Abstract
Objectives We examined vestibular schwannoma tumor dimension and direction of growth to determine
whether these correlate with facial nerve outcome as well as extent of resection (EOR).
Design Retrospective review of prospectively maintained databases.
Participants 206 patients were a part of this study.
Main Outcome Measures Tumor dimensions were measured using preoperative magnetic resonance imaging, and
a series of ratios were then calculated to further characterize tumor dimension. Regression
analyses were performed to investigate correlation with facial nerve outcome and EOR.
Results Patients with tumor extending >1.5 cm anterior to the internal auditory canal (IAC)
(AB measurement) were three times more likely to have postoperative House-Brackman
grades of 3 or worse. We also found that an EB/BF ratio (representing elongated growth
parallel to the IAC axis) ≥1.1 was associated with half the risk of poor facial nerve
outcome. Tumors with anterior-posterior diameter (AC measurement) >1.9 cm were five
times less likely to undergo gross total resection (GTR). Furthermore, an increased
degree of tumor extension into the IAC (DE measurement >2.4 cm) or an increased amount
of brainstem compression (EB measurement >1.1 cm) were each associated with a nearly
3-fold decrease in the likelihood of GTR.
Conclusion Our study demonstrates that anterior extent of the tumor is as important as tumor
size to facial nerve outcome and degree of resection for vestibular schwannomas.
Keywords
acoustic neuroma - anterior extension - facial nerve outcome - tumor dimension - vestibular
schwannoma
