OAEs & AEPs - exam 2 Flashcards by elise beckman

objective tests

not tests of hearing

can infer if the structures are working

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immittance measurements

objective tests of middle ear function & acoustic reflex pathway

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OAEs are an _____ (objective/subjective) test of _____ (middle ear, cochlear,
auditory nerve and brainstem) function

objective

cochlear function

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BRs are an _____ (objective/subjective) test of _____ (middle ear, cochlear,
auditory nerve and brainstem) function

objective

auditory nerve & brainstem

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OAEs

otoacoustic emissions

result from both OHC responses & non-linearities on the BM

OHC movement results in sound going out of the ear (anything that moves creates sounds)

sound can be reliably elicited, measured, & used diagnostically

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OAE function

OHC primary sensor for sound

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can hearing loss occur w/ normal OAEs

yes

retrocochlear

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OAEs only measure afferent sound

true or false

false

can be used to measure both afferent (going up) & efferent (going down) auditory system

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eliciting & measuring OAEs

test probe inserted & sealed into external auditory canal

probe presents signal

mic picks up emission signal which is converted into an electrical signal & measured

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spontaneous OAEs

w/out any stimulation

rare

some normal cochleae produce sounds in the absence of external stimulation

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evoked OAEs

purposely introduce stimulus to evoke a response

occur in response to acoustic stimulation

used clinically

transient
distortion product

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transient evoked OAEs

click introduced into the ear

amplitude of response decreases

broadband stimuli & response

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distortion product OAEs

2 tones that vary in freq are presented to the ear

normal cochlea will respond by producing energy at an additional freq

vary initial freqs to span the cochlea

elicited OAE depends on the ration of stimulus freqs - response occurs at 2f1-f2

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what affects OAEs

any process that affects OHC function will reduce amp of OAEs

decreased or absent OAEs may precede increased thresholds on an audiogram

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SNHL & OAEs

SNHL > 30 dB HL = absent or highly decreased OAEs

OAEs may still be present w/ mild SNHL

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OAEs & tymps

Type B & type As tymps generally lead to absent OAEs

if OAEs are absent, always measure tymps

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when are OAEs measured

universal newborn hearing screening

monitor ototoxicity

monitor noise-induced hearing loss

difficult to test pops

check behavioral thresholds

separate cochlear from retrocochlear dysfuntion

interpretation of present OAEs

consistent w/ hearing thresholds of 30 dB HL or better

suggests conductive pathway is clear

does not rule out retrocochear pathology

interpretation of abnormal or absent OAEs

check conductive pathway

if conductive pathway normal –> likely SNHL greater than 30 dB HL

auditory evoked potentials

record neural responses evoked by a sound

test of neural synchrony

measure both latency & amp of responses

latency

how long after the auditory stimulus the occurrence of the response happens

auditory brainstem response

most commonly used clinically

measures early latency response to a sound

stimuli is clicks, chirps, or tone bursts

clicks vs chirps

clicks - get high freq back first due to sound hitting the base of the cochlea before the peak

chirps - clicks w/ a high freq lag
stimulates entire cochlea at the same time

wave/peak & generator

I: distal auditory nerve

II: proximal auditory nerve

III: cochlear nucleus

IV: superior olivary complex / lateral lemnisucs

V: lateral lemniscus / inferior colliculus

ABR set up

transducer - insert headphones surface electrodes measure neural response

how many electrodes in ABR

4 right, vertex, ground, left vertex - measures voltage drop

ABR instructions

can be sleeping or anesthetized one ear tested at a time using either clicks (1-4kHZ) or tones (more freq specific) place electrodes on scalp (on mastoid & top of forehead / scalp) put transducer in ear

ABR peaks

characterized by latency & amp amp - how large is the response latency - when is the response occurring

absolute peak latencies

time at which each peak occurrs

interpeak / wave latencies

time between peaks

ABR clinical applications

threshold estimation newborn screening neurodiagnostic intraoperative monitoring

We use wave _____ (I, III, V) for threshold estimations

V "big fall" threshold is the lowest level at which we observe an ABR typically corresponds to within 10-15 dB of threshold in adiometry start w/ clicks bcs biggest, most reliable response then tones for more specific info

what would you expect to see (amp & latency) w/ a conductive hearing loss

amp decrease latency increase

ABR newborn screening

typically w/ click at 35 dB presentation level remains constant computer determines if wave V is present or absent results are either pass or refer not usually completed by AuD

intraoperative monitoring (IOM)

to reduce risk of neural damage during surgery, watch for - prolongations in latency - obliteration of wave forms - severe reductions in amp to determine appropriate neural site for some surgically implanted devices

emissions present & agree w/ behavioral pure tone data

no immediate recommendations

emissions present, but behavioral pure tone data suggests a HL

recommend ABR testing

emissions are absent, normal ME function, behavioral pure tone data suggests HL

recommend ABR testing

acoustic steady state response (ASSR)

stimuli is modulated by some freq phase locking to the modulation rate & its harmonics of the carrier is encoded in neural activity analysis is in the freq rather than the time domain

acoustic change complex (ACC)

cortical potential - late latency response to a change in an ongoing sound stream (surprise) insensitive to attention can be used to assess auditory discrimination ability