title: Radiosurgery for para-IAC meningiomas: the effect of radiation dose to the cochlea on hearing outcome.
abstract: OBJECTIVE
  This study was performed to assess the radiosurgical results of meningiomas extending into the internal acoustic canal (para-IAC meningiomas), with a particular focus on the effect of radiation dose to the cochlea on hearing outcome.
  
  
  METHODS
  A total of 50 patients who underwent radiosurgery for para-IAC meningiomas between 1998 and 2009, which were followed for 2 years, were enrolled. The mean age was 55.8 years (range, 15-75). The mean tumor volume was 6.1 cm(3) (range, 1.0-19.0), the mean tumor length in the IAC was 6.9 mm (range, 1.3-13.3), and the mean prescribed marginal dose was 13.1 Gy (range, 10-15) at an isodose line of 50%. The mean follow-up duration was 46 months (range, 24-122).
  
  
  RESULTS
  Eight (16.0%) patients had nonserviceable hearing at the time of surgery. At the last follow-up, the tumor control rate was 94%; unchanged in 17 patients, decreased in 30 patients, and increased in 3 patients. Among 42 patients with serviceable hearing at the time of radiosurgery, it was preserved in 41 (97.6%) patients at the last follow-up. The maximal and mean radiation doses to the cochleae of these 41 patients were 5.8 Gy ± 0.3 (range, 3.1-11.5) and 4.3 Gy ± 0.2 (range, 2.2-7.5), respectively. The maximal dose to the cochlea of the patient who lost hearing after radiosurgery was 4.7 Gy.
  
  
  CONCLUSIONS
  The radiation dose to the cochlea may have the minimal toxic effect on the hearing outcome in patients who undergo radiosurgery for para-IAC meningiomas.
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: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003051:Cochlea / Q000528:radiation effects*; D005260:Female; D006309:Hearing / Q000528:radiation effects*; D006801:Humans; D015192:Infratentorial Neoplasms / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000601:surgery*; D008579:Meningioma / Q000601:surgery*; D008875:Middle Aged; D011829:Radiation Dosage; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult