title: Hearing outcomes after stereotactic radiosurgery for unilateral intracanalicular vestibular schwannomas: implication of transient volume expansion.
abstract: OBJECTIVE
  We evaluated the prognostic factors for hearing outcomes after stereotactic radiosurgery (SRS) for unilateral sporadic intracanalicular vestibular schwannomas (IC-VSs) as a clinical homogeneous group of VSs.
  
  
  METHODS
  Sixty consecutive patients with unilateral sporadic IC-VSs, defined as tumors in the internal acoustic canal, and serviceable hearing (Gardner-Roberson grade 1 or 2) were treated with SRS as an initial treatment. The mean tumor volume was 0.34±0.03 cm3 (range, 0.03-1.00 cm3), and the mean marginal dose was 12.2±0.1 Gy (range, 11.5-13.0 Gy). The median follow-up duration was 62 months (range, 36-141 months).
  
  
  RESULTS
  The actuarial rates of serviceable hearing preservation were 70%, 63%, and 55% at 1, 2, and 5 years after SRS, respectively. In multivariate analysis, transient volume expansion of ≥20% from initial tumor size was a statistically significant risk factor for loss of serviceable hearing and hearing deterioration (increase of pure tone average≥20 dB) (odds ratio=7.638; 95% confidence interval, 2.317-25.181; P=.001 and odds ratio=3.507; 95% confidence interval, 1.228-10.018; P=.019, respectively). The cochlear radiation dose did not reach statistical significance.
  
  
  CONCLUSIONS
  Transient volume expansion after SRS for VSs seems to be correlated with hearing deterioration when defined properly in a clinically homogeneous group of patients.
authors.affiliation: Department of Neurosurgery, Seoul National University Bundang Hospital, Seongnam-si, Korea.
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Kim
authors.forename: Dong Gyu
authors.initials: DG
authors.lastname: Kim
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Han
authors.forename: Hyun-Tai
authors.initials: HT
authors.lastname: Chung
authors.forename: In Kyung
authors.initials: IK
authors.lastname: Kim
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Song
authors.forename: Jeong-Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Jin Wook
authors.initials: JW
authors.lastname: Kim
authors.forename: Yong Hwy
authors.initials: YH
authors.lastname: Kim
authors.forename: Chul-Kee
authors.initials: CK
authors.lastname: Park
authors.forename: Chae-Yong
authors.initials: CY
authors.lastname: Kim
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Paek
authors.forename: Hee-Won
authors.initials: HW
authors.lastname: Jung
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003051:Cochlea / Q000528:radiation effects; D004424:Ear Canal; D005260:Female; D005500:Follow-Up Studies; D006309:Hearing / Q000528:radiation effects*; D034381:Hearing Loss / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D011379:Prognosis; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D012307:Risk Factors; D013997:Time Factors; D047368:Tumor Burden; D055815:Young Adult