Objective: To create a simple tool to aid in selection of the proper target for Deep Brain Stimulation (DBS) in Parkinson’s Disease (PD).

Background: Two targets exist for DBS in PD, the subthalamic nucleus (STN) and globus pallidus interna (GPi). Although there are advantages and disadvantages to implanting in either target, current evidence does not guide selection of the appropriate target in the individual patient.  We believe that in select cases, certain factors can help to determine the ideal target for patients.  We also believe that the decision to implant into one site or another is a major factor in DBS outcomes.

Methods: We performed a Pubmed search of all available DBS studies comparing STN to GPI between 1998 and 2016, identifying 14 such studies.  We then identified the following 13 factors that we believe could help guide our decision: tremor, dyskinesia, gait, bradykinesia, rigidity, medication reduction, depression, cognition, dysphagia, dystonia, quality of life, battery life, and ease of programming. Based on the results of each study and statistical significance of the data, we assigned a value of 0.25, 0.5 or 1.0 to either GPi or STN for each of the 13 factors.  A 0.5 was assigned if there was a small difference between GPi and STN or if only one study showed statistically significant change. A 1.0 was assigned if there was a moderate difference noted between the two targets and there were at least 2 studies that showed a statistically significant change. A 0.25 was assigned to 3 non-ratable subgroups.

Results: Our literature review revealed factors favoring each of the targets. Advantages of STN include: reduction of tremor, bradykinesia and rigidity, desire for medication reduction, and better battery life. Advantages of GPi include: ease of programming, improvement in dyskinesia, dystonia and quality of life, less gait dysfunction, depression, cognitive dysfunction and dysphagia. In addition to the history and physical, a Unified Parkinson’s Disease Rating Scale (UPDRS), Montreal Cognitive Assessment Score (MOCA), and Global Dystonia Scale Score (GDS) would be performed to complete the assessment.

Conclusions: We have created a preliminary tool that we plan to use in our Multidisciplinary DBS Center that we hope will aid in the decision on where to implant.  We hope that the use of such a tool will improve the eventual outcome for patients undergoing DBS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/an-objective-tool-to-guide-target-selection-for-dbs-in-pd-gpi-vs-stn/