Early Intervention of Children identified with Auditory Neuropathy

Early Intervention of Children identified with Auditory Neuropathy Karen M. Ditty, Au.D. 1,2 Sharon M. Parham, M.S.3 National Center for Hearing Assessment and Management Logan, UT1 Texas ENT Specialists, PA Houston, TX2 Northwest Harris County Cooperative for the Hearing Impaired Houston, TX3

What is Auditory Neuropathy / Dys-Synchrony (AN / AD)?

Auditory Neuropathy / Dys-synchrony Auditory Neuropathy / Dys-synchrony is a term used to describe a condition found in some patients ranging in age from infants to adults. Characteristics are: •Normal outer hair cell function (Normal Otoacoustic Emissions) •Abnormal neural function at the level of the VIIIth nerve abnormal Auditory Brainstem Response test (ABR) http://www.medschool.lsuhsc.edu/Otorhinolaryngology/deafness_article1.asp

In other words…. • Is a hearing disorder in which sound comes in to the inner ear normally, but the conduction of the signals from the inner ear to the brain are impaired • May involve damage to the inner hair cells or may be due to faulty links between the inner hair cells and the nerve leading from the inner ear to the brain

Possible sites of Auditory Neuropathy / Dys-synchrony •Inner hair cells •Tectorial membrane •Synaptic juncture between the inner hair cells •Auditory neurons in the spiral ganglion, •VIIIth nerve fibers, or any combination above (Starr et al., 1996; Berlin et al., 1998) •Neural problems may be axonal or demyelination. •Afferent as well as efferent pathways may be involved. http://www.medschool.lsuhsc.edu/Otorhinolaryngology/deafness_article1.asp

Pathway for Hearing from "Promenade around the cochlea" EDU website www.cochlea.org by Rémy Pujol et al., INSERM and University

What Causes Auditory Neuropathy / Dys-Synchrony?

Possible etiologies of Auditory Neuropathy / Dys-synchrony •Hyperbilirubinemia (Jaundice)12-16 cc/dl, (probably #1) •Neurodegenerative diseases, e.g., FriedReich's ataxia •Neurometabolic diseases •Hereditary motor sensory neuropathies: e.g.: Charcot-Marie-Tooth syndrome •Demyelinating diseases •Inflammatory neuropathies

Possible Etiologies of Auditory Neuropathy / Dys-synchrony continued • Ischemic/hypoxic neuropathy • Hydrocephalus • Abnormality with neurotransmitter release • Cerebral palsy • Infectious disease such as mumps • Immune Disorders • Severe developmental delay

What does auditory neuropathy / dys-synchrony (AN / AD) sound like?

Computer simulation of what Auditory Neuropathy / Dys- Synchrony may sound like Developed speech waveforms based on simulations of different degrees of Auditory Neuropathy / Dys- synchrony Funding agency: National Institutes of Health (DC02618) PI: Arnold Starr; Co-investigator: Fan-Gang Zeng “Communication difficulties in individuals with auditory neuropathy / dys-synchrony, even with mild hearing loss are more severe than individuals with cochlear hearing loss of 60dB HL or more.” Kumar, et al

Study Findings • Intensity processing is not significantly affected by AN/AD • Frequency discrimination is significantly affected at low frequencies but not high frequencies • Temporal processing deficits in AN/AD provide direct evidence for an important role of neural synchrony in auditory perception • Data accounts for the speech recognition deficit that is disproportional to pure tone hearing loss Funding agency: National Institutes of Health (DC02618) PI: Arnold Starr; Co-investigator: Fan-Gang Zeng

Study Findings continued: • Patients can perceive sound and usually have normal cortical potentials and negative brain imaging results • New Hearing aids that accentuate the temporal envelope or cochlear implants that produce highly synchronous neural activity may be more effective than the conventional hearing aids in the clinical management of AN / AD Funding agency: National Institutes of Health (DC02618) PI: Arnold Starr; Co-investigator: Fan-Gang Zeng

Study Findings continued: • Real time DSP technology should be able to implement such an envelope expansion algorithm and may help solve the “I can hear but do not understand problem” Funding agency: National Institutes of Health (DC02618) PI: Arnold Starr; Co-investigator: Fan-Gang Zeng

Are all Auditory Neuropathy / Dys- synchrony infants the same? • Clearly NOT! There are large individual differences – Hearing may improve over time (most commonly seen when the cause is hyperbilirubinemia) – Hearing may stay the same – Hearing may get worse and show signs that the outer hair cells no longer function (OAE’s become absent) – Hearing loss may fluctuate over time (periods of “good hearing” and other times function as deaf)

Patient Variation continued: • Some have clear hereditary sensory-motor neuropathy. • Some have less apparent neuropathy that is only evident on clinical exam. • Some demonstrate no signs of neuropathy other than the auditory findings. • Some have unilateral auditory neuropathy • Some have temperature sensitive AN/AD • Some show a familial tendency which may suggest genetic causes. Hood (2002)

Are there really that many kids with Auditory Neuropathy? • 10% of children seen with severe-to-profound deafness may have a neural rather than a hair cell disorder (Kraus et al., 1984; Rance et al., 1999) • 1 in 183 of persons with Sensory neural hearing loss (.005) have AN based on a retrospective review of cases in India (Kumar & Jayaram, 2006) • There appears to be an equal distribution of male (55%) and female (45%) with AN (Sininger / Starr 2001) • 27% of AN patients have no associated medical conditions or family history before age 2 (Sininger/Star 20001) • 80% had either family or neonatal risk factors

How are individuals with Auditory Neuropathy / Dys-Synchrony Distinguished from individuals with Auditory Processing ?

Characteristics are similar but: SIMILARITIES: – Poor understanding, even simple sentences in competing noise-despite the fact that they can understand some words or sentences in quiet. – Learning speech and language through the auditory channel exclusively is very difficult BUT: – AN/AD refers to a disorder of peripheral portions of the auditory pathway, between the outer hair cells and brainstem. – Peripheral measures such as Absent Acoustic Reflexes, ABR abnormalities in the presence of Present OAEs helps to distinguish AN/AD from auditory processing.

Can we predict outcomes for individual infants? • Until we can clinically distinguish what caused the infant’s AN/AD, it will be difficult to make any predictions on improvement or decline of auditory functioning • Currently we can only determine changes in auditory ability through long-term follow up • Research; however, is ongoing!

How do we Audiologically manage infants with Auditory Neuropathy / Dys-Synchrony?

Audiological Management of Auditory Neuropathy / Dys-Synchrony • Complete Medical / Case history • Otoscopy: Outer Ear and Ear Canal • Otoacoustic Emissions testing: Cochlea (outer hair cells) • Brainstem Response testing: Auditory nervous system • Behavioral Audiometry: Brain • Tympanometry w/ acoustic reflexes: Middle ear and reflex arc

Medical Case History • ASHA Guidelines for the Audiologic Assessment of children From Birth to 5 years of Age 2004 has a simple, but relatively comprehensive case history that can be obtained from families • http://www.asha.org/members/deskref- journals/deskref/default

Why is Case History so important? • Provides information about medical complications prior to birth, during birth and after birth. • Provides invaluable information regarding risk indicators for progressive or late onset hearing loss .(i.e.: family history of hearing loss) • Also tells you what type of screen was performed in the hospital and whether a similar re-screen should also be performed.

Otoacoustic Emissions • Auditory Neuropathy / Dys-Synchrony (AN/AD) : is characterized by robust, or present OAEs

Transient OAE results

Distortion Product OAE

OAE Summary •OAEs are objective evidence of healthy cochlear function . Looks at ‘pre-neural’ response. •The majority of hearing loss in the low-risk population is a result of cochlear/outer hair cell system malfunction. This is the most sensitive part of the hearing mechanism tested by OAEs. •Auditory neuropathy / dys-synchrony is statistically rarer in the low-risk, well baby population than in the special care population,

Auditory Brainstem Response (ABR) •An electrophysiological test is used to assess auditory function in infants and young children using electrodes on the head to record electrical activity from the hearing nerve. • Looks at ‘neural’ response.

Cochlear Microphonic Reverses Kraus et al,2000

Latency does not shift with stimulus rate change Kraus et al,2000

Latency does not shift with stimulus intensity Kraus et al,2000

ABR in summary • Large CM appears to be an “ABR”, but reverses with stimulus polarity • Waves may be absent or severely abnormal

Behavioral Audiometry • VRA: a pediatric hearing test procedure in which the child's responses to sound are reinforced with a visual event (e.g., a moving toy). This procedure is most appropriate for children in the 6 month to 3 year age range. • Looks at response of ‘brain’

Observing Auditory Behaviors • Regardless of outcome of electrophysiologic / acoustic tests, it is recommended that audiologists: – Examine auditory behaviors – Query family regarding their observations – Describe auditory function in relationship to electrophysiologic & acoustic test results – Comment if findings are not in accord Gravel et al., 1989

Tympanometry • a measure of tympanic membrane (eardrum) mobility. Tympanometric are typically normal

Tympanometry • Acoustic reflexes: Absent or severely elevated ipsilaterally and contralaterally despite normal tympanometry

Test Results with Bilateral Auditory neuropathy / dys-synchrony • Otoacoustic Emissions : • Tympanograms • Middle-ear muscle reflexes: • Cochlear microphonic: Normal Normal Absent Present, invert with stimulus polarity reversal • Auditory Brainstem Response: Absent, severely abnormal • Masking level difference: • OAE suppression: • Speech recog. In noise: • Speech recog. In quiet • Pure-tone thresholds: No MLD No suppression Generally poor Normal to severe Variable (normal to profound ranges)

Infants with AN/AD require a Multidisciplinary Approach to Management • Audiologist • Neurodiagnostician • Geneticist • Early Interventionist / Deaf and Hard of Hearing Educator • Speech Pathologist • Occupational Therapists • Physical Therapist • Ophthalmologist

Patient Outcomes • Some actually get better, start to hear and speak within a year or two. Some get worse, lose their emissions and cochlear microphonics. Some stay the same. Some develop peripheral neuropathies later in life. (This latter category more commonly describes adult onset AN. ) • • •

Ongoing Audiological / Educational Management Strategies for AN / AD • Provide up-to-date information regarding the present understanding of AN, this is important in making decisions. – Parents and Educators • Children with AN/AD should have access to appropriate early intervention and/or education programs. – Develop a personalized plan (Individualized Family Services Plan (IFSP) or Individual Education Plan (IEP) • .

Ongoing Audiological / Educational Management Strategies for AN / AD • Determine the functional profile of each child. • Assessment needs to measure skills in a variety of developmental domains – Communication – Language – Functional auditory skills – Speech – Cognition • Repeat testing at regular intervals to monitor achievement of identified goals

Ongoing Audiological / Educational Management Strategies for AN / AD • Suggested Assessment Procedures – Family Assessment of Multi-disciplinary Interactional Learning for the Young Child (Stredler-Brown & Yoshinaga-Itano) – Functional Auditory Performance Indicators: an integrated Approach to Auditory Development (Stredler-Brown & Johnson C) – Auditory-verbal ages & stages of development (Estabrooks) – The Development of Listening Function (Razack) – The Developmental Approach to Successful Listing II (DASL) (Stout & Windle)

Ongoing Audiological / Educational Management Strategies for AN / AD • Intervention should be competency-based where the interventionist identifies the strengths exhibited in the child’s developmental profile and identifies strategies to address delays. • Language development is critical – Visual Communication methods (cued speech, sign language, signed English) are necessary for language development. (Auditory verbal in these cases are not recommended) • Functional auditory skills should be evaluated on a regular basis • Provide comprehensive neurological evaluations

Ongoing Audiological / Educational Management Strategies for AN / AD •Follow patients audiologically: Define hearing sensitivity with behavioral Audiometry There may be a change in auditory function over time •Consider hearing aid fitting if no progress is seen. Distinguish detection (sensitivity) from discrimination (especially in noise) when evaluating hearing aid benefit. •Consider FM system this technology has benefited many infants •Consider cochlear implantation if: Progress is not indicated and cochlear implant team considers the infant a good candidate for the procedure

Goal of Treatment • Ongoing diagnostic testing by individuals capable of providing such services • Development of language – Develop a profile of child’s skills in all developmental domains • Recognize that identification takes time in these cases and re-assure the family • Inform the family of resources available to not only educate but to provide emotional support • Educate the educators working with these infants

Early Intervention of Children identified with Auditory Neuropathy