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Differentiating Auditory Processing
Disorders from Auditory Neuropathy
Spectrum Disorders in the
Deaf-Blind Population
Charles I. Berlin Ph.D.
Clinical Professor of Otolaryngology
Head and Neck Surgery and CSD at
University of South Florida, and Clinical
Coordinator All Children's Hospital
Center for Auditory Neuropathy
What does it sound like to have:
• Peripheral Hearing loss vs. Auditory
Neuropathy vs. CAPD
• Digression into underlying auditory physiology
beginning with some of the relationships of
speech to hearing.
• Demonstrations and videos.
Auditory Neuropathy Spectrum
Disorders vs. CAPD
• Very easy to differentiate with the use of
tympanometry, middle ear muscle reflexes,
otoacoustic emissions and, if needed, an
Auditory Brainstem Response.
How do we test for them
• Peripheral hearing loss, stemming from
damage to the outer hair cells and cochlea.
• (Central) Auditory Processing Disorders
• Auditory neuropathy spectrum disorders:
– Tympanometry
– Middle Ear Muscle Reflexes
– Otoacoustic Emissions
– Auditory Brainstem response
Tympanometry Alone
http://vimeo.com/ncdb/tympanometry-alone
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Tympanometry (3x) and Middle Ear
Muscle Reflexes
http://vimeo.com/ncdb/tympanometry-reflexes
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Otoacoustic Emissions by Distortion
Products
http://vimeo.com/ncdb/otoacoustic-emissions
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Auditory Brainstem Response with
clicks being presented rapidly to the
ear.
http://vimeo.com/ncdb/abr-to-clicks
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Behavioral Observation by localization
http://vimeo.com/ncdb/behavorial-audiometry
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Auditory Processing Disorders
Thierry Morlet, Ph.D.
Auditory Processing
• How our brain processes the sounds we
hear
• Central auditory processing includes
auditory mechanisms that underlie the
following abilities:
–
–
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–
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Sound localization/lateralization
Auditory discrimination
Auditory pattern recognition
Temporal aspects of audition
Auditory performance with competing signals
Auditory performance with degraded acoustic signal
Auditory Processing and Language
• The development of language is dependent on the
identification of sounds (including assessment of factors
such as intensity, frequency and timing). This capacity
enables the detection of phonemes and is the basis of
auditory language reception and utilization.
• Production of a sound mirrors the perception individuals
have of the sound.
• Central auditory processing manifests differently in
every individual child.
Auditory Processing Disorders
• In children, auditory processing disorder (APD) presents as
difficulty processing speech despite audiometrically normal
hearing.
• Commonly, this difficulty is most pronounced in the presence
of competing background noise, which, unfortunately,
represents most typical real-world listening situations.
• The causes of APD are not known, and in all likelihood, APD as
broadly defined represents a family of auditory processing
deficits stemming from multiple causes.
Auditory Processing Disorders
• Approximately 5% of school-aged children have
some type of APD.
• APD can impair a child’s speech and language
development, leading to listening and learning
deficits.
• Its diagnosis is complex and often is not made
until learning deficits are well established
impairing the child’s development for several
years.
• The lack of knowledge regarding the etiology of
APD makes its management unpredictable.
Auditory Processes that are affected
•
•
•
•
•
Awareness/ detection
Discrimination
Recognition
Figure Ground
Synthesis
• Memory and sequential
memory
• Temporal resolution
• Closure
• Binaural separation/
integration
• Attention
 Auditory processing disorders are difficult to
differentially diagnose apart from other learning
disorders
Indicators of APD Disorders
•
•
•
•
•
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Poor reading & spelling
Low class participation
Withdrawn
Responds inappropriately
Poor receptive/expressive language
Difficulty understanding in poor acoustical
settings
• Attention problems
Risk Factors for APD
• Neurologic dysfunction and disorders, e.g.,
– neonatal risk factors (e.g., asphyxia, CMV)
– head injury
– seizure disorders
•
•
•
•
Chronic otitis media in preschool years
Academic underachievement or failure
Family history of academic underachievement
Co-existing disorder (s)
Co-existing Disorders:
The Same Brain
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
APDs
Specific language impairment (SLI)
Learning disabilities (LDs)
Reading disorders (dyslexia)
AD/HD
Emotional & psychological disorders
Developmental delay
Other neurologic deficits
and Autism spectrum disorders
Neurologic Bases
APD
• Understanding the source of a communication
problem
– Peripheral or central or both?
• Physiologic “versus” behavioral methods
• Application of cortical auditory evoked potentials
• Documenting effect of training
– Neural plasticity
• Importance of tests battery and cross-check
Diagnosis of APD
• Ideal minimal test battery
– Electrophysiological measures
• Immittance measures: Tympanometry AND acoustic
reflexes
• Otoacoustic Emissions
• Auditory evoked potentials
– Behavioral measures
• Pure tone & speech audiometry in quiet and in noise
• Assessing all of the individual processes of CAP
Auditory Physiologic Responses
• Middle ear muscle reflexes
• Otoacoustic Emissions (OAE)
– Suppression of OAEs
• Auditory Brainstem Response (ABR)
– Eight nerve and brainstem
• Middle Latency Response
– Thalamo-cortical pathways
• Cortical Responses
– N1-P2 or vertex response
– P300 response
– Mistmatch negativity (MMN)
Auditory Neuropathy Spectrum
Disorder or APD?
• Auditory Neuropathy/Dys-Synchrony
– Synchrony disorder, possible pre-neural site
– Cochlear implants a management option
– ABR, MEMR absent
• Central APD
– More diffuse in nature, peripheral synchrony usually
within normal limit
– Cochlear implant not useful
– ABR, MEMR usually normal
APD and the Peripheral Auditory
System
• One possible cause of APD that has received attention recently is a
disruption of processes in the peripheral auditory system; this led to
the reclassification of central auditory processing disorder as APD.
• Studies of peripheral auditory afferent pathways using click auditory
brainstem responses in children with APD have been inconclusive.
• ABRs are present in children with APD.
• However, recent measures of speech auditory brainstem response
show that the response in children with APD is delayed and less
precisely timed, suggesting that their difficulties in higher-level
language processes may have roots in the basic representation of
sound as low as the brainstem.
Middle Latency Responses
• The middle latency responses arises from the upper
brainstem and primary auditory projection areas.
• MLR latencies decrease with age in normal children.
• Changes can be seen well into childhood, and adult
characteristics are not reached until 10-12 years of age.
• Longer MLR latencies in children with APD.
Auditory Evoked Related Potentials
•
AERPs provide an objective means of
evaluating how the auditory cortex codes
acoustico-phonetic cues crucial to speech and
language processing with high temporal
precision, including in presence of background
noise.
•
AEPRs also inform about hemispheric
lateralization.
•
Can be obtained regardless of whether the
subject is attending to the stimuli or not which
excludes the factor attention as a possible
confounding factor (MMN).
•
The obligatory AERP consist of a series of
vertex positive and negative peaks (P1, N1, P2
and N2).
•
Mature by mid teens
– Can be recorded at younger ages
•
Neural Plasticity
From Wunderlich and Cone-Wesson, 2006
Asymmetries of the Auditory
System
• In normally hearing individuals, anatomical and functional
observations from the cochlea up to the cortex are in favor of a right
ear advantage (REA), a feature hypothetically linked to the fact that in
almost all right handed and most left handed people, speech is
processed predominantly in the left cerebral hemisphere.
• Both afferent and efferent auditory pathways show asymmetrical
features which suggests that competing signals from both ears are
processed with a REA which enables the left hemisphere to process
speech appropriately in difficult listening situations.
• Stimuli with complex speech-like acoustic properties, including rapid
spectrotemporal changes, yield greater activation in auditory cortex
over the left hemisphere, regardless of whether right ear, left ear, or
binaural stimulation is used.
• The left hemisphere is specialized from birth for processing specific
properties of speech and children exhibit the right ear advantage as
early as the first year of life.
Asymmetries in children with APD
• Evidence of abnormalities in the cortical development of auditory areas in
children with APD
• Abnormal asymmetries in the perisylvian region of the temporal lobe with
an absence of left hemispheric advantage for this region.
• Abnormalities in auditory hemispheric specialization, in right ear
advantage and in AERP have been reported in children with APD.
• Abnormal functioning of the left temporal cortex in some children with
APD suggest that the functional specialization of both hemispheres is
impaired in these children and that damage to the left hemisphere
disrupts mechanisms critical for processing brief, rapidly changing acoustic
cues.
• Enlarged AERP response in the right hemisphere could indicate differences
in hemispheric lateralization in that children with APD may rely more on
right hemisphere function when processing language, which has been
suggested to serve as a compensation for improper functioning of the left
hemisphere language areas.
P300
• Dependent on focusing of attention and
subtle cognitive processes
• Can use speech stimuli of various types
(discrimination, semantic distinctions, etc…)
• Can probe psychophysical function
(discrimination of two tones, etc…)
• P300 is present in children with APDs but with
longer latencies and reduced amplitudes as
compared to controls.
Mismatch Negativity
• Neuronal response to minimal changes in
acoustic stimuli
• Objective
• Passively elicited
• Pitch, phonemes, temporal and spectral cues,
etc…
• Diminished mismatch negativity (MMN)
responses to rapidly changing stimuli in APD
compared to normal children.
Efferent
Auditory
Pathways
Efferent Auditory Pathways
• The medial olivocochlear system (MOCS) innervates the outer
hair cells. This implies that the acoustic signal stimulating the
cochlea can be modified before it reaches the brain.
• The MOCS constitutes one of the physiological mechanisms
underlying perceptual intensity discrimination in noise.
• In normally hearing adults and children, activation of the MOCS
improves speech-in-noise intelligibility.
• The MOCS is active after term birth in humans. Its development
is asymmetrical (in favor of the RE).
MOCS in Children with APD
• Recent studies showed some evidence of an impairment of MOCS
function in children with APD or language impairment with a decrease
in TEOAE suppression despite normal hearing thresholds.
• MOCS dysfunction has been shown in subjects with other deficits such
as in autistic children and children with selective mutism.
• Several studies showed an inverted pattern of MOCS asymmetry in
children with specific language impairment and in children with
selective mutism versus controls.
• Auditory training can change MOCS asymmetry in children with
specific language impairment leading to bigger suppression in the right
ear than the left ear after training. This finding was observed as well in
children with reading disabilities following audiovisual training.
Efferent Suppression in Normal Children
4
RMS (dB)
3
2
1
0
LEBin REBin LECon RECon LEIpsi REIpsi
Suppression in Children with APD
4
RMS (dB)
3
2
1
0
LEBin
REBin
LECon
RECon
LEIpsi
REIpsi
Management of APD
• Requires interdisciplinary approach
• Should
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Be extensive
Maximize opportunities for generalization
Reduce functional deficits
Include salient reinforcement to induce learning
• Comprehensive intervention management should
include
– Direct skill remediation by SLP
– Compensatory strategies by Aud
– Environmental changes by teachers and/or parents
Intensive & Computer-Based Programs for
Development of Auditory Processing Skills
• Cognitive Concepts
– Earobics
– cogcon.com
• Scientific Learning
– FastForword (FFW)
– scilearning.com
• Lindamood Bell Learning Processes
– LIPPS and Seeing Stars
– Lindamoodbell.com
Intervention
Language Skills Pre and
Post Fast Forword
CELF-3 Results
105
100
Receptive
95
Expressive
90
Total
85
Pre FFW
Post FFW
Efferent Suppression Pre-FFW
Impaired
0.5
Controls
1.0
Impaired
1.5
Controls
Suppression (dB)
2.0
0.0
Left Ear
Right Ear
Contr
Cont
Efferent Suppression Post-FFW
Impaired
0.5
Impaired
1.0
Controls
1.5
Controls
Suppression (dB)
2.0
0.0
Left Ear
Right Ear
MLRs Pre and Post FFW
MLRs Pre and Post FFW
Conclusions
• Like children with ANSD, children with APD
have the basic difficulty of understanding any
speech signal presented under less than
optimal conditions.
• We are still not sure what causes APD.
Diagnosis is complicated and usually not
realized in a timely fashion. Management of
APD is difficult and success is not guaranteed.
• Despite sharing many common outcomes with
ANSD, APD can easily be distinguished from
ANSD.