An Update on Auditory Neuropathy - PhonakPro€¦ · Overview Auditory neuropathy spectrum disorder...
Transcript of An Update on Auditory Neuropathy - PhonakPro€¦ · Overview Auditory neuropathy spectrum disorder...
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An Update on Auditory Neuropathy
Spectrum Disorder in Children
Gary Rance PhD The University of Melbourne
Sound Foundations Through Early Amplification Meeting, Chicago, Dec 2013
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Overview
Auditory neuropathy spectrum disorder (ANSD) often described as
“a newly identified form of hg loss”
1984: Kraus et al. presented children with inconsistency between
auditory evoked potential and audiometric results
1991: Starr et al. described ANSD in an adolescent subject
1999: Rance et al. presented a group of infants with ANSD pattern
1671 scientific papers
Today’s presentation
– Provide an overview of what we have learnt
– Consider some of the current clinical challenges
– Research questions for the future
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Auditory Neuropathy Spectrum Disorder (ANSD)
Also referred to as: auditory neuropathy, auditory
dys-synchrony, auditory synaptopathy…
Hearing impairment in which cochlear outer hair
cell function is “normal” but afferent neural
transmission is disordered
Indicated by the presence of pre-neural responses
(OAE / CM) with absent or severely disrupted
auditory neural responses (ABR)
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CM /ABR assessment for a 3 mo old with ANSD
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Paediatric ANSD
Congenital/Perinatal
»anoxia
»hyperbilirubinaemia
Progressive
– Neurodegenerative disease
» Onset physical symptoms usually in adolescence
» Identified earlier (routinely see 1-4 yr olds in clinic)
» Hearing difficulties often the first presenting symptom
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Possible mechanisms producing the ANSD result pattern
Cochlear damage restricted to the inner hair cells (IHC)
IHC/auditory nerve synapse
Auditory nerve abnormality
– reduced neuronal population
– disruption of neural synchrony
– cochlear nerve deficiency
– tumour
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Axonal & Demyelinating ANSD
Charcot-Marie-Tooth Syndrome
Progressive genetic disorder characterized by
loss of muscle tissue and touch sensation
(motor & sensory neuropathies)
CMT1: demyelinating process
CMT2: axonal loss
Later stages see absent ABR but early in the
disease course responses still present
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2 4 10 6 8 14 12 0 ms
I V I
V
III
Control : 90dBnHL III I
V
CMT 2: axonal loss
(N=8)
0.5
µV
/Div
V
III I CMT 1: demyelination
(N=18)
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ANSD Clinical Profile Prevalence
– Congenital/Perinatal ANSD
» 1 in 800-1000 children show permanent hearing loss
» 5-15% of those present with the ANSD result pattern
– Neurodegenerative disease
» List of diseases associated with ANSD growing
FRDA/CMT/LHON/ADOA...
» relatively rare
» Friedreich ataxia most common: ≈ 1 in 20,000
All show ANSD at some point in the disease course
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2 4 10 6 8 14 12 0 ms
FRDA1: 9 yrs
I III
V
V III FRDA1: 4 yrs
Control I
III V
I
0.7
5
V/D
iv
FRDA1: 6 yrs
* *
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ANSD Clinical Profile
Behavioural audiogram
– Level: normal hearing to profound loss
– All configurations: 30% low frequency
– Fluctuating hearing
Acoustic reflexes
– Typically absent (regardless of hearing level)
Functional hearing
– Impaired speech perception
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Speech Perception
Consistently reported problem in both
adults and children with ANSD
Difficulties out of proportion with the
behavioural audiogram
– Abnormal speech perception in subjects with
“normal hearing”
– Subjects with elevated hearing thresholds show
speech perception poorer than for SN loss of
equivalent degree
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0
20
40
60
80
100
0 20 40 60 80 100
3-Frequency Average (dBHL)
Op
en
-Set
Sp
eech
Sco
re (
%) Yellin et al., 1989
Open-set Speech Perception v Hg Level
for Children & Adults with ANSD
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Open-set Speech Perception v Hg Level
for Children & Adults with ANSD
0
20
40
60
80
100
0 20 40 60 80 100
3-Frequency Average (dBHL)
Op
en
-Set
Sp
eech
Sco
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%)
Word score
Sentence score
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Why is speech perception often
poorer than expected?
Signal distortion
Timing of neural conduction disrupted
Impaired perception of temporal cues in speech
– Inability to judge vowel duration
» eg. hid vs heed
– Inability to discriminate consonants based on timing cues
» eg. pin vs bin
tin vs din
Degree of distortion not consistent across children
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Speech Perception in Noise
Extreme difficulty reported in adults and children with ANSD
(Kraus et al., 2000; Rance et al., 2007; 2010; 2012; Starr et al., 1998)
Some cases show normal understanding in quiet and negligible perception in
“everyday” listening conditions
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0
25
50
75
100
S/N Ratio (dB)
CN
C P
ho
nem
e S
co
re (
%)
+5 +10 0 Quiet
Rance et al, 2007; 2010, 2012
Speech Perception in Noise for Children with ANSD (essentially normal sound detection)
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0
25
50
75
100
S/N Ratio (dB)
CN
C P
ho
nem
e S
co
re (
%)
+5 +10 0
Speech Perception in Noise for Children with ANSD (essentially normal sound detection)
Quiet
Rance et al, 2007; 2010, 2012
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0
25
50
75
100
S/N Ratio (dB)
CN
C P
ho
nem
e S
co
re (
%)
+5 +10 0 Quiet
Rance et al, 2007; 2010, 2012
Speech Perception in Noise for Children with ANSD (essentially normal sound detection)
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0
25
50
75
100
S/N Ratio (dB)
CN
C P
ho
nem
e S
co
re (
%)
+5 +10 0 Quiet
Rance et al, 2007; 2010, 2012
Speech Perception in Noise for Children with ANSD (essentially normal sound detection)
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Why is speech perception in noise a particular
problem in ANSD?
Gap listening
– Impaired ability to use brief quiet
periods in the noise to access the signal
Spatial processing
– Impaired ability to use inter-aural timing
cues to localize sound sources
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Spatial Processing
Affected in ANSD as the neural representation of
timing cues in left/right auditory nerves is degraded
inter-aural difference cues [<1 msec] can’t be
effectively combined in the brainstem
Listening in Spatialized Noise Test (LiSN-S)
– sentences in noise
– spatial advantage: the improvement in speech
perception when the signal and background noise
are presented from different directions
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-21
-18
-15
-12
-9
-6
-3
0
0 2 4 6 8 10 12 14
Spatial Advantage (dB)
15
0 H
z A
M D
ete
cti
on
(d
B)
Spatial Advantage (LiSN-S) for Children with ANSD
Rance et al. 2012
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-21
-18
-15
-12
-9
-6
-3
0
0 2 4 6 8 10 12 14
Spatial Advantage (dB)
15
0 H
z A
M D
ete
cti
on
(d
B)
Spatial Advantage (LiSN-S) for Children with ANSD
Rance et al. 2012
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-21
-18
-15
-12
-9
-6
-3
0
0 2 4 6 8 10 12 14
Spatial Advantage (dB)
15
0 H
z A
M D
ete
cti
on
(d
B)
r = -0.652, P=0.001
Spatial Advantage (LiSN-S) for Children with ANSD
Rance et al. 2012
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Clinical Management of ANSD
Children with ANSD form a heterogeneous group
– Range of different aetiologies
– Different clinical presentations
Range of different management challenges
Some questions explored in the recent literature include:
– How should ANSD children with normal sound detection be managed?
– Should hearing aids and CI be used in concert?
– Should the contra-lateral ear be occluded in children with unilateral CI?
– Can we predict cochlear implant outcomes for ANSD children in the pre-
operative phase?
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Management of Children with ANSD
Hearing Aids vs Cochlear Implants
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Conventional Amplification
– Arguments against amplification
» Inherent pathway limitations
» Potential for cochlear damage
– Argument for amplification
» Increased access to the speech signal
(if sufficient gain is provided)
– Speech perception outcomes
» 40-50% show significant benefit
Digital Speech Processing Aids
– Manipulate speech signal to make
temporal cues more salient
» Limited results/success (so far)
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Cochlear Implantation
– Currently the option of choice for
most individuals with ANSD
– Speech Perception Outcomes
»Most reported cases have
performed at levels similar to
peers with SN-loss
»Some poor results
» Teagle et al. (2010)
» 52 children with open-set scores
» 27% of cases showed speech
perception scores <30%
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ANSD Management: Hearing Aids / Cochlear Implants
Melbourne Long-Term Outcome Study
– Infant ANSD first identified in Melb (1989)
– Tracking these individuals from infancy to adulthood
Longitudinal data
– Audiometry
– Basic auditory perception (temporal/frequency processing)
– Speech perception (quiet/noise)
– Hearing disability ratings
– Expressive/receptive language development
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Long-term Language Development in ANSD
Receptive Language
– Peabody Picture Vocabulary Test (PPVT)
– determines an “equivalent language age” based on norms for normally hearing/developing children
Longitudinal data: (4 yrs – 20 yrs)
Subjects (November 2013)
– Aided ANSD children (n=8)
– Implanted ANSD children (n=6)
– Implanted SNHL children (n=6)
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Receptive Language (PPVT)
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Longitudinal Study Conclusions (Preliminary)
Most implanted children with ANSD show
long-term language outcomes equivalent to
those of young implantees with SN-loss
Some children with ANSD managed with
conventional hearing aids can perform as
well as the average implantee
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Clinical Challenge
How to predict whether a newly diagnosed baby will perform
better with conventional hearing aids or CI?
Considerations
– Anatomy: if a child has no nerve then a CI will not be
beneficial
– Sound detection thresholds: if hg levels are in the
severe/profound range the child is unlikely to benefit from
amplification (same audiologic selection criteria as for SN-loss)
– Auditory capacity: perceptual ability in cases with hg. levels in
the mild/severe loss range determined by the degree of
temporal distortion
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Measuring Auditory Capacity in Infancy
Measuring the degree of temporal processing
deficit predicting long-term outcomes remains
a major challenge
Current research directions
– Behavioural techniques
» Conditioned psychophysics (VRA)
» Unconditioned psychophysics
Eg. eye tracking technologies
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Measuring Auditory Capacity in Infancy
Measuring the degree of temporal processing
deficit predicting long-term outcomes remains
a major challenge
Current research directions
– Evoked potential techniques
» Cortical Auditory Evoked Potentials
Acoustic Change Complex (where the response is elicited
by temporal variations in the stimulus)
» Auditory Steady State Responses
where the potential is elicited by fluctuations in a
continuous stimulus
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Summary & Conclusions
20+ years of experience with paediatric
ANSD has led to significant advances
– Understanding of mechanisms
– General pattern of functional outcomes
Results in individual children are highly
variable and so the management of affected
youngsters remains a challenge…
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Thankyou