Re-evaluating sources of electrode deviation in deep brain stimulation: surgical technique versus patient-specific brain mechanics.

Abstract

Accurate electrode placement is crucial for optimizing outcomes in deep brain stimulation (DBS). Although reported mean radial deviations are 1.5 mm, a substantial amount deviate more than 2 mm, necessitating revision. Studies to date have largely focused on improving surgical techniques to improve target accuracy, but the role of brain mechanics remains understudied. The aim of this study was to evaluate MR elastography (MRE)-derived patient-specific mechanical factors, as well as surgical technique factors, as contributors to electrode deviation in DBS. Seventeen patients undergoing DBS to treat Parkinson's disease or essential tremor underwent preoperative MRI and MR elastography (MRE). Electrodes were implanted using a robotic image-guided image-verified technique. Insertion and rotation of the radiofrequency probe was captured with intraoperative video. The final electrode location was evaluated on postoperative CT. Local deviations along the entire intracranial path of the electrode were measured and aligned with brain biomechanical properties extracted from coregistered MRE data. Statistical analysis included t-tests, correlation analysis, and multiple linear regression. Laterality, probe insertion speed, probe rotational speed, and MRE metrics (stiffness, damping ratio, and their gradients) were independent variables for modeling electrode deviation along the trajectory. Thirty-three trajectories were collected and analyzed using a consistent multiple linear regression model framework. All trajectory models yielded significant results (model p < 0.05) with a mean R2 of 0.71. MRE metrics explained a mean 71.27% of local deviation variance across 22 well-fitted trajectories (R2 > 0.7), while 11.50% was attributed to insertion and rotational speed and 17.23% was not explained by included variables. Trajectories with unacceptable target deviations were associated with increased range of stiffness and variation in stiffness, lower stiffness and damping ratios (p < 0.0028), and greater duration of disease (p = 0.04). This study demonstrated that brain biomechanical properties as measured via MRE are dominant predictors of persistent electrode deviation in DBS surgery. The findings suggest the need for a personalized patient-specific biomechanics-informed approach to improve targeting precision and surgical outcomes.