title: Length of tumor-cochlear nerve contact and hearing outcome after surgery for vestibular schwannoma.
abstract: OBJECTIVE
  Tumor size is likely to be a major determinant of hearing preservation after surgery for vestibular schwannoma. Findings in some large case series have not supported this concept, possibly due to variation in the technique used for tumor measurement. The authors sought to determine if the length of tumor-cochlear nerve contact was predictive of hearing outcome in adults undergoing resection of a vestibular schwannoma.
  
  
  METHODS
  Patients who underwent a hearing-preserving approach for resection of a vestibular schwannoma at one institution by a neurosurgeon/neurotologist team between 2001 and 2005 were screened. Patients with American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Class A or B hearing preoperatively were included. Magnetic resonance images were reviewed and used to calculate the length of tumor-cochlear nerve contact. Tumors were also measured according to AAO-HNS guidelines.
  
  
  RESULTS
  Thirty-one patients were included, 8 (26%) of whom had hearing preservation. Univariate analysis revealed that extracanalicular length of tumor-cochlear nerve contact (p = 0.0365), preoperative hearing class (p = 0.028), I-V interpeak latency of the brainstem auditory evoked potential (p = 0.021), and the interaural I-V interpeak latency difference (p = 0.018) were predictive of hearing outcome. Multivariate analysis confirmed the predictive value of extra-canalicular length of contact and preoperative hearing class (p = 0.041 and p = 0.0235, respectively).
  
  
  CONCLUSIONS
  Vestibular schwannomas with greater lengths of tumor-cochlear nerve contact increase a patient's risk for hearing loss after surgery with attempted hearing preservation. Involvement of the internal auditory canal produces a constant risk of hearing loss. Data from the experience of a single surgical team can be used to estimate the probability of good hearing outcome for any given patient with serviceable hearing and a vestibular schwannoma.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Raymund L
authors.initials: RL
authors.lastname: Yong
authors.forename: Brian D
authors.initials: BD
authors.lastname: Westerberg
authors.forename: Charles
authors.initials: C
authors.lastname: Dong
authors.forename: Ryojo
authors.initials: R
authors.lastname: Akagami
mesh_terms: D000328:Adult; D001299:Audiometry; D003056:Cochlear Nerve / Q000473:pathology* / Q000601:surgery*; D015331:Cohort Studies; D005260:Female; D034381:Hearing Loss / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D011237:Predictive Value of Tests; D020127:Recovery of Function; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome