Otoacoustic emissions: A new method to diagnose hearing impairment in children

Abstract

Otoacoustic emissions (OAEs) are epiphenomena of sensitive, amplifying processes during hearing which can be detected in persons with normal inner ear function. They originate from the cochlea and are interpreted as an energy leakage of cochlear processes, perhaps resulting from active outer hair cell movements. OAEs travel from the cochlea through the middle ear to the external auditory canal where they can be detected using sensitive miniature microphones. Transient evoked (TEOAE) tests allow to otoacoustic emissions non-invasively check the integrity of the cochlea. In the neonatal period, registration of OAEs can be accomplished during natural sleep. In infants and neonates TEOAEs can be used as screening test with a screening level at 30 dB HL in paediatric audiology. They are less time consuming and elaborate than auditory brainstem responses (ABR) and they are more sensitive than behavioral tests. TEOAEs are constant over long periods of time and they are reduced or absent due to various adverse influences in the inner ear. These latter characteristics may allow monitoring of the inner ear function over time e.g. during disease and/or during ototoxic therapeutic interventions. Limitations of this new method are due to the fact that TEOAEs are absent in patients with a more than 30 dB HL hearing loss. Thus a hearing threshold cannot be determined. Diseases of the inner ear which are common in early childhood (like otitis media) reduce the transfer of TEOAEs and may wrongly indicate a cochlear hearing disorder. New methods for evaluation and interpretation of TEOAE test results are currently developed which may allow to circumvent this problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal hearing screening

“…Spontaneous EOAEs are produced without an external acoustic stimulus. Transient EOAEs (TEOAEs) are detected after an acoustic stimulus has been applied [19,25,27,30,41,51]. Depending on the stimulus used TEOAEs can be detected in up to 98% of humans with normal hearing and are absent when there is a hearing impairment of more than 20-40 dB [25,30].…”

“…The probe must be carefuly fixed and acoustically shielded sealing the outer ear canal. In the newborn hypoxia or infection may result in a reversible reduction in the amplitude spectrum of the TEOAEs [51]. Children with non-organic hearing loss or hearing loss primarily due to involvement of the auditory pathway may have completely normal EOAEs [3,30].…”

Transient evoked otoacoustic emissions in superior canal dehiscence syndrome

“…OAEs travel from the cochlea through the middle ear to the external auditory canal where they can be detected using sensitive miniature microphones. Transient evoked otoacoustic emissions (TEOAEs) using click stimuli allow to noninvasively check the integrity of the cochlea [4]. Pytel and Büki [5] developed a unique off-line analysis technique enabling the determination of TEOAEs' duration known as moving time window analysis (MTWA).…”

Click-evoked oto-acoustic emission measurement in preterm infants

“…These CEOAE arise in the form of a broadband acoustic signal of up to 20ms duration after the click and can easily be measured with a sensitive microphone placed in the external ear canal. This particular kind of OAE has proven its clinical merits as a sensitive, non-invasive and objective screening tool for normal cochlear function [18,25]. CEOAE have a nearly 100% incidence among normal hearing subjects and have proven to be generally absent in patients with sensorineural hearing losses exceeding 30±35 dB HL.…”

“…Oto-acoustic emissions (OAE) are a form of acoustic energy emitted by the inner ear [18,25]. It ®nds its origin in the process of perception in the organ of Corti.…”