Implantation order and pneumocephalus independently predict radial electrode deviation in bilateral subthalamic nucleus deep brain stimulation: A single-surgeon analysis

BACKGROUND: Precise electrode placement is essential for optimal outcomes in deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson’s disease. Intraoperative brain shift caused by cerebrospinal fluid loss and pneumocephalus may reduce stereotactic accuracy, particularly during bilateral implantation. We evaluated whether implantation order and pneumocephalus independently predict radial electrode deviation. METHODS: This retrospective, single-surgeon study included 45 consecutive patients who underwent bilateral STN DBS (90 electrodes). Planned coordinates from preoperative magnetic resonance imaging were fused with postoperative computed tomography (CT) to determine actual lead positions. Radial deviation was defined as horizontal (ΔX–ΔY) displacement in millimeters. Pneumocephalus volume was quantified using postoperative CT volumetry. Associations were assessed using univariate analysis and multivariate linear regression. RESULTS: Mean radial deviation was 2.18 ± 0.52 mm. Second-implanted electrodes showed significantly greater deviation than first-implanted electrodes (2.46 ± 0.55 mm vs. 1.89 ± 0.41 mm; P < 0.001). Mean pneumocephalus volume was 11.6 ± 6.9 cm 3 and was positively correlated with radial deviation ( r = 0.48, P = 0.001). On multivariate analysis, pneumocephalus volume ( β = 0.031 mm/cm 3 ; P = 0.001) and implantation order ( β = 0.49 mm; P < 0.001) independently predicted deviation, whereas surgical state, micro-electrode recording, and incision strategy were not significant. The model explained 40% of the variance. CONCLUSIONS: Electrode deviation in bilateral STN DBS is independently associated with cumulative brain shift and implantation sequence. Minimizing pneumocephalus and optimizing operative workflow may improve stereotactic accuracy.