Objective: The clinical impact of direct globus pallidus internus (GPi) targeting and electrode localization in patients with primary dystonia is investigated. Specifically, it aims to determine how a lateral trajectory toward the posteroventral GPi influences the therapeutic window and improves outcomes.

Background: Primary dystonia syndromes present significant clinical challenges due to diverse pathophysiological mechanisms.(1) Bilateral GPi DBS is an effective treatment for primary dystonia; however, an superior targeting technique to GPi has not yet been established.(2,3)

Method: This retrospective study included patients with primary dystonia who underwent bilateral GPi DBS surgery between 2000 and 2023. Preoperative and postoperative BFMDRS scores and clinical follow-ups were documented. Stereotactic planning and analysis were conducted using CT-T2/SWI MRI fusion for direct targeting, and trajectories were reconstructed as 3D GPi.

Results: Total of 27 patients were enrolled in the study. Postoperative BFMDRS scores demonstrated an average improvement of 70.52% [table 1]. Electrodes were advanced with 27º anterior and 29º lateral Zenith inclinations to GPi [figure 1]. Electrodes advanced to the lateral wall of GPi with 48.6° inclination and the tip positioned in the medial ½ and posterior ½ of the ventral GPi [figure 2]. Electrode positioning with a large lateral inclination toward the posteroventral GPi was associated with superior clinical outcomes, underscoring the importance of an accurate targeting method in GPi DBS.

Conclusion: GPi DBS is an effective treatment for medically refractory dystonia. The direct targeting method provides enhanced visualization, improved surgical field control, and higher targeting accuracy. Utilizing a large lateral inclination allows electrodes to traverse from the lateral upper border of the GPi to the medial posteroventral GPi. This approach enhances overall dystonic control, contrary to earlier studies suggesting that a more vertical approach is more effective.(4,5) Given the variability in motor segmentation within the GPi and the heterogeneous clinical pathophysiology of dystonia syndromes, employing a lateral trajectory toward the posteroventral target in the GPi offers a larger therapeutic window and improved overall dystonic control.

Figure 1

Figure 2

Table 1

References: 1. Breakefield XO, Blood AJ, Li Y, Hallett M, Hanson PI, Standaert DG. The pathophysiological basis of dystonias. Nat Rev Neurosci. 2008;9(3):222–34.
2. Elkouzi A, Tsuboi T, Burns MR, Eisinger RS, Patel A, Deeb W. Dorsal GPi/GPe stimulation induced dyskinesia in a patient with Parkinson’s disease. Tremor Hyperkinetic Mov [Internet]. 2019 [cited 2024 Jan 21];9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6744811/
3. Dietz N, Neimat J. Neuromodulation: deep brain stimulation for treatment of dystonia. Neurosurg Clin. 2019;30(2):161–8.
4. Bertino S, Basile GA, Bramanti A, Anastasi GP, Quartarone A, Milardi D, et al. Spatially coherent and topographically organized pathways of the human globus pallidus. Hum Brain Mapp. 2020;41(16):4641–61.
5. da Silva NM, Ahmadi SA, Tafula SN, Cunha JPS, Bötzel K, Vollmar C, et al. A diffusion-based connectivity map of the GPi for optimised stereotactic targeting in DBS. Neuroimage. 2017;144:83–91.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/direct-targeting-technique-of-the-globus-pallidus-interna-in-primary-dystonia-an-analysis-of-the-clinical-results-and-localization-of-dbs-electrodes/