Evolution of transient evoked otoacoustic emissions in preterm newborns: a preliminary study

Maturation of the auditory system: 1. Transient otoacoustic emissions as an index of inner ear maturation

The transiently evoked otoacoustic emission amplitude of 42 preterm babies (84 ears; post-conceptional age [PCA] 30-36 weeks) was compared with the TEOAE amplitude of 39 full-term babies (78 ears; PCA 37-45 weeks) in order to trace the inner ear maturation characteristics. An ILO-92 otoacoustic emission recording system was used with linear clicks of 70 dB peak equivalent SPL. The results obtained indicated: (1) There was no statistically significant difference between preterm and full-term ears; (2) There was no significant difference between males and females; (3) There was a significant difference between left and right ear TEOAE amplitude; (4) The interaction of ear with age in relation to TEOAE amplitude was statistically significant; (5) Noise and stimulus parameters did not reveal any significant differences between right and left ears; (6) A positive correlation existed between birthweight and TEOAE amplitude; and (7) A negative correlation existed between aminoglycoside treatment and TEOAE amplitude. The results indicate subtle changes in TEOAE amplitude over time, showing a natural development of the inner ear function during the process of maturation.

Feasibility of neonatal hearing screening program with two-stage transient otoacoustic emissions in Turkey

BACKGROUND

The objective of this study was to investigate the incidence of hearing loss in neonates and evaluate the feasibility of a two-stage Transient Evoked Otoacoustic Emission (TEOAE) screening test. Maternal concerns about hearing screening were also studied.

METHODS

Neonatal intensive care patients and well babies were screened using a two-stage TEOAE test, which was followed by an Auditory Brainstem Response (ABR) test for those babies who failed the first test twice.

RESULTS

In total, 711 neonates were screened. At the end of the two TEOAE tests, the cumulative pass rate was 99.3% and false-positive rate was 0.3%. Five neonates (0.7%) were referred for the ABR test. Sensorineural hearing loss was found in three of them (0.4%). Of these three neonates, one was from the well baby nursery and two were from the NICU population. Families generally welcomed the screening program, with no refusals. Positive test results have not caused important maternal concerns.

CONCLUSIONS

Congenital hearing impairment is a prevalent disease in Turkey. The two-stage TEOAE program is suitable for the neonatal hearing screening program. In general, hearing screening tests do not cause notable maternal concerns.

Low prevalence of hearing impairment among very low birthweight infants as detected by universal neonatal hearing screening

OBJECTIVES

To (a) study the prevalence of hearing impairment in a cohort of very low birthweight (VLBW) infants and (b) evaluate the effectiveness of transient evoked otoacoustic emissions (TEOAE) as a first stage in-hospital hearing screening tool in this population.

STUDY DESIGN

The study group was a cohort of 346 VLBW infants born in 1998-2000 at The Sheba Medical Center. The prevalence of hearing impairment in the study group was compared with that of all other newborn infants participating in a universal newborn hearing screening programme during the same period. To evaluate the effectiveness of TEOAE, a control group of 1205 healthy newborns who had no known risk factors for hearing impairment was selected. The results and follow up of hearing screening for these infants were examined retrospectively.

RESULTS

Only one VLBW infant (0.3%) was diagnosed with bilateral sensory-neural hearing loss. In addition, nine infants (2.7%) were diagnosed with conductive hearing loss. Bronchopulmonary dysplasia and low Apgar score were the most significant factors for predicting the occurrence of conductive hearing loss. The percentage of VLBW infants who successfully passed the in-hospital TEOAE screening was 87.2, compared with 92.2% in the full term control group. No false negative cases were detected on follow up.

CONCLUSIONS

The study shows a low incidence of sensory-neural hearing loss in a cohort of VLBW infants and a relatively high incidence of conductive hearing loss. TEOAE screening was found to be an effective first stage in-hospital hearing screening tool in this population.

Development of human cochlear active mechanism asymmetry: involvement of the medial olivocochlear system?

To study the functional development of the medial olivocochlear system, transient-evoked otoacoustic emission suppression experiments were conducted in 73 ears of 38 pre-term and 11 full-term neonates. The continuous contralateral stimulation was a broad band white noise, presented at 70 dB SPL. Efferent suppression was determined by subtracting the without-contralateral stimulation condition from the with-contralateral stimulation condition. Across this population, a mean suppression effect of contralateral stimulation on transient-evoked otoacoustic emissions was found, with most of the suppression effect observed after 8 ms. The amount of suppression is linearly, positively correlated with the conceptional age. In the subgroup of bilaterally tested neonates, the suppression of transient-evoked otoacoustic emissions is similar in the right ear and the left ear in subjects whose conceptional age is less than 36 weeks and significantly higher in the right ear than in the left ear in older neonates. This last observation was seen at frequencies where transient-evoked otoacoustic emission amplitudes became higher in the right ear than in the left ear as the conceptional age increased, a finding already reported in adults. This study shows that the functional adult pattern of the medial efferent system, probably involved in the detection of signals in noise such as speech sounds, seems to appear gradually in neonates and represents one of the several arguments in favor of functional auditory lateralization in humans, with a right ear advantage.

Predischarge screening of very low birthweight infants by click evoked otoacoustic emissions

OBJECTIVE

To evaluate the role of transient evoked otoacoustic emission (TEOAE) in screening very low birthweight (VLBW) neonatal intensive care unit (NICU) graduates for hearing loss in comparison with visual reinforcement orientation audiology (VROA) at 10 months.

METHODOLOGY

The study population was all VLBW neonatal survivors discharged from a single regional NICU at John Hunter Childrens Hospital (JHCH), Newcastle, New South Wales, Australia, between April 1994 and March 1996. A TEOAE screen was performed prior to discharge and repeated if necessary until a pass was obtained in at least one ear. Infants were further screened by VROA at their local Australian Hearing Services (AHS) office at 10 months corrected age. Repeated TEOAE failures were referred directly for an ENT opinion.

RESULTS

A total of 193 infants were eligible for enrolment during the study period. One hundred and forty-four (75%) received TEOAE testing. The median age of first screen was 36 weeks gestational age. Ninety-five (66%) of infants tested passed on a single screen. Of the remaining 49 infants, 26 passed on retesting (overall pass rate 84%). Twenty-three (16%) were deemed to have failed the TEOAE screen. Of the 121 infants who passed TEOAE, only 67 (55%) completed VROA. Two of these infants have a high frequency sensorineural loss and one of them has been aided. In the 23 who failed TEOAE, nine have subsequently had normal VROA, another, though not tested is clinically normal. three have hearing loss with middle ear disease and eight have confirmed sensorineural deafness, all aided. One infant has died and an infant with Down's syndrome has been adopted out of the area. It is of interest to note that the eight aided infants are all of less than 28 weeks gestation. If we restrict analysis to infants with completed VROA testing, the TEOAE has a 97% negative predictive value for sensorineural deafness and a 38% positive predictive value.

CONCLUSIONS

This study has highlighted both the prevalence of hearing impairment in the very premature survivors and difficulties in compliance with a VROA based hearing screen. We see an advantage in directing resources towards an early screening test, such as TEOAE, that can be applied while the target population is still captive.