title: Irradiation of cochlear structures during vestibular schwannoma radiosurgery and associated hearing outcome.
abstract: OBJECTIVE
  The purpose of this study was to measure the dose of radiation delivered to the cochlea during a Gamma knife surgery (GKS) procedure for treatment of patients with vestibular schwannomas (VSs), and to analyze the relationship between cochlear irradiation and the hearing outcome of these patients.
  
  
  METHODS
  Eighty-two patients with VSs were treated with GKS using a marginal dose of 12 Gy. No patient had neurofibromatosis Type 2 disease, and all had a Gardner-Robertson hearing class of I to IV before treatment, and a radiological and audiological follow-up of at least 1-year after GKS. The dosimetric data of the volume of the cochlea were retrospectively analyzed and were correlated with the auditory outcome of patients.
  
  
  RESULTS
  The mean radiation dose delivered to the cochlear volume ranged from 1.30 to 10.00 Gy (median 4.15 Gy). The cochlea received significantly higher radiation doses in patients with worsening of hearing after GKS. A highly significant association between the cochlear and the intracanalicular dose of radiation delivered during GKS was found.
  
  
  CONCLUSIONS
  During GKS for VSs, relatively high doses of radiation can be delivered to the cochlea. Worsening of hearing after GKS can be the consequence of either radiation injury to the cochlea or the irradiation dose delivered into the auditory canal, or both.
authors.affiliation: Gamma Knife Center, University Hospital Erasme, Brussels, Belgium. nmassage@ulb.ac.be
authors.forename: Nicolas
authors.initials: N
authors.lastname: Massager
authors.forename: Ouzi
authors.initials: O
authors.lastname: Nissim
authors.forename: Carine
authors.initials: C
authors.lastname: Delbrouck
authors.forename: Isabelle
authors.initials: I
authors.lastname: Delpierre
authors.forename: Daniel
authors.initials: D
authors.lastname: Devriendt
authors.forename: Françoise
authors.initials: F
authors.lastname: Desmedt
authors.forename: David
authors.initials: D
authors.lastname: Wikler
authors.forename: Jacques
authors.initials: J
authors.lastname: Brotchi
authors.forename: Marc
authors.initials: M
authors.lastname: Levivier
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003051:Cochlea / Q000502:physiology / Q000528:radiation effects; D003056:Cochlear Nerve / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D005500:Follow-Up Studies; D006309:Hearing; D034381:Hearing Loss / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D011183:Postoperative Complications; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014725:Vestibular Nerve / Q000601:surgery*