HEARLab training Harvey Dillon, Bram Van Dun, Lyndal Carter, Kirsty Gardner-Berry HEARing CRC National Acoustic Laboratories (NAL) www.hearingcrc.o With thanks to John Seymour, Suzanne Purdy, Maryanne Golding, Hsiuwen Chang, Barry Clinch, Lars Kirk 3 September 2010 - Version 1 NAL: Dillon, Van Dun, Carter, Gardner-Berry
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HEARLab training Harvey Dillon, Bram Van Dun, Lyndal Carter, Kirsty Gardner-Berry HEARing CRC National Acoustic Laboratories (NAL) With.
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HEARLab training
Harvey Dillon, Bram Van Dun, Lyndal Carter, Kirsty Gardner-Berry
HEARing CRC
National Acoustic Laboratories (NAL)
www.hearingcrc.org
With thanks to John Seymour, Suzanne Purdy,
Maryanne Golding, Hsiuwen Chang, Barry Clinch, Lars Kirk
3 September 2010 - Version 1 NAL: Dillon, Van Dun, Carter, Gardner-Berry
INTRODUCTIONINTRODUCTION
NAL: Dillon, Van Dun, Carter, Gardner-Berry
The need for a new The need for a new measurement toolmeasurement tool
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Evaluation of aided functioning in infantsEvaluation of aided functioning in infants
Universal new born screeningUniversal new born screening
Early fitting of hearing aidsEarly fitting of hearing aids
Need for an evaluation methodNeed for an evaluation method
Confirmation Confirmation of fittingof fitting
Fine-tuning Fine-tuning neededneeded
Cochlear Cochlear implant implant neededneeded
NAL: Dillon, Van Dun, Carter, Gardner-Berry
So baby, how does it sound?So baby, how does it sound?
Objective hearing aid Objective hearing aid evaluation for: evaluation for:
• young infantsyoung infants• difficult-to-test difficult-to-test
peoplepeople
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Language at 6 m onths after im plantat ionW ilks lambda=.71507, F(2, 28)=5.5785, p=.00914
< 12m 12m +
Im plant age c ategory
40
50
60
70
80
90
100
110
120
PLS
-4 standard scores
Cov ar iate means :MonFit: 10.97917
CA 6P_A C CA 6P_EC
Why the rush?Why the rush?Language ability 6 months after implantationLanguage ability 6 months after implantation
NAL: Dillon, Van Dun, Carter, Gardner-Berry
(Computed f or c ov ar iates at their means )
V ertic al bars denote 0.95 c onf idenc e interv als
F itt ing age c ategory
PLS
-4 standard scores
< 6m > = 6m60
70
80
90
100
110
120
< 6m > = 6m
Cov ar iate means :F6A V 3FA : 57.11296
A 6P_A C A 6P_EC
Pre s : N AL Pre s : D SL
Significant effect of age of fitting: p = 0.001*
Early intervention leads to better language development at 6 months after fitting (n=90)
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Why use Why use corticalcortical responses? responses?
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Why cortical responses to evaluate hearing Why cortical responses to evaluate hearing aid fitting in infants?aid fitting in infants?
• Reliably present in awake young infants Reliably present in awake young infants
• More likely to correlate well with More likely to correlate well with perceptionperception
• Can be elicited by a range of speech Can be elicited by a range of speech phonemes – close to desired outcomesphonemes – close to desired outcomes
• Stimuli handled reasonably by hearing aidsStimuli handled reasonably by hearing aids
• Can be very frequency specific if neededCan be very frequency specific if needed
Practical implementation of Practical implementation of cortical testing: HEARLabcortical testing: HEARLab
DisclosureDisclosure: NAL will get a royalty for each unit sold.: NAL will get a royalty for each unit sold.
Thank you:Thank you: The HEARLab development team – The HEARLab development team – Teck Loi, Barry Clinch, Isabella Tan, Ben Rudzyn, Teck Loi, Barry Clinch, Isabella Tan, Ben Rudzyn, Lyndal Carter, Dan Zhou, Scott Brewer Lyndal Carter, Dan Zhou, Scott Brewer
NAL: Dillon, Van Dun, Carter, Gardner-Berry
NAL: Dillon, Van Dun, Carter, Gardner-Berry
NAL: Dillon, Van Dun, Carter, Gardner-Berry
NAL: Dillon, Van Dun, Carter, Gardner-Berry
In combination with:
Ambu Blue Sensor Ndisposable electrodes
2. Differential Amplification
• Two electrodes detect the “response (signal)” to varying degrees plus “noise”, with reference to a third electrode,
• By inverting the electrical activity at one of the two main sites, and finding the difference between them, some noise cancellation occurs and thesignal size is increased,
• This improves the signal-to-noise ratio (SNR) to some degree.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
2. Differential amplification
Inverting
Non-inverting+
-
Ground
NAL: Dillon, Van Dun, Carter, Gardner-Berry
From: Hall, J.W. (1992) Handbook of Auditory Evoked Potentials
(Excerpts from Figure 5-13)
Electrode input: + - Ground
Pre-amp Active Reference GroundNon-inverting Inverting Reference
3. Averaging
Averaging is the single most powerful technique for improving SNR
For repeated auditory stimulation, the neurons of the auditory system will be activated in the same sequence, at the same point in time,
We can say then that this neuronal activity is “time-locked” to the presentation of the stimulus.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
3. Averaging
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• Repeated stimulation with the same sound is required to view the auditory response (i.e., to have an adequate signal-to-noise ratio),
• The number of stimulations required depends on the size (i.e., amplitude) of the response.
3. Averaging
NAL: Dillon, Van Dun, Carter, Gardner-Berry
4. Filters
• A device which permits some frequencies through and not others, • High Pass (low freq) filters reject lower energy and Low Pass (high freq) reject energy above.
The most appropriate filters are those which preserve thefrequency region of the response and exclude others
NAL: Dillon, Van Dun, Carter, Gardner-Berry
4. Filters
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• Choice of stimulus depends on our clinical objective and from where in the auditory system we are recording.
• Responses from the early parts of the auditory system are best generated using very brief stimuli such as a “click”. Responses from late in the auditory system can be generated using tones, speech sounds or clicks.
• Stimuli may be delivered by headphone, insert earphone,bone conduction or loud speaker.
5. Stimuli
NAL: Dillon, Van Dun, Carter, Gardner-Berry
0 5 10 15 20 25 30-1
0
1G
Am
pli
tud
e
Time (ms)
0 5 10 15 20 25 30-1
0
1M
Am
pli
tud
e
Time (ms)
0 5 10 15 20 25 30-1
0
1T
Am
pli
tud
e
Time (ms)
Three speech sounds: /m/ /g/ /t/
0
10
20
30
40
50
60
70
125
200
315
500
800
1250
2000
3150
5000
8000
Frequency (Hz)
1/3
oct
ave
spec
tra
(dB
SPL)
/m/
/g/
/t/
5. Stimuli
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Automatic detection of cortical Automatic detection of cortical responsesresponses
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Why automated method?Why automated method?
• variable shape across agesvariable shape across ages• variable shape with auditory experiencevariable shape with auditory experience• variable shape from person to personvariable shape from person to person• variable shape from time to time (state of person, especially sleepiness)variable shape from time to time (state of person, especially sleepiness)• variable shape with stimulusvariable shape with stimulus• Variable shape with inter-stimulus intervalVariable shape with inter-stimulus interval
high skill level needed to read responsesNAL: Dillon, Van Dun, Carter, Gardner-Berry
• Large responses are more easily detectedLarge responses are more easily detected
• Response amplitude grows with sensation levelResponse amplitude grows with sensation level
• Response amplitude at low SL is larger for Response amplitude at low SL is larger for people with sensorineural hearing loss that for people with sensorineural hearing loss that for people with normal hearingpeople with normal hearing
• Responses are more easily detected when Responses are more easily detected when residual noise is low (<3.4 residual noise is low (<3.4 µV for infants; < 1.5 µV for infants; < 1.5 µV for adults)µV for adults)
Good agreement between CAEP and Good agreement between CAEP and audiometric thresholds in awake adultsaudiometric thresholds in awake adults
Tsui, Wong & Wong 2002 NAL: Dillon, Van Dun, Carter, Gardner-Berry
Cortical threshold vs behavioural Cortical threshold vs behavioural threshold - adultsthreshold - adults
0 20 40 60 80 100 120
Behav io ra l thresho ld (dB HL)
0
20
40
60
80
100
120
Co
rtical th
resh
old
(dB
HL
)
r2 = 0.77; r = 0.88, p < 0.0001; y = 9.7 + 0 .914*x
NAL: Dillon, Van Dun, Carter, Gardner-Berry
outliers in about 7% of threshold estimates!(reported byseveral studies)
Cortical thresholds minus Behavioral thresholds
68% +5 dB
84%+10 dB
91%+15 dB
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Conclusions: Estimating behavioural Conclusions: Estimating behavioural thresholds in hearing-impaired adults thresholds in hearing-impaired adults
• Cortical thresholds overestimate behavioural Cortical thresholds overestimate behavioural thresholds by 2.4 dB, on averagethresholds by 2.4 dB, on average
• Standard deviation of cortical – behavioural threshold Standard deviation of cortical – behavioural threshold differences is 6.3 dBdifferences is 6.3 dB
• About 7% overestimates hearing thresholds severely About 7% overestimates hearing thresholds severely (by 20 dB or more).(by 20 dB or more).
• Applications: hearing compensation, clients unable to Applications: hearing compensation, clients unable to respondrespond
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Cortical potentials to assess Cortical potentials to assess speech audibility for infantsspeech audibility for infants
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Clinical implications of corticalsClinical implications of corticals
Significant Significant response is response is obtained to obtained to speech at 65 speech at 65 dB SPLdB SPL
No significant No significant response is response is obtained to obtained to speech at 65 speech at 65 dB SPL or to dB SPL or to speech at 75 speech at 75 dB SPLdB SPL
Morphology Morphology normal for agenormal for age
Morphology Morphology abnormal for abnormal for
ageage
Low residual Low residual noisenoise
High residual High residual noisenoise
All is wellAll is well
Repeat testRepeat test
Re-check fitting;Re-check fitting;
Consider all optionsConsider all options
Draw no conclusion !Draw no conclusion !
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Noisy results - chewingNoisy results - chewing
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Clinical implications of corticals (cont)Clinical implications of corticals (cont)
No /t/ No /t/ responseresponse
Draw no conclusions from Draw no conclusions from missing response !missing response !
Mixed results Mixed results (and noise is (and noise is
low)low)
No /g/ No /g/ responseresponse
No /m/ No /m/ responseresponse
Review HF gain Review HF gain or loss estimateor loss estimate
Review mid-freq Review mid-freq gain or loss gain or loss
estimateestimate
Mixed results Mixed results (and noise is (and noise is
high)high)
Review LF gain or loss Review LF gain or loss estimateestimate
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Hearing loss at birth ….. for parentsHearing loss at birth ….. for parents
Parental denial
Working towards a solution
Pessimism and
hopelessness
Unaided testing at
conversational levels
Aided testing at
conversational levels
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Detection of corticals in infants
However, some caution is recommended.
For speech sounds exceeding 10 dB Sensation Level
23% of evoked corticals are NOT present / detected
This means that any audiological decisions should not be made based on cortical measurements alone!
NAL: Dillon, Van Dun, Carter, Gardner-Berry
CASE STUDIESCASE STUDIES
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 1
• Age at aided cortical testing– Visit 1
6 weeks old (Initial hearing aid fitting day)
– Visit 23 months old
No cortical responses, and the results helped the parents accept
the need for cochlear implants
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Tone-burst ABR (Estimated levels in dB nHL)
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right >95 >95 >95 >95
Left >95 >95 >95 >95
Estimated Audiogram (dB HL) at Visit 1
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 85 90 95 95
Left 85 90 95 95
Estimated Audiogram (dB HL) at Visit 2
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 90 100 105 105
Left 90 100 105 105
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 1
Increase gain at all frequencies
P < 0.05 ? …. No
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 2
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• The infant received bilateral cochlear implants at 5 months of age.
• Email from the baby’s parents ~ “Thank you so much for the information
you gave us on the previous testing as it helped us with our decision to proceed with the implants.”
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 2
• Age at aided cortical testing– Visit 1
13 weeks old – Visit 2
17 weeks old– Visit 3
21 weeks old
• Hearing aid fitting at 8 weeks of age
No cortical responses, even after hearing aids have been increased in gain for the third time and the parents don’t want a
cochlear implant for their baby
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Estimated Audiogram (dB HL) at Visit 1
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 90 80 80 85
Left 85 75 75 95
Estimated Audiogram (dB HL) at Visit 2
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 100 90 90 95
Left 95 85 85 95
Estimated Audiogram (dB HL) at Visit 3
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 100 100 100 100
Left 100 100 100 100
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 1
Increase gain at all frequencies
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 2
Right aidedLeft aided
Increase gain at all frequencies
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 3
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• The parents still believe that their baby boy can be oral by using hearing aids.
• They are hoping to see that their baby can benefit from more powerful hearing aids.
• The baby’s hearing aids were changed from Siemens Explorer 500 P to Phonak Una SP after Visit 3.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 3
• Age at aided cortical testing– Visit 1
4.5 months old
– Visit 25.5 months old
• Hearing aid fitting at 5 weeks of age
Corticals provided reassurance about the baby hearing well
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Tone-burst ABR (Estimated levels in dB nHL)
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 40 DNT 60 70
Left 40 DNT 70 80
Estimated Audiogram (dB HL) at Visit 1
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 30 40 55 65
Left 30 45 65 75
Estimated Audiogram (dB HL) at Visit 2
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 40 45 55 65
Left 40 50 65 75NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 1
Increase low- and mid-frequency gain
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 2
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Email from mother:
“We feel very relieved, as our faith has been restored in the hearing aids as a result of what we discovered from the results.”
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 4
• Age at aided cortical testing– Visit 1
8 months old – Visit 2
9 months old
• Hearing aids have been increased in gain two weeks before the second visit.
• Hearing aid fitting at 9 weeks of age
Too few significant cortical responses, and the aid gain was
increased, resulting in more cortical responses
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Estimated Audiogram (dB HL) at Visit 1
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 45 50 55 55
Left 45 55 65 55
Estimated Audiogram (dB HL) at Visit 2
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 55 50 55 55
Left 55 55 65 55
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Visit 1 Visit 2
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 5
• Age at testing: 4.5 years
• Multiple disabilities
• A reliable behavioural audiogram has not yet been obtained.
A case where cortical testing was not possible
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• She was moving all the time.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
At her quietest state, but this only lasted for a few seconds.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
• Cortical testing at 8 months of age, nine days after the initial hearing aid fitting
A case where the unaided /m/ was present but the aided /m/
was absent.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Case 6
Estimated Audiogram
500 Hz 1000 Hz 2000 Hz 4000 Hz
Right 40 35 40 45
Left 40 35 40 45
NAL: Dillon, Van Dun, Carter, Gardner-Berry
AidedUnaided
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Hearing Aid Coupler Gain at 65 dB SPL Input
250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz
<0 0 7 15 20
* Both hearing aids are set the same.
NAL: Dillon, Van Dun, Carter, Gardner-Berry
Auditory neuropathyAuditory neuropathy
NAL: Dillon, Van Dun, Carter, Gardner-Berry
WP ASA 2004
250 500 750 1000 1500 2000 3000 4000 6000 8000
0
10
20
30
40
50
60
70
80
90
100
110
HE
AR
ING
LE
VE
L S I
N D
EC
IBE
LS
FREQUENCY (Hz)
ABR
28/8/03 - NR
ABR ABR (CM only)(CM only)
ABR ABR (CM only)(CM only)
NAL: Dillon, Van Dun, Carter, Gardner-Berry
WP ASA 2004
250 500 750 1000 1500 2000 3000 4000 6000 8000
0
10
20
30
40
50
60
70
80
90
100
110
HE
AR
ING
LE
VE
L S I
N D
EC
IBE
LS
FREQUENCY (Hz)
ABR
28/8/03 - NR
CAEP
14/10/03
m g t m g t
ABR ABR (CM only)(CM only)
ABR ABR (CM only)(CM only)
NAL: Dillon, Van Dun, Carter, Gardner-Berry
WP ASA 2004
250 500 750 1000 1500 2000 3000 4000 6000 8000
0
10
20
30
40
50
60
70
80
90
100
110
HE
AR
ING
LE
VE
L S I
N D
EC
IBE
LS
FREQUENCY (Hz)
ABR
28/8/03 - NR
15/3/04 - NR
CAEP
14/10/03
30/3/04
ECochG 15/3/04
ECochG ECochGECochG ECochGECochG ECochGECochG
m g t m g t
ABR ABR (CM only)(CM only)
ABR ABR (CM only)(CM only)
(abnormal potentials only)
NAL: Dillon, Van Dun, Carter, Gardner-Berry
WP ASA 2004
250 500 750 1000 1500 2000 3000 4000 6000 8000
0
10
20
30
40
50
60
70
80
90
100
110
HE
AR
ING
LE
VE
L S I
N D
EC
IBE
LS
FREQUENCY (Hz)
ABR
28/8/03 - NR
15/3/04 - NR
CAEP
14/10/03
30/3/04
ECochG 15/3/04
VROA
29/4/04
m g t m g t
ECochG ECochGECochG ECochGECochG ECochGECochG
ABR ABR (CM only)(CM only)
ABR ABR (CM only)(CM only)
(abnormal potentials only)
NAL: Dillon, Van Dun, Carter, Gardner-Berry
The HEARing CRC Member Organisations
This research was financially supported by the HEARing CRC established and supported under the Australian Government’s Cooperative Research Centres Program