title: Gamma Knife radiosurgery for facial nerve schwannomas: a multicenter study.
abstract: OBJECTIVE
  Facial nerve schwannomas (FNSs) are rare intracranial tumors, and the optimal management of these tumors remains unclear. Resection can be undertaken, but the tumor's intimate association with the facial nerve makes resection with neurological preservation quite challenging. Stereotactic radiosurgery (SRS) has been used to treat FNSs, and this study evaluates the outcome of this approach.
  
  
  METHODS
  At 8 medical centers participating in the North American Gamma Knife Consortium (NAGKC), 42 patients undergoing SRS for an FNS were identified, and clinical and radiographic data were obtained for these cases. Males outnumbered females at a ratio of 1.2:1, and the patients' median age was 48 years (range 11-76 years). Prior resection was performed in 36% of cases. The mean tumor volume was 1.8 cm(3), and a mean margin dose of 12.5 Gy (range 11-15 Gy) was delivered to the tumor.
  
  
  RESULTS
  At a median follow-up of 28 months, tumor control was achieved in 36 (90%) of the 40 patients with reliable radiographic follow-up. Actuarial tumor control was 97%, 97%, 97%, and 90% at 1, 2, 3, and 5 years postradiosurgery. Preoperative facial nerve function was preserved in 38 of 42 patients, with 60% of evaluable patients having House-Brackmann scores of 1 or 2 at last follow-up. Treated patients with a House-Brackmann score of 1 to 3 were more likely to demonstrate this level of facial nerve function at last evaluation (OR 6.09, 95% CI 1.7-22.0, p = 0.006). Avoidance of temporary or permanent neurological symptoms was more likely to be achieved in patients who received a tumor margin dose of 12.5 Gy or less (log-rank test, p = 0.024) delivered to a tumor of ≤ 1 cm(3) in volume (log-rank test, p = 0.01).
  
  
  CONCLUSIONS
  Stereotactic radiosurgery resulted in tumor control and neurological preservation in most FNS patients. When the tumor is smaller and the patient exhibits favorable normal facial nerve function, SRS portends a better result. The authors believe that early, upfront SRS may be the treatment of choice for small FNSs, but it is an effective salvage treatment for residual/recurrent tumor that remain or progress after resection.
authors.affiliation: University of Virginia, Charlottesville, Virginia;
authors.forename: Jason P
authors.initials: JP
authors.lastname: Sheehan
authors.affiliation: University of Pittsburgh, Pennsylvania;
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kano
authors.affiliation: University of Virginia, Charlottesville, Virginia;
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Yale University, New Haven, Connecticut;
authors.forename: Veronica
authors.initials: V
authors.lastname: Chiang
authors.affiliation: Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Quebec, Canada and.
authors.forename: David
authors.initials: D
authors.lastname: Mathieu
authors.affiliation: Cleveland Clinic, Cleveland, Ohio;
authors.forename: Samuel
authors.initials: S
authors.lastname: Chao
authors.affiliation: University of Pittsburgh, Pennsylvania;
authors.forename: Berkcan
authors.initials: B
authors.lastname: Akpinar
authors.affiliation: University of Pennsylvania, Philadelphia, Pennsylvania;
authors.forename: John Y K
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Yale University, New Haven, Connecticut;
authors.forename: James B
authors.initials: JB
authors.lastname: Yu
authors.affiliation: Yale University, New Haven, Connecticut;
authors.forename: Judith
authors.initials: J
authors.lastname: Hess
authors.affiliation: Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Hsiu-Mei
authors.initials: HM
authors.lastname: Wu
authors.affiliation: Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Wen-Yuh
authors.initials: WY
authors.lastname: Chung
authors.affiliation: University of Pennsylvania, Philadelphia, Pennsylvania;
authors.forename: John
authors.initials: J
authors.lastname: Pierce
authors.affiliation: Cleveland Clinic, Cleveland, Ohio;
authors.forename: Symeon
authors.initials: S
authors.lastname: Missios
authors.affiliation: New York University, New York, New York;
authors.forename: Douglas
authors.initials: D
authors.lastname: Kondziolka
authors.affiliation: University of Pennsylvania, Philadelphia, Pennsylvania;
authors.forename: Michelle
authors.initials: M
authors.lastname: Alonso-Basanta
authors.affiliation: Cleveland Clinic, Cleveland, Ohio;
authors.forename: Gene H
authors.initials: GH
authors.lastname: Barnett
authors.affiliation: University of Pittsburgh, Pennsylvania;
authors.forename: L Dade
authors.initials: LD
authors.lastname: Lunsford
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003390:Cranial Nerve Neoplasms / Q000601:surgery*; D005154:Facial Nerve / Q000601:surgery*; D005155:Facial Nerve Diseases / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000601:surgery*; D016634:Radiosurgery / Q000295:instrumentation*; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
keywords: FNS = facial nerve schwannoma; GKRS = Gamma Knife radiosurgery; Gamma Knife; NAGKC = North American Gamma Knife Consortium; SRS = sterotactic radiosurgery; facial nerve; facial schwannoma; meningioma; radiosurgery; stereotactic radiosurgery