What are OAES
they are otoacoustic emissions.
there are different types of these
What are SOAEs
Spontaneous otoacoustic emissions.
Cochleas are capable of producing sounds without external stimulation.
it is usually inaudiable to the person.
Why does SOAEs happen
believed to be caused by outer hair cell movement generating waves that cause hearing to move backwards.
hair cells>cochlea>ossicular chair>TM
What are EOAEs
evoked otoacoustic emissions.
its when OAEs happen after acoustic stimulation to use for diagnostics.
How do you test EOAEs
There is a probe with a rubber tip to produce air tight seal. in the tube there is a speaker and a microphone.
Testing environment must be quiet
What is signal averaging
if the same waveform (pitch/sound) is produced at the same frequency over and over, all the background noise will average to cancel out.
What are the two types of EOAEs
transient and distortion product emission
What do OAEs measure for
does a person have healthy hair cells
What are transient evoked otoacoustic emissions
click stimulus to measure overall function of cochlea. not frequency specific. complex aperiodic.
what are distortion-product otoacoustic emissions
frequency specific information.
probe presents two tones at the same time. these have different frequencies and will cause the cochlea to produce energy to make a third frequency.
What would results of an OAE show?
present or absent emissions
What is the diagnostic significance of OAEs
can test infants/small children and other difficult to test patients
consistency (non organic hearing loss)
monitoring ototoxic medication effects
middle ear dysfunction
What is a disadvantage of OAE
only tests to the point of cochlea, may miss a diagnosis of auditory neuropathy
What are Auditory Evoked Potentials
once sound reaches the inner ear, it is transmitted to the brain through neuroelectric events.
the connections occur through a series of nuclei.
a spike of electrical activity causes action potential. these potentials can be measured when they are evoked by auditory stimuli.
what are auditory brainstem responses
Auditory evoked potentials that occur in the first 10 to 15 ms after introduction of signal.
originates in the auditory nerve and brainstem
what is latency
time period that elapses between introduction of stimulus and occurrence of response
what is amplitude
strength of magnitude of the auditory evoked potentials.
When is ABR testing used
for infants or individual who cannot partake in behavioral testing
AEPs at later latencies can be measured and are believed to originate where
cortex
What is the ABR procedure
AEP are measured with an EEG which picks up electrical activity from the brain by electrodes placed on the scalp.
transducers present tones or clicks to the patient’s ear.
signal averaging is used in this process.
what is the restriction with the abr process
patients must be either completely relaxed, or asleep, or sedated
what do waves on the monitor represent for the ABR procedure
neuroelectric activity at one or more site along the auditory brainstem pathway.
What is the importance of ABR?
compare latency and amplitude results to normative values
find thresholds by determining lowest stimuli level where wave V is still detectable
wave V has the largest amplitude
what is the diagnostic significance of ABR
determine degree/type/configuration of hearing loss on infants and children or individuals who are hard to test.
compare air and bone conduction
determine presence/absence of auditory neuropathy
determine presence or absense of other auditory nerve brainstem pathology like tumors (mainly use MRIs now)
