SHS 221 Module 7 Part 2

Otoacoustic Emissions

What does OAE stand for?

Outer hair cell function and cochlear integrity

What do OAEs measure?

Sensory cells in the cochlea that amplify sound vibrations and improve the sensitivity and frequency selectivity of the cochlea

What are outer hair cells (OHCs)?

They improve hearing sensitivity and frequency selectivity

How do outer hair cells improve hearing?

Dr. David Kemp in 1977 in the United Kingdom

Who first detected OAEs, and when?

Healthy cochlear function

What does the presence of OAEs usually indicate?

Possible sensorineural hearing loss or a middle ear problem

What can absent or reduced OAEs indicate?

Spontaneous OAEs (SOAEs) and evoked OAEs

What are the two main types of OAEs?

Low-level signals recorded without an external stimulus; reflect the activity of the cochlear amplifier

What are spontaneous OAEs (SOAEs)?

They occur in only about 50% of normal-hearing people, so their absence is not abnormal

Why do SOAEs have limited clinical use?

Otoacoustic emissions (OAEs)

Sounds produced by the OHCs in the cochlea in response to sound stimulation

1979

When was the first clinical OAE recording system was designed without a computer?

1987

When was the first commercial OAE recording system with a computer made?

OAEs produced in response to an external sound stimulus

What are evoked OAEs?

Transient Evoked OAEs (TEOAEs) and Distortion Product OAEs (DPOAEs)

What are the two types of evoked OAEs?

A brief, broadband click

What stimulus is used to record TEOAEs?

Approximately 0.5—4 kHz

What frequency range do TEOAEs generally cover?

Two pure tones presented simultaneously

What stimulus is used to record DPOAEs?

The two pure-tone stimulus frequencies

What do the frequencies f1 and f2 represent in DPOAE testing?

Nonlinear interaction between the two tones in the cochlea

What causes distortion product OAEs?

2f1— f2

Which DPOAE frequency is most commonly used clinically?

Commonly 0.5—8 kHz or wider, depending on equipment

What is the typical frequency range of DPOAEs?

Newborn hearing screening and assessment of cochlear function

What are the clinical uses of TEOAEs?

Frequency-specific assessment of cochlear function and hearing monitoring

What are the clinical uses of DPOAEs?

A soft-tipped probe is placed in the ear canal and plays sounds while a microphone records emissions

How is an OAE test performed?

A speaker and a microphone

What two parts inside the OAE probe?

In the ear canal

Where is the OAE probe placed?

Plays a click or two tones into the sealed ear canal

What does the speaker in the probe do?

OAEs are present, indicating normal outer hair cell function

What does a PASS result mean?

OAEs are absent, suggesting a possible cochlear or middler ear problem

What does a REFER result mean?

No. Earwax, blockage, or middle ear fluid can also cause a REFER result

Does a REFER result always mean hearing loss?

The background noise level measured during the test

What is the noise floor?

When the response is 6—8 dB above the noise floor

When is an OAE response considered present?

• Newborn screening

• Site-of-lesion testing

• Ototoxicity monitoring

• Early signs of noise-induced hearing loss

• Non-organic hearing loss (malingering)

What are five clinical uses of OAEs?

OAEs reflect OHC function; they do not give hearing thresholds

Limitations of OAEs: not a hearing test

OAEs are usually absent once cochlear loss exceeds about 30-40 dB HL, so they cannot show how much loss there is

Limitations of OAEs: degree of loss

Wax, debris or middle ear fluid can block the emission. A REFER does not always mean cochlear damage

Limitations of OAEs: outer and middle ear

Present OAEs do not rule out auditory neuropathy. Pair with ABR when a neural problem is suspected

Limitations of OAEs: neural pathway

Movement, breathing and room noise raise the noise floor and can mask a real response

Limitations of OAEs: noise