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AUDE 5410 - Acquired Auditory-Vestibular Disorders > Presbycusis > Flashcards

Presbycusis Flashcards

1
Q

What are the two most common causes of hearing loss?

A

Advanced age
Noise exposure

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2
Q

What is presbycusis?

A

Age related hearing loss
Gradual decline of hearing
Onset and rate of progression is variable

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3
Q

What causes presbycusis?

A

Progressive loss/degeneration of endocochlear potential, IHCs, and synapses
Changes in the peripheral and central auditory system

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4
Q

Why does the human auditory system decline?

A

Because it lacks the ability to regenerate

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5
Q

Does presbycusis have a varied and not well-understood etiology?

A

Yes

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6
Q

Is the auditory system susceptible to wear and tear due to living?

A

Yes, no one lives in a bubble
Wear starts early and intensively in civilized societies rich in noise

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7
Q

What were the early findings of presbycusis site of lesion?

A

Primary site was the cochlea and secondary was central involvement due to reduced sensory input

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8
Q

What are the recent findings regarding site of lesion?

A

Central auditory system undergoes direct morphological and physiological changes independently of peripheral involvement

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9
Q

Does the prevalence of hearing loss increase with age?

A

Yes

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10
Q

Do men tend to have worse hearing as they grow older than women?

A

Yes

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11
Q

Do African Americans consistently show lower incidence of hearing loss in the elderly population?

A

Yes

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12
Q

What is the formula for presbycusis?

A

Genetics/(ototoxic drugs + noise exposure + age)

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13
Q

Why is there difficulty studying the effects of purely aging?

A

Environmental noise exposure (lifetime of continuous noise and some high level noise exposure)
Drugs (some are ototoxic, others may have effects after long term use)
Genetics

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14
Q

How did they determine that there is age related hearing loss and not just related to environmental noise?

A

Animal models and studies

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15
Q

Does extremely high aerobic metabolism take place in the lateral wall of the cochlea?

A

Yes
Oxygen based metabolism
Anything that effects the blood supply will cause problems with hearing (oxygen in blood)

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16
Q

What do we need high metabolism for?

A

Maintenance of K+ gradient between endolymph and perilymph
Generation of the endocochlear potential (EP)

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17
Q

Where is mechanical and metabolic damage observed most commonly?

A

At the basilar end and basal turn of the cochlea

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18
Q

What type of hearing loss is presbycusis?

A

Slowly progressive
Sloping
High frequency SNHL

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19
Q

What is age-related hearing loss that is not complicated by environmental factors caused by?

A

Degenerative changes/pathologies of the lateral cochlear wall and not just simply due to a loss of cochlear hair cells

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20
Q

What are the three systems of the cochlea that provide sound sensitivity particularly for high frequencies?

A

The cochlear amplifier
The power supply
The transduction mechanism

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21
Q

What is the cochlear amplifier?

A

The active processes located in the OHCs that amplify sound vibrations inside the cochlea

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22
Q

What is the power supply?

A

The cochlear lateral wall tissue, including stria vascularis, that provides the power the cochlear amplifier needs to function effectively

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23
Q

What is the transduction mechanism?

A

IHCs and afferent nerve fibers of the auditory nerve that receive the amplified vibrations from the OHCs
They convert the vibrations into neural excitation patterns that are sent to the brain

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24
Q

How much sensitivity loss occurs with the loss of OHCs?

A

40 to 50 dB HL

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25
What is the amplification provided by the OHCs dependent on?
The potential difference between the scala media and scala tympani (across the OHCs) This is called the endocochlear potential
26
Why is the endocochlear potential unique?
It is an extracellular resting potential rather than an intracellular one It has a positive voltage It is unusually large (80 to 100 mV) It is generated from the stria vascularis by the sodium potassium pump It acts as a battery to drive current through the cochlear hair cells when they move in response to sound stimulation
27
Does the EP varies from the base to the apex of the basilar membrane?
Yes Greater that the basal end, where we see the biggest effect
28
Does the utricle, saccule, and SCC have much smaller resting potentials?
Yes
29
Is the cochlear amplifier dependent on the EP?
Yes If the EP drops by 30 mV, the sensitivity to higher frequencies decreases by about 30 dB
30
What is age-related hearing loss caused from?
Deterioration of the cochlear battery (EP)
31
What is the cochlear power supply?
Made up of the cochlear lateral wall tissues including the stria vascularis (generates the EP)
32
What is the power supply dependent on?
Potassium recycling Pulling it back into the endolymph after the hair cells push it into the perilymph Generation of the EP in the stria vascularis
33
How does the recycling pathway work?
This recycling pathway uses a network of cochlear supporting cells along the BM and ion transport fibrocytes along the lateral wall The supporting cells and the fibrocytes are connected by gap junctions
34
What is the potential gradient at the top of the OHCs?
About 160 mV 80 mV in the endolymph and -80 mV in the body of the hair cells
35
Is there a constant flow of current from the scala media into the hair cells due to the potential?
Yes The potential changes produced by the flow of these electric currents is the cochlear microphonic (CM)
36
What is the transduction mechanism?
Consists of the IHCs and the afferent auditory nerve fibers IHCs passively detect BM vibrations and excite the afferent auditory nerve fibers that synapse at the base of the IHCs In young animal ears raised in quiet, the sensitivity range of afferent nerve fibers covers an intensity of 0 to 90 dB SPL
37
Are IHCs generally less susceptible to damage than OHCs?
Yes Even so, animals raise in quiet still showed significant shrinkage and loss of afferent nerve fibers Still observed with normal IHCs Indicates a pure aging effect independent of environmental factors
38
What are some common manifestations of presbycusis?
Loss of sensitivity for high frequency sounds (> 1000 Hz) resulting in a sloping high frequency SNHL Difficulties with speech perception especially in noisy and otherwise adverse acoustic environments (e.g., reverberation + noise) becomes more pronounced Distorted loudness perception, i.e., recruitment
39
Do speech discrimination abilities become progressively worse as high frequency hearing loss increases beyond 2000 Hz?
Yes
40
Is the audibility of low energy high frequency consonants attenuated by peripheral hearing loss?
Yes When you start losing your hearing, it is very hard to understand the meaning of sound (losing those consonants)
41
Can upward spread of masking also deteriorate speech perception?
Yes
42
What is the most common configuration of presbycusis?
Sloping SNHL
43
What other configurations can be seen besides sloping?
Flat configurations Mid to late stages Present the least problems with speech perception abilities (less distortion)
44
When is the poorest performance on WRS observed?
Between the ages of 71 to 90 Due to increasing age and reduced hearing sensitivity beyond 60 dB HL Cognitive decline could play a role too
45
Why is there a need to classify different presbycusis?
To improve differential diagnosis Individualized biomedical intervention (requires the knowledge of the site of lesion)
46
What is schuknecht's classification of presbycusis?
4 types of presbycusis based on postmortem histopathological evaluation
47
What are the types of presbycusis by schuknecht's classification?
Sensory presbycusis - loss of primary cochlear outer hair cells and supporting cells Neural presbycusis- loss of afferent cochlear neurons Metabolic/strial presbycusis- atrophy of the stria vascularis and lateral wall and loss of EP Mechanical presbycusis (no evidence) - stiffening of BM and organ of corti (may be a severe case of metabolic presbycusis)
48
What is Killion and Fikret-Pasa classification?
3 types of SNHL on loudness sensations and intelligibility considerations Goal was to make a better hearing aid Wanted to look at other considerations other than pure-tones
49
What was type 1 of presbycusis in the Killion and Fikret-Pasa classification?
Mild to mod SNHL (no worse than 45 to 55 dB HL), normal loudness sensation, consistent with OHC loss only with normal IHC function
50
What was type 2 of presbycusis in the Killion and Fikret-Pasa classification?
Moderately severe hearing loss (about 60 dB HL) with no region of completely normal loudness sensation Partial recruitment OHC and some IHC loss Less information being transmitted to the brain with fewer available redundant speech cues (work harder to understand) Deficits in speech intelligibility, especially in noise, even with the best hearing aids
51
What was type 3 of presbycusis in the Killion and Fikret-Pasa classification?
Severe hearing loss (about 75 dB or greater) Loudness and intelligibility is considerably affected Loudness ceases to be a primary concern IHC loss Speech understanding range is narrow Do best when speech is presented close to UCL Recruitment common
52
What is NIHL anatomically characterized by?
Loss of hair cells (initially OHCs) Loss of secondary or supporting cells Secondary neural degeneration
53
What is NIHL physiologically characterized by?
Threshold elevations of APs of the VIIIth N, ABR, and evoked potentials Loss of cochlear nonlinearities (OAEs absent) Endocochlear potential is generally unaffected in NIHL Degeneration of stria vascularis not typical
54
What is presbycusis anatomically characterized by?
Degeneration of the stria vascularis and lateral cochlear wall Compromised blood supply (due to the degeneration of the stria) Mostly normal sensory cells except in the most basal and apical turns Degeneration of the spiral ganglion
55
What is presbycusis physiologically characterized by?
Reduction of the endocochlear potential
56
Is presbycusis a vascular, metabolic, and neural disorder?
Yes
57
What is the gold standard test for hearing?
Audiogram Measures auditory thresholds and is a sensitive gauge of cochlear hair cell damage
58
What is the loss of connection between auditory nerve fibers and hair cells?
Synaptopathy A kind of hidden hearing loss
59
Does synaptopathy occur before the threshold elevates?
Yes
60
Is the audiogram a good indicator of damage to auditory nerve fibers?
No
61
Is synaptopathy an important component of noise induced and age related hearing loss?
Yes, it has become widely accepted now Even TTS can be an indication of immediate and irreversible damage to auditory nerve fibers and beginnings of hidden hearing loss
62
Might hidden hearing loss be the reason that elderly individuals can hear but cannot understand what people are saying?
Yes

AUDE 5410 - Acquired Auditory-Vestibular Disorders (11 decks)

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