title: Gamma Knife surgery for patients with facial nerve schwannomas: a multiinstitutional retrospective study in Japan.
abstract: OBJECTIVE
  The aim of this study was to explore the efficacy and safety of stereotactic radiosurgery for patients with facial nerve schwannomas (FNSs).
  
  
  METHODS
  This study was a multiinstitutional retrospective analysis of 42 patients with FNSs treated with Gamma Knife surgery (GKS) at 1 of 10 medical centers of the Japan Leksell Gamma Knife Society (JLGK1301). The median age of the patients was 50 years. Twenty-nine patients underwent GKS as the initial treatment, and 13 patients had previously undergone surgery. At the time of the GKS, 33 (79%) patients had some degree of facial palsy, and 21 (50%) did not retain serviceable hearing. Thirty-five (83%) tumors were solid, and 7 (17%) had cystic components. The median tumor volume was 2.5 cm(3), and the median prescription dose to the tumor margin was 12 Gy.
  
  
  RESULTS
  The median follow-up period was 48 months. The last follow-up images showed partial remission in 23 patients and stable tumors in 19 patients. Only 1 patient experienced tumor progression at 60 months, but repeat GKS led to tumor shrinkage. The actuarial 3- and 5-year progression-free survival rates were 100% and 92%, respectively. During the follow-up period, 8 patients presented with newly developed or worsened preexisting facial palsy. The condition was transient in 3 of these patients. At the last clinical follow-up, facial nerve function improved in 8 (19%) patients, remained stable in 29 (69%), and worsened in 5 (12%; House-Brackmann Grade III in 4 patients, Grade IV in 1 patient). With respect to hearing function, 18 (90%) of 20 evaluated patients with a pure tone average of ≤ 50 dB before treatment retained serviceable hearing.
  
  
  CONCLUSIONS
  GKS is a safe and effective treatment option for patients with either primary or residual FNSs. All patients, including 1 patient who required repeat GKS, achieved good tumor control at the last follow-up. The incidence of newly developed or worsened preexisting facial palsy was 12% at the last clinical follow-up. In addition, the risk of hearing deterioration as an adverse effect of radiation was low. These results suggest that GKS is a safe alternative to resection.
authors.affiliation: Department of Neurosurgery, Komaki City Hospital, Komaki;
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hasegawa
authors.affiliation: Department of Neurosurgery, Komaki City Hospital, Komaki;
authors.forename: Takenori
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Neurosurgery, Kamiiida Daiichi General Hospital, Nagoya;
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kida
authors.affiliation: Department of Neurosurgery, Tokyo Women's Medical University, Tokyo;
authors.forename: Motohiro
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Nagoya Radiosurgery Center, Nagoya Kyoritsu Hospital, Nagoya;
authors.forename: Takahiko
authors.initials: T
authors.lastname: Tsugawa
authors.affiliation: Department of Neurosurgery, Osaka City General Hospital, Osaka;
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Iwai
authors.affiliation: Department of Neurosurgery, Kitanihon Neurosurgical Hospital, Gosen;
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Sato
authors.affiliation: Department of Neurosurgery, Takashima Hospital, Yonago;
authors.forename: Hisayo
authors.initials: H
authors.lastname: Okamoto
authors.affiliation: Department of Neurosurgery, Institute of Brain and Blood Vessels, Mihara Memorial Hospital, Isesaki;
authors.forename: Tadashige
authors.initials: T
authors.lastname: Kano
authors.affiliation: Department of Neurosurgery, Shonan Fujisawa Tokushukai Hospital, Fujisawa;
authors.forename: Seiki
authors.initials: S
authors.lastname: Osano
authors.affiliation: Department of Neurosurgery, Chiba Cerebral and Cardiovascular Center, Ichihara; and.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nagano
authors.affiliation: Department of Neurosurgery, Brain Attack Center, Ota Memorial Hospital, Fukuyama, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nakazaki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D003390:Cranial Nerve Neoplasms / Q000601:surgery*; D018450:Disease Progression; D005155:Facial Nerve Diseases / Q000473:pathology / Q000601:surgery*; D005158:Facial Paralysis / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000453:epidemiology; D016634:Radiosurgery / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
keywords: CPA = cerebellopontine angle; FNS = facial nerve schwannoma; GKS = Gamma Knife surgery; Gamma Knife; HB = House-Brackmann; PTA = pure tone average; SRS = stereotactic radiosurgery; facial nerve schwannoma; functional neurosurgery; functional outcome; stereotactic radiosurgery; tumor control