title: Intraoperative round window recordings to acoustic stimuli from cochlear implant patients.
abstract: OBJECTIVE
  Acoustically evoked neural and hair cell potentials can be measured from the round window (RW) intraoperatively in the general population of cochlear implant recipients.
  
  
  BACKGROUND
  Cochlear implant performance varies greatly among patients. Improved methods to assess and monitor functional hair cell and neural substrate before and during implantation could potentially aid in enhanced nontraumatic intracochlear electrode placement and subsequent improved outcomes.
  
  
  METHODS
  Subjects (1-80 yr) undergoing cochlear implantation were included. A monopolar probe was placed at the RW after surgical access was obtained. The cochlear microphonic (CM), summating potential (SP), compound action potential (CAP), and auditory nerve neurophonic (ANN) were recorded in response to tone bursts at frequencies of 0.25 to 4 kHz at various levels.
  
  
  RESULTS
  Measurable hair cell/neural potentials were detected to 1 or more frequencies in 23 of 25 subjects. The greatest proportion and magnitude of cochlear responses were to low frequencies (<1,000 Hz). At these low frequencies, the ANN, when present, contributed to the ongoing response at the stimulus frequency. In many subjects, the ANN was small or absent, whereas hair cell responses remained.
  
  
  CONCLUSIONS
  In cochlear implant recipients, acoustically evoked cochlear potentials are detectable even if hearing is extremely limited. Sensitive measures of cochlear and neural status can characterize the state of hair cell and neural function before implantation. Whether this information correlates with speech performance outcomes or can help in tailoring electrode type, placement or audiometric fitting, can be determined in future studies.
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7070, USA.
authors.forename: Baishakhi
authors.initials: B
authors.lastname: Choudhury
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Fitzpatrick
authors.forename: Craig A
authors.initials: CA
authors.lastname: Buchman
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Wei
authors.forename: Margaret T
authors.initials: MT
authors.lastname: Dillon
authors.forename: Shuman
authors.initials: S
authors.lastname: He
authors.forename: Oliver F
authors.initials: OF
authors.lastname: Adunka
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001299:Audiometry; D001300:Audiometry, Evoked Response / Q000379:methods*; D001309:Auditory Threshold / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation; D003055:Cochlear Microphonic Potentials; D003056:Cochlear Nerve / Q000502:physiology; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006198:Hair Cells, Auditory / Q000502:physiology; D034381:Hearing Loss / Q000209:etiology / Q000601:surgery / Q000628:therapy; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009474:Neurons / Q000502:physiology; D012405:Round Window, Ear / Q000502:physiology*