2026 Poster Presentations
P509: RADIOLOGIC ANALYSIS OF ACOUSTIC NEUROMA POSITION ON SURGICAL OUTCOMES
Hayley A Granberg, BA; Alireza Zonnour, MD; Gabriela S Navarro-Parga; Kenneth Thomas, BS; Krish Suresh; Michael Brandel, MD; Douglas Bennion, MD, PhD; Rick Friedman, MD, PhD; Marc Schwartz, MD; University of California San Diego
Background: Large vestibular schwannomas (VS) often compress the brainstem and have variable anatomic relationships to the internal auditory canal (IAC). These factors can be identified on preoperative imaging, however their significance is unknown. Thus, the aim of this retrospective cohort study is to quantitatively assess the impact of brainstem compression (BSC) and position relative to the IAC on surgical outcomes in VS.
Methods: We identified 196 patients with sporadic unilateral VS larger than 3 centimeters who underwent surgery at a single academic institution between 2017-2022. Patients with neurofibromatosis 2 were excluded. MRI T1 post-contrast axial images were used for measurements. BSC was quantified by drawing a baseline from the brainstem anteriorly to the cerebellum posteriorly, then drawing a second perpendicular line to the point of maximal compression. Anterior and posterior IAC extension were measured relative to a line bisecting the IAC from porus to fundus. Additional variables included demographics, surgical approach, postoperative facial nerve function, extent of resection, length of stay, and postoperative complications including CSF leak and meningitis.
Results: Greater anterior extension relative to the IAC was significantly associated with decreased likelihood of achieving a gross total resection (GTR) in both univariate (OR=1.12, 95% CI 1.015-1.256, p=0.03) and partially adjusted multivariate analysis (OR=0.884, 95% CI 0.789-0.982, p=0.0256), but not after full adjustment for age and tumor size (p=0.18). Greater BSC was significantly associated with worse facial nerve function at 2-3 weeks postoperatively (OR=1.08, 95% CI 1.01-1.16, p=0.036). Posterior extension was significantly associated with increased LOS in univariate analysis (b=217.57 minutes, 95% CI 29.76-405.37, p=0.024), but this relationship lost significance after adjusting for age and other patient-level characteristics. Anterior extension and BSC was not significantly associated with LOS.
Conclusion: Anterior tumor extension and BSC are radiographic features that may influence extent of resection and transient facial nerve outcomes, respectively. Posterior extension may impact hospital LOS, though this appears to be confounded by demographic factors. These findings may support individualized preoperative counseling and surgical planning for patients with large VS.