Quantitative Intracranial Pressure Changes in Endoscopic Skull Base Surgery

Background: Endoscopic skull base surgery (ESBS) is increasingly utilized for anterior skull base pathologies, yet postoperative management protocols—especially those restricting patient maneuvers to avoid intracranial pressure (ICP) fluctuations—are largely based on anecdotal evidence. This study aims to provide quantitative data on ICP changes during common intraoperative maneuvers to inform evidence-based postoperative care. Methods: Eight adult patients undergoing ESBS with preoperative lumbar drain (LD) placement and no intraoperative CSF leak were prospectively enrolled. Intraoperative ICP was measured continuously via a LD transduction system during two sets of maneuvers: (1) incremental Valsalva maneuvers (0, 10, 20, 30, 40 cm H 2 O) and (2) head of bed (HOB) elevation at -15°, 0°, 15°, 30°, and 45° ( Table 1 ). Average ICP and standard error were calculated for each condition. Linear regression was used to assess the relationship between maneuver intensity and ICP change. Effect sizes (Cohen’s d) and 95% confidence intervals were computed for key comparisons. Results: ICP increased linearly with Valsalva pressure (R 2 = 0.96), rising from 9.75 ± 0.86 mm Hg at baseline to 14.75 ± 1.33 mm Hg at 40 cm H 2 O (Δ = +4.75 ± 0.82 mm Hg) ([ Fig. 1 ]). HOB elevation produced a linear decrease in ICP (R 2 = 0.98), from 14.00 ± 1.48 mm Hg at -15° to -1.50 ± 1.89 mm Hg at 45° (Δ = -10.83 ± 1.19 mm Hg) ([ Fig. 2 ]). Effect sizes were large for both Valsalva 40 vs 0 cm H 2 O (Cohen’s d = 2.42, 95% CI: [0.95, 3.89]) and HOB changes (HOB -15 vs 0: d = 2.15, [0.80, 3.50]; HOB 45 vs 0: d = 2.30, [0.89, 3.71]). Conclusion: Both Valsalva maneuvers and HOB elevation result in significant, predictable changes in ICP during ESBS. Valsalva increases ICP in a dose-dependent manner, while HOB elevation decreases ICP, with both effects being large and clinically meaningful. These findings provide quantitative support for current postoperative precautions and highlight the need for further study in awake, postoperative patients to refine evidence-based protocols. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany