater agreement of selecting the optimal electrode from 1 to 6 months.

Twenty-one patients were enrolled. There was fair inter-rater agreement at 1 month and moderate at 6 months. There was minimal intra-rater agreement between 1 and 6 months.

The data refuted our hypothesis. Potential reasons for low agreement include (1) the arduous/subjective nature of identifying the optimal electrode in d-DBS systems, especially in well-placed electrodes; and/or (2) acute changes to the location of stimulation delivery offering temporary improvement in symptoms. Key takeaways gathered were it may, (1) behoove the programmer to explore different electrode montages after a period of time; and (2) be more efficient to review the directional electrode montage only when dictated by clinical symptoms/disease progression.