t he s ounds of l ife c enter at u mass m emorial current technique in the audiologic evaluation of...

TTHEHE S SOUNDSOUNDS OFOF L LIFE IFE CCENTER ENTER

AT AT UUMASS MASS MMEMORIALEMORIAL

Current Technique in the Audiologic Evaluation Current Technique in the Audiologic Evaluation of Infantsof Infants

Todd B. Sauter, M.A., CCC-A Director of Audiology- UMass Memorial Medical Center

PhD Candidate – University of Massachusetts Amherst Instructor – Dept. of Otolaryngology

University of Massachusetts Medical School



Growing Repertoire of Tools at the Disposal of Audiologist

•Auditory Brainstem Response (ABR)

•Auditory Steady-State Response (ASSR)

•Otoacoustic Emissions (OAE)

•Multiple Frequency Tympanometry

•Middle Ear Muscle Reflexes



Questions about Infant Testing by Questions about Infant Testing by Audiologists (And Others)Audiologists (And Others)

• Which of these tests are most important?Which of these tests are most important?

• Which of these tests should come first?Which of these tests should come first?

• Do I have to do all these tests on every Do I have to do all these tests on every child or just one test?child or just one test?



Best Practices in Infant TestingBest Practices in Infant Testing

Evidence-Based Clinically Efficient



Overview of TestsOverview of Tests



What is an ABR?What is an ABR?

• The Auditory The Auditory Brainstem Response Brainstem Response is the representation is the representation of electrical activity of electrical activity generated by the generated by the eighth cranial nerve eighth cranial nerve and brainstem in and brainstem in response to auditory response to auditory stimulationstimulation



How is an ABR recorded?How is an ABR recorded?

• Electrodes are placed on the scalp and coupled Electrodes are placed on the scalp and coupled via leads to an amplifier and signal averager. via leads to an amplifier and signal averager. EEG activity from the scalp is recorded while EEG activity from the scalp is recorded while the ear(s) are stimulated via earphones with the ear(s) are stimulated via earphones with brief clicks or tones.brief clicks or tones.

• A series of waveforms unique to the auditory A series of waveforms unique to the auditory neural structures is viewed after time-locking neural structures is viewed after time-locking the EEG recording to each auditory stimulus the EEG recording to each auditory stimulus and averaging several thousand recordings. and averaging several thousand recordings.



Example Normal HearingExample Normal Hearing

18 Month-Old – 2000 Hz Tone-Burst

70 dBnHL

10 dBnHL



Distortion Product Otoacoustic Distortion Product Otoacoustic

Emissions (DPOAE)Emissions (DPOAE)

Janet Stockard Sullivan 2003



What does the presence or absence of What does the presence or absence of OAEs tell us?OAEs tell us?

• Presence = There is Presence = There is no significant conductive no significant conductive lossloss (no need for bone conduction ABR) (no need for bone conduction ABR) andand threshold sensitivity is better than ~35 dBHL threshold sensitivity is better than ~35 dBHL (except in cases of auditory (except in cases of auditory neuropathy/asynchrony)neuropathy/asynchrony)

• Absence = Possible conductive component Absence = Possible conductive component and/orand/or sensorineural hearing loss ~35 dBHL or sensorineural hearing loss ~35 dBHL or greatergreater



TympanometryTympanometry

Janet Stockard Sullivan 2003



What does Tympanometry tell us?What does Tympanometry tell us?

• If sound energy is being lost in the outer or middle ear If sound energy is being lost in the outer or middle ear due to fluid, vernix, anatomical abnormalities, etc. due to fluid, vernix, anatomical abnormalities, etc. (conductive component to loss)(conductive component to loss)

• Provides cross-check with bone conductionProvides cross-check with bone conduction

• Had poor sensitivity in the past due to adult settings Had poor sensitivity in the past due to adult settings being used in infant ears (different!).being used in infant ears (different!).

• Now more appropriate equipment settings (1000 Hz Now more appropriate equipment settings (1000 Hz probe tone) and normative data for infants is available.probe tone) and normative data for infants is available.



Middle Ear Muscle ReflexMiddle Ear Muscle Reflex• Also known as acoustic reflex or stapedial reflexAlso known as acoustic reflex or stapedial reflex• Measured using same equipment/probe as tympanometryMeasured using same equipment/probe as tympanometry• Looking for sharp reduction in middle ear admittance in Looking for sharp reduction in middle ear admittance in

response to loud sound due to contraction of middle ear response to loud sound due to contraction of middle ear muscles.muscles.

• Should not be present with conductive loss, severe or Should not be present with conductive loss, severe or profound sensorineural hearing loss, or auditory profound sensorineural hearing loss, or auditory neuropathy/asynchrony.neuropathy/asynchrony.

• Ideally is not used as a stand-alone test, but as a cross-check Ideally is not used as a stand-alone test, but as a cross-check against ABR, OAE, etc.against ABR, OAE, etc.

• Best elicited in infants using a 1000 Hz probe-tone and Best elicited in infants using a 1000 Hz probe-tone and broadband noise stimulus.broadband noise stimulus.



What is Auditory Steady-State Response What is Auditory Steady-State Response (ASSR)?(ASSR)?

• Similar to ABR, but EEG activity is Similar to ABR, but EEG activity is analyzed in frequency domain rather analyzed in frequency domain rather than time domain.than time domain.

• Stimulus is modulated pure toneStimulus is modulated pure tone

• If response, EEG activity will modulate If response, EEG activity will modulate at same frequency as the stimulusat same frequency as the stimulus

• Statistical computer algorithm Statistical computer algorithm determines if response or no response determines if response or no response



Advantages of ASSRAdvantages of ASSR– Can test up to limits of transducer (through severe/profound range)Can test up to limits of transducer (through severe/profound range) *** Artifactual results? (See Gorga 2004, Small and Stapells 2004) from stimulus artifact *** Artifactual results? (See Gorga 2004, Small and Stapells 2004) from stimulus artifact

or vestibular systemor vestibular system– Has potential to be a faster test than ABR when perfectedHas potential to be a faster test than ABR when perfected– Some equipment can test multiple frequencies and both ears simultaneouslySome equipment can test multiple frequencies and both ears simultaneously– Uses same basic set-up and equipment as ABRUses same basic set-up and equipment as ABR



Limitations of ASSR• Cannot analyze raw data, must trust pass/fail criteria given by equipment for each run (can be viewed as advantage)

• Extremely limited published clinical database (improving)

• Bone conduction not yet perfected for clinical use (Can’t determine conductive vs. sensorineural with ASSR alone)

• Large threshold estimation range for normal hearing and mild loss (20 db)

•High intensity steady state stimuli may cause acoustic trauma



What we still need to learn about What we still need to learn about ASSRASSR

• Conductive vs. Sensorineural lossConductive vs. Sensorineural loss

• Effects of auditory asynchrony, Effects of auditory asynchrony, retrocochlear disease, etc. on ASSRretrocochlear disease, etc. on ASSR

• Sedation effectsSedation effects

• Are responses at very high levels (>100 Are responses at very high levels (>100 dB) truly auditory or artifactual?dB) truly auditory or artifactual?

• Reliable bone conduction testingReliable bone conduction testing



Gold-Standard: Tone-burst Auditory Gold-Standard: Tone-burst Auditory Brainstem ResponseBrainstem Response

Tone-Burst ABR

Click ABR OAE ASSR

High-Frequency Tympanometry

Middle Ear Muscle Reflex



Myths about ABR in Infant Threshold Myths about ABR in Infant Threshold AssessmentAssessment

1.1. It’s too slow It’s too slow

2.2. It isn’t accurate It isn’t accurate

3.3. It isn’t frequency-specific enough It isn’t frequency-specific enough

4.4. It is difficult to interpretIt is difficult to interpret



Myth #1: It’s too slowMyth #1: It’s too slow

• Slow stimulus rates (<20/sec) are not Slow stimulus rates (<20/sec) are not necessary in most patients but are still necessary in most patients but are still employed by many centers routinely. employed by many centers routinely.

• The click latency-intensity function is not The click latency-intensity function is not necessary in most patients and results in necessary in most patients and results in too much valuable test time being spent too much valuable test time being spent testing above threshold.testing above threshold.



Rate Effects Above ThresholdRate Effects Above Threshold

11.1/sec

39.1/sec

21.1/sec

55.9/sec

Time for 4000 sweeps – 6 minutes Time for 4000 sweeps – 3 minutes

Time for 4000 sweeps – 1 minute, 42 sec Time for 4000 sweeps – 1 minute, 10 sec



Rate Effects Near Threshold Rate Effects Near Threshold

21.1/sec 39.1/sec 55.9/sec

- At low stimulus intensities or near threshold, the early ABR waveforms are absent, while wave V amplitude stays relatively consistent. The use of slow-stimulus rates, in most cases, gains you nothing but longer test times. This is not true in cases of neurological impairment or auditory asynchrony.



Myth #2: It Isn’t AccurateMyth #2: It Isn’t Accurate

• A strict review of tone-burst ABR A strict review of tone-burst ABR literature with testing done literature with testing done under under appropriate parametersappropriate parameters found threshold found threshold accuracy of ± 5 dB accuracy of ± 5 dB (95 % Confidence Interval)(95 % Confidence Interval) for 500- for 500-4000 Hz. (Stapells 2000)4000 Hz. (Stapells 2000)

• Poor accuracy is likely most often Poor accuracy is likely most often associated with either poor technique or associated with either poor technique or attempts to interpret poor dataattempts to interpret poor data



Broadband Click ABR – Poorly Used Broadband Click ABR – Poorly Used as Estimate of 2000-4000 Hzas Estimate of 2000-4000 Hz



Broadband Click ABR – Poorly Used Broadband Click ABR – Poorly Used as Estimate of 2000-4000 Hzas Estimate of 2000-4000 Hz

Stapells 1998



Myth #3: It isn’t frequency specific enoughMyth #3: It isn’t frequency specific enough

Stapells 1995



Myth #4: It is Difficult to InterpretMyth #4: It is Difficult to Interpret

- Poor Data - Only Averaged ~ 1000 Sweeps - Difficult to Interpret - Waveforms marked Incorrectly

- Clean Data - Averaged 4000+ Sweeps - True Wave Vs are only significant EEG deflection

50

30

20



Most Common Mistakes in Infant Most Common Mistakes in Infant ABR (IMHO)ABR (IMHO)

• Click stimulus used as estimate of 2-4 KHz

• Underaveraging of signal

• Lack of an consistent test sequence algorithm



Sample Test SequenceSample Test Sequence

Present Absent Present Absent Present Absent Present Absent 60 Present Absent 95 Present < 80 dB

Present > 80 db or absent UMass Memorial Audiology AER Decision Matrix

DPOAE

Bone 2K 30 dB

Air 2K 30 dB

Air .5, 1, 4 KHz 30 dB

Bone 2K Thresh

Bone Click

Air 2 KHz Threshold

Air Click Threshold

ASSR

Air .5-4 KHz Threshold

Tymp/ Reflex If Necessary



Testing Sequence for New InfantsTesting Sequence for New Infants• Based on answering the most important questions Based on answering the most important questions

first while the child is asleep:first while the child is asleep:

1.1. Is hearing normal at the most important speech Is hearing normal at the most important speech intelligibility frequency? intelligibility frequency?

2.2. Both ears? Both ears?

3.3. If hearing is not normal, is it a permanent loss? If hearing is not normal, is it a permanent loss?

4.4. How severe is it? How severe is it?

5.5. Other frequencies? (500-4000 Hz)Other frequencies? (500-4000 Hz)

6.6. If profound loss, is there residual hearing?If profound loss, is there residual hearing?

7.7. Could it be Auditory Neuropathy/Asynchrony?Could it be Auditory Neuropathy/Asynchrony?

8.8. Will other tests support the diagnosis?Will other tests support the diagnosis?



Testing SequenceTesting Sequence1.1. Is hearing normal at the most important speech Is hearing normal at the most important speech

intelligibility frequency?intelligibility frequency?- Low intensity (30 dB) 2000 Hz air-conduction tone - Low intensity (30 dB) 2000 Hz air-conduction tone burst ABRburst ABR

2.2. Both ears?Both ears?- Get 2000 Hz on - Get 2000 Hz on each eareach ear before moving on before moving on

3.3. If hearing is not normal, is it a permanent loss?If hearing is not normal, is it a permanent loss?- Get 2000 Hz bone-conduction information early in - Get 2000 Hz bone-conduction information early in the testing to determine if loss is conductive or the testing to determine if loss is conductive or sensorineural in nature. Not necessary if DPOAEs sensorineural in nature. Not necessary if DPOAEs are present.are present.



Testing SequenceTesting Sequence

4.4. How severe is it?How severe is it?

- Use aggressive bracketing technique - search in 30 - Use aggressive bracketing technique - search in 30 dB intervals before using smaller (5/10 dB) steps to dB intervals before using smaller (5/10 dB) steps to mark thresholdmark threshold

5.5. Other frequencies?Other frequencies?

- Use a logical sequence of frequencies to get the most - Use a logical sequence of frequencies to get the most useful information first – 2000 Hz, then 500 Hz, then useful information first – 2000 Hz, then 500 Hz, then 4000, etc.4000, etc.




6.6. If profound loss, is there residual hearing?If profound loss, is there residual hearing?

- If no tone-burst response, test click ABR at 90 dB - If no tone-burst response, test click ABR at 90 dB and ASSR up to 115 dB (never this high if DPOAE and ASSR up to 115 dB (never this high if DPOAE present)present)

7.7. Could it be auditory neuropathy/asynchrony?Could it be auditory neuropathy/asynchrony?

- Obtain 90 dB slow-rate click ABR at both - Obtain 90 dB slow-rate click ABR at both rarefaction and condensation polarities to look for rarefaction and condensation polarities to look for presence of cochlear microphonic (hair-cell response) presence of cochlear microphonic (hair-cell response)




8.8. Will other tests support the diagnosis?Will other tests support the diagnosis?

- If conductive hearing loss or auditory asynchrony is - If conductive hearing loss or auditory asynchrony is suspected, cross-check with tympanometry and suspected, cross-check with tympanometry and middle-ear muscle reflexes.middle-ear muscle reflexes.



Questions?Questions?

[email protected]

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