Predictive factors associated with interval changes in STN-DBS lead-tip position between immediate and delayed...

Brain shift during deep brain stimulation (DBS) surgery may contribute to changes in lead position. Although intracranial air volume is considered an important factor, other intraoperative factors may also influence lead displacement. This study evaluated interval changes in subthalamic nucleus (STN)-DBS lead-tip position between immediate and delayed postoperative computed tomography (CT) and investigated factors associated with these changes, including intracranial air volume and intraoperative head position.

We retrospectively analyzed 42 DBS leads implanted bilaterally in the STN of 21 patients with Parkinson's disease. Lead-tip coordinates were assessed using Elements software (Brainlab) on CT obtained immediately after implantation and after resolution of intracranial air. Interval displacement was defined as the difference in lead-tip coordinates between the delayed and immediate postoperative CT scans. Intraoperative head position was quantified as "Angle A," measured from the horizontal reference line to the anterior commissure-posterior commissure line. Associations between potential explanatory factors and lead-tip displacement were assessed using linear mixed-effects models with patient included as a random intercept to account for within-patient correlation between bilateral leads.

Lead-tip positions showed significant interval displacement in the lateral, anterior, and caudal directions. In univariable mixed-effects analysis, intracranial air volume was significantly associated with anterior displacement (β = 0.033, 95% CI 0.018-0.048, p < 0.001), whereas Angle A was not (β = -0.030, 95% CI - 0.067-0.007, p = 0.111). In a multivariable mixed-effects model including intracranial air volume and Angle A, intracranial air volume remained significantly associated with anterior displacement (β = 0.0289, 95% CI 0.0110-0.0469, p = 0.002), while a larger Angle A was associated with less anterior displacement (β = -0.0270, 95% CI - 0.0535 to - 0.0004, p = 0.047).

Intracranial air volume was consistently associated with anterior STN-DBS lead-tip displacement between immediate and delayed postoperative CT. Intraoperative head position was also associated with anterior displacement after adjustment for intracranial air volume, although this finding was of borderline statistical significance and should be considered exploratory. These findings support efforts to minimize intracranial air entry during DBS implantation, while the potential influence of intraoperative head positioning requires further prospective investigation.