title: Stereotactic radiosurgery for vestibular schwannomas in patients with neurofibromatosis type 2: an analysis of tumor control, complications, and hearing preservation rates.
abstract: OBJECTIVE
  Vestibular schwannomas present significant management challenges in patients with neurofibromatosis Type 2 (NF2). We evaluated the results of gamma knife radiosurgery for the management of these tumors, focusing on tumor response, hearing preservation, and other factors affecting outcomes.
  
  
  METHODS
  Stereotactic radiosurgery was performed to manage 74 schwannomas in 62 patients. Ipsilateral serviceable hearing was present in 35% of tumors before the procedure. The mean tumor volume was 5.7 cm3. The mean margin and maximum dose used were 14 and 27.5 Gy, respectively. Cox regression analyses were performed to identify factors affecting outcomes.
  
  
  RESULTS
  The median follow-up period was 53 months, and two patients were lost to follow-up. Actuarial local control rates at were 85, 81, and 81% at 5, 10, and 15 years, respectively. Tumor volume was significant as a predictor of local control. Since 1992, using current radiosurgery techniques (magnetic resonance imaging scan targeting and reduced margin dose to 14 Gy or less), the actuarial serviceable hearing preservation rate is 73% at 1 year, 59% at 2 years, and 48% at 5 years after radiosurgery. Facial neuropathy occurred in 8% of tumors, trigeminal neuropathy occurred in 4%, and vestibular dysfunction occurred in 4%. Radiation dose and tumor volume were predictive of development of new deficits. No radiosurgery-associated secondary tumors or atypical or malignant changes were noted.
  
  
  CONCLUSIONS
  Stereotactic radiosurgery is a safe and effective management modality for neurofibromatosis Type 2 vestibular schwannomas. Although results do not seem to be as good as for patients with sporadic unilateral tumors, gamma knife radiosurgery results seem favorable and indicate that radiosurgery should be strongly considered for primary tumor management in selected patients.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh School of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: David
authors.initials: D
authors.lastname: Mathieu
authors.forename: Douglas
authors.initials: D
authors.lastname: Kondziolka
authors.forename: John C
authors.initials: JC
authors.lastname: Flickinger
authors.forename: Ajay
authors.initials: A
authors.lastname: Niranjan
authors.forename: Richard
authors.initials: R
authors.lastname: Williamson
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Martin
authors.forename: L Dade
authors.initials: LD
authors.lastname: Lunsford
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000453:epidemiology* / Q000601:surgery*; D016518:Neurofibromatosis 2 / Q000453:epidemiology* / Q000601:surgery*; D010414:Pennsylvania / Q000453:epidemiology; D016634:Radiosurgery / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D016896:Treatment Outcome