Radiologic analysis of large vestibular schwannoma position on surgical outcomes

Large vestibular schwannomas (VS) often compress the brainstem and differ in their relation to the internal auditory canal (IAC); the significance of these radiographic features on postoperative outcomes remains unclear. This study quantifies the impact of brainstem compression (BSC) and position relative to the IAC on surgical outcomes in VS.

We retrospectively identified 116 patients with sporadic unilateral VS ≥ 3 centimeters (2017-2022). Neurofibromatosis 2 cases were excluded. BSC was quantified with MRI T1 post-contrast axial images as the perpendicular distance from the brainstem-cerebellum to the point of maximal compression. Anterior and posterior IAC extension were measured relative to a line bisecting the IAC from the porus to fundus. Outcomes included postoperative facial nerve (FN) function, extent of resection (EOR), and length of stay (LOS).

Greater anterior extension was associated with decreased EOR in univariate analysis (OR = 1.12, p = 0.03), but not after controlling for tumor size and age (OR = 1.09, p = 0.158). Greater BSC was associated with worse FN function at 2-3 weeks postoperatively on univariate (OR = 1.08, p = 0.036) and approached significance on multivariate analysis (OR = 1.07, p = 0.08). Posterior extension was associated with increased LOS in univariate (β = 217.57 min, p = 0.024), but not multivariate analysis. Neither anterior extension nor BSC were associated with LOS. Older age correlated with a lower rate of GTR and longer LOS in multivariate analysis (EOR: OR = 1.05, p = 0.003; LOS: β = 79.84 min, p = 0.026).

BSC is a radiographic feature that may be associated with short-term FN outcomes. EOR and LOS do not appear to be influenced by anterior or posterior extension, respectively, but rather appear to be confounded by age. These findings may inform individualized preoperative counseling and surgical planning for large VS.