Quiz 3 (Presbycusis)

Question 1

what is presbycusis

Answer 1

age related HL
it is gradual, variable in age of onset & its progression rate
variable in how it progresses

Question 2

what type of HL is seen in presbycusis

Answer 2

always SNHL because it is in teh inner ear and due to a lack of regeneration of the sensory system

Question 3

two most common causes of HL

Answer 3

advanced age
noise exposure

Question 4

presbycusis results from progressive loss of

Answer 4

EP, sensory cells, & other peripheral & central auditory system

Question 5

results in a decline of auditory function

Answer 5

as inability to regenerate structures that cause audition

Question 6

what was previously thought and now thought about etiology of ARHL

Answer 6

varied and not understood well
might be degenerative disase due to early start & noisey areas (city)

previously → cochlea was primary site & central involvement was secondary due to reduced sensory input

recently → CAS also has changes as a result of aging that is independent of peripheral involvement

Question 7

incidence of ARHL

Answer 7

HL prevalence increases with age & is to increase as the US age continues to increase

WRS decline more rapidly in men & poorer in all aged men than women

socioeconomic & ethnic variations
African americans show lower incidence of HL in elderly population

Question 8

Formula that leads to Presbycusis

Answer 8

genetics / (age + noise + ototoxic drugs)

Question 9

why is there so much variation in HL in ARHL

Answer 9

because individual hearing relies on genetics

ototoxicity, noise, and age play a role on hl too

Question 10

3 Variables that make it hard to study effects of pure aging on physiology & morphology

Answer 10

environmental noise exposure
drugs
genetics

Question 11

accounts for variability seen among the elderly in hearing abilities

Answer 11

genetics

Question 12

age-related HL is unique to aging & not a result of environmental factors (can contribute to HL)

Answer 12

true

Question 13

where does high aerobic metabolism occur

Answer 13

in lateral wall of cochlea

Question 14

why is high metabolism needed in cochlea

Answer 14

K+ maintenance bw endolymph & perilymph
EP generation

Question 15

where is mechanical & metabolic damage the most common

Answer 15

basilar membrane at the basal turn of cochlea

Question 16

ARHL is what type of HL

Answer 16

slowly progressive, sloping, HF SNHL

Question 17

why is ARHL slowly progressive, sloping, HF SNHL

Answer 17

becuase damage is most common at the basilar membrane of the basal turn

Question 18

presbycusis not related to environmental factors is just due to loss of cochlear hair cells

Answer 18

false
it is also caused by degenerative changes/pathologies of the lateral cochlear wall & not just the above

Question 19

what are the three cochlear systems implicated in presbycusis

Answer 19

cochlear amplifier

power supply

transduction mechanism

Question 20

what is the pathophysiology seen at cochlear amplifier system in presbycusis

Answer 20

cochlear amplifier = OHCs

loss of this reduces sensitivity by ~ 40 to 50 dB HL

this active process amplify sound vibrations in cochlea and this relies on EP found in scala media (ENDOLYMPH)

Question 21

what is the cochlear battery

Answer 21

EP

Question 22

describe EP

Answer 22

extracellular resting potential with +80 to +100 mV

created from stria vascularis by the Na+/K+ pump and in turn provides energy for cochlear transduction = battery of the cochlea

Question 23

where is EP larger

Answer 23

at the base (also why we see HF HL with ARHL)

Question 24

1mv = _____dB gain in cochlear amplifier

Answer 24

~ 1 dB

Question 25

if EP drops by 30 mv, sensitivity to HF decreases by about ____ dB

Answer 25

30

Question 26

aging effects in the cochlea can be result of

Answer 26

deterioration of cochlear battery (EP) & not loss of hair cells

Question 27

how is research restoring EP

Answer 27

adding external battery by injecting current directly into scala media &/or regenerating the old batter by using stem cells to repopulate stria vascularis these could recharge power supply to cochlear amplifier, regain some of HF sensitivity loss & reduce speech perception issues with aging

Question 28

what provides the power the OHCs need to function effectively

Answer 28

cochlear lateral wall, including stria vascularis

Question 29

what is the power supply of cochlea

Answer 29

cochlear lateral wall tissue including SV that generates EP

Question 30

what is the power supply dependent on

Answer 30

K+ recycling - actively putting it back into the endolymph after it is released into perilymph through supporting cells & fibrocytes that move it through gap junctions = generating EP

Question 31

describe K+ recycling during power supply in cochlea

Answer 31

top of OHCs has potential gradient of ~ 160 mV RP (+80mV endolymph and -80 mV in the body of the hair cells due to the resting potential of the hair cells), potential gradient causes constant flow of current from the scala media to inside of hair cells, potential changes produced by this flow of the electrical current is the cochlear microphonic

Question 32

what is a cochlear microphonic

Answer 32

potential gradient causes a flow of current from scala media to inside of hair cells and these potential changes that are produced by the flow of electrical current is CM

Question 33

what is transduction mechanism in cochlea

Answer 33

transduction of cochlear vibration to neural impulses IHCs passively detect vibration that in turn excites the afferent nerve fibers of CN VIII fibers that are synapses at base of iHCs these impulses are then sent to the brain

Question 34

what are common characteristics of presbycusis

Answer 34

HF SNHL sloping speech perception issues espectially in noise & reverberation recruitment

Question 35

what are the classification of presbycusis

Answer 35

Schuknecht's & Killion & Fikret-Pasa

Question 36

why is classifying presbycusis in older adults important

Answer 36

improved differential diagnosis changes to individualized intervention that leads to improved auditory function in older adults

Question 37

describe schuknech't classificatioin of ARHL

Answer 37

based on postmortem eval of temporal bones sensory presbycusis primary loss of OHC & supporting cells neural presbycusis loss of afferent cochlear neurons metabolic/strial presbycusis loss of EP & atrophy of strial & lateral wall mechanical presbycusis stiffening of BM & organ of corti (no evidence)

Question 38

what is the primary goal of K &FP ARHL classification and what is it based on

Answer 38

develop a system which appropriate amplification based on other considerations than the pure-tone audiogram develop a system which appropriate amplification based on other considerations than the pure-tone audiogram

Question 39

describe Killion & Fikret-Pasa classification of ARHL

Answer 39

type 1 mild - moderate SNHL (no worse than ~ 45 to 55 dB HL) normal loudness sensation findings consistent w/ loss of OHC fxn ONLY w/ normal IHC fxn type 2 moderately severe HL (~ 6 dB HL) presence of partial recruitment assumed there is OHC loss WITH ICH loss have issues w. speech intelligibility (especially in noise) even with the best HA’s because there is less info transmitted to the brain & fewer redundant speech cues are available type 3 severe HL (~75 dB HL) loudness & intelligibility are affected & recruitment is common intelligibility becomes the primary concern speech range that can be heard in noise is narrowed these individuals do well when speech is presented close to UCLs OHC, IHC & nerve fiber losses

Question 40

NIHL is anatomically characterized by

Answer 40

loss of hair cells (initially OHCs) loss of supporting cells secondary neural degeneration

Question 41

Presbycusis is anatomically characterized by

Answer 41

mostly degeneration of the stria vascularis and lateral cochlear wall Compromised blood supply correlated with the extent of strial degeneration Presence of mostly normal sensory cells except in the most basal and apical turns of the cochlea

Question 42

NIHL is physiologically characterized by

Answer 42

Threshold elevations of APs of the auditory nerve, ABR, and higher level evoked responses The distinctive feature is loss of cochlear nonlinearities for ex: OAEs The endocochlear potential (EP) is generally unaffected in NIHL Degeneration of the stria vascularis is not typical in NIHL

Question 43

Presbycusis is physiologically characterized by

Answer 43

Reduction of endocochlear potential (EP) → due to degeneration of the stria (the batter of the cochlea)

Question 44

ARHL is, therefore, a ___, ______, & _____ disorder

Answer 44

vascular, metabolic, and neural

Question 45

describe long term relationship of NIHL & ARHL

Answer 45

NIHL early can make ARHL worse and over time ARHL can flatten the noise notch

Question 46

what is hidden hearing loss

Answer 46

synaptopathy (auditory nerve damage) causes it TTS can be indicative of immediate & irreversible damage to auditory n fibers & beginnings of HHL loss of connection from the auditory nerve to the hair cells causes HL not seen on an audiogram

Question 47

may be significant contributor to classic complaint “I can hear but I can’t understand what people are saying”

Answer 47

HHL