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AUDE 5410 > Presbycusis > Flashcards

Presbycusis Flashcards

1
Q

what are the 2 most common causes of HL

A

1)age
2) noise induced HL

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2
Q

what is presbycusis

A

age related hl

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3
Q

how can presbycusis happen?

A

progressive loss/degeneration of endocochlear potential, sensory hair cells, synapses, and other degenerative changes within the peripheral and central auditory system
-degeneration of PNS and CNS

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4
Q

what is the site of damage for presbycusis?

A

-primary site for age-related hearing loss - presbycusis, with secondary central involvement due to reduced sensory input

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5
Q

what is the formula for presbycusis

A

genetics
————– =individual hearing
ototoxic drugs +noise exposure+ age

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6
Q

why is it hard to measure presbycusis

A

because of the affects of environmental noise exposure, drugs, and genetics

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7
Q

how is presbycusis identified as?

A

it is a is a slowly progressive, sloping, high frequency SNHL

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8
Q

what degree of HL does the loss of OHC give us ?

A

Loss of just OHCs can reduce sensitivity by ~ 40 to 50 dB HL

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9
Q

amplification provided by the OHC are dependent on what ?

A

on the potential difference (voltage) between scala media and scala tympani and, therefore, across the OHCs
-the voltage is endocochlear potential (EP)
»»This endocochlear potential is seen in the endolymphatic space (scala media) of the cochlea

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10
Q

why are endocochlear potentials intriguing and unusual?

A

-It is an extracellular resting potential when most resting potentials are intracellular
-It is a resting potential, which means it’s a potential at rest that does not require sound stimulation to be generated
-It has a +ve voltage, unusual for a resting potential
-It also has an unusually large voltage of ~ +80 to +100 mV
-It is generated from the stria vascularis by the NA+/K+ ATPase pump providing a source of energy for cochlear transduction
-It acts as a battery to drive current through cochlear hair cells when they move in response to sound stimulation

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11
Q

what 3 systems is the cochlea divided into ?

A

1) cochlear amplifier
-The ohc
2)the power supply
-The cochlear lateral wall tissue, including stria vascularis, that provides the power the cochlear amplifier needs to function effectively
-how much amplification is needed
3)the transduction mechanism
-They convert or transduce, the vibrations to neural excitation patterns, which are then sent to the brain

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12
Q

what is the purpose of endocochlear potential ?

A

-they are the battery of the cochlea
-it powers the ohc and the transduction mechanism

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13
Q

where is endocochlear potential higher?

A

in high frequencies so high frequencies are affected by tonotopic organization but also because endocochlear potentials are also affected because thats where most endocochlear potentials are

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14
Q

what is draining that battery of e.p?

A

-noise and drug exposure, aging effects in the cochlea may largely be the result of deterioration of the cochlear battery (the EP) and not necessarily loss of hair cells

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15
Q

what is the power supply made up of?

A

The power supply is made up of the cochlear lateral wall tissues including the stria vascularis that generates the EP

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16
Q

what is the power supply dependent on?

A

The power supply is dependent on the K+ recycling pathway that actively pulls K+ back into the endolymph as it is pushed from the hair cells into the perilymph

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17
Q

what is the last step to cochlear power supply?

A

The last step of K+ recycling is generation of the EP in the stria vascularis

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18
Q

look at slide 18

A
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19
Q

what is cochlear transduction?

A

The third system necessary for healthy cochlear function is the transduction of cochlear vibration to neural impulses

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20
Q

what does the cochlear transduction mechanism consist of?

A

This system 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

21
Q

which hair cell is susceptible to damage

A

inner

22
Q

how do we know that when age is affecting hearing loss

A

because with that study with the rats, we were able to identify that even with a perfect environment, we still have hearing loss. so this means that aging effects are independent of enviroment

23
Q

what are some characteristics of presbycusis ?

A

-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

24
Q

how does speech discrimination look like in presbycusis ?

A

Speech discrimination abilities become progressively worse as high frequency hearing loss increases beyond 2000 Hz

25
Q

why is it hard to understand the meaning of sound with speech?

A

consonants become attenuated because they’re high frequencies,

26
Q

what else deteriorate speech perception ?

A

upward spread of masking

27
Q

what configuration do we see with presbycusis ?

A

sloping high freq SNHL
also flat configurations in the mid to late stages

28
Q

just know that WRS is also affected by presbycusis

A
29
Q

what is schuknecht classifications ?

A

1) sensory presbycusis

2) neural presbycusis

3)Metabolic/strial presbycusis

4)Mechanical presbycusis

30
Q

what is sensory presbycusis ?

A

loss of primary cochlear OHC and supporting cells

31
Q

what is neural presbycusis ?

A

-loss of afferent cochlear neurons

32
Q

what is matabolic/strial presbycusis?

A

atrophy of the stria vascularis and lateral wall and loss of EP

33
Q

what is mechanical presbycusis ?

A

-stiffening of the basilar membrane and organ of corti

34
Q

what is the first type of hl in Killion & Fikret-Pasa classifications?

A

-Mild to moderate SNHL (no worse than ~ 45 to 55 dB HL)
-Normal loudness sensation
-These findings are consistent with loss of outer hair cell (OHC) function only with normal inner hair cell (IHC) function

35
Q

what is the 2nd type of Killion & Fikret-Pasa’s Classification

A

-Moderately severe hearing loss (~ 60 dB HL) with no region of completely normal loudness sensation
-Presence of partial recruitment (Killion & Fikret-Pasa, 1993)
-A loss of 60 dB HL is too large to be explained by the loss of OHCs alone, therefore, it is assumed that there is some IHC loss as well (Killion, 1995)
-These individuals have less information being transmitted to the brain with fewer available redundant speech cues
-They will have deficits for intelligibility for speech, especially in noise, even with the best of hearing aids

36
Q

what is the 3rd type of Killion & Fikret-Pasa’s Classification

A

-Severe hearing loss (~ 75 dB HL)
-Loudness and intelligibility are both considerably affected
-When hearing loss has progressed to the 70 to 80 dB HL range, loudness ceases to be the primary concern
-The IHC loss (and resultant loss of auditory nerve fibers and redundant speech cues) is so great that one concern dominates - intelligibility
-The range over which speech can be understood in noise also is greatly narrowed
These individuals do best when speech is presented close to uncomfortable listening levels (UCLs)
-Recruitment is common

37
Q

what is the site of lesion for presbycusis ?

A

the cochlea

38
Q

what are anatomical characteristics of noise induced HL

A

1)loss to the hair cells (specifically to ohc)
2)loss of secondary or supporting cells
3)secondary neural degeneration

39
Q

what are physiological characteristics of noise induced hearing loss

A

-Threshold elevations of compound action potentials of the auditory nerve, ABR, and higher level evoked responses
-The distinctive feature is loss of cochlear nonlinearities
-ex OAEs will be absent in elder adults
-The endocochlear potential (EP) is generally unaffected in NIHL
-Degeneration of the stria vascularis is not typical in NIHL

40
Q

what are anatomical characteristics of presbycusis

A

1)The dominant pathology of degeneration of the stria vascularis and lateral cochlear wall
2)Compromised blood supply correlated with the extent of strial degeneration
3)Presence of mostly normal sensory cells except in the most basal and apical turns of the cochlea
4)Significant degeneration of spiral ganglion in the presence of sensory cells

41
Q

presbycusis is physiologically characterized by ?

A

-Reduction of endocochlear potential (EP)

42
Q

what type of disorder is age related hearing loss ?

A

it is a vascular, metabolic and neural disorder

43
Q

how does age related hearing loss tie with noised induced hearing loss ?

A

1) noise induced hearing loss can worsen age related hearing loss
2)In later life, presbycusis can cause poorer thresholds in the higher frequencies decreasing/eliminating the noise notch

44
Q

what is something that will help us see if hidden hearing loss is present

A

the audiogram because It measures auditory thresholds and is a sensitive gauge of cochlear hair cell damage
BUT it does not tell us any damage to auditory nerve fibers

45
Q

what is synaptopathy ?

A

the loss of connections between auditory nerve fibers and hair cells

46
Q

when does synaptopathy happen ?

A

occurs before the threshold elevations associated with hair cell loss

47
Q

what is synaptopathy considered as

A

considered as a kind of hidden hearing loss

48
Q
A

AUDE 5410 (9 decks)

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