Otoacoustic Emissions Low-level sounds produced by the cochlea and recordable in the external ear...

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!) Supported by almost simultaneous

discovery of OHC motility Movement into Clinical Use:

Screening for hearing loss Role in Audiologic Battery

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

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.

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

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

Recording OAEs

Spectrum of Sound in Ear Canal

Stimulus Tones

Emission Frequency

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OAE as Measure of Cochlear Health

Tone Decay:

Loss of audibility for a tone that is on continuously.

Greater decay is indicative of retrocochlear problem.

There are different methods:

Some Tone Decay Tests

Carhart: begin at 0 SL, up in 5 dB steps until tone is heard for a full minute

Olson-Noffsinger: begin at 20 SL, up until heard for full minute.

Tone Decay Results:

Type I: no decay: norm, conduct or cochlear

Type II: heard for longer times as level is increased: cochlear

Type III: No growth with increasing level: retrocochlear

TONE DECAY SUCCESS?

Sensitivity = 75% Specificity = 91%

Auditory Brainstem Response:

Response within 10 ms of stimulus waves labeled with Roman

numerals Peaks I, III, and V most useful Latencies are the key measure Disorders will produce delays

ABR SUCCESS?

Sensitivity = 97% Specificity = 88%