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7/29/2015 Auditory Neuropathy Spectrum Disorder: A Review Ashley Barr, Au.D. UfgalAudloloO, PennSlatthenNyWaMCenthr 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 • • • • • 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 1 7/29/2015 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 2 7/29/2015 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 3 7/29/2015 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 4 7/29/2015 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 5 7/29/2015 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 6 7/29/2015 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 7 7/29/2015 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 8 7/29/2015 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? 9 7/29/2015 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 10 7/29/2015 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 11 7/29/2015 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% 12 7/29/2015 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 13 7/29/2015 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 14 7/29/2015 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 15 7/29/2015 Findings • Open-set sentence recognition by 36 months post activation — Group 1: 73% — Group 2: 30% — Group 3: % 38 • 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 16 7/29/2015 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 17 7/29/2015 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! 18