Prognostic Factors of Hearing Outcome in Untreated Vestibular Schwannomas: Implication of Subdivision of Their Growth by Volumetric Analysis.

Background: Conservative wait-and-scan management for vestibular schwannomas (VSs) is an important treatment option, but its role is unclear because of discordance between tumor growth and hearing outcomes.

Methods: The present study was a retrospective analysis of 97 patients with sporadic VSs without treatment who were followed-up between 2003 and 2012. Tumor volume was measured by 3-dimensional volumetry at each follow-up visit. The median follow-up duration was 47 months (range, 13-122 months). The relationship between the tumor growth rate and hearing outcome was compared according to stratification of the initial tumor volumes.

Results: Hearing impairment was related significantly to the initial hearing status (Gardner-Robertson grade ≥2), initial tumor volume (≥0.1 cm3), and tumor growth (≥0.10 cm3/year). During 4 years of follow-up, 26% and 42% of the patients with untreated VS showed rapid tumor growth and hearing impairment, respectively. For tumors with an initial volume of 0.1-3.0 cm3, hearing impairment during the conservative management period was inversely proportional to the tumor volume.

Conclusions: Conservative management could be especially valid for small (<0.10 cm3), noncystic VSs in patients with Gardner-Robertson grade 1 at diagnosis. However, for tumors with a small-to-medium initial volume (0.10-3.0 cm3), future hearing impairment might be inversely proportional to tumor growth rate. Therefore, small-to-medium sized tumors should be followed-up more closely regardless of the initial hearing impairment.