title: Acoustic neuroma surgery: absent auditory brainstem response does not contraindicate attempted hearing preservation.
abstract: OBJECTIVE
  Absence of auditory brainstem response (ABR) waveforms has been associated with a poor likelihood of hearing preservation following resection of acoustic neuromas. Our experience is reviewed for patients with absent preoperative ABR regarding hearing preservation, hearing improvement, and return of ABR.
  
  
  METHODS
  Retrospective review of 22 cases of acoustic neuroma resection. Nine patients with absent preoperative ABR were identified. All underwent tumor resection utilizing intraoperative cochlear nerve action potential (CNAP) monitoring. Postoperative hearing results and ABR waveforms were examined.
  
  
  METHODS
  Charts were reviewed and tabulated for age, sex, tumor side, tumor size, preoperative and postoperative audiometric and ABR results, intraoperative monitoring results by ABR and CNAP, and surgical complications.
  
  
  RESULTS
  Hearing preservation was achieved in seven of nine patients (78%) with absent preoperative ABR, as well as six of seven patients (86%) with tumors less than or equal to 20 mm in greatest dimension. Although intraoperative ABR monitoring was not possible in any of these patients, CNAP monitoring was successful in all. Return of ABR waveforms was observed in four of the six patients (67%) tested from 3 to 22 months postoperatively. Four of the seven patients (57%) enjoyed improvement in hearing class as defined by the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery.
  
  
  CONCLUSIONS
  Absent ABR waveforms have not been a negative prognostic sign regarding hearing preservation. CNAP monitoring is possible in these patients and likely helps to minimize iatrogenic cochlear nerve trauma. Patients with no ABR waveforms have hope of hearing preservation and even improvement following acoustic neuroma resection performed utilizing CNAP monitoring and hearing preservation surgical techniques.
authors.affiliation: California Ear Institute at Stanford, Stanford University Medical Center, Palo Alto, California 94304-1608, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Roberson
authors.forename: L E
authors.initials: LE
authors.lastname: Jackson
authors.forename: J R
authors.initials: JR
authors.lastname: McAuley
mesh_terms: D000368:Aged; D003055:Cochlear Microphonic Potentials; D005072:Evoked Potentials, Auditory; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000503:physiopathology* / Q000601:surgery*; D012189:Retrospective Studies; D016896:Treatment Outcome