title: Safety and Efficacy of Gamma Knife Radiosurgery for the Management of Koos Grade 4 Vestibular Schwannomas.
abstract: BACKGROUND
  Gamma Knife radiosurgery (GKRS) is commonly used in treating small vestibular schwannomas; however, its use for larger vestibular schwannomas is still controversial.
  
  
  OBJECTIVE
  To assess the long-term safety and efficacy of treating eligible Koos grade 4 vestibular schwannomas with GKRS.
  
  
  METHODS
  We conducted a single-center, retrospective evaluation of patient undergoing GKRS for Koos grade 4 vestibular schwannomas. We evaluated clinical, imaging, and treatment characteristics and assessed treatment outcome. Inclusion criteria were tumor size of ≥4 cm and follow-up of at least 6 months. Patients with neurofibromatosis type 2 were excluded. Primary outcomes measured were tumor control rate, hearing and facial function preservation rate, and complications. All possible factors were analyzed to assess clinical significance.
  
  
  RESULTS
  Sixty-eight patients met inclusion criteria. Median follow-up was 47 months (range, 6-125 months). Baseline hearing was serviceable in 60%. Median tumor volume at radiosurgery was 7.4 cm (range, 4-19 cm). The median marginal dose used was 12 Gy at the 50% isodose line. Actuarial tumor control rates were 95% and 92% at 2 and 10 years, respectively. Actuarial serviceable hearing preservation rates were 89% and 49% at 2 and 5 years, respectively. Facial nerve preservation was 100%. Clinical complications included balance disturbance (11%), facial pain (10%), facial numbness (5%), and tinnitus (10%). Most complications were mild and transient. Hydrocephalus occurred in 3 patients, requiring ventriculoperitoneal shunt insertion. Larger tumor size was significantly associated with persisting symptoms post-treatment.
  
  
  CONCLUSIONS
  Patients with Koos grade 4 vestibular schwannomas and minimal symptoms can be treated safely and effectively with GKRS.
authors.affiliation: *Neurosurgery Division, Université de Sherbrooke, Centre Hospitalier Universitaire de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Quebec, Canada; ‡Saudi National Neuroscience Institute, Riyadh, Saudi Arabia.
authors.forename: Christian
authors.initials: C
authors.lastname: Iorio-Morin
authors.forename: Fahd
authors.initials: F
authors.lastname: AlSubaie
authors.forename: David
authors.initials: D
authors.lastname: Mathieu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005154:Facial Nerve; D005157:Facial Pain / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006309:Hearing; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology / Q000601:surgery; D006987:Hypesthesia / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D061214:Patient Safety; D011183:Postoperative Complications; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods*; D012189:Retrospective Studies; D012678:Sensation Disorders / Q000209:etiology; D014012:Tinnitus / Q000209:etiology; D016896:Treatment Outcome; D017287:Ventriculoperitoneal Shunt; D055815:Young Adult