title: Do we really still need an open surgery for treatment of patients with vestibular schwannomas?
abstract: BACKGROUND
  Gamma Knife surgery (GKS) should be considered a standard treatment option for small and medium-sized vestibular schwannomas (VSs). It results in a tumor control rate similar to that seen with microsurgery and provides better preservation of facial nerve function and hearing.
  
  
  METHODS
  From December 2002 to April 2011, a total of 260 patients with VS underwent GKS using Leksell Gamma Knife model 4C with an automatic positioning system. There were 30 Koos stage I tumors, 112 stage II, 100 stage III, and 18 stage IV. All patients were treated with the use of high-resolution magnetic resonance imaging; creation of the highly precise conformal and selective multi-isocenter dose planning with small collimators, carefully sparing adjacent cranial nerves of any excessive irradiation; and creation of a wide 80 % isodose area within the tumor while applying a low marginal dose (mean 11.9 Gy) at the 50 % isodose line.
  
  
  RESULTS
  Among 182 patients who were followed for more than 3 years after treatment, the tumor control and shrinkage rates were 98.4 % and 76.4 %, respectively. Volume reduction of >50 % was marked in 54.9 % of VSs. Preservation of facial nerve function and hearing at the pretreatment level was noted in 97.8 % and 87.9 %, respectively. There was marked improvement of facial nerve function and hearing after GKS in 2.2 % and 3.8 %, respectively. There was no major morbidity.
  
  
  CONCLUSIONS
  Due to contemporary technological and methodological achievements GKS can be focused not only on growth control but on shrinking the VS, with possible reversal of the neurological deficit.
authors: Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan. gkrmoto@aol.com
authors: Motohiro
authors: M
authors: Hayashi
authors: Mikhail F
authors: MF
authors: Chernov
authors: Samuel M
authors: SM
authors: Lipski
authors: Noriko
authors: N
authors: Tamura
authors: Shoji
authors: S
authors: Yomo
authors: Ayako
authors: A
authors: Horiba
authors: Shyunsuke
authors: S
authors: Tsuzuki
authors: Masahiro
authors: M
authors: Izawa
authors: Yoshikazu
authors: Y
authors: Okada
authors: Yoshihiro
authors: Y
authors: Muragaki
authors: Hiroshi
authors: H
authors: Iseki
authors: Pavel
authors: P
authors: Ivanov
authors: Jean
authors: J
authors: Régis
authors: Kintomo
authors: K
authors: Takakura
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D009493:Neurosurgery / Q000379:methods*; D016634:Radiosurgery / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods; D016896:Treatment Outcome