title: Acoustic neuroma surgery: use of cochlear nerve action potential monitoring for hearing preservation.
abstract: OBJECTIVE
  To compare the hearing preservation results obtained with use of two intraoperative eighth nerve monitoring methods, cochlear nerve action potential (CNAP) and auditory brainstem response (ABR), during complete acoustic neuroma (AN) resection.
  
  
  METHODS
  Retrospective.
  
  
  METHODS
  Tertiary referral center.
  
  
  METHODS
  Thirty-three consecutive patients who underwent hearing preservation AN surgery.
  
  
  METHODS
  Intraoperative monitoring by CNAP and/or ABR during AN resection.
  
  
  METHODS
  Postoperative hearing. Hearing preservation was considered achieved for pure-tone average < or =50 dB and speech discrimination > or =50%.
  
  
  RESULTS
  Thirty-two patients met inclusion criteria for the study. Monitoring was successfully performed in 23 of 25 patients (92%) who underwent attempted CNAP monitoring and 13 of 27 (48%) who underwent attempted ABR monitoring. When tumor size was < or =20 mm in greatest dimension, hearing preservation was achieved in 12 of 18 patients (67%) monitored with CNAP, versus 2 of 8 patients (25%) not monitored with CNAP (p = 0.05). Monitoring by ABR did not improve hearing preservation rates compared with those not monitored with ABR (40% vs. 63%). At the completion of surgery, the presence or absence of CNAP predicted the presence or absence of hearing preservation in 18 of 23 cases (p = 0.01), while ABR successfully predicted hearing results in 10 of 13 cases (p = 0.05).
  
  
  CONCLUSIONS
  When CNAP and ABR monitoring techniques during AN surgery were compared, CNAP was more frequently obtainable. Monitoring by CNAP was significantly associated with a higher chance of hearing preservation. Monitoring by ABR did not have a positive influence on hearing preservation results. Both ABR and CNAP were useful for predicting postoperative hearing.
authors.affiliation: California Ear Institute at Stanford, Division of Otolaryngology, Stanford University Medical Center, Palo Alto 94304-1608, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Jackson
authors.forename: J B
authors.initials: JB
authors.lastname: Roberson
mesh_terms: D000328:Adult; D000368:Aged; D001301:Audiometry, Pure-Tone / Q000379:methods; D001309:Auditory Threshold / Q000502:physiology; D003056:Cochlear Nerve / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009464:Neuroma, Acoustic / Q000601:surgery*; D011182:Postoperative Care; D012189:Retrospective Studies