title: The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes.
abstract: OBJECTIVE
  Observation is an important consideration when discussing management options for patients with vestibular schwannoma (VS). Most data regarding clinical outcomes after conservative management come from modestsized series performed at individual centers. The authors performed an analysis of the published literature on the natural history of VSs with respect to hearing outcome. Their objective was to provide a comprehensive and unbiased description of outcomes in patients whose disease was managed conservatively.
  
  
  METHODS
  The authors identified a total of 34 published studies containing hearing outcome data in patients with VSs < 25 mm in largest diameter who underwent observation management. The effects of initial tumor size and tumor growth rate on hearing function at latest follow-up were analyzed. Data from individual and aggregated cases were extracted from each study. Patients with poorer hearing (American Association of Otolaryngology-Head and Neck Surgery Classes C or D, or Gardner-Robertson Classes III, IV, or V) at the time of presentation were excluded.
  
  
  RESULTS
  A total of 982 patients met the inclusion criteria for this analysis, with a mean initial tumor size of 11.3 +/- 0.68 mm. The mean growth rate was 2.9 +/- 1.2 mm/year. The length of follow-up for these studies ranged from 26 to 52 months. Patients with preserved hearing at latest follow-up had a statistically larger initial tumor size than those whose hearing declined during the observation period (11.5 +/- 2.3 mm vs 9.3 +/- 2.7 mm, p < 0.0001), but the 2-mm difference of means was at the limit of imaging resolution and observer reliability. In contrast, patients with lower rates of tumor growth (<or= 2.5 mm/year) had markedly higher rates of hearing preservation (75 vs 32%, p < 0.0001) compared with patients with higher tumor growth rates. Interestingly, the authors' analysis found no difference in the rate of reported intervention for patients in either group (16 vs 18%, p = not significant).
  
  
  CONCLUSIONS
  These data suggest that a growth rate of > 2.5 mm/year is a better predictor of hearing loss than the initial tumor size for patients undergoing observation management of VSs < 25 mm in largest diameter.
authors.affiliation: Department of Neurological Surgery, University of California at San Francisco, California 94143, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Sughrue
authors.forename: Isaac
authors.initials: I
authors.lastname: Yang
authors.forename: Derick
authors.initials: D
authors.lastname: Aranda
authors.forename: Khadja
authors.initials: K
authors.lastname: Lobo
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Pitts
authors.forename: Steven W
authors.initials: SW
authors.lastname: Cheung
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Parsa
mesh_terms: D005155:Facial Nerve Diseases / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D006309:Hearing; D006311:Hearing Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D009464:Neuroma, Acoustic / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D011379:Prognosis