title: Outpatient gamma knife surgery for vestibular schwannoma: definition of the therapeutic profile based on a 10-year experience.
abstract: OBJECTIVE
  The purpose of the study was to define the therapeutic profile of outpatient gamma knife surgery (GKS) for vestibular schwannoma (VS) by using sequential tumor volumetry to quantify changes following treatment.
  
  
  METHODS
  A total of 111 patients met the inclusion criteria. The median follow-up duration was 7 years (range 5-9.6 years). Thirty-seven patients (33%) had undergone surgery before GKS and 10 (9%) had neurofibromatosis Type 2 (NF2). The median VS volume was 1.6 cm3 (range 0.08-8.7 cm3). The actuarial 6-year tumor control rate after a single GKS treatment was 95%. Tumor swelling was observed in 43 patients (38.7%). Recurrence was significantly associated with NF2 (p < 0.003) and the reduced dose (p < 0.03) delivered to these tumors. The incidence of facial nerve neuropathy was mainly determined by surgery prior to GKS (p < 0.0001). Facial nerve radiation toxicity was mild and transient. No permanent facial nerve toxicity was observed. Trigeminal neuropathy occurred in 13 patients, and this was correlated with the VS volume (p < 0.02). The median hearing loss was -10 dB (range + 20 dB to -70 dB). The risk of hearing loss was correlated with age and transient tumor swelling (p < 0.05) but not with dose parameters or NF2.
  
  
  CONCLUSIONS
  Outpatient GKS is feasible, effective, and safe. Its therapeutic profile compares favorably with that of microsurgery.
authors.affiliation: Gamma Knife Center Munik, and Department of Neurosurgery and Ear, Nose, and Throat Surgery, Ludwig-Maximilians- University, Klinikum Grosshadern, Munich, Germany. wowra@gammaknife.de
authors.forename: Berndt
authors.initials: B
authors.lastname: Wowra
authors.forename: Alexander
authors.initials: A
authors.lastname: Muacevic
authors.forename: Anja
authors.initials: A
authors.lastname: Jess-Hempen
authors.forename: John-Martin
authors.initials: JM
authors.lastname: Hempel
authors.forename: Stefanie
authors.initials: S
authors.lastname: Müller-Schunk
authors.forename: Jörg-Christian
authors.initials: JC
authors.lastname: Tonn
mesh_terms: D000553:Ambulatory Care; D005158:Facial Paralysis / Q000209:etiology / Q000503:physiopathology; D005500:Follow-Up Studies; D006801:Humans; D009464:Neuroma, Acoustic / Q000150:complications / Q000601:surgery*; D011829:Radiation Dosage; D016634:Radiosurgery / Q000295:instrumentation*; D014277:Trigeminal Neuralgia / Q000209:etiology / Q000503:physiopathology; D047368:Tumor Burden / Q000528:radiation effects