INTRODUCTION: 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.
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Teschner et al. (2012) studied this question.