IAPA Summer School 2008 Neonatal Hearing Screening and Auditory Neuropathy Berlin, Germany April 10th and 11th UPDATING THE ELECTROPHYSIOLOGY IN NEONATAL HEARING EVALUATION José J. Barajas de Prat

WHAT SHOULD THE IDEAL INFANT HEARING ASSESSMENT? Must be applicable to neonates and children Must be applicable to neonates and children Measure Hearing sensitivity from kHz Measure Hearing sensitivity from kHz Assess hearing sensitivity for mild to severe- profound hearing loss Assess hearing sensitivity for mild to severe- profound hearing loss Objectively detect an infant´s response to sound Objectively detect an infant´s response to sound

ELECTROPHYSIOLOGIC TECHNIQUES Click and tone- burst evoked ABR Click and tone- burst evoked ABR Evoked potentials for tones that are amplitude and/or frequency modulated Evoked potentials for tones that are amplitude and/or frequency modulated Auditory-steady state responses (ASSR) Auditory-steady state responses (ASSR) AMLR and 40 Hz AMLR and 40 Hz Cortical AEPs Cortical AEPs

LIMITATIONS OF CONVENTIONAL EVOKED POTENTIAL TESTS Click ABR: Click ABR: Cannot be used to estimate the 4 frequency ( Hz) audiogram Cannot be used to estimate the 4 frequency ( Hz) audiogram TB-ABR: TB-ABR: Lenghtly procedure, relies on subjective analysis of waveforms Lenghtly procedure, relies on subjective analysis of waveforms AMLR, 40 Hz and CAEP: AMLR, 40 Hz and CAEP: Unreliable during natural or sedated sleep on infants and children Unreliable during natural or sedated sleep on infants and children CAEP methods with quietly awake infants may hold promise for estimates of thresholds and speech feature discrimination abilities CAEP methods with quietly awake infants may hold promise for estimates of thresholds and speech feature discrimination abilities

AUDITORY STEADY STATE RESPONSE (ASSR) Can be recorded in neonates and children Can be recorded in neonates and children Are evoked by frequency –specific tonal stimuli Are evoked by frequency –specific tonal stimuli Correlate with elevation in the hearing thresholds Correlate with elevation in the hearing thresholds Can be objectively evaluated Can be objectively evaluated Are used to estimate an audiogram Are used to estimate an audiogram

Jose J. Barajas. (1985). Auditory Brainstem and Middle Latency Response in Early Detection of Hearing Loss in Infants. New dimensions in otorhinolaryngology – head and neck surgery (1); pp

40 Hz Jose J. Barajas. (1988). Middle Latency and 40 Hz Auditory Evoked Responses in normal hearing children: 500 Hz thresholds.Scand Audiol Supp 30:99-104

Picton TW, John MS, Dimitrijevic A, Purcell D. Human auditory steady-state responses. Int J Audiol Jun;42(4): MEASUREMENTS OF SIGNAL AND NOISE AT DIFFERENT RATES

UPDATING THE ELECTROPHYSIOLOGY IN NEONATAL HEARING ASSR in newborns ASSR in newborns AEP and early hearing aid fitting and validation AEP and early hearing aid fitting and validation ASSR ASSR CAEP (Obligatory Cortical Auditory Evoked Potentials) CAEP (Obligatory Cortical Auditory Evoked Potentials) AEP: Cochlear Implants validation AEP: Cochlear Implants validation

ASSR IN NEWBORNS ASSR characteristics in newborns: ASSR characteristics in newborns: The neonatal ASSR The neonatal ASSR Amplitude Development in Infants Amplitude Development in Infants Detection of ASSR in the neonatal infant period Detection of ASSR in the neonatal infant period ASSR threshold in babies ASSR threshold in babies

THE NEONATAL ASSR AVERAGED AMPLITUDE FOR NORMAL- HEARING INFANTS AND ADULTS Luts H, Desloovere C, Wouters J Clinical application of dichotic multiple-stimulus auditory steady-state responses in high-risk newborns and young children. Audiol Neurootol.;11(1):24-37.

AMPLITUDE DEVELOPMENT Johns MS, Brown DK, Muir PJ, Picton TW (2004). Recording Auditory Steady State responses in young infants. Ear Hear Dec, 25 (6)

DETECTION OF ASSR IN THE NEWBORN Is determine by: Amplitude of the response: Amplitude of the response: Stimulus type Stimulus type Modulation rate Modulation rate Carrier frequency Carrier frequency Electrode configuration Electrode configuration Amplitude of the background noise: Amplitude of the background noise: State of arousal State of arousal EEG frequency range EEG frequency range Test duration Test duration

OPTIMAL MODULATION RATE FOR EACH CARRIER Rickards FW, Tan LE, Cohen LT, Wilson OJ, Drew JH, Clark GM. (1994). Auditory steady-state evoked potential in newborns. Br J Audiol.;28(6): Hz 1500 Hz 4000 Hz

ASSR THRESHOLDS IN BABIES Threshold values Threshold values Threshold changes in infancy Threshold changes in infancy Development mechanism affecting ASSR Development mechanism affecting ASSR ASSR vs Tone burst ABR in neonates ASSR vs Tone burst ABR in neonates

ASSR THRESHOLD IN BABIES Luts, H. “Diagnosis of Hearing Loss in Newborns. Clinical Application of Auditory Steady- State responses”. Director: Prof. Dr. J. Wouters. Katholieke Universiteit Leuven, Faculty of Medicine, 2005

ASSR THRESHOLD CHANGES IN INFANCY Rance, G. & Tomlin, D. (2006). Maturation of ASSR in nomal babies. Ear & Hearing, 27,

Rance G, Tomlin D. (2006). Maturation of auditory steady-state responses in normal babies. Ear Hear.;27(1):20-9. DEVELOPMENTAL MECHANISMS AFFECTING ASSR THRESHOLD IN INFANCY

ASSR & TONE-BURST ABRs IN NEONATES Rance G (2008). Assr in Neonates & Infants. In Auditory Steady-State Response Generation, Recording, and Clinical Applications. Gary Rance

HEARING LEVEL PREDICTION Sensation level Sensation level Regresion formula describing ASS behavioral regression Regresion formula describing ASS behavioral regression

ASSRs IN HEARING IMPAIRED BABIES Rance G (2008). ASSR in Neonates & Infants. In The Auditory Steady-State Response: Generation, Recording, and Clinical Applications. Edited by Gary Rance. In review.

For older children and adult subjects ASSR/behavioral threshold correlation has been empirically established For older children and adult subjects ASSR/behavioral threshold correlation has been empirically established In normally developing babies this relationship is NOT well defined. In normally developing babies this relationship is NOT well defined. ASSR threshold variance in babies is higher than for adults (> 30 dB) ASSR threshold variance in babies is higher than for adults (> 30 dB) Ear canal differences. Ear canal differences. Neural development. Neural development. HEARING LEVEL PREDICTION

CONCLUSION Maturation factors affect ASSR. Maturation factors affect ASSR. Normally hearing babies present lower amplitudes than adults and older children. Normally hearing babies present lower amplitudes than adults and older children. Neonatal period threshold higher and more variable. Neonatal period threshold higher and more variable. Need to determine typical response levels for babies of different ages and developmental stages. Need to determine typical response levels for babies of different ages and developmental stages.

UPDATING THE ELECTROPHYSIOLOGY IN NEONATAL HEARING EVALUATION ASSR in newborns ASSR in newborns AEP and early hearing aid fitting and validation AEP and early hearing aid fitting and validation ASSR ASSR CAEP (Obligatory Cortical Auditory Evoked Potentials) CAEP (Obligatory Cortical Auditory Evoked Potentials) AEP: Cochlear Implants Evaluation AEP: Cochlear Implants Evaluation

LOUDNESS AND ASSR Zenker Castro F., Barajas de Prat JJ & Larumbe Zabala E. (2008): Loudness and Auditory Steady State responses in normal hearing subjects. International Journal of Audiology. In press.

HEARING AID PRESCRIPTION FROM ASSR Zenker F. & Barajas J.J.(2008) ASSRs: Their role in hearing device fitting. In: The Auditory Steady State response: generation, recording and clinical application. Edited by Gary Rance.

UPDATING THE ELECTROPHYSIOLOGY IN NEONATAL HEARING ASSR in newborns ASSR in newborns AEP and early hearing aid fitting and validation AEP and early hearing aid fitting and validation ASSR ASSR CAEP (Obligatory Cortical Auditory Evoked Potentials) CAEP (Obligatory Cortical Auditory Evoked Potentials) AEP: Cochlear Implants validation AEP: Cochlear Implants validation

TYPES OF AER THAT HAVE BEEN USED TO OBJECTIVELY EVALUATE HEARING AIDS FUNCTION Auditory Brainstem Responses (ABR) Auditory Brainstem Responses (ABR) Auditory Steady state Responses (ASSR) Auditory Steady state Responses (ASSR) Obligatory Cortical Auditory Evoked Potential (CAEP) Obligatory Cortical Auditory Evoked Potential (CAEP)

Why are we using obligatory cortical responses to evaluate hearing aid function? More likely to correlate well with perception. More likely to correlate well with perception. Can be elicited by a range of speech phonemes. Can be elicited by a range of speech phonemes. Reliable present in awake young infants. Reliable present in awake young infants. Can be present in children with auditory neuropathy/dys-synchrony. Can be present in children with auditory neuropathy/dys-synchrony.

Suzanne C. Purdy et al. (2004). Aided cortical auditory evoked potentials for hearing instrument evaluation. 3rd Pediatric Conference “A Sound Foundattion through early amplification”. Chicago, Illinois CAEP

MATURATIONAL EFFECTS ON CORTICAL EVOKED RESPONSE Ponton et al. (2000) Maturation human central auditory system activity: evidence from multi-channel evoked potentials. Clinical Neurophysiology 111 (2):

CAEP CAN ELICITED BY DIFFERENT SPEECH PHONEMES IN NEWBORNS 9 D. KURTZBERG 1989

HEARING AID GAINS AND CAEP AMPLITUDE Suzanne C. Purdy et al. (2004). Aided cortical auditory evoked potentials for hearing instrument evaluation. 3rd Pediatric Conference “A Sound Foundattion through early amplification”. Chicago, Illinois

P1 IN HEARING AIDS Anu Sharma, Emily Tobey, Michael Dorman, Sneha Bharadwaj, Kathryn Martin, Phillip Gilley, Fereshteh Kunkel. Central Auditory Maturation and Babbling Development in Infants With Cochlear Implants. ARCH OTOLARYNGOL HEAD NECK SURG/VOL 130, MAY 2004.

P1 IN COCHLEAR IMPLANTS Anu Sharma, Michael F. Dorman, Andrej Kral. (2005). The influuence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants. Hearing Research 203, 134–143.

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