The Clinical Application of the HearLAB Cortical Evoked
Response System For Determining Aided Benefit And
Adjustment of Hearing Aids in Children.
Vanessa Salisbury, Clinical Scientist, Brighton and Sussex
University Hospital Trust
Dr Laura Booth, Clinical Scientist, Royal Berkshire Hospital
NHS trust
The Auditory Cortex
The end of the road
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
The auditory cortex
Auditory cortex orientation
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
The Cortical Auditory Evoked Potential
(CAEP)
• Also known as the P1, N1, P2 complex
• Latency
• P1- 60ms, N1- 100ms, P2- 180 ms
• Infant response
• N1 absent in young infants
• P1, N1, P2 mature at different rates (Kushnerenko
et al., 2002)
• Maturation complete by 19 years old (Ponton et al.,
2000)
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Adult CAEP
Adult
P2
5.0
N1
2.5
µV
P1
0.0
-2.5
0
100
200
300
400
500
600
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
Paediatric CAEP
• Infant CAEP
Infants
P
10
µV
5
N
0
-5
-100
0
100
200
300
ms
400
500
600
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
Clinical uses of the CAEP
• Assessment of adult thresholds (Richards and De Vidi, 1995;
Tsu et al., 2002)
• Children who are unable to provide reliable behavioural
thresholds
• Renewed interest in the verification of hearing aid
amplification in infants (Purdy, 2005)
• Universal newborn hearing screening
• Confirming hearing loss at younger age
• Fitting hearing aids at younger age - at least 60 % of children
fitted before 6 months (Wood et al., 2006)
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Hearing aid fitting in young infants
• Current U.K. best practice
• Auditory Brainstem Response (ABR) threshold or
Auditory Steady State Response (ASSR) threshold
• Real Ear to Coupler Difference (RECD)
• DSL5
• Parental and professional observations
• Provides valuable feedback regarding general
audibility of environmental sounds and speech
• How do we measure speech audibility in young
infants?
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Speech Evoked CAEPs in Infants
• Clinical need for objective assessment of speech
audibility
• Speech stimulus can be used for CAEP assessment
(Ostroff et al., 1998)
• Speech is useful when testing aided function
• Longer duration stimulus subject to hearing aid
processing
• Speech audibility - aim of hearing aid fitting.
EUHA 2010, Hannover
Speech Evoked CAEPs in Infants
• Correlates well to behavioural thresholds (Purdy 2005;
Tsu et al., 2002, Carter et al., 2010)
• Significant correlation to functional measures of
hearing aid performance in children (Golding et al.,
2007)
• Additional information for children with ANSD (Rance
2002)
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Speech evoked CAEPs in infants
• Not widely used in a clinical environment.
• Variable waveform morphology and latency
particularly associated with infants (Ponton et al.,
2000; Kushnerenko et al., 2002; Kurtzberg, 1984)
• Maturation,
• Mental alertness,
• Movement,
• Experienced eye needed to interpret waveforms
(Ponton et al., 2000)
EUHA 2010, Hannover
Current Speech evoked CAEP assessment
methods
• Existing ERA equipment
• Stimulus presented via soundfield
• Aided and unaided assessment
• WAV speech files
– Various speech sounds
– Various intensity levels
• Experienced clinician interprets the results
– Repetition of waveforms
– Latency and morphology characteristics
EUHA 2010, Hannover
Current Speech Evoked CAEP assessment
methods
• HearLAB
• Developed at NAL laboratories, Sydney, Australia
• Speech stimulus sampled from running speech
– /m/ (0.25 – 0.5 kHz),
– /g/ (0.8 – 1.6 kHz),
– /t/ (2 – 8kHz),
• 3 intensity levels
– Soft speech (55dB),
– conversational speech (65dB),
– loud speech (75dB)
• Aided and unaided speech
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Hearlab Speech Stimulus
70.0
1/3 octave SPL
60.0
50.0
40.0
30.0
20.0
10.0
0.0
-10.0
-20.0
100
GAE
TAE
MAE
ILTASS @ 65
1000
Frequency
EUHA 2010, Hannover
10000
Automatic CAEP waveform detection
• Automatic waveform detection
• Statistical analysis Hotellings T2 (p-value)
• ‘As good as if not better than the human eye’
• Normally hearing infants (Carter et al., 2010)
– 30 dB SL = 85% correctly identified as present when speech was
audible
– 5% false alarm rate
• Children with SNHL (Van Dun et al., submitted for publication)
– 10 dB SL = 75% correctly identified as present when speech was
audible
– 5 % false alarm rate
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The HearLAB
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
CAEP infant assessment
• Straightforward for an experienced paediatric
audiologist
• Infant awake and facing speaker
• Fed, watered, nappy changed!
• Appropriate play
• Maintain alert state
• Minimise myogenic noise
• 3 electrode placement (vertex, mastoid, forehead
(common)
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CAEP assessment
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HearLAB assessment screen
NAL: Dillon, Van Dun, Carter, Gardner-Berry
EUHA 2010, Hannover
Child 1- verifying speech audibility with a
softband BAHA
• Child 1 has a right sided cleft lip and palate and
developmental delay.
• 8 weeks old – bilateral asymmetrical moderate to
severe conductive hearing loss, confirmed using ABR.
• 9 weeks – fitted with softband BAHA
• 9 months old – unable to obtain reliable behavioural
data due to developmental delay
• Child 1 recently discovered BAHA as a new toy!
Parents finding BAHA difficult to manage.
• Unable to verify benefit of BAHA
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Child 1
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Child 1 – unaided CAEP results
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Child 1 aided CAEP results
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Child 1 - outcome
• Without BAHA
• CAEPs present for /t/ at 65 dB
• CAEP was not present for /g/ at 65 dB but present at 75 dB.
• With BAHA
• CAEP present for /g/ at 65 dB
• Conclusion
• The BAHA provides significant benefit by making a wider
range of speech sounds audible at average conversational
level.
• Parents were reassured and encouraged by results -both
unaided and aided.
• Subsequent VRA behavioural assessment confirmed a bilateral
moderate upward sloping conductive hearing loss
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Child 2 - verifying speech audibility with
hearing aids
• 7 weeks old- bilateral moderate to severe sloping
sensorineural hearing loss confirmed using ABR
• 9 weeks – fitted with Nios Micro hearing aids using
sound recover
• 8 months – reliable behavioural assessment
confirmed ABR levels were accurate and stable
• Required confirmation that full range of speech
sounds were audible
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Child 2
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Child 2 – Aided CAEP results
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Child 2 – outcome
• CAEP was present for /g/ and /t/ at 65 and 55 dB with
hearing aids in place.
• Conclusion – Hearing aids are maintaining the
audibility of speech at soft and louder levels in both
mid and high frequencies.
• Child 2’s parents – ‘we’re pleased to know his hearing
aids are doing their job. It’s reassuring to see that he
can hear speech’.
EUHA 2010, Hannover
Child 3- verifying high frequency speech
audibility with hearing aids
•
•
•
•
•
6 weeks old – confirmed bilateral mixed profound hearing loss
8 weeks old – fitted with bilateral hearing aids
2 years old- Bilateral grommets inserted
Behavioural results confirmed bilateral severe hearing loss
2yrs 10 months - recently became very difficult to test reliably
although results obtained indicate hearing levels are stable.
• Parents are concerned that Child 3’s speech sounds ‘flat’
• Clinical need to confirm hearing aids are providing access to
speech – particularly high frequencies.
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Child 3 – aided CAEP results
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Child 3
outcome
• CAEP present for /t/ at 65dB. /m/
• CAEP absent for /m/ at 65 dB.
• Child 3 is able to hear high frequency speech at least
at conversational level
• Parents and clinicians reassured re. hearing aid fitting.
• 55 dB speech would have been useful but Child 3
became too distressed. To be completed at next
appointment.
EUHA 2010, Hannover
Child 4 – verifying hearing aid prescription
• Child 4 has downs syndrome
• 8 months - diagnosed with bilateral moderate mixed
hearing loss using ABR and fitted with bilateral
hearing aids
• 21 months - unable to obtain any reliable behavioural
information.
• Child 1 recently removing aids.
• No up to date behavioural information to verify
hearing aid prescription
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Child 4 – unaided CAEP results
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Child 4 – aided CAEP results (1)
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Child 4 - outcome
• Unaided
• CAEP absent using /t/ and /m/ 65 dB
• Aided 1
• CAEP absent for /m/ at 65 dB and 75 dB,
• Present for /t/ at 65dB
• Response seen only to high frequency stimulus with current hearing aid
prescription.
• Changed hearing aid prescription to increase gain in low frequencies.
• Aided 2
• CAEP present for /t/ at 65dB
• CAEP absent for /m/ at 65dB
• ABR repeated and showed a deterioration in hearing thresholds particularly
in low frequencies. Hearing aid prescription altered and CAEP now present
for both low and high freq speech at quiet and conversation speech sounds.
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Child 4 – Aided results (2)
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Child 5- confirm speech audibility with
hearing aids.
• 11 days old – whooping cough, ECMO treatment
• Developmental delay
• 13 months – bilateral severe to profound
sensorineural hearing loss confirmed using
behavioural and ABR data, hearing aid fitted.
• 3 years old – speech and language therapist
concerned that he is able to hear speech
• Need to confirm speech audibility.
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Child 5 – Aided CAEP results
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Child 5 outcome
• CAEP present for /t/ and /m/ at 65 dB with hearing
aids
• A range of speech is audible at average conversational
level.
• There is cortical activation to speech stimulus within
the auditory cortex
• Informs speech and language therapy
EUHA 2010, Hannover
Child 6- Is speech audible?
• 3 years 9 months
• Developmental delay including delayed speech
production
• Recent MRI confirmed brain damage
• Behavioural assessments inconsistent but indicate an
overall high frequency severe sensorineural hearing
loss.
• DPOAEs present bilaterally.
• Can she hear high frequency speech?
• Does she need a hearing aid?
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Child 6 – Unaided CAEP results
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Child 6 – conclusion
• CAEP present to /t/ and /m/ at 65 and /t/, /g/ and
/m/ at 55 dB
• High frequency speech is audible at average and quiet
conversational levels.
• Parents reassured
• Hearing aid not indicated
• ? Implications for neurologist re. cortical activation.
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Child 7 – Auditory neuropathy spectrum
disorder (ANSD)
• Child 3 born 3 months premature
• 5 months gestational age (g.a.) - diagnosed with Auditory
neuropathy spectrum disorder (ANSD) using ABR and CMs.
• 10 months g.a.- reliable behavioural assessment shows an
asymmetrical moderate to severe hearing loss.
• 10 months g.a. – Bilateral hearing aids fitted
• Ongoing delayed speech development and attention
difficulties. He uses total communication.
• Parents report fluctuating understanding of speech
• ABR shows fluctuating response
• 6 years old – A referral for consideration of cochlear
implantation has been made
• Assessment of speech evoked CAEPs
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Child 7 – Aided CAEP results
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Child 7 - outcome
• CAEP present for /t/ and /g/ at 65dB
• Speech is audible for low and high frequency speech
sounds at average conversational levels ……today.
• Indicates potential for speech development….today.
EUHA 2010, Hannover
Are Speech evoked CAEPs useful in clinical
practice?
• Methodology straightforward and fun for an experienced
paediatric audiologist and the parents.
• Allow ~ 45 minute appointment
• Children are awake!
• ‘Real world’ stimulus.
• They can complement current audiology good practice
• Infants too young for behavioural assessment
• ANSD
• Children for whom speech and or behavioural testing is not
reliable.
EUHA 2010, Hannover
Are Speech evoked CAEPs useful in clinical
practice?
• Inform parents and clinician re. child’s access to
speech
• Verify changes in hearing aid prescription.
• Indicate further assessment or onward referral
• Cochlear implant,
• ABR under general anaesthetic/sedation/ evening
home visit
• Inform other health professionals e.g. speech and
language therapy, neurology.
• Indicate maturity of auditory system
• Auditory training
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Is the Hearlab a useful clinical tool?
• Yes!
• Automatic waveform detection makes speech
evoked CAEP assessment more accessible to
audiologists whatever their experience.
• Analysis is consistent across clinicians.
• Speech sounds cover relevant speech range both
for frequency and intensity.
• Instant results!
EUHA 2010, Hannover
Is the Hearlab a useful clinical tool?
• However….
• Automatic waveform detection could restrict new applications
of infant CAEPs
• Software upgrades available to reflect up to date research
• Clinicians may want a wider range of speech sounds and
intensity levels.
• Software updates may be available should the clinical need
arise
• Portability.
• Overall, It has become an invaluable addition to our clinical
toolkit.
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Thank you!
• Dr Laura Booth, Clinical Scientist, Audiology
Department, Reading, U.K.
• Dr Bram Van Dun, NAL laboratories, Sydney, Australia
• Dr Rob Low, Clinical Scientist, Audiology department,
Brighton.
EUHA 2010, Hannover