Objective: To evaluate distance between the physiologically defined subthalamic nucleus (STN) target and final lead placement, and its influence on the clinical outcome at 6 months follow-up of DBS therapy in patients with Parkinson’s disease (PD).

Background: Stereotactic strategies for deep brain stimulation (DBS) include image planning and electrophysiological intraoperative mapping. Those techniques have shown to improve accuracy. Nevertheless, manipulation of the chronic DBS lead during the implantation may result in implantation site mismatching to the physiologically defined target.

Methods: A retrospective group of PD patients who underwent STN DBS surgery since 2012 with at least six month follow up period were included. Targets were planned using imaging techniques merged into a software (Leksell GammaPlan-Functional Planning) and physiologically corrected using intraoperative microrecording and electrical stimulation. After functional target confirmation, chronic DBS lead was implanted. Pre-surgery planning and post-surgery images together with intraoperative functional coordinates, were analyzed by the same software. Implant coordinates were calculated for each lead, and deviations from desired trajectories defined by intrasurgical functional target confirmation were reported as error distances. Then, two measures were calculated: anteroposterior and lateromedial error; also an absolute error measure obtained from the previous was calculated. Correlations between errors and relative improvements after 6 months in Unified Parkinson’s disease Rating Scale part 3 scores (UPDRSIII) were explored.

Results: 21 patients were included, 13 were male (61.9%). Right STN errors were: anteroposterior -0.85±1.52mm; lateromedial -0.97±1.11mm. Left STN errors were: anteroposterior -0.43±1.21mm; lateromedial -0.20±1.09mm. Absolute errors were: right STN 1.86±1.29mm; left STN 1.49±0.71mm. Paired samples T-test, only showed significant differences between lateromedial shifts (p<0.023) confirming increased errors to medial regions in right STN. No correlation between clinical improvement and the gap between physiological defined target and final lead position was found.

Conclusions: Mismatches in localizations of implanted DBS electrodes compared to the physiologically defined targets are minimal and, did not influence clinical outcome in PD patients as measured by UPDRSIII score.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/difference-between-physiologically-defined-subthalamic-nucleus-target-and-final-lead-placement-influence-in-clinical-outcome/