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Otoacoustic Emissions

Otoacoustic Emissions. Low-level sounds produced by the cochlea and recordable in the external ear canal. Spontaneous Click-evoked Distortion Product Stimulus Frequency. History. First described by Kemp (1977 & 1978), But predicted by Gold (1948!)

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Otoacoustic Emissions

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  1. Otoacoustic Emissions • Low-level sounds produced by the cochlea and recordable in the external ear canal. • Spontaneous • Click-evoked • Distortion Product • Stimulus Frequency

  2. History • First described by Kemp (1977 & 1978), • But predicted by Gold (1948!) • Supported by almost simultaneous discovery of OHC motility • Movement into Clinical Use: • Screening for hearing loss • Role in Audiologic Battery

  3. Anatomy and Physiology • Generators = Outer Hair Cells • “Pre-neural” • Low-level event//High level stimuli produce their own distortions • Reduction/Loss of emission in NITTS • SOAEs correlated to number of rows of OHCs

  4. Energy Path: • “Reverse Traveling Wave” is debated • Through Middle Ear: Filtering and attenuation • Into ear canal Note: requirement of healthy middle ear and clear outer ear.

  5. Clinical Utility -- Neonatal Hearing Screening • Transient and Distortion-Product OAEs • Rationale: quick, relatively inexpensive, possibly catching losses in a broader frequency range than ABR • NIH (1994) recommended two-stage protocol combining OAEs and ABR

  6. Clinical Utility-- in the Audiologic Battery • Assessment of cochlear health in site-of lesion testing • Objective info on peripheral auditory functioning • Correlation to audiogram • Assessment of Auditory Efferents through Contralateral Suppression

  7. Recording OAEs

  8. Spectrum of Sound in Ear Canal Stimulus Tones Emission Frequency Background Noise

  9. OAE as Measure of Cochlear Health

  10. Caveats--Remember: • there is more to “Hearing” than a healthy cochlea • what lies between your equipment and the source? • high level stimuli evoke response from inanimate cavities (e.g. in cadavers)

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