Transient evoked otoacoustic emissions in newborns in the first 48 hours after birth

Efficacy of a community-based infant hearing screening program utilizing existing clinic personnel in Western Cape, South Africa

OBJECTIVE

Screening programs at primary health care immunization clinics have been proposed as an alternative to hospital-based programs in South Africa. The objective of this study was to evaluate the first systematic community-based infant hearing screening program in a developing South African community in the Western Cape.

METHODS

A community-based universal infant hearing screening program initiated at eight primary health care clinics in the Cape Metropolitan area was evaluated over a 19-month research period. During this time 6227 infants that were candidates for screening attended their 6, 10 or 14-week immunization visit at the relevant clinic. Clinic nurses were trained as screening personnel. A two-stage distortion product otoacoustic emissions screening protocol was utilized. The target disorder was uni- or bilateral hearing loss and infants referring the first screen were scheduled for a 4-week follow-up visit at the clinic. Diagnostic audiological and medical evaluations were scheduled at referral hospitals when indicated. The study evaluated the efficacy of the program based on coverage, referral and follow-up rates and diagnostic outcomes according to guidelines specified by the Health Professions Council of South Africa 2007 Position Statement.

RESULTS

Overall coverage rate across the eight clinics was 32.4% with 2018 infants (aged 0-14 weeks) screened. The mean age of the sample at first stage screen was 3.9 weeks of age and 13.5 weeks of age for first hospital visit. Overall first stage screen referral rate was 9.5% with 62 subjects (3%) referred for diagnostic services at hospital level after a follow-up screen. The average follow-up rate for rescreens at clinic level was 85.1% and for initial diagnostic assessments at hospital level it was 91.8%. Prevalence rates were 4.5/1000 with significant hearing loss, including sensorineural (1.5/1000) and conductive (3/1000) losses, and 12.9/1000 for subjects with middle ear effusion.

CONCLUSIONS

The community-based infant hearing screening program was valuable in attaining high follow-up return rates but reaching sufficient coverage may require dedicated screening personnel as opposed to existing nursing personnel.

The influence of epidural anesthesia on new-born hearing screening: A pilot study

Objective:

The main aim was to establish if epidural anesthesia had an influence on new-born hearing screening results in newborns born via elective Cesarean section in healthy pregnancies. Specific objectives included determining screening results in a group of newborns born to mothers who had undergone epidural anesthesia during Cesarean section childbirth (experimental group); and comparing the findings with those of a group of newborns born to mothers who had undergone natural delivery without epidural anesthesia (comparison group); while establishing if the time of screening following delivery had any effect on the overall screening results.

Materials and Methods:

The above objectives were achieved through the use of a prospective quasi-experimental repeated measures design with a comparison group, where 40 newborns (20 in the experimental and 20 in the comparison group) were screened at three different times through transient otoacoustic emissions (TEOAEs) and automated auditory brainstem response (AABR) measures. All participants were screened while resting quietly in open bassinets in an empty new-born nursery. For both test measures, the results were recorded as either pass or refer. Data were analyzed through both descriptive and inferential statistics.

Results:

Findings indicated that hearing screening earlier than four hours after birth, for both the experimental and comparison groups yielded more false positive findings than testing conducted after 24 hours. An index of suspicion in relation to the influence of epidural anesthesia on Automated Auditory Brainstem Response (AABR), when conducted less than four hours after birth, was raised, as statistically significant findings (P<0.05) were obtained.

Conclusions:

The findings have implications for timing of screening where universal newborn hearing screening is being implemented.

Making universal newborn hearing screening a success

OBJECTIVE

Following a long period of pilot study, Iaso maternity hospital established a universal newborn hearing screening program based on transiently evoked otoacoustic emissions (TEOAEs). The aim of this study is to present the improvement of outcome measures of this program, comparing the results of two groups of newborns screened successively.

METHODS

We analyzed data from two groups of full-term newborns screened at our setting. The first group included all newborns born and screened during the initial 3 years of application of the program and the second group included all newborns born and screened during the next 2 years. TEOAEs were performed during the first days after birth. All newborns who failed the initial test underwent repeat testing with TEOAEs before hospital discharge. Newborns with absence of otoacoustic emissions were referred to follow-up test after 1 month. Results were compared between the two groups.

RESULTS

The first group included 22,195 newborns-examined during 3 years and the second group included 25,032 newborns-examined during 2 years, due to reduction of the rate of newborns who missed screening. Refer rate was 3.1% for the first group and 2.1% for the second group. "Missed to follow-up" rate was reduced from 72.2% in the first group to 58.2% in the second group.

CONCLUSIONS

The rate of newborns who did not undergo screening and the rate of "missed to follow-up" newborns were reduced in time, due to various modifications of the protocol. Universal newborn hearing screening may be, thus, a feasible and cost effective method of identifying congenital hearing loss.

Decreasing test time in newborn hearing screening

This study examined the effect of reducing the number of accepted responses in transiently evoked otoacoustic emissions based on the results of a universal neonatal hearing screening program. Our intention was to decrease the test time of newborns. A total of 464 ears were examined by using a universal newborn hearing-screening program implemented in a private maternity hospital. ILO88 Otodynamics Analyzer Quickscreen program was used for all testing and a two-stage procedure was adopted. In the first stage, the results were continuously evaluated for the 'pass' criteria, during the test, after at least 20 low-noise sweeps had been presented. As soon as the criteria were met, the test was interrupted and the results were recorded. In the second stage of the procedure, the test was continued and finally terminated after 260 quiet samples had been recorded. The results of each stage of this procedure were compared and evaluated. A total of 402 ears had normal otoacoustic emissions and only 62 ears had absent emissions. It was concluded that after a minimum of 20 averaged quiet responses, which we consider necessary in order to record reliable emissions and as soon as the 'pass' criteria were fulfilled the test could be terminated without affecting the 'pass-fail' rates which were similar in both stages. However, we believe that for diagnostic and clinical purposes, all 260 quiet samples must be used, because the results after the second stage indicated statistically better scores in response and reproducibility measures.

Click-evoked ABR at high stimulus repetition rates for neonatal hearing screening

A new, fast screening algorithm based on auditory brainstem response (ABR) recorded at a high click repetition rate is proposed. Response detection is carried out in the frequency domain by a statistical test procedure which includes the fundamental frequency and the harmonics below 800 Hz. First, the method was tested in 25 young adults. ABRs were recorded in the repetition rate range 20/s to 400/s. With a mean response detection time of 31 s, a click repetition rate of 140/s was found to be the optimum rate among the adult group. The method was then tested using a group of 114 neonates in whom the repetition rate range 60/s to 200/s was examined. At the repetition rate 90/s, which was found to be the optimum rate in neonates, the mean detection time was 24.6 s. In addition to the fast ABR detection, the proposed screening algorithm also allows simultaneous hearing screening of both ears using a one-channel data recording.

Surdez infantil

A Surdez Infantil é considerada actualmente um verdadeiro problema de Saúde Pública devido não só à sua elevada prevalência, mas sobretudo às múltiplas conseqüências que acarreta sob os mais variados prismas. Trata-se de um tema em constante evolução, sendo necessárias freqüentes actualizações por forma a acompanhar os avanços da técnica e do conhecimento. Este trabalho visa abordar de uma forma global mas sucinta o problema Surdez Infantil, dando particular ênfase aos Modelos de Rastreio e aos Métodos utilizados com esse fim.

An animal model for assessment of amniotic fluid clearance from the middle ear

HYPOTHESIS

To determine the time needed for clearance of amniotic fluid from the middle ear after birth, an animal model study was performed.

BACKGROUND

Before birth, the middle ear is full of amniotic fluid, and there is controversy about the time it takes for it to clear postnatally. This is of importance because it is suspected that amniotic fluid in the middle ear of the newborn may affect results of screening of hearing when using otoacoustic emissions.

METHODS

Adult and neonatal guinea pigs underwent a right-side cochleotomy followed by baseline otoscopy, tympanometry, and auditory nerve- and brainstem-evoked response (ABR) measurements of the left ear. Subsequently, the animals' left middle ears were filled with saline through a hole drilled in the bulla. Over the next few days, assessment of saline clearance was conducted by repeated left-side otoscopy, tympanometry, and measurement of ABR.

RESULTS

After filling the middle ear with saline, the tympanic membrane was opaque, a type B tympanogram was obtained, and the ABR threshold was elevated. After an average of 6.3 +/- 3.0 days, air bubbles were seen in otoscopy, a type C tympanogram was obtained, and the ABR threshold improved. Finally, after an average of 9.5 +/- 2.7 days, all 3 parameters returned to their baseline values.

CONCLUSION

Taking into consideration that this is an animal study, the results suggest that clearance of amniotic fluid from the newborn middle ear takes longer than has been generally thought. In addition, an animal model for assessing the clearance of fluid from the middle ear has been developed.