OAEs & AEPs - exam 2 Flashcards
objective tests
not tests of hearing
can infer if the structures are working
immittance measurements
objective tests of middle ear function & acoustic reflex pathway
OAEs are an _____ (objective/subjective) test of _____ (middle ear, cochlear,
auditory nerve and brainstem) function
objective
cochlear function
BRs are an _____ (objective/subjective) test of _____ (middle ear, cochlear,
auditory nerve and brainstem) function
objective
auditory nerve & brainstem
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
OAE function
OHC primary sensor for sound
can hearing loss occur w/ normal OAEs
yes
retrocochlear
OAEs only measure afferent sound
true or false
false
can be used to measure both afferent (going up) & efferent (going down) auditory system
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
spontaneous OAEs
w/out any stimulation
rare
some normal cochleae produce sounds in the absence of external stimulation
evoked OAEs
purposely introduce stimulus to evoke a response
occur in response to acoustic stimulation
used clinically
transient
distortion product
transient evoked OAEs
click introduced into the ear
amplitude of response decreases
broadband stimuli & response
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
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
SNHL & OAEs
SNHL > 30 dB HL = absent or highly decreased OAEs
OAEs may still be present w/ mild SNHL
OAEs & tymps
Type B & type As tymps generally lead to absent OAEs
if OAEs are absent, always measure tymps
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
