Download 7/29/2015 Proposal of Auditory Neuropathy Auditory Neuropathy

7/29/2015
Auditory Neuropathy Spectrum
Disorder: A Review
Ashley Barr, Au.D.
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share&innvu,du
Aupst10.2015
Here's the plan:
ANSD defined
Risk factors
Proposed sites of lesion
Diagnostic Criteria
Treatment options
— Protocols
• Case studies — the "real deal"
• Take-home messages
• Questions/Discussion
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Proposal of Auditory Neuropathy
• 1996 by Starr et al.
• 10 patients (children/young adult)
• Normal cochlear function
— Outer hair cells
— Present cochlear microphonic
• Distorted Auditory Brainstem Response test
• Variation of hearing loss
• Poor speech discrimination
— Not expected with degree of hearing loss
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ANSD defined:
• "Demonstration of outer hair cell integrity in
conjunction with the inability to record
evoked neural activity at the level of the VIII
nerve and brainstem" — (Rance, 2005)
• "Retrocochlear" hearing loss
Auditory Neuropathy Spectrum
Disorder
• Previously described as "Auditory
Neuropathy" or "Auditory Dys-synchrony"
• Now known as "Auditory Neuropathy
Spectrum Disorder" or ANSD
• Term coined by panel at International
Newborn Hearing Screening Conference in
Italy 2008
• Referred to as a "spectrum" disorder to reflect
various sites of lesion
Prevalence
• ANSD accounts for approximately 8% of
permanent hearing loss in children
• Difficult to determine prevalence in adults
— Screening/diagnostic tests mainly
used in pediatric population
— If have symmetric thresholds and decent speech
understanding, ANSD testing unlikely considered
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ANSD Causes:
• Genetic
— OTOF gene mutation
• Acquired
—
Extended NICU stay
—
Hypoxia
—
Prematurity ('32 weeks)
—
Hyperbilirublnemla (>20mg/dI)
•
•
Cause greater IHC damage than OHC
Selective loss of IHC
•
Damage of auditory brainstem nuclei and spiral
ganglion of the auditory nerve
ANSD Causes:
• ANSD expressed later in life•.
— Peripheral neuropathies due to genetic or disease
processes
— Charcot-Marie-Tooth
• May affect both motor and sensory nerves
• Subtypes may affect demyellnating or axonal
neuropathies of the AN
— Friedreich's ataxia
— Immune responses, infections, systemic diseases,
toxic substances, endoriopathies
Inner Ear (Sensorineural) hearing loss
• When we are unable to distinguish sensory vs
neural
• Could be a combination
• Hearing loss results from dysfunction occurring at
various sites in the peripheral and central auditory
pathways
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Inner Ear Hearing Loss
Sensory
Neural
• Most common permanent
hearing loss
• Least common type of
hearing loss
• Abnormality In the cochlea:
— Outer and/or Inner hair
cell loss
— Endocochtear potential RIC
disruption of driving force)
• Abnormal transmission of
neural signals through the
auditory pathway
• Disordered processing of
those signals in the
brainstem
he diagnostic tools today, we wouldn't be a
di inguishthe type of inner ear hearing loss. 4.
Proposed Sites of Lesion
Inner hair cells
— Abnormal ABR with OHC preservation
— Animal studies confirm this as a possibility
— Mutation of OTOF gene
— No 'living" human diagnostic testing available
Proposed Sites of Lesion
S y n aps e be twe e n in n e r h ai r ce l l s an d CN V III
— Base of the IHC are structures involved with storage and
release of neurotransmitters
— Neurotransmitters act upon receptor sites In the AN
dendrites and initiate the generation of action potentials
— Could be presynaptic or postsynaptic
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Proposed Sites of Lesion
• Bipolar neurons:
— Auditory Nerve: Axon, myelin sheath, and dendrites
— Spiral ganglion cells
— Central auditory pathway in the brainstem
Proposed Sites of Lesion
• Inner hair cells"
• Synapse between inner hair cells and CN VIII"
• Auditory nerve itself
Food for thought:
`Lesions at these areas can lead to positive cochlear Implant
outcomes because the signal introduced by the CI bypasses
the site of lesion**
Diagnostic Criteria
• Sensorineural hearing loss
— Bilateral or unilateral
— Essentially normal to profound
• Poorer than expected word recognition
scores
— Especially in the presence of noise
• Absent acoustic reflexes in the presence of
normal tympanograms
— Muscle In middle ear not getting signal
from nerve
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Diagnostic Criteria
• Likely present DPOAEs
— Although may be absent
• Absent or grossly abnormal ABR
• Present cochlear microphonic
Otoacoustic Emissions
• Release of sound energy in the cochlea that is
recordable in the ear canal
• Sound presented into the cochlea — "echo" is
recorded
• Present OAEs = normal OHC function
• Absent OAEs = abnormal OHC function
— Middle ear dysfunction
— Cochlear hearing loss
Otoacoustic Emissions
• Can be tricky
• Disappear overtime after initial presence
— Middle ear disease
— Use of amplification
— Unknown!
• Studies have noted disappearance of OAEs
over time without above factors
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ABR - Why?
• Failed newborn hearing screening follow-up
— Too young to raise their handl
• Unreliable results in the soundbooth
— Ma lingering
• Patient unable to cooperate for testing
— Not tolerate anything on ears
• Unable to get MRI (neurodiagnostic)
— Tumor on AN (uncommon)
ABR
• Used both as a screening and diagnostic
measure for over 30 years
• Close correlation between hearing level and
ABR threshold
— Correction factors!
ABR setup
Electrodes on forehead
and behind ears
Sound delivered
through insert phones
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ABR threshold search
• Estimate hearing thresholds from neural
response
• Decrease in intensity, the presence of Wave V
increases in latency
How do you get an audiogram
estimation from an ABR?
• ABR threshold detection
— Identify Wave V at supra-threshold levels,
decrease intensity until Wave V not present
— Children with SNHL have absent Wave V at
higher intensities
ABR waves with ANSD
• We do not see pretty waves I-V from the AN or
other generator sites
• We see what is called a cochlear microphonic
— Response from the cochlea
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Cochlear Microphonic
• Electrical response from the outer hair cells
• Does not increase in latency as the stimulus Intensity
decreases
• Follows the characteristics of the external stimulus
• Direction will reverse with changes in polarity of the
stimulus — direct phase relationship
dormai
Abnormal
Polarity
• Polar = opposites
• Rarefaction vs Condensation
• Helps us look for a "flip" in ABR response
The Grey Area
• What do we do when we find an abnormal
ABR, present OAEs?
• Typically use MR to determine hearing
thresholds to program hearing aids,
• Hearing aids?
• Cochlear implants?
• What is the best option?
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Treatment Options for ANSD
Auditory
Non-Auditory
• Monitoring of auditory
function
• Genetic Counseling
• Speech Reading
• Hearing ald(s)
• Cued Speech
• Assistive listening devices
— FM Technology
• Cochlear implant(s)
• Sign Language
• Speech and Language
Therapy
• Family Counseling
• Support Groups
• Psychological Counseling
Treatment Options
• Individualized treatment plan
• Example:
- Bill Daniels Center for Children's Hearing
• Sponsored the 2008 ANSD conference in Como, Italy
• Diverse protocol with each individual patient
• Appropriate referrals
Hearing Aid Trial Controversy
• Previous research has stated concerns:
− Over-amplification may cause damage to
functioning outer hair cells
− Amplification may produce a distorted signal
− Behavioral thresholds and ABR morphology may
improve over time
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Common practice
• As we know, unable to estimate threshold
levels with MR
— Hearing can range from normal to profound
present OAEs = rule out greater than a
mild cochlear hearing loss
• With
• May program aids to a flat mild hearing loss
• Research shown low gain aids may provide
benefit vs no amplification
— Monitoring I
So...
•
Something to think about:
— While improving audibility with hearing aids does
not guarantee good speech recognition,
withholding amplification will prevent those
infants who could benefit from hearing aids from
accessing the sounds of speech necessary to help
develop spoken language.
Monitor progress - Questionnaires
•
MAIS or IT-MAIS (Infant-Toddler Meaningful
Auditory Integration Scale)
• 10 questions via clinician Interview
• Promote discussion — not Yes/No answers
• Points 0-4 assigned to each answer
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MAIS/IT-MAIS
• Question Example:
− What we want to know: Is the child's vocal
behavior affected while wearing his/her hearing
aid(s)?
− Discussion: Describe Johnny's vocalizations
when you first put his/her device on each day.
− How It's scored: Does Johnny respond 100%
of the time? 75%? 50%? 25%? Or 0%?
• If 100% = 4 points, 75% = 3 points, etc.
Monitor progress - Questionnaires
PEACH (Parent's Evaluation of Aural/Oral
Performance of Children)
- Evaluates effectiveness of amplification in infants
and children
- 13 items
-Assess hearing aid usage, loudness discomfort,
responses in noise
- Given to parent directly to complete
PEACH
• Question Example:
− When asked, does your child follow simple
instructions or do a simple task in a quiet
environment?
- When you call does your child respond to his/her
name in a noisy situation when he/she can't see
your face?
• ScoredsimilartoMAIS/IT-MAIS
—100%,75%,50%,25%or0%
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Cochlear Implants and ANSD
• Provide electrical stimulation to the auditory nerve
• May lead to improved neural synchrony
• Consider Cl when:
• Lack of progress with hearing aids
• Regardless of audiometric thresholds!
• Poor CI candidates:
— Modlolus Is severely depleted of
spiral ganglion cells
— CN VIII is Inexcitable
When do we talk about cochlear
implants?
• Patient is in the hearing aid trial...
• Lack of progress...
• Time to start the conversation!
Hearing aids vs Cochlear Implants
• Video
• A family contemplates the decision between
hearing aids and cochlear implants with their
child with ANSD
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CI Candidacy Criteria (not ANSD):
•
12-24 months:
Pediatric
— Profound SNHL, AU
— No medical contraindications
— Lack of progress In development of auditory skills with
hearing aids/amplification
— High motivation and appropriate expectations from family
•
25 months to 17 years, 11 months:
— Severe to profound SNHL, AU
— Speech scores of 30% or less in the best-aided condition
— Lack of progress M the development of auditory skills
with hearing aids/amplification
— No medical contraindications
— High motivation and appropriate expectations
• Child (when appropriate) and family members
ANSD & Cochlear Implantation
• P a t i e n t s w h o pe r f o r m w e l l wi t h C l s m a y h a v e a
disorder solely of the IHC
• P o o r p e r f o r m a n ce m a y b e a s s o c i a t e d w i t h
" t r u e " a u d i t o r y n e u r o p a t h y o f t h e c oc h l e a r
nerve
Beneficial to make this
distinction prior to implantation
ANSD & Cochlear Implantation
Electrically
Evoked
Auditory
Brainstem
Response
(EABR)
— Verify neural function of patients under consideration for
cochlear implantation
— In combination with radiological findings, inter-ear differences In
EABR threshold can be applied in the estimation of neural
survival and nerve stimulability
— Relationship between preoperative EABR findings and postoperative CI performance is not clear-cut
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Supporting Research
• Article:
— Role of Electrically Evoked Auditory 8rainstem
Response in Cochlear Implantation of Children With
Inner Ear Malformations
• Authors:
— Kim, Kileny, Arts, El-Kashlan, Telian, & Zwolan
• Journal:
— Otology & Neurotology, 29, 626-634
• Year:
— 2008
Background
• Current preoperative testing does not routinely
involve assessment of electric excitability of the
cochlear nerve
• However, doing so may prevent an implant from
being surgically placed in an ear that may not
respond adequately to electrical stimulation
Summary
•
•
•
Study Design:
— Retrospective analysis
Participants:
— 43 children with congenital inner ear malformations
Speech Perception Testing
— Glendonald Auditory Speech Perception Test for words
(GASP-W) and sentences (GASP-S)
— Northwestern University-Children's Perception
(NU-CHIPS) Test
— Minimal Pairs
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Findings
• Open-set sentence recognition by 36 months
post activation
— Group 1: 73%
— Group 2: 30%
—
Group 3:
%
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• Larger Wave V amplitudes and shorter latency were
associated with better speech performance
• Individuals with lower EABR threshold (<600 pA)
have better speech performance postoperatively
Findings
•
•
•
Results support the use of EABR to:
— Determine If the ear responds to electrical
stimulation — Analyze the better ear for implantation
Narrow IAC anatomy is not a contraindication to
cochlear implantation
— Preoperative EABR results indicate effective electrical
stimulation of the auditory pathway
EABR results may also provide prognostic
information regarding implanted speech perception
Clinical Application of EABR
•
•
Preoperatively:
— Stimulability or Integrity of the auditory nerve
and brainstem using trans-tympanic promontory
stimulation
Intraoperatively:
— Confirmation of the functional integrity of the
cochlear implant
— Estimation of the physiologic threshold for electrical
stimulation
— Provide a reasonable starting point for programming
cochlear Implants
— Provides estimations of the dynamic range for
cochlear Implant performance
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So, then why doesn't everyone do
EABRs?
• Transtympanic stimulation
• Additional research is needed to determine
whether normal preoperative EABR is
associated with better speech perception
outcomes
— Current research is limited
• Current equipment
preoperative EABR
limitations
regarding
Case Study #1
Case Study #2
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Take-Home Messages
• Normal outer hair cell function with abnormal
afferent neural conduction in the auditory
pathway
• A form of hearing impairment —Can
have normal to profound thresholds!
• Poor speech discrimination
— Background noise
Take Home Messages
• Auditory Neuropathy Spectrum Disorder can
have multiple sites of lesion
— Site of lesion can affect treatment outcomes
• Cochlear implant evaluations should be
recommended for patients with ANSD if
hearing aids do not provide adequate benefit
regarding speech perception
• More research is needed!
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