title: Validity of cochlear microphonics at high sound pressure levels as an important clinical aspect.
abstract: BACKGROUND
  Cochlear microphonics are electrical stimulus responses of the inner ear, generated by mechanical displacement of the hair cells caused by acoustic stimulation. As cochlear microphonics are often used in the diagnosis of hearing impairment and deafness, in preliminary investigations it was seen that obliteration or ossification have no effect on the extent to which cochlear microphonics can be recorded at high sound pressure levels. As artifacts at high sound pressure levels suggested, measurements were subsequently conducted using temporal bone specimens.
  
  
  METHODS
  In a test setup equivalent to that for electrocochleography, a needle electrode was placed on the cochlear promontory and used to record potentials following application of an acoustic stimulus.
  
  
  RESULTS
  Curves comparable to cochlear microphonics were registrable down to a threshold of 80 dB HL. Additional measurements conducted on damp cloths yielded comparable findings.
  
  
  CONCLUSIONS
  Registration of cochlear microphonics at high sound pressure levels does not serve as an indicator of hair cell function, but should instead be regarded as artifacts. The possible sources are discussed.
authors.affiliation: Department of Otolaryngology, Medical University of Hannover, Carl Neuberg Strasse 1, Hannover, Germany. teschner.magnus@mh-hannover.de
authors.forename: M
authors.initials: M
authors.lastname: Teschner
authors.forename: T
authors.initials: T
authors.lastname: Lenarz
authors.forename: R-D
authors.initials: RD
authors.lastname: Battmer
mesh_terms: D000161:Acoustic Stimulation; D001300:Audiometry, Evoked Response; D002102:Cadaver; D003055:Cochlear Microphonic Potentials / Q000502:physiology*; D003056:Cochlear Nerve / Q000503:physiopathology*; D003638:Deafness / Q000503:physiopathology*; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006801:Humans; D011312:Pressure; D015203:Reproducibility of Results; D013016:Sound