Presbycusis

Question 1

what are the 2 most common causes of HL

Answer 1

1)age
2) noise induced HL

Question 2

what is presbycusis

Answer 2

age related hl

Question 3

how can presbycusis happen?

Answer 3

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

Question 4

what is the site of damage for presbycusis?

Answer 4

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

Question 5

what is the formula for presbycusis

Answer 5

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

Question 6

why is it hard to measure presbycusis

Answer 6

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

Question 7

how is presbycusis identified as?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

amplification provided by the OHC are dependent on what ?

Answer 9

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

Question 10

why are endocochlear potentials intriguing and unusual?

Answer 10

-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

Question 11

what 3 systems is the cochlea divided into ?

Answer 11

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

Question 12

what is the purpose of endocochlear potential ?

Answer 12

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

Question 13

where is endocochlear potential higher?

Answer 13

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

Question 14

what is draining that battery of e.p?

Answer 14

-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

Question 15

what is the power supply made up of?

Answer 15

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

Question 16

what is the power supply dependent on?

Answer 16

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

Question 17

what is the last step to cochlear power supply?

Answer 17

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

Question 18

look at slide 18

Question 19

what is cochlear transduction?

Answer 19

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

Question 20

what does the cochlear transduction mechanism consist of?

Answer 20

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

Question 21

which hair cell is susceptible to damage

Answer 21

inner

Question 22

how do we know that when age is affecting hearing loss

Answer 22

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

Question 23

what are some characteristics of presbycusis ?

Answer 23

-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

Question 24

how does speech discrimination look like in presbycusis ?

Answer 24

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

Question 25

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

Answer 25

consonants become attenuated because they're high frequencies,

Question 26

what else deteriorate speech perception ?

Answer 26

upward spread of masking

Question 27

what configuration do we see with presbycusis ?

Answer 27

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

Question 28

just know that WRS is also affected by presbycusis

Question 29

what is schuknecht classifications ?

Answer 29

1) sensory presbycusis 2) neural presbycusis 3)Metabolic/strial presbycusis 4)Mechanical presbycusis

Question 30

what is sensory presbycusis ?

Answer 30

loss of primary cochlear OHC and supporting cells

Question 31

what is neural presbycusis ?

Answer 31

-loss of afferent cochlear neurons

Question 32

what is matabolic/strial presbycusis?

Answer 32

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

Question 33

what is mechanical presbycusis ?

Answer 33

-stiffening of the basilar membrane and organ of corti

Question 34

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

Answer 34

-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

Question 35

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

Answer 35

-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

Question 36

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

Answer 36

-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

Question 37

what is the site of lesion for presbycusis ?

Answer 37

the cochlea

Question 38

what are anatomical characteristics of noise induced HL

Answer 38

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

Question 39

what are physiological characteristics of noise induced hearing loss

Answer 39

-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

Question 40

what are anatomical characteristics of presbycusis

Answer 40

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

Question 41

presbycusis is physiologically characterized by ?

Answer 41

-Reduction of endocochlear potential (EP)

Question 42

what type of disorder is age related hearing loss ?

Answer 42

it is a vascular, metabolic and neural disorder

Question 43

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

Answer 43

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

Question 44

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

Answer 44

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

Question 45

what is synaptopathy ?

Answer 45

the loss of connections between auditory nerve fibers and hair cells

Question 46

when does synaptopathy happen ?

Answer 46

occurs before the threshold elevations associated with hair cell loss

Question 47

what is synaptopathy considered as

Answer 47

considered as a kind of hidden hearing loss