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Diagnostic Audiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What are the 4 behavioural audiometry/psychoacoustic tests?

A
  1. Pure tone audiometry
  2. Clinical decisions
  3. Speech audiometry
  4. Masking
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2
Q

What is identification?

A

Identifying that there is a problem
- a hearing loss
- a vestibular problem
- problems hearing at school

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3
Q

Identification is too light of a description to count as a ____

A

Diagnosis

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4
Q

What is diagnosis?

A
  • Determining the nature of the condition (based on assessment)
  • This may or may not include etiology (the underlying cause of the condition)
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5
Q

What are some things audiologists diagnose?

A
  1. A moderate sloping to severe
  2. Sensorineural hearing loss bilaterally
  3. BPPV
  4. Auditory processing disorder
  5. Auditory neuropathy spectrum disorder
  6. noise-induced mild 4 kHz notch
    pulsatile tinnitus
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6
Q

You often don’t know the ____ behind a diagnosis

A

Etiology

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7
Q

Can audiologists diagnose?

A

Yes, it is within our scope of practice

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8
Q

Where CAN’T audiologists diagnose?

A

Ontario

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9
Q

Ontario’s language confuses ____ with ____

A

Diagnosis, etiology

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10
Q

Audiologists in ontario can’t diagnose, instead they can ____ and ____

A

Assess, describe

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11
Q

What two things can audiologists identify in Ontario?

A

ANSD and APD (considered to be symptoms and not disorders)

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12
Q

What wording should be used in ontario?

A

In Ontario, use wording like ‘this is consistent with’ or ‘this may suggest’

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13
Q

As audiologists, what is our ultimate focus?

A

Hearing function and communication

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14
Q

Tight link between ____ and ____ means that a good audiologist should understand both

A

Physiology, perception

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15
Q

What things must be diagnoses by an otlogist?

A
  • Schwannoma
  • Infections
  • Meniere’s
  • Otosclerosis
  • PET
  • Superior canal dehiscence
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16
Q

What are the 3 ways to talk about an audiogram?

A
  1. Y axis
  2. X axis
  3. Z axis
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17
Q

Explain the key points of the Y axis

A

The level
- dB HL (air and bone)
- Loudness Contours and Growth
- Intensity Discrimination

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18
Q

Explain the key points of the X axis

A

Frequency
- Place Specificity
- The Basalward Shift

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19
Q

Explain the key point of the X axis

A

Temporal Integration

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20
Q

What is the purpose of the audiogram?

A
  • Provides information about likely communication problems
  • Critical for audiologic treatment
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21
Q

What are 4 limits of the audiogram?

A
  1. Poor for distinguishing sensory versus neural loss
  2. May miss significant loss of hair cells
  3. Does not assess temporal processing
  4. It is the beginning of assessment, not the end
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22
Q

What is behavioural audiometry looking to find?

A
  • Functional characterization of clinically relevant psychoacoustic details
    • How is this person different from what we expect
  • Goal is not description of ability, but description of different ability
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23
Q

What is MAF?

A

Minimal audible field (open ears)

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24
Q

What is MAP?

A

Minimal audible pressure (headphones)

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25
Q

Do outer ear effects play an important role in diagnostics?

A

No, usually we have the ear plugged when testing and treating

However, in everyday life we hear better with MAF because of the gain from the outer ear

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26
Q

The middle ear is not good at transferring ____ frequencies

A

Low

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27
Q

The ____ coupled with the ____ is responsible for MAF

A

Middle ear, outer ear

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28
Q

The shape of hearing reflects ____ and ____

A

Middle ear, outer ear

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29
Q

Is the natural shape of the absolute threshold curve relevant for diagnosis? What needs to be done?

A

No
dB HL is a flattened version of the MAP

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30
Q

How do we find the HL from SPL?

A

dB SPL - RETSPL = dB HL

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31
Q

What is RETSPL?

A

Reference equivalent threshold sound pressure level

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32
Q

What does RETSPL represent

A

Middle ear transfer function

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33
Q

What are RETSPLs?

A
  • Levels in dB SPL that correspond to 0 dB HL, as measured at a calibration point
  • Inserts: 2cc coupler
  • TDH: 6cc coupler
  • Speakers: microphone in centre of head
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34
Q

What is 0 on an audiogram?

A

The average lowest threshold

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35
Q

Explain the importance of understanding why not every ear is the same?

A

The actual sound level at the eardrum at a given dB HL is…
1. Not the same across individuals
2. Not the same across different earphones for a given individual

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36
Q

Can dB HL change due to different ear canal size?

A
  • Smaller ears, more pressure, hear at a softer level
  • Larger ears, less pressure, hear at a higher level
  • Hearing ability doesn’t change, ear canal size changes how you hear
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37
Q

What will a leak with insert and TDH headphones show? What also shows this?

A

Low frequency drops, perforations

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38
Q

What is the best to use to get the best predictor of real-world hearing? But why is it bad?

A

Sound field, but its not good because you cant control which ear the sound is going to

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39
Q

____ may be less similar to sound field (less predictive of real-world hearing)

A

Inserts

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40
Q

____ are just as correct for occluded-ear hearing (trough a hearing aid or airpods)

A

Inserts

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41
Q

Will bone conduction be affected by perforation?

A

No

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42
Q

What are the 5 mechanisms of bone conduction? Which are the most important? Which is the largest effect?

A
  1. Sound radiated into the external ear canal
  2. Middle ear ossicle inertia
  3. Inertia of the cochlear fluids
  4. Compression of the cochlear walls
  5. Pressure transmission from the cerebrospinal fluid

Top 3 most important (3 is largest effect)

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43
Q

Mechanisms of BC (1)
Sound radiated into the external ear canal
- open eear
- closed ear

A
  • Open ear: minimal contribution
  • Plugged ear: most important contribution from ~400-1200 Hz (radiates from cartilage and TM); occlusion effect
44
Q

Mechanisms of BC (2)
Middle ear ossicle inertia
- how much contribution
- what does it explain

A
  • Contributes a small amount between 1000 and 3000 Hz
  • Helps explain Carhartt’s notch
45
Q

Mechanisms of BC (3)
Inertia of the cochlear fluids

A
  • The most important source, especially when ear is open
  • Fluid is fixed in the cochlea, so moving back and forth, the fluid pushes against the hair cells
46
Q

Mechanisms of BC (4)
Inertia of the cochlear fluids
- how much contribution

A

Possibly small contribution above 4 kHz

47
Q

Mechanisms of BC (5)
Pressure transmission from the cerebrospinal fluid
- how much contribution

A

Possibly a small contribution

48
Q

Explain the inertia of cochlear fluids (what is the fluid doing)?

A
  • While the bone vibrates, the perilymph tries to stay put.
  • The oval window has very high impedance, so the fluid is forced to move with the bone to some degree
  • The inertia of the fluid is the main contributor to BC hearing
49
Q
  • Your client is concerned about his hearing. He reports that he hears too many sounds. He can hear his footsteps.
  • Using insert phones, you measure normal thresholds (worst threshold is 15 dB HL at 250 Hz, with an air-bone gap)
  • Why the ABG?
A
  • Leak from inserts
  • Hyperacusis
  • Superior canal dehesince
    AC results in pressure to the OW that is dissipated towards the third window, so air thresholds are poorer (ABG)
50
Q

What do audiometric responses depend on?

A

Pathways of sound

51
Q

Bone conduction thresholds depend on ____ major pathways

A

3

52
Q

Air conduction thresholds depend on ____

A

Air conduction thresholds depend on transducer/coupling to ear

53
Q

What are our best AC thresholds determined by?

A

Our best air thresholds are determined primarily by the shape of the middle ear transfer function—and outer ear resonances if done in sound field

54
Q

Why do air and bone thresholds ‘match’ in dB HL (e.g., average normal threshold is 0 dB HL)?

A

We calibrate our equipment so that:
- Air and bone conduction thresholds match
- Average threshold is a flat 0 dB HL for every transducer
- Assuming an average ear!

55
Q

Why are audiograms shown as a flat line?

A

Audiograms show normal as a flat line; makes deviations (hearing loss, ABGs) easier to see

56
Q

Can you see some abnormal variations in AC and BC that have nothing to do with hearing loss?

A

Differences in ear canal acoustics (e.g., size), middle ear transfer functions, ossicular inertia etc. will all lead to some variation in AC and BC thresholds across people (that have nothing to do with hearing loss!)

57
Q

Can BC thresholds be worse than AC thresholds?

A

Only if there is a calibration issue or if the person isn’t close to “average” (because they are calibrated to be equal on an average)

58
Q

Where are equal loudness contours referenced?

A

Referenced to loudness at 1kHz

59
Q

Where does loudness grow most quickly?

A

Low frequencies

60
Q

Are 70dBHL sounds at 200 and 1000Hz equally loud?

A
  • Loudness at 200 and 1000 are about the same
  • 100 and 1000 are different
61
Q

Loudness scaling - SS Stevens’

A
  • Referenced to loudness at 1 kHz, 40 phons
  • Loudness doubles with a 10 dB increase (Stevens)
62
Q

Loudness scaling - RM Warren

A
  • Loudness scaling experiments are imperfect, since subjects ‘calibrate’ scales to range of stimuli presented
  • Warren made only one measurement per subject, and found that doubling corresponds to 6 dB instead of 10 dB
63
Q

What is recruitment?

A

With cochlear hearing loss, loudness tends to grow more quickly

64
Q

What is someone has normal hearing in one ear and a cochlear loss in the other?

A

When one ear is normal, recruitment can be detected with the ABLB: the alternate binaural loudness balance test

65
Q

What was Jerger’s idea on recruitment?

A

If loudness grows more quickly in impaired ears, then perhaps they can detect small changes in level better (test idea from Jim Jerger)

66
Q

What test did Jerger make to determine recruitment and how did it work?

A
  • The SISI (short-increment sensitivity index) for diagnosing recruitment
  • Jerger suggested that recruitment might give rise to better level discrimination
67
Q

Explain how the SISI works

A
  • A tone is a level that is changing by 5dB (they tell you when it changes in level)
  • After presenting five 5dB changes, it presents 1 dB changes in level
  • Count # 1 dB changes identified (out of 20), at 20 dB SL
  • If you can hear them, recruitment is diagnosed
68
Q

Explain Weber’s law

A
  • The smallest detectable change is a constant proportion of stimulus magnitude
  • In wide-band noise, we can detect an intensity change of about 10-30% (0.5-1 dB)
69
Q

What is the near miss of Weber’s law?

A
  • Weber’s law does not hold for pure tones… level discrimination improves at high levels
    • 1.5 dB at 20 dB SL
    • 0.3 dB at 80 dB SL
  • “Near miss to Weber’s law” (loudness discrimination gets better at high levels)
    At high levels can hear very small levels in change
70
Q

Is the SISI a good test of recruitment?

A
  • The SISI test always diagnoses recruitment because loudness discrimination is naturally better at high levels (the “near miss to Weber’s law”)
  • It has no clinical value for diagnosing recruitment
71
Q

What causes recruitment in normal ears?

A

Faster growth of loudness at LF because of the middle ear

72
Q

Is recruitment pathological?

A

No

73
Q

What causes recruitment in hearing loss?

A
  • Inability to hear soft sounds is a function of loss of mechanical amplification (OHCs) for soft sounds
  • Loud sounds may create similar velocity on BM, since OHCs were not involved
  • Recruitment can be fully explained by BM mechanics – no neural pathology required
74
Q

Do audiologists diagnose recruitment?

A

No

75
Q

Even though the SISI isn’t good for diagnosing recruitment, what can it diagnose?

A

The high level SISI (at 80dB) can help diagnose neural problems (if they cant detect the 1dB difference it can mean a neural loss in that ear)

76
Q

The x-axis on the audiogram is for ___ and ____

A

Pure tone frequency & place specificity

77
Q

What is place specificity?

A

Presenting a tone at a certain frequency goes to specific spot on the BM (it will stimulate a specific spot at a very soft level)

78
Q

What happens to place specificity as you go up in sound level?

A

More of the BM will be stimulated

79
Q

Auditory nerve response picture
- what do you see at 20dB
- what do you see at 70dB

A
  • At 20dB, you can see where it is stimulating the BM
  • At 70dB, a lot of the BM is being stimulated
80
Q

Many ____ neurons respond at high levels

A

Off-frequency

81
Q

Place selectivity is ____ at high levels

A

Poor

82
Q

Place selectivity is looking at the response of what?

A

Response of a single auditory neuron to tones of different frequency

83
Q

What kind of tone (low frequency or high frequency) is likely to elicit responses across the widest number of neurons?

A

High frequency

84
Q

What kind of tone is being played to show the CF?

A

Low frequency

85
Q

How is functional sensitivity determined?

A

By the shape of neural tuning curves

86
Q

What is the shape of the tuning curve created by?

A

Shaped by the travelling wave which depends on the structure of the basilar membrane

87
Q

Why does a neuron not respond to any sound higher than the CF?

A

Because of the shape of the travelling wave

88
Q

What gives the sharp dip in the tuning curve?

A

The hair cell active component

89
Q

The primary determinants of hearing sensitivity are ____

A

Peripheral (structure of middle ear, basilar membrane etc.)

90
Q

At high levels, the x-axis poorly represents ____

A
  • Place
  • The OHC aren’t doing much at high levels (we are looking at broad traveling waves)
91
Q

Explain isointensity curves

A
  • As we change the level of the stimulus, there is a shift in frequency on the BM
  • Isointensity curve response along the BM for different levels (measuring the BM at a particular place)
  • As we raise stimulus level, it stimulates a lower CF better
92
Q

What happens to the peak of the travelling wave as you go from soft to loud sound level?

A
  • At a soft level, traveling waves peaks and as level is increases, the peak of the traveling wave peaks more towards the base
  • A neuron may respond best to 2k at high levels and 1k at low levels
93
Q

Maximum velocity is more basal at ____ levels

A

High

94
Q

Bob and Larry picture

A

Bob is responding to 2K at high levels and 1K at low levels

95
Q

What makes an audiogram look the way it does?

A

The traveling wave mechanics and the basal shift

96
Q

What explains why we get 4k noise notches?

A

The basalward shift (people often get 4k because the peak frequency is around 2700Hz, therefore that’s where most sound is, however due to the basal shift, most hair cells are damaged at 4k)

97
Q

____ losses are always steeper than ____ losses

A

HF, LF

98
Q

The z-axis is showing us ____

A

Time (temporal integration)

99
Q

What are 3 important points about the tone being presented?

A
  • Threshold becomes lower as the length of the tone is increased
  • Thresholds are stable as long as tones are > ¼ second
  • We can ignore time if tones are sufficiently long
100
Q

Make sure tones are loud enough to allow for ____

A

Temporal integration

101
Q

Why is the RETSPL so large at low frequencies?

A

ME transfer function

102
Q

Why does a third window create an ABG and lead to dizziness with loud sounds?

A

Inertia of cochlear fluids

103
Q

Why does a large low-frequency dip in insert thresholds suggest a perforation?

A

Leak of sound

104
Q

Why don’t we see reverse ski-slope audiograms?

A

Basalward shift

105
Q

Why don’t we see right-corner audiograms?

A

Basalward shift

106
Q

Why can BC thresholds be worse than AC thresholds?

A

Ear canal size

107
Q

Why does noise-induced hearing loss typically start with loss at 4 kHz?

A

Basalward shift from the peak of the ear

Diagnostic Audiology (7 decks)

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