Objective: Deep brain stimulation (DBS) involves placement of electrodes in the STN followed by stimulation. Outcome of the surgery is dependent on the accuracy of the lead placement. Though classical teaching has been to place the electrode in the dorsolateral portion of STN, its analysis in axial sections is not standardized for postoperative evaluation. This study aimed at evaluating the position of the lead in relation to the planned target and its motor outcomes.

Background: Parkinson’s disease patients represent the largest cohort of patients treated with DBS. Success of DBS is directly dependent on the accuracy of electrode placement in the target nuclei. An electrode that is slightly off target is unlikely to confer the maximal potential benefit and also likely to be associated with undesirable side effects as neighbouring structures are ‘stimulated’ by current spread. Furthermore, verification of the position of the implanted electrodes is required postoperatively to interpret clinical results and to enhance understanding of basal ganglia physiology.

Method: A total 23 patients of Parkinson’s disease operated between Jan 2019 to Sep 2019, with a follow-up of six months were included in study. Location of electrode were measured following fusion of the preoperative plan and the Post operative MRI and were recorded in three dimensions (X-, Y-, and Z-). Relation of Post DBS electrode position were analyzed in relation to planned target point, considered to be the centre.  Effect on motor outcomes was done by evaluation of UPDRS III postoperatively after 6 months in OFF and ON state.

Results: There were 15 male (65.21 %) and 8 (34.78 %) female patients in the study. Mean age was 55.82 ± 8.30 years. Median delay from onset of symptoms to surgery was 7.52 ± 4.31 years. Mean Preoperative UPRDS III was 55.52 ± 12.20 in OFF phase and 15.21 ± 5.78 in ON phase. Actual target was posteromedial in 52.17 % cases on right side and anteromedial in 39.13 % on left side in relation to planned target. Mean UPDRS III and Levodopa Equivalent drug dosage (LEDD) in postoperative 6 months period was least in patients with electrode position anterolateral as compared to proposed target.

Conclusion: Final electrode position in anterolateral position has more favourable outcome in Subthalamic nucleus DBS. However further research on long term motor outcomes is also warranted to identify optimal stimulation site.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/interim-analysis-of-electrode-position-and-motor-outcomes-at-6-months-in-stn-dbs-for-parkinsons-disease/