title: Hearing preservation after gamma knife stereotactic radiosurgery of vestibular schwannoma.
abstract: BACKGROUND
  To evaluate the hearing preservation rate and to determine its prognostic factors after gamma knife (GK) stereotactic radiosurgery (SRS) in patients with vestibular schwannoma, the authors used a prospective study design to analyze these patients.
  
  
  METHODS
  Between December 1997 and January 2002, 25 patients with vestibular schwannoma with serviceable hearing were enrolled in the current study. The median tumor volume was 3.0 cc (0.16-9.1 cc). The prescription dose was 12.0 +/- 0.7 gray at an isodose line of 49.8 +/- 1.1%. The tumor control rate and complications were evaluated by focusing on hearing preservation and its prognostic factors.
  
  
  RESULTS
  Based on radiologic study, the tumor control rate was 92% during the median follow-up period of 45 months. The trigeminal and facial nerve preservation rates were 95% and 100%, respectively. Thirteen (52%) of the 25 patients preserved serviceable hearing and 9 (36%) patients retained their pre-GK G-R grade levels after GK SRS. However, 16 patients showed hearing deterioration > 20 dB within 3-6 months and this trend continued for 24 months after the treatment. The maximum radiotherapy dose delivered to the cochlear nucleus was the single, significant prognostic factor of hearing deterioration.
  
  
  CONCLUSIONS
  The authors concluded that a more sophisticated strategy to prevent hearing deterioration during the first 6 months post-GK SRS is necessary to improve long-term hearing preservation.
authors.affiliation: Department of Neurosurgery, Seoul National University College of Medicine, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea.
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Paek
authors.forename: Hyun-Tai
authors.initials: HT
authors.lastname: Chung
authors.forename: Sang Soon
authors.initials: SS
authors.lastname: Jeong
authors.forename: Chul-Kee
authors.initials: CK
authors.lastname: Park
authors.forename: Chae-Yong
authors.initials: CY
authors.lastname: Kim
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Kim
authors.forename: Dong Gyu
authors.initials: DG
authors.lastname: Kim
authors.forename: Hee-Won
authors.initials: HW
authors.lastname: Jung
mesh_terms: D000328:Adult; D000368:Aged; D003056:Cochlear Nerve / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D034381:Hearing Loss / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D011446:Prospective Studies; D016634:Radiosurgery; D013238:Stereotaxic Techniques; D016896:Treatment Outcome; D047368:Tumor Burden