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Electrophysiology > Otoacoustic Emissions > Flashcards

Otoacoustic Emissions Flashcards

1
Q

Who first demonstrated OAEs in an experimental context?

A

British physicist David Kemp, in 1978

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2
Q

What are OAEs?

A

the sounds measured in the ear canal that represent the movement of the OHCs in the cochlea

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3
Q

The energy produced by the movement of the OHCs serves as a what?

A

a cochlear amplifier, which contributes to better hearing (sharper fx resolution)

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4
Q

What do OAEs allow AuDs to do clinically?

A
  • early detection of inner ear abnormalities of various etiologies, including non-pathologic ones like noise exposure and aging
  • can sometimes prevent serious consequences of hearing loss
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5
Q

OAEs can be described as … because?

A

pre-neural; their activity occurs before the very first synapse in the afferent auditory system

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6
Q

How do OAEs present in individuals with no auditory nerves, severed nerves, or improper neurotransmitters?

A
  • they can be normal
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7
Q

What are the 4 types of OAEs?

A
  • spontaneous
  • transient
  • distortion product
  • sustained frequency
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8
Q

Spontaneous OAEs

A

sounds emitting from the OHCs without an acoustic stimulus

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9
Q

Transient (evoked) OAEs

A
  • sounds emitted from the OHCs in response to a stimulus of very short/brief duration (usually clicks, sometimes tone bursts)
  • presented at 80 dB SPL
  • generally recorded at 500-4000 Hz
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10
Q

Distortion product OAEs

A
  • sounds emitted from the OHCs in response to 2 simultaneous pure tones (f1, f2) of different frequencies
  • stimuli presented at 55 and 65 dB SPL
  • typically recorded from 500-8000 Hz, sometimes even higher
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11
Q

Sustained frequency OAEs

A

sounds emitted from the OHCs in response to a continuous tone

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12
Q

Which types of OAEs are mostly used in clinical settings?

A
  • distortion product
  • transient evoked
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13
Q

In what settings are sustained frequency OAEs typically used?

A

for research

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14
Q

What types of OAEs can be measured clinically with FDA-approved equipment?

A
  • distortion product
  • transient evoked
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15
Q

What type of HL can transient OAEs detect?

A
  • mild HL
  • faster to administer, so it’s popular for screening babies
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16
Q

What type of HL can distortion product OAEs detect?

A

moderate or higher HL

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17
Q

What are 2 other conditions that can be indicated by absent OAEs in the lower frequencies?

A
  • middle ear infections
  • Ménière’s disease
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18
Q

What are some advantages of OAEs?

A
  • don’t require behavioral responses, so it’s good for babies, infants, and younglings
  • good for nontraditional testing due to factors like language, cognitive function, motivation, and attention
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19
Q

What is the advantage of OAEs involving specificity?

A
  • OAEs are ear specific, unlike free-field behavioral responses
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20
Q

Do OAEs require a sound-treated room?

A

NO, and they’re portable too! An averaging process reduces background noise, and the ear is tightly sealed with a probe.

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21
Q

OAEs are also advantageous for using with kids because?

A

they are super quick; about 30-45 seconds per ear is common. Also pretty inexpensive as a screening tool!

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22
Q

What are some disadvantages of OAEs?

A
  • susceptible to noise; more sound = more difficult to record
  • ME status is important!! any dysfunction in the ME can stifle the OAE response
  • we only get info about the hair cells, nothing else
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23
Q

Smaller ear canals result in a what?

A

higher effective SPL

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24
Q

Recording Parameters for Spontaneous OAEs

A
  • measured in narrow frequency bands (< 30 Hz bandwidth)
  • no stimulus needed
  • multiple recordings should be made for replicability and to distinguish responses from the noise floor
  • usually span the 500-7000 Hz range
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25
Q

Recording Parameters for Transient OAEs

A
  • clicks are the most common stimuli, but can be tone bursts too
  • typically presented at 80-85 dB SPL
  • stimulation rate is <60 stimuli/second
  • generally recorded over approximately 20 msec
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26
Q

Recording Parameters for Distortion Product OAEs

A
  • stimuli = 2 pure tones at 2 frequencies (f1, f2; f2>f1) and 2 intensities (L1, L2)
  • relationship between L1L2 and f1f2 dictates the frequency response
  • for optimal response, set intensities so that L1 equals or exceeds L2
  • intensity typically set at 65/55 dB SPL L1/L2
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27
Q

What are the prereqs for obtaining OAEs?

A
  • unobstructed ear canal
  • proper seal with the probe
  • optimal positioning of the probe
  • no ME pathology
  • quiet, still patient
  • relatively quiet recording environment
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28
Q

What is the general OAE procedure?

A
  • non-invasive and simple to record, only requiring a few minutes to record
  • sedation not indicated, even for children
  • no behavioral response required
  • soft probe tip is inserted into the external ear canal
  • mini speaking within the probe generates the stimulus at a moderate intensity level
29
Q

How can OAE test protocol be modified?

A

there are specific protocols for different clinical settings (diagnostics vs screening vs ototoxicity monitoring)

30
Q

What are some important things to remember about the probe fit for OAEs?

A
  • deep probe insertion essential
  • there’s an inverse relationship between canal volume and OAE stim/response
  • a good fit helps reduce external noise
31
Q

What should be remembered about selecting an eartip for recording OAEs?

A
  • maximum OAE amplitudes are achieved with a deeply sealed eartip
  • shallow placement of the eartip in the ear canal reduces both the stimuli level and the measured level of the emission
32
Q

What can verify a deep insertion of the ear tip?

A

2-3 mm of the tip should be visible

33
Q

What are some non pathological problems that can cause OAEs to be absent?

A
  • poor probe tip placement/poor
  • cerumen occlusion of canal, or it’s blocking the probe
  • debris and foreign objects in the ear canal
  • vernix in neonates (common after birth)
  • uncooperative patient(s)
34
Q

What are some pathologic problems that can cause the absence of OAEs?

A
  • outer ear stenosis
  • external otitis
  • abnormal ME pressure
  • TM = perforation; PE tubes don’t necessarily prevent good recordings
  • ME otosclerosis
  • ME disarticulation
  • cholesteatoma
  • cyst
  • ototoxic medication or noise exposure (including music) = OAE changes may precede threshold changes in the conventional fx range
  • any other cochlear pathology
35
Q

What are some conditions that do NOT affect OAEs?

A
  • CN VIII pathology (only affects OAEs if the cochlea is affected as well)
  • central auditory disorder
36
Q

What is an example of a CN VIII pathology that could affect OAEs?

A
  • a vestibular schwannoma that impinges on the cochlear vascular supply
37
Q

What are some conditions that elicit abnormal OAEs and normal behavioral thresholds?

A
  • tinnitus: could have abnormal OAEs in the fx region of the tinnitus
  • excessive noise exposure (may cause increase or decrease in amplitude)
  • ototoxicity (can cause vestibular pathology)
38
Q

What are some conditions that elicit normal OAEs and abnormal behavioral thresholds?

A
  • functional HL
  • attention deficits
  • autism
  • IHC damage, but normal OHCs (no human reports yet)
  • auditory neuropathy (includes CANS dysfunction and CN VIII dysfunction)
39
Q

What are the 3 general steps for OAE analysis?

A
  1. verify adequate measurement conditions
  2. determine whether repeatable OAEs are recorded
  3. the difference between OAE amplitude and noise floor should be > 6 dB SPL
40
Q

How can you verify adequate measurement conditions?

A
  • noise levels should be sufficiently low (typically less than 10 dB SPL)
  • stimulus intensity levels should be close to the desired levels
41
Q

How can we ensure we are obtaining repeatable, reliable OAE measurements?

A

the OAE amplitudes should exceed the noise level by 6 dB or more at the test frequencies

42
Q

In approximately how many normal hearing individuals do spontaneous OAEs occur?

A

40-50% (about 30-60% are adults, and about 25-80% are babies)

43
Q

In which individuals are spontaneous OAEs not typically observed?

A

those with hearing thresholds above 30 dB HL (thus, the absence of SOEAs is not necessarily abnormal)

44
Q

Characteristics of spontaneous OAEs

A
  • typically bilateral (typically more present in the right than left if unilateral)
  • occur more often in females, across all ages
  • usually not associated with tinnitus
  • seldom used for clinical hearing screenings
45
Q

What is the main purpose of transient OAEs?

A
  • to screen infant hearing
  • to validate behavioral/electrophysiologic auditory thresholds
  • to assess cochlear function relative to the site of the lesion
46
Q

Stimulus parameters for transient OAEs

A
  • very short (transient) stimulus
  • has limited fx specificity
47
Q

The transient OAEs emanate from what?

A

very broad cochlear regions

48
Q

What does the presence of a transient OAE in a fx band generally indicate?

A

that the cochlear sensitivity of that region is approximately 20-40 dB HL or better

49
Q

Most clinicians use the presence of transient OAEs in particular octave bands as a suggestion of what?

A

that hearing sensitivity should be 30 dB HL or better, unless a functional or neural component is present

50
Q

Recording Parameters for Transient OAEs

A
  • usually uses a click stimulus that contains a broad fx range (also possible to use a tone burst, but they’re limited fx)
  • can usually be measured between 1000 - 4000 Hz
51
Q

When will transient OAEs most often be absent?

A

when a hearing loss is greater than 35 dB HL

52
Q

When do Robinette, Cevette, & Probst indicate that transient OAEs are present 99% of the time?

A

when all pure-tone thresholds are better than 20 dB HL

53
Q

When are transient OAEs ALWAYS absent?

A

when pure-tone thresholds are greater than 40 dB HL

54
Q

In what scenario would transient OAEs be or not be present?

A

when pure-tone thresholds are 25-35 dB HL

55
Q

What stimulus activates distortion product OAEs?

A
  • 2 pure tones (f1, f2)
  • f2>f1
56
Q

What actually is a distortion product OAE?

A

it is a 3rd tone created in response to f1 and f2

57
Q

What does the expression 2f1-f2 signify?

A

the largest distortion product that can be evoked by tonal stimulation in the human ear

58
Q

What range do distortion product OAEs usually test?

A

1000-6000 Hz/500-8000Hz, sometimes even higher (varies with manufacturer)

59
Q

Distortion product OAEs allow greater what?

A

frequency specificity; they can record at higher frequencies that transient OAEs

60
Q

Distortion product OAEs can be useful for detection of what conditions?

A
  • ototoxicity
  • noise induced HL
61
Q

When is the reliability of distortion product OAEs greatest?

A

above 1000 Hz

62
Q

Which OAE protocols are using for infant hearing screenings?

A

distortion product and transient

63
Q

Which OAE protocol is more established for assessing/predicting behavioral thresholds?

A

transient OAEs

64
Q

Which OAE protocol usually represents the audiometric configuration of a cochlear hearing loss?

A

distortion product OAEs

65
Q

Describe the clinical applications of OAEs.

A
  • question/validate other threshold measures
  • provide information about a lesion site
  • screen hearing
  • partially estimate hearing sensitivity within a limited range
  • monitor for ototoxicity
  • diagnostic assessment of tinnitus and auditory dysfunctions
  • differentiate between the sensory and neural components of SNHL
  • test for functional HL
66
Q

Describe the clinical limitation of OAEs.

A

They can’t fully describe an individual’s auditory thresholds.

67
Q

How are OAE screening outcomes described?

A
  • as pass or fail
  • pass = when OAEs are present (>6dB above the noise floor) for the majority of test frequencies
68
Q

What should AuDs do for patients who have a refer outcome for their OAE screening?

A

they should be referred for a diagnostic assessment, and possible audiological/medical management

Electrophysiology (5 decks)

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