title: Gamma knife surgery for skull base meningiomas. The effectiveness of low-dose treatment.
abstract: BACKGROUND
  The surgical removal of skull base meningiomas has a high morbidity rate, even by modern microsurgical standards. We evaluated the results of gamma knife surgery for skull base meningiomas using a relatively low radiation dose for the tumor margins.
  
  
  METHODS
  We reviewed 24 cases of skull base meningiomas during a 30-month period. The locations of the tumors were the petroclival region in 11 cases, the cavernous sinus region in 9 cases, and the cerebellopontine angle region in 4 cases. Eight patients (33%) had been operated on previously and fourteen patients (67%) had been treated by neuroimaging. The marginal doses for the tumors were 8 Gy to 15 Gy (median, 10.6 Gy). A large petroclival tumor 58 mm in diameter was treated with a staged treatment protocol with a 6-month interval between treatments.
  
  
  RESULTS
  Tumor regression was observed in 46% of the patients imaged during the follow-up period (median, 17.1 months). No patients revealed tumor growth in the follow-up period (100% tumor control rate). Eleven patients (46%) had improved clinically by the time of the follow-up examinations. Preexisting cranial nerve deficit in one patient worsened because of radiation injury.
  
  
  CONCLUSIONS
  Although a longer follow-up period is required, the relatively low minimum tumor radiation dose treatment for skull base meningiomas using a gamma knife seems to be an effective treatment with low morbidity.
authors.affiliation: Department of Neurosurgery, Osaka City General Hospital, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Iwai
authors.forename: K
authors.initials: K
authors.lastname: Yamanaka
authors.forename: T
authors.initials: T
authors.lastname: Yasui
authors.forename: M
authors.initials: M
authors.lastname: Komiyama
authors.forename: M
authors.initials: M
authors.lastname: Nishikawa
authors.forename: H
authors.initials: H
authors.lastname: Nakajima
authors.forename: H
authors.initials: H
authors.lastname: Kishi
mesh_terms: D000328:Adult; D000368:Aged; D002426:Cavernous Sinus; D002530:Cerebellopontine Angle; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008579:Meningioma / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008875:Middle Aged; D010579:Petrous Bone; D016634:Radiosurgery / Q000295:instrumentation*; D019292:Skull Base Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome