Objective Measures

Question 1

Acoustic Immittance

Answer 1

we are measuring a change in sound pressure level in external auditory canal–tone has set frequency and intensity —- at what point is max sound pressure level being admitted into middle ear

if have healthy TM–would have high admittance, sound tone is going into ME, stimulating cochlea—but change air pressure in canal to make it really positive (stiffens ME system) very little admittance at this point because increase in sound pressure level in ear canal relative to when there was no pressure–point with highest admittance is the peak (MEASURING ADMITTANCE OF SOUND INTO MIDDLE EAR SPACE–NOT MOVEMENT OF EARDRUM)

1kHZ tone for kids under 6 months because their system is still mass-dominated–resonant frequency is higher because ossicles are more gelatinous at this point —resonant frequency: vibrates most efficiently–with HF tone, nowhere near resonant frequency so it is indicative of middle ear system NOT resonant frequency

Question 2

Acoustic Reflexes

Answer 2

Acoustic reflex threshold: how well low level nervous system, stapedius muscle is contracting to loud noises–if kid is screaming for tymps, don’t sit them through threshold measures–will be pointless — we are measuring CHANGE IN ADMITTANCE/SOUND PRESSURE LEVEL—we are presenting loud sound triggering ME muscles to contract so measuring as change of admittance in ear canal!!!!!!!

Acoustic Reflex Threshold: do not do this if get flat Tymp because, cannot see change in admittance because there is no change of admittance measurable because of fluid in ME cavity

Question 3

1000 Hz Tymp Probe Tone

Answer 3

Used for kids under 7 months because ME system is mass dominated and this is useful for checking for ME effusion in children

Question 4

ABR

Answer 4

temporal relationship exists between stimuli and neural response–high latency is associated as go further up the auditory system

Question 5

Effects of Intensity on ABR latency

Answer 5

Wave V is MOST important when trying to get measure of pt’s threshold of hearing—most robust waveform in ABR, therefore we are able to follow wave V as we decrease intensity of a stimulus–it takes Wave V longer and longer to show as you decrease intensity—LEADS to INCREASE in latency (INVERSE RELATIONSHIP

Question 6

Effects of stimuli on ABR

Answer 6

Click: abrupt sound, no sound to max intensity to no sound again–the most abrupt signal we have but because of nature of click stimulus it is broad frequency stimulus–stimulates majority of basilar membrane —do not know what LF, MF, HF hearing is like—all you can say is there is or isn’t a response to click stimulus–used in screenings because gives you overall picture of health of nervous system

Tone Bursts: can be used to measure more frequency specific information—can get frequency specific info with ABR 500Hz, 1000Hz, 2000Hz and 4000Hz tone bursts are most typical
1msec:

Pure tone: sine wave–do not elicit ABR because of length of time it takes to go to absence of signal to max of signal

Question 7

Patient factors that can influence ABR

Answer 7

Middle ear pathology
tumors
Auditory neuropathy, MS
hearing loss
age

Question 8

Age & ABR response

Answer 8

Maturation occurs at 18 months

as early as 27-28 weeks CA an ABR can be run and only waves 1,3,5 can be observed at birth

infants are more sensitive to changes in click rate

Wave 1: more prominent, is lower in pathway, have a better chance to cochlea to mature —fewer neural connections in the way to disrupt the signal—start to cross over after this point–more interactions in brainstem

Question 9

Infant ABR Screenings

Answer 9

alternate polarity
screen at 30-35dB
Clicks

-pass or fail–delayed waveform, completely absent waveform, small amplitude waveform? NO CLUE about underlying cause

Question 10

Pros & Cons of ABR screens

Answer 10

Cons: may miss a precipitous HF HL, may miss LF HL

Pros: can catch AN, quick, doesn’t need to be performed by audiologist

Question 11

Diagnostic ABR

Answer 11

tone bursts at 500, 1000, 2000, 4000
bone or air conduction
clicks are within 5dB of behavioral threshold

Question 12

Sedated ABR

Answer 12

kids 6 months-5 years of age
kids at risk for neurological dysfunction

need to be administered by physician – need to monitor oxygen saturation rate, level of consciousness (every 15 min), pulse and respiratory rate

Question 13

Auditory Steady State Response

Answer 13

pure tone stimuli, frequency specific

80-90dB is max output of my equipment of ABR and have no response—can go up to 120dB with the ASSR therefore a lot of CI programs want to see an ASSR on a kid to see if there is any usable hearing at all —if no waves this high, maybe there is no stimulable fluid

Question 14

OAEs

Answer 14

not a test of hearing, depend on integrity of middle ear, preneural, depend on blood flow to the cochlea (anoxia could effect)

No OAEs after 30-40dB HL

very low intra-subject variability—remain pretty much the same for the person in 3 weeks….3 months….3 years…. –> Good for monitoring ototoxic medication
very different OAEs from person to person

Question 15

OAEs pros

Answer 15

tester experience can effect how well you measure OAEs

• can do it in noisy well baby unit and still get decent readings
• OAEs are faster and less expensive
• OAEs are VERY susceptible to ME pathology — can get high fail rate in babies

Question 16

TEOAEs

Answer 16

transient evoked oaes
broadband click stimuli
considered present if 3dB above background noise
shows more HF information
larger amplitude over most frequency ranges by ~10dB

Question 17

TEOAEs in kids vs adults

Answer 17

could be different because of auditory maturation
size and resonance of middle ear
cochlear differences?

Question 18

DPOAEs

Answer 18

non linear actions between 2 pure tone frequencies
very frequency specific

needs to have 5dB SNR
noise floor shouldn’t be more than -15 and amplitude response shouldnt be less than -10

Question 19

What can affect OAEs

Answer 19

probe insertion depth
ME status
Cochlea
tester experience
Noise (inner and external)