Pneumocephalus after deep brain stimulation in Parkinson's disease: The role of brain volume in brain shift.

BACKGROUND: Parkinson's disease (PD) is characterized by dopaminergic neuron loss, causing motor symptoms such as bradykinesia and tremor. Deep-brain stimulation (DBS) targeting the subthalamic nucleus or internal globus pallidus is a standard treatment for advanced stages. However, intraoperative factors such as pneumocephalus and cerebrospinal fluid leakage can induce brain shift, potentially compromising electrode placement. This study investigated the relationships between pneumocephalus, cerebral atrophy, and brain shift. METHODS: A retrospective review was conducted on PD patients who underwent DBS. Pneumocephalus and total intracranial volume (TIV) were segmented from postoperative computed tomography scans using 3D Slicer, while brain volume was calculated through Computational Anatomy Toolbox (CAT12). The brain index was defined as brain volume/TIV. Associations were analyzed using multiple linear regression. RESULTS: Thirty-eight patients were included (45 surgeries; 70% male). Mean electrode tip displacement was 1.11 mm (standard deviation [SD] = 3.43), 0.75 mm (SD = 0.86), and 0.54 mm (SD = 1.70) along the x, y, and z axes, respectively. The regression model explained 42.8% of the variance in pneumocephalus (adjusted R2 = 0.355; p < 0.001). TIV (β = -0.497; p = 0.011), procedure duration (β = 0.361, p = 0.011) and female sex (p = 0.001) were significant predictors. Conversely, brain index (p = 0.651) and DBS target (p = 0.284) showed no significant association. CONCLUSION: Pneumocephalus after DBS is influenced by total cranial volume, surgical duration, and sex. While brain atrophy was not a predictor. Pneumocephalus causes linear and angular brain shift, affecting electrode positioning across axes. These findings may inform strategies to enhance surgical precision.