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AUDE 5410 Aud-Vestib Disorders > Quiz 3 (ANSD) > Flashcards

Quiz 3 (ANSD) Flashcards

1
Q

what is ANSD

A

disruption of neural synchrony

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2
Q

define ANSD

A

characterized by disruption to temporal coding of acoustic signals in the auditory n causing impairment of auditory perceptions relying in temporal cues

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3
Q

the phenotype of ANSD reults from

A

selective loss/damage of synaptic junctions of IHCs
NT release disorder by IHC synapses
injury to spiral ganglion
demyelinatioin/damage to myelin sheath, cell body or axon of CN VIII → can spread to BS
auditory n hypoplasia/absence

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4
Q

improve sound detection

A

OHCs

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5
Q

what is present in ANSD

A

pre-neural & cochlear OHC
in tact OAEs
CM

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6
Q

why are OAEs in tact with ANSD

A

because OAEs relate to OHC fxn and these are in tact with ANSD but they may disappear in later stages

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7
Q

what creates cochlear microphonics

A

OHCs

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8
Q

temporal resolution is not affected in ansd but frequency resolution is

A

false
temporal resolution is affect & frequency res is not

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9
Q

what do ABR results look like in ANSD

A

absent or abnormal
becauase ABR is generated by neural structures → neural integrity of 8th n & lower BS pathways are affected

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10
Q

ECochG and ARTs also are absent because of

A

CN VIII N involvement

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11
Q

critical for sound discrimination

A

IHC

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12
Q

what are ribbon synapses

A

highly specialized, encode sound w/ sub-millisecond temporal precision, mediated by calcium channels
vesicles that contain NTs

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13
Q

synapse w/ VIII N fibers

A

IHCs

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14
Q

DFNB9 & its relation to ANSD

A

AR
deafness gene that results in mutation in OTOF gene

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15
Q

what does OTOF gene do

A

encodes for protein otoferlin

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16
Q

why is otoferlin important

A

calcium sensor for vesicle fusion & pool replenishment at IHC ribbon synapses

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17
Q

what is research showing with mic.e without otoferlin

A

they are profoundly deaf because sound evoked NT fails to release at IHC synapse even with normal sensory epithelium structure of the IHC

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18
Q

site of lesion of ANSD

A

spectrum disorder due to multiple sites of lesions

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19
Q

what is auditory/cochlear synaptopathy

A

loss of synchrony of neural firing causing loss of temporal resolution
could be at dorsal cochlear nucleus because of synaptic damage at IHC and/or at level of spiral ganglion
adversely affects fine speech structure decoding & speech perception especially in noise
also seen in ANSD

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20
Q

Majority of NICU babies had a _____ hearing loss but ~ 20% had a ______ hearing loss

A

bilateral, unilateral

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21
Q

what is etiology of ANSD

A

idiopathic, genetic, or environmental

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22
Q

sound audibility & auditory perception are different. What does this mean

A

children w/ ANSD present w/ common pattern of electrophysiologic & electroacoustic results BUT auditory capabilities can vary vastly

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23
Q

PT population is heterogeneous for

A

etiology, presentation & management outcomes

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24
Q

Sensory IHCs & CN VIII N fibers in tact with this condition

A

DFNB9

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25
Q

nosology for ANSD

A

auditory neuropathy
presynaptic & postsynaptic n disorder
auditory neuropathy/dys-synchrony
auditory synaptopathy
more recently → cochlear synaptopathy or hidden hearing loss

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26
Q

incidence of ANSD

A

10-15% of deaf population
more babies in nicu
Majority of NICU babies had a bilateral hearing loss but ~ 20% had a unilateral hearing loss

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27
Q

etiology of ANSD

A

idiopathic genetic or environmental

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28
Q

what are genetic based ANSD’s

A

non syndromic
syndromic
mitochondrial

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29
Q

non syndromic genetic ANSD

A

AR → mutations of Connexin 26 & Otoferlin (DFNB9)
otoferlin is localized to IHC & often with synapse of IHC to VIII N fibers

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30
Q

syndromic genetic ANSD

A

associated w/ peripheral neuropathies
Charcot Marie Tooth & Friedrich’s ataxia

31
Q

mitochondrial genetic ANSD

A

comes from mom 100% (all m and f affected)
will males transmit the gene?
no because they shed their cytoplasm that contains the mitochondria
Leber’s hereditary optic neuropathy

32
Q

immune disorders deafness typical to ANSD

A

Guillian-Barre syndrome
affects proximal nerve roots & portions of VIII N
deafness & paralysis w/ lengthy recovery period

33
Q

metabolic disorders & ANSD

A

diabetic neuropathy → typically acquired in adults

34
Q

environmental based ANSD

A

viral infections

35
Q

if VIII N primarily affect for any reason, clinical picture is

A

ANSD

36
Q

if arterial supply unaffected,

A

OAEs CM & sometimes wave 1 of ABR can be identified

37
Q

if arterial supply affected,

A

both neural & cochlear receptor elements are disrupted
OHCs affected & OAEs & ABR may be absent which confuses clinical picture of ANSD

38
Q

what are peripheral neuropathies?

A

Charcot Marie Tooth & Friedreich’s ataxia

39
Q

audiologic findings (summary)

A

present OAEs for most unless cochlear blood supply is compromised

ABS ABR w/ present CM → confirmed w/ 2 polarity click stimulus at 70-90 dB nHL

Abnormal ARTs → also present with any test of CN VIII fxn

poor WRS in noise

audio can have varying severity & configuration → not a measure of neural dys-synchrony

PT vary in characteristics & management needs
some benefit with amp
some with CI’s
some with neither

40
Q

what do OAEs show for ANSD

A

they are tests of cochlear hair cell fxn
can use TEOAE & DPOASE
present in early years of ANSD and can become absent when OHC blood supply is compromised

41
Q

what does contralateral OAE suppression show

A

normally shows decrease in OAE amplitude when masking is in the contra ear

in ANSD, the involvement of efferent VIII N fibers doesn’t let the neural impulses reach the OHCs creating no suppresison = abnormal

42
Q

what is a click evoked abr

A

test of auditory nerve function
ABR & CM

43
Q

what normally happens with intensity and latency in ABR

A

as intensity decreases, intensity increases
amp also decreases

44
Q

what is seen with ABR in ANSD

A

latency of wave 5 doesn’t increase
ansd mimics a true abr
present CM
no amplitude decrease of waves I, II, V

45
Q

waht should be done with ABR once you identify ANSD

A

stop the abr becuase it is useless

46
Q

what are risk factors for ANSD

A

premature & low birth weight
prolonged NICU stay
O2 deficiency
seizures
hyperbilirubinemia

47
Q

why does hyperbilirubinemia raise the question how long ABR status should be monitored and when CI should be considered?

A

because in few cases of it with transient ANSD spontaneous improvement can occur within first 2 years of life but they do not know if neural synchrony at the brainstem level restores and results in normal auditory processing so they typically wait 2 years before considering CIs

48
Q

describe hyperbilirubinemia in terms of ANSD

A

may be reversible & spontaneously improve w/in 2 yrs of life

primary site of lesion is NOT VIII N → damage in CANS & BS (primarily Cochlear nucleus) and descends to VIII N
bilirubin accumulates in auditory BS & VIII n ganglion cells
nerve death or dysfunction will occur but IHC unaffected

49
Q

what tests will be abnormal with ANSD

A

any test involving 8th nerve

word, reflexes, echog, contralateral suppression w/ OAEs

50
Q

what is the site of lesion for ANSD

A

synapse bw 8th nerve & IHC, 8th nerve, spiral ganglion?

51
Q

what are used to diagnose ANSD

A

careful case history
OAEs
ABR
MEAR
behavioral assessment
speech audiometry
ECochG
vestib assessment if needed
questionnaires for young children

52
Q

describe OAE findings with ANSD

A

present because it is test of OHC fxn which is peripheral to 8th n

can be absent later with compromised blood supply

Contralateral OAE suppression (a normal phenomenon) is absent because the signal has to cross to the other ear, which can’t happen if we have nerve damage in the efferent nerve system

53
Q

describe ABR findings in ansd

A

performed at high level click stimulus (70-90 dB nHL) w/ 2 polarities - NO ALTERNATING)

CM reverses w/ polarity change, no latency increase with intensity decrease = ANSD

54
Q

combo of what is essential for ANSD diagnosis

A

OAE & ABR w/ 2 polarities

55
Q

why should alternating polarities not be used in suspected cases of ANSD?

A

Because it is the sum of condensation & rarefaction polarities so it will not show response reversal

56
Q

what if CM is not present even with ANSD presence

A

due to clinician error or alternating polarity was used

57
Q

describe MEAR findings in ansd

A

abnormal or absent even with normal/mild SNHL (we expect reflexes even with SNHL up to 60 dB HL)

58
Q

why is MEAR absent with ANSD

A

reflexes require functioning 8th nerve so if it is affected reflexes will not happen

59
Q

why do we use behavioral assessment with ANSD

A

because abr cannot be performed

60
Q

describe behavioral assesment findings in ANSD

A

hearing sensitivity ranges from normal/mild to severe to profound SNHL w/ varying configurations

unilateral or bilateral

~ 30 to 40% show a rising configuration hearing loss

fluctuations in hearing can occur

61
Q

can the audio tell us about ANSD

A

NO

it doesn’t give us anything about dys-synchrony

62
Q

describe speech audiometry results in ANSD

A

significant impact no matter hearing thresholds due to IHC & CN VIII involvement

some may be functionally deaf & some may have some intact intelligibility in quiet but poor in noise

63
Q

what is recommended with speech audiometry? why?

A

SPEECH IN NOISE
poor word rec scores worse in noise because there is neural involvement

64
Q

describe echog findings with ANSD

A

abnormal becuase APs generate at VIII N which are affected

65
Q

what if you didn’t do two polarities? can you still pick up ANSD?

A

yes because as intensity decreases latency should increase so if wave 5 only exists and it stays the same, indicative of ANSD

66
Q

ANSD is a continuum/spectrum

A

true

67
Q

how is ANSD a spectrum

A

some can have no auditory complaints

others can do poor in noise & MEMRs are absent, inconsistent auditory responses

or some can have total lack of sound awareness

68
Q

what other assessments can be done with ANSD

A

otologic eval with imaging of cochlea & auditory n

genetic eal

ophthalmologic if perifpheral neuropathies

neurologic eval

communication assessment

69
Q

what is important to keep in mind with ANSD & management

A

variable auditory capabilities
question is not how severe the HL is but how severe the dys-synchrony is

70
Q

when are CI’s successful

A

when pathophysicology is either biochemical abnormality of NT substances or synaptic deficits bw IHC & auditory n

71
Q

when are CI’s sometime successful

A

if neural integrity is compromised → loss of myelin, loss of neural elements (including VIII N)

72
Q

how can ANSD be managed educationally

A

with auditory and visual stimulation

manual communication like cued speech or ASL

a formal education to facilitate literacy & self-dependence

73
Q

how can ANSD be managed

A

HAs & FM systems trials
most successful is CI’s
gene therapy

74
Q

how does gene therapy help ANSD

A

adeno-associated virus (AAV) carries version of human OTOF gene used to introduce gene back into the innner ear through surgery

deaf children reported hearing sounds & understanding speech

AUDE 5410 Aud-Vestib Disorders (18 decks)

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