title: Gamma Knife Radiosurgery as Primary Treatment for Large Vestibular Schwannomas: Clinical Results at Long-Term Follow-Up in a Series of 59 Patients.
abstract: BACKGROUND
  Gamma Knife radiosurgery (GKRS) represents a well-accepted treatment for small-medium vestibular schwannomas (VS); however, its application in larger VS is still controversial.
  
  
  METHODS
  Among the 523 patients treated at our institution for VS between 2001 and 2010, we included 59 patients with a VS larger than 25 mm, treated by GKRS as primary treatment, not affected by neurofibromatosis type 2, and with a clinical follow-up of at least 36 months. Five patients underwent ventriculoperitoneal shunt placement before radiosurgery. Clinical follow-up (mean, 79.4 months) was obtained in all patients. Patients' age ranged from 24 to 85 years (mean, 63.8 years). Mean tumor volume was 5.98 cm3(maximum, 14.3 cm3) and median marginal dose was 13 Gy. A statistical analysis was performed to correlate clinical outcome with tumor radiologic features, dose-planning parameters, and patients' characteristics.
  
  
  RESULTS
  Tumor control was achieved in 98.3% of cases. At last follow-up, 86.4% of VS showed volume reduction. Recorded complications were 3 cases (5.1%) of new permanent facial nerve deficit, 4 cases (6.8%) of new or worsened trigeminal impairment, and 10 new cases (18.5%) of hydrocephalus requiring ventriculoperitoneal shunt. Larger tumor size was significantly associated with a subsequent ventricular enlargement. Overall, functional hearing preservation rate was 31.3% (66.7% among patients with Gardner-Robertson I).
  
  
  CONCLUSIONS
  Surgical resection remains the primary approach for large VS with symptomatic brainstem compression. GKRS can be considered a safe and effective option in particular in patients who are not good candidates for surgery.
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Bailo
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy. Electronic address: boari.nicola@hsr.it.
authors.forename: Nicola
authors.initials: N
authors.lastname: Boari
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Franzin
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Gagliardi
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Alfio
authors.initials: A
authors.lastname: Spina
authors.affiliation: Service of Medical Physics, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Del Vecchio
authors.affiliation: Service of Neuro-anesthesia, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Gemma
authors.affiliation: Service of Radiation Oncology, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Bolognesi
authors.affiliation: Department of Neurosurgery, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy; Service of Medical Physics, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy; Service of Neuro-anesthesia, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy; Service of Radiation Oncology, I.R.C.C.S. Ospedale San Raffaele, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Mortini
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D005155:Facial Nerve Diseases / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D034381:Hearing Loss / Q000453:epidemiology* / Q000503:physiopathology; D006801:Humans; D006849:Hydrocephalus / Q000453:epidemiology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000532:radiotherapy*; D016634:Radiosurgery; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016896:Treatment Outcome; D020433:Trigeminal Nerve Diseases / Q000453:epidemiology; D047368:Tumor Burden; D017287:Ventriculoperitoneal Shunt; D055815:Young Adult
keywords: Acoustic Neuroma; Gamma Knife; Hearing preservation; Large; Radiosurgery; Vestibular Schwannoma