Auditory brainstem response in premature and full-term children

The frequency-following response in late preterm neonates: a pilot study

Introduction

Infants born very early preterm are at high risk of language delays. However, less is known about the consequences of late prematurity. Hence, the aim of the present study is to characterize the neural encoding of speech sounds in late preterm neonates in comparison with those born at term.

Methods

The speech-evoked frequency-following response (FFR) was recorded to a consonant-vowel stimulus /da/ in 36 neonates in three different groups: 12 preterm neonates [mean gestational age (GA) 36.05 weeks], 12 "early term neonates" (mean GA 38.3 weeks), and "late term neonates" (mean GA 41.01 weeks).

Results

From the FFR recordings, a delayed neural response and a weaker stimulus F0 encoding in premature neonates compared to neonates born at term was observed. No differences in the response time onset nor in stimulus F0 encoding were observed between the two groups of neonates born at term. No differences between the three groups were observed in the neural encoding of the stimulus temporal fine structure.

Discussion

These results highlight alterations in the neural encoding of speech sounds related to prematurity, which were present for the stimulus F0 but not for its temporal fine structure.

Brain auditory evoked potentials in pediatric Intensive Care Unit: diagnostic role on encephalopathy and central respiratory failure on infants

BACKGROUND

Encephalopathy of different etiologies in infants is often the reason for central respiratory insufficiency which eventually leads patients to the Pediatric Intensive Care Unit. Magnetic resonance imaging (MRI) and brainstem auditory evoked potentials (BAEPs) may be useful to identify brainstem alterations among patients with respiratory insufficiency of central origin. MRI is a compulsory technique to identify brain abnormalities, but may fail to detect brainstem lesions of small dimensions. BAEPs play a highly sensitive role on brainstem dysfunction identification because of the generators of different peaks which are related to specific brainstem structures.

METHODS

The study included ten infants affected by encephalopathy of different etiologies and early neurological respiratory failure. To evaluate BAEPs, the surface electrodes were placed at the vertex (Cz) and on each mastoid side.

RESULTS

All subjects presented alteration of BAEPs. The brain MRI revealed selective injury of the brainstem in four patients and supratentorial alterations in six patients.

CONCLUSIONS

The early identification of brainstem lesions in mechanically ventilated infants with encephalopathy may reduce the weaning off mechanical ventilation's attempt numbers and provide early informative discussions with families and clinical caregivers about treatment options, such as tracheostomy, long term ventilation and the reduction of their length of PICU stay. Furthermore, this would support the evaluation process concerning the affected children, their families and the needs of other social groups, including health systems.

Auditory Pathway Maturation in Full-term Small for Gestational Age Children: A Systematic Review with Meta-analysis

Introduction  Factors of intrauterine growth restriction have been responsible for the births of full-term babies small for their gestational age (SGA). Scientific evidence points that this restriction can cause changes in the neural maturation process. Objectives  To analyze the absolute latencies and interpeak intervals of brainstem auditory evoked potential waves in full-term and SGA children to investigate whether there are changes of neural maturation in this population. Data Synthesis  The search for articles that reported the assessment of brainstem auditory evoked potential in SGA newborns compared with a control, appropriate for their gestational age, both born full-term, for the entire period available in the database research until October 31, 2021 was performed based on the MEDLINE/PubMed Central and on the Latin America and the Caribbean Health Sciences Literature and Virtual Health Library electronic databases. A total of 311 studies were found in the database research. Out of this total, 10 studies were included in the review, 5 of which were eligible for the meta-analysis, involving a total of 473 participants of both genders, with 193 participants belonging to the study group and 280 to the control group. Differences between the groups were only observed in the absolute latency of wave V (95% confidence interval [CI]: 0.02-0.15; p  < 0.01). Conclusion  The SGA condition is responsible for the appearance of brainstem neural conduction dysfunction measured by the brainstem auditory evoked potentials, probably by the maturation process of the auditory pathway of this population.

Deficits in neural encoding of speech in preterm infants

Preterm children show developmental cognitive and language deficits that can be subtle and sometimes undetectable until later in life. Studies of brain development in children who are born preterm have largely focused on vascular and gross anatomical characteristics rather than pathophysiological processes that may contribute to these developmental deficits. Neural encoding of speech as reflected in EEG recordings is predictive of future language development and could provide insights into those pathophysiological processes. We recorded EEG from 45 preterm (≤ 34 weeks of gestation) and 45 term (≥ 38 weeks) Chinese-learning infants 0-12 months of (corrected) age during natural sleep. Each child listened to three speech stimuli that differed in lexically meaningful pitch (2 native and 1 non-native speech categories). EEG measures associated with synchronization and gross power of the frequency following response (FFR) were examined. ANCOVAs revealed no main effect of stimulus nativeness but main effects of age, consistent with earlier studies. A main effect of prematurity also emerged, with synchronization measures showing stronger group differences than power. By detailing differences in FFR measures related to synchronization and power, this study brings us closer to identifying the pathophysiological pathway to often subtle language problems experienced by preterm children.

Effects of neurodevelopmental risk factors on brainstem maturation in premature infants

BACKGROUND

Interpeak latencies (IPL), as measured by the auditory brainstem-evoked responses (ABR) test, represent the conduction time, and therefore the maturation of the brainstem auditory pathway. We aimed to study the effect of various risk factors for the neurodevelopmental delay on the conduction time in the auditory pathway among normal hearing premature infants, at term postmenstrual age (PMA).

METHODS

Retrospective analysis of 239 premature infants (gestational age 32.5 ± 2.1 weeks, birth weight 1827 ± 483 g). Interpeak latencies, demographic data, and risk factors were recorded.

RESULTS

Sex, PMA at ABR test, being small for gestational age (SGA), intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL), and days of invasive ventilation were found to significantly affect the IPL's in the auditory pathway in a univariate analysis. Multivariable regression analysis revealed that male sex and less advanced PMA at the examination were independent factors associated with prolonged IPL's, while bronchopulmonary dysplasia, IVH or PVL and being SGA shortened the IPL's. Non-invasive mechanical ventilation, did not affect the caudal part of the auditory pathway, despite its high noise level.

CONCLUSIONS

Among various risk factors for the neurodevelopmental delay, male sex was associated with delayed, while IVH or PVL, BPD and SGA could be associated with accelerated auditory brainstem maturation.

IMPACT

Auditory brainstem-evoked response (ABR) test, among normal hearing infants, can serve as a clinical tool to assess brainstem auditory maturation. Different neurodevelopmental risk factors could have different effects on the maturity of the auditory pathway. Male sex is significantly associated with prolonged interpeak latencies (IPL) among preterm and term infants, while intraventricular hemorrhage or periventricular leukomalacia, bronchopulmonary dysplasia, and being small for gestation age may be associated with shortened IPL The corrected age at ABR testing is of significance, among preterm and term infants.

Delayed Auditory Brainstem Responses (ABR) in children after sight-recovery

Studies in non-human animal models have revealed that in early development, the onset of visual input gates the critical period closure of some auditory functions. The study of rare individuals whose sight was restored after a period of congenital blindness offers the rare opportunity to assess whether early visual input is a prerequisite for the full development of auditory functions in humans as well. Here, we investigated whether a few months of delayed visual onset would affect the development of Auditory Brainstem Responses (ABRs). ABRs are widely used in the clinical practice to assess both functionality and development of the subcortical auditory pathway and, provide reliable data at the individual level. We collected Auditory Brainstem Responses from two case studies, young children (both having less than 5 years of age) who experienced a transient visual deprivation since birth due to congenital bilateral dense cataracts (BC), and who acquired sight at about two months of age. As controls, we tested 41 children (sighted controls, SC) with typical development, as well as two children who were treated (at about two months of age) for congenital monocular cataracts (MC). The SC group data served to predict, at the individual level, wave latencies of each BC and MC participant. Statistics were performed both at the single subject as well as at the group levels on latencies of main ABR waves (I, III, V and SN10). Results revealed delayed response latencies for both BC children compared with the SC group starting from the wave III. Conversely, no difference emerged between MC children and the SC group. These findings suggest that in case the onset of patterned visual input is delayed, the functional development of the subcortical auditory pathway lags behind typical developmental trajectories. Ultimately results are in favor of the presence of a crossmodal sensitive period in the human subcortical auditory system.

Central auditory processing: behavioral and electrophysiological assessment of children and adolescents diagnosed with stroke

INTRODUCTION

Central auditory processing refers to the efficiency and effectiveness with which the central nervous system uses auditory information: it may be altered in neurological disorders and brain injuries, such as strokes. However, despite evidence of probable alterations in the pediatric population, functional abilities and post-stroke limitations are still not well documented in the literature.

OBJECTIVE

To analyze the findings of the electrophysiological and behavioral evaluations of central auditory processing of children and adolescents diagnosed with stroke from a reference outpatient clinic, as well as to investigate possible associations with the variables: type and location of the stroke and age group.

METHODS

The present study is characterized as comparative cross-sectional. The sample, for convenience, included individuals aged 7-18 years divided into two groups: study group, composed of individuals with a diagnosis of stroke, and control group, composed of individuals with typical development. The evaluation consisted of the following procedures: anamnesis, basic audiological evaluation, behavioral evaluation of the auditory processing disorder (dichotic digit test, dichotic consonant-vowel, synthetic sentence identification/pediatric speech intelligibility, gaps in noise, pitch pattern sequence, masking level difference), and electrophysiological evaluation (P300 and mismatch negativity).

RESULTS

Nineteen children and adolescents were included in the study group. The control group was composed of 19 children and adolescents with typical development. In the comparison between the groups, a worse performance is observed for the study group in all the evaluated tests, behavioral and electrophysiological. In the behavioral evaluation of central auditory processing, there was a statistical difference for all tests, except for masking level difference and dichotic digit test, binaural separation step on the left. In the electrophysiological evaluation, there was a statistical difference in the latency of mismatch negativity and P300. No associations were found between the behavioral and electrophysiological findings and the location of the stroke and age group variables.

CONCLUSION

Children and adolescents diagnosed with stroke present a worse performance in the electrophysiological and behavioral evaluations of central auditory processing when compared to a control group.

Auditory Brainstem Evoked Response Patterns in the Neonatal Intensive Care Unit

OBJECTIVE

Delayed maturation of auditory brainstem pathway in neonates admitted to the neonatal intensive care unit (NICU) may lead to misdiagnosis of children with normal peripheral hearing and inappropriate use of amplification devices. The aim of this study is to determine the pattern of auditory brain stem response in neonates admitted to the NICU for proper hearing assessment in this high-risk population.

STUDY DESIGN

This prospective study was conducted on 1,469 infants who were admitted to the NICU, of which 1,423 had one or more risk factors for permanent congenital hearing loss and were screened with automated auditory brain stem response (AABR). A total of 60 infants were referred for diagnostic ABR analysis after failure on AABR screening. The control group comprised 60 well-baby nursery neonates with no risk factors for PCHL.

RESULTS

Mean values of absolute latencies of waves III and V; interpeak latencies I-III, III-V, and I-V; amplitude of waves I, and V; and I/V amplitude ratio at 90 dBnHL measured for the right and left ears at 1 and 3 months of age show significant difference in NICU neonates compared with controls (p < 0.05). All the diagnostic ABR measurements significantly improved at the age of 3 months (p < 0.001) except wave I absolute latency of both groups (p > 0.05). Significant correlations were found between ABR readings at the age of 1 and 3 months and the gestational age of the NICU neonates (p < 0.05).

CONCLUSION

Diagnostic ABR findings in NICU neonates suggested delayed maturation of the auditory brainstem pathway with a great impact of gestational age on this maturation. Auditory maturational changes were observed at 3 months of age of patient and control groups.

Hearing brain evaluated using near-infrared spectroscopy in congenital toxoplasmosis

Congenital toxoplasmosis (CT) is a known cause of hearing loss directly caused by Toxoplasma gondii. Hearing loss might result from sensory, neural, or sensorineural lesions. Early treated infants rarely develop hearing loss, but retinochoroidal lesions, intracranial calcifications and hydrocephalus are common. In this study, we aimed to evaluate the brain evoked hemodynamic responses of CT and healthy infants during four auditory stimuli: mother infant directed speech, researcher infant directed speech, mother reading and researcher recorded. Children underwent Transitionally Evoked Otoacoustic Emission Auditory Testing and Automated Brainstem Auditory Response tests with normal auditory results, but with a tendency for greater latencies in the CT group compared to the control group. We assessed brain hemodynamics with functional near-infrared spectroscopy (fNIRS) measurements from 61 infants, and we present fNIRS results as frequency maps of activation and deactivation for each stimulus. By evaluating infants in the three first months of life, we observed an individual heterogeneous brain activation pattern in response to all auditory stimuli for both groups. Each channel was activated or deactivated in less than 30% of children for all stimuli. There is a need of prospective studies to evaluate if the neurologic or auditory changes course with compromise of children outcomes.

Changes in auditory function in premature children: A prospective cohort study

OBJECTIVES

To analyze the age-specific pattern of auditory function in preterm children as a function of their gestational age at birth.

STUDY DESIGN

longitudinal cohort study.

METHODS

a prospective cohort study involved 271 preterm children aged from 6 months to 15 years old. Children were divided into two groups: 70 children with a gestational age at birth of 32-36 weeks (Group 1) and 201 children with a gestational age of 22-31 weeks (Group 2). Hearing was assessed by ABR, ASSR, OAE, behavioral audiometry, and pure tone audiometry. Additionally, for some children, CT, MRI, and GBJ2 evaluations were performed. Assessments of hearing impaired children were performed 3-4 times a year for children under 2 years of age; 2-3 times a year for children from 2 to 5 years of age; and 1-2 times a year for children over 5 years of age. Infants without any hearing problems were examined 2-3 times during their first year of life, followed by annual examinations as they aged.

RESULTS

The initial hearing examination identified SNHL and ANSD in 18 children (25.7%) and 64 children (31.8%) in Group 1 and Group 2, respectively. No significant difference in the occurrence of auditory impairment in the two groups was found at the initial assessment (p > 0.05). Further long-term follow-up revealed changes in hearing in 16 children: 15 from Group 2 and only one child from Group 1. Four different kinds of hearing changes were noted: hearing recovery to normal levels in children with ANSD; late onset hearing loss; the transformation of ANSD to SNHL, and vice versa. The age, factors, and possible mechanisms of such changes are discussed in the article.

CONCLUSION

The auditory function in prematurely born children tends to be unstable, especially at a very early age. In very preterm infants, it may either deteriorate or improve. Infants born before 31 weeks' gestation require long-term follow-up at least until they are 3-4 years of age. Caution is advised regarding very early cochlear implantation for children born before 32 weeks of gestation age.

Brainstem Auditory Evoked Potentials in infants aged 1 to 24 months during a hearing health care service

OBJECTIVES

Assessing infants' hearing is of utmost importance, as hearing at this phase is required for the development of oral language. Through hearing, human beings are capable of developing communication. The Brainstem Auditory Evoked Potentials are an indispensable test to diagnose deafness in infants. This study aimed to analyze the results of the Brainstem Auditory Evoked Potentials in children with risk factors for hearing loss.

METHODS

This cross-sectional study analyzed the Brainstem Auditory Evoked Potentials in 123 infants aged 1 to 24 months at a hearing health care service. The Vivosonic Integrity V500 equipment, which enabled the child to be awake while the testing was carried out, was used in this study. The data were compared by gestational age and sex, according to the standards suggested in the equipment handbook.

RESULTS

A significant difference was verified for age ranges 4 to 6 months, 13 to 15 months (waves I and V), and 7 to 9 months (wave V). The lower values in absolute wave latencies were comparable to data from the equipment handbook, justifying the need for standardization of the screening process.

CONCLUSION

There are some differences between the standards in the equipment handbook and those observed in our study. These results will serve as a reference for the standardization of the equipment used in the hearing health care service.

Changes in Auditory Brainstem Response in very preterm and late preterm infants

AIM

Aim of this study was to compare the absolute and interpeak latencies of Auditory Brainstem Responses (ABR) in very preterm and late preterm infants at 1 month and 3 months of corrected age.

METHOD

ology: ABR traces were obtained from 80 preterm infants (40 very preterm and 40 late preterm) at 1 month and 3 months of corrected age in a prospective, comparative cohort study. Auditory click stimuli at 70 dBnHL and 30 dBnHL, with repetition rate of 11.1/s were used. Absolute latencies of peak I, III, V and interpeak latencies of peak I-V, I-III and III-V were analyzed and compared between preterm groups at 1 month and 3 months of corrected age. Wilcoxon Signed Ranks test was used to compare the ABR variables. Mann Whitney test was used to make inferences between groups.

RESULTS

There was a statistically significant difference in absolute latencies and interpeak latencies between very preterm and late preterm infants at 1 month of corrected age (p < 0.05). Absolute latency of peak I was similar among both groups of preterms. Absolute latencies of peak III, V and interpeak latencies I-III, III-V and I-V were prolonged in very preterm infants at 1 month of corrected age. However, these latencies were significantly reduced at 3 months of corrected age. This indicated accelerated maturation/myelination of the central auditory nervous system in very preterm infants. Absolute latencies of peak III and V and interpeak interval I-V was reduced in late preterm infants at 3 months of corrected age and this was statistically significant. This reduction in latency was considered to be a normal age dependent change.

CONCLUSION

Findings of the current study revealed that there was no deviation in the pattern of auditory maturation among preterms; it followed the typical 'caudal to rostral' form of maturation. Very preterm infants have less mature neuronal development compared with late preterm infants at 1 month of corrected age which catches up at 3 months of corrected age.

Risk Factors and Prognostic Factors of Hearing Impairment in Neonatal Intensive Care Unit-Treated Infants

BACKGROUND

Infants admitted to the neonatal intensive care unit (NICU) have a higher incidence of congenital hearing loss compared with the healthy newborn population.

OBJECTIVES

To clarify the relationship between risk factors for hearing impairment in NICU-treated infants and deterioration of the auditory brainstem response (ABR) threshold during childhood.

METHOD

We screened 1,071 high-risk infants admitted to the NICU for hearing impairment. One-hundred forty-eight infants exhibited an abnormal ABR threshold of ≥40 dB nHL. We analyzed the correlation of change in ABR threshold with risk factors for future hearing impairment.

RESULTS

Among infants treated in the NICU, 148 (13.8%) exhibited an ABR threshold of ≥40 dB nHL; 107 of these 148 (72.3%) showed hearing change in the process (102 showed improvement to normal hearing level, whereas 5 showed further deterioration). Our analysis showed that the factors contributing to the elevation of ABR threshold were oxygen administration and chromosomal aberrations.

CONCLUSIONS

Factors related to the elevation of ABR threshold were oxygen administration and the presence of chromosomal aberrations. Awareness of risk factors that are more likely to cause hearing loss in infants may aid in follow-up treatment of these children.

Verbal abuse during pregnancy increases frequency of newborn hearing screening referral: The Japan Environment and Children's Study

BACKGROUND

Verbal abuse during pregnancy has a greater impact than physical and sexual violence on the incidence of postnatal depression and maternal abuse behavior towards their children. In addition, exposure of children (aged 12 months to adolescence) to verbal abuse from their parents exerts an adverse impact to the children's auditory function. However, the effect of verbal abuse during pregnancy on fetal auditory function has not yet been thoroughly investigated.

OBJECTIVE

The objective of the study was to examine the relationship between intimate partner verbal abuse during pregnancy and newborn hearing screening (NHS) referral, which indicates immature or impaired auditory function.

PARTICIPANTS AND SETTING

The Japan Environment and Children's Study is an ongoing nationwide population-based birth-cohort study designed to determine environmental factors during and after pregnancy that affect the development, health, or wellbeing of children. Pregnant women living in 15 areas of Japan were recruited between January 2011 and March 2014.

METHODS

Multiple imputation for missing data was performed, followed by multiple logistic regression using 16 confounding variables.

RESULTS

Of 104,102 records in the dataset, 79,985 mother-infant pairs submitted complete data for questions related to verbal and physical abuse and the results of NHS. Of 79,985 pregnant women, 10,786 (13.5%) experienced verbal abuse and 978 (1.2%) experienced physical abuse. Of 79,985 newborns, 787 (0.98%) received a NHS referral. Verbal abuse was significantly associated with NHS referral (adjusted odds ratio: 1.44; 95% confidence interval: 1.05-1.98).

CONCLUSIONS

Verbal abuse should be avoided during pregnancy to preserve the newborn's auditory function.

Maturation of auditory brainstem response in early term infants at 6 weeks and 9 months

BACKGROUND

Emerging evidence indicates that infants who were born between 37 and 38 weeks of gestation are at higher risk of adverse long-term neurodevelopmental outcomes. Yet little is known about the auditory neural maturation during the first year of their life.

AIM

To compare the development of auditory brainstem response in early term (ET, 37-38 weeks gestational age, GA) and full term (FT, 39-41 weeks GA) infants.

METHODS

126 infants received ABR testing at 6 weeks. 107 of them returned for the second assessment at 9 months, among which, 93 completed the ABR recordings. Comparison of the ABR variables were made depending on gestational age.

RESULTS

Analysis of covariance (ANCOVA) was used to identify the differences in ABR outcomes between two groups. After controlling for confounders, latencies for wave III, V and I-III, III-V and I-V intervals were prolonged in ET group compared with FT group at 6 weeks (all p<0.03). ABR parameters of both groups developed as the infants got older. At 9 months, ET infants remain showing the longer wave V latency and I-V interval (all p < 0.02) than FT infants.

CONCLUSION

During early postnatal life, ET has a different pattern of functional auditory brainstem development comparing with FT infants. The prolonged auditory conduction time suggests less mature of the central auditory system in ET infants before 9 months.

Hearing Loss and Failed Newborn Hearing Screen

Hearing loss is the most common congenital defect. With early diagnosis and intervention, we are able to improve speech and language outcomes in this population. In this article, we discuss the implications of the newborn hearing screen, as well as diagnostic interventions, management, and intervention, and the increasing role of congenital cytomegalovirus screening.

Auditory brainstem response in very preterm, moderately preterm and late preterm infants

BACKGROUND

Auditory brainstem response across preterm infants help in understanding difference if any in auditory maturation.

OBJECTIVE

To analyze and compare absolute and interpeak latencies of ABR in very preterm, moderate preterm and late preterm infants at term age.

METHOD

ABR traces were obtained from 148 ears of preterm infants (52 of very preterm, 44 of moderately preterm & 52 of late preterm) at term age. ABR was recorded with 11.1/s clicks at different intensity levels.

RESULTS

Absolute latencies of peak I, III, V and interpeak latencies of peak I-V, I-III and III-V were analyzed and compared between three preterm groups. One way ANOVA was used to compare ABR parameters between three groups of preterm infants and also to compare ABR parameters across various gestation ages. There were no overall differences in absolute latencies, interpeak latencies and amplitude of ABR between preterm groups and across various gestation ages (P>0.05). Pearson correlation was used to find the correlation between gestation age and ABR parameters. However, no correlation was found. ABRs were similar among preterm groups at term age which reflects that the brainstem maturation is similar among preterm groups.

CONCLUSION

Gestational age at birth does not seem to influence absolute and interpeak latencies of ABR at term age. In preterm neonates, the findings lead to suggest that maturation of auditory pathway occurs in a similar manner in preterm infants regardless of gestational age at birth. We conclude that preterm birth alone as a risk factor does not appear to have any marked effect on the development of ABR at term age.

Acoustic Reflex Testing in Neonatal Hearing Screening and Subsequent Audiological Evaluation

PURPOSE

The aims of the study were to examine the acoustic reflex screening and threshold in healthy neonates and those at risk of hearing loss and to determine the effect of birth weight and gestational age on acoustic stapedial reflex (ASR).

METHOD

We assessed 18 healthy neonates (Group I) and 16 with at least 1 risk factor for hearing loss (Group II); all of them passed the transient evoked otoacoustic emission test that assessed neonatal hearing. The test battery included an acoustic reflex screening with activators of 0.5, 1, 2, and 4 kHz and broadband noise and an acoustic reflex threshold test with all of them, except for the broadband noise activator.

RESULTS

In the evaluated neonates, the main risk factors were the gestational age at birth and a low birth weight; hence, these were further analyzed. The lower the gestational age at birth and birth weight, the less likely that an acoustic reflex would be elicited by pure-tone activators. This effect was significant at the frequencies of 0.5, 1, and 2 kHz for gestational age at birth and at the frequencies of 1 and 2 kHz for birth weight. When the broadband noise stimulus was used, a response was elicited in all neonates in both groups. When the pure-tone stimulus was used, the Group II showed the highest acoustic reflex thresholds and the highest percentage of cases with an absent ASR. The ASR threshold varied from 50 to 100 dB HL in both groups. Group II presented higher mean ASR thresholds than Group I, this difference being significant at frequencies of 1, 2, and 4 kHz.

CONCLUSIONS

Birth weight and gestational age at birth were related to the elicitation of the acoustic reflex. Neonates with these risk factors for hearing impairment were less likely to exhibit the acoustic reflex and had higher thresholds.

Cortical auditory evoked potentials in full-term and preterm neonates

Purpose

To measure the exogenous components of the cortical auditory evoked potential (CAEP) in term and preterm newborns and compare them considering the variables latency and amplitude.

Methods

This is a cross-sectional, prospective, comparative, contemporary study. One hundred twenty-seven newborns were evaluated; 96 of these were included in the study after analysis of the exams by three referees. Participants were divided into two groups: Term Group: 66 infants and Preterm Group: 30 neonates. The recordings of CAEP were performed using surface electrodes with newborns comfortably positioned in the lap of their mothers and/or guardians in natural sleep. To this end, binaural verbal stimuli were presented with /ba/ as the frequent stimulation and /ga/ the rare stimulus, at an intensity of 70 dB HL, through insert earphones. The presence or absence of exogenous components and the latency and amplitude of P1 and N1 were analyzed in both groups. Pertinent tests were used in the statistical analysis of data.

Results

The latency of the waves P1 and N1 was smaller in participants in the Term Group. However, there were no statistically significant differences in the amplitude of P1 and N1 between the groups. No difference between the groups was found when comparing the presence and absence of the components P2 and N2.

Conclusion

It is possible to measure the CAEP in term and preterm neonates. There was influence of the maturational process only on the measure of latency of the components P1, binaurally, and N1, in the left ear, which were smaller in participants in the Term Group.

Auditory brainstem maturation in normal-hearing infants born preterm: a meta-analysis

AIM

Children born preterm often have neurodevelopmental problems later in life. Abnormal maturation of the auditory brainstem in the presence of normal hearing might be a marker for these problems. We conducted a meta-analysis of auditory brainstem response (ABR) latencies at term age to describe differences in auditory brainstem maturation between normal-hearing preterm and term-born infants.

METHOD

Computerized databases were searched for studies published between 1995 and 2014 that reported ABR measurements at term age in infants born preterm in a case-control design. Five peaks reflect the conduction of a neural signal along the brainstem auditory pathway. We collected I to V interpeak latency data, and III to V interpeak latency data, which refers to the more central part of the pathway.

RESULTS

Preterm-born infants' III to V interval is significantly longer compared to infants born at term (0.081ms, effect-size=0.974), which also reflects on the I to V interval. Moreover, significantly increased ABR interpeak latencies of infants born preterm are related to lower gestational age and the need for neonatal intensive care treatment.

INTERPRETATION

The delayed conduction time towards and into the auditory brainstem at term age suggests atypical maturation of the brainstem in normal-hearing infants born preterm. Both the duration of gestation and the consequences of the preterm birth (intensive care needed) negatively affect maturation of the auditory brainstem, which may influence later development.

Age-Related Maturation of Wave V Latency of Auditory Brainstem Response in Children

BACKGROUND AND OBJECTIVES

Auditory brainstem response (ABR) is a noninvasive measurement of a stimulus-locked, synchronous electrical event. ABR provides information concerning the functional integrity of brainstem nuclei. Age is a key factor in the interpretation of ABR peak latency among different age groups. Progressively with time it follows a "maturation pattern" during which latencies decrease. Wave V is very prominent and reliable for detection of threshold in children. The present study was performed to see the effect of age related auditory maturation on ABR wave V latency in children.

SUBJECTS AND METHODS

The study involved 80 subjects ranging in age from birth to 12 years. The subjects were divided equally into eight age groups. ABR were elicited by an acoustic click stimuli, brainstem responses collected through electrode and recorded at the same time. Latency of wave V was acknowledged.

RESULTS

Wave V latency decreased rapidly in early childhood, became slower after 3 years of age and completely matured by 12 years of age. There was no significant difference in latency of wave V between the ears with age.

CONCLUSIONS

There is a distinct maturation pattern of wave V latency in ABR for both ears. ABR is a reliable test to assess the functional maturation of wave V in children.

Longitudinal Comparison of Auditory Steady-State Evoked Potentials in Preterm and Term Infants: The Maturation Process

Introduction  Preterm neonates are at risk of changes in their auditory system development, which explains the need for auditory monitoring of this population. The Auditory Steady-State Response (ASSR) is an objective method that allows obtaining the electrophysiological thresholds with greater applicability in neonatal and pediatric population.

Objective  The purpose of this study is to compare the ASSR thresholds in preterm and term infants evaluated during two stages.

Method  The study included 63 normal hearing neonates: 33 preterm and 30 term. They underwent assessment of ASSR in both ears simultaneously through insert phones in the frequencies of 500 to 4000Hz with the amplitude modulated from 77 to 103Hz. We presented the intensity at a decreasing level to detect the minimum level of responses. At 18 months, 26 of 33 preterm infants returned for the new assessment for ASSR and were compared with 30 full-term infants. We compared between groups according to gestational age.

Results  Electrophysiological thresholds were higher in preterm than in full-term neonates ( p  < 0.05) at the first testing. There were no significant differences between ears and gender. At 18 months, there was no difference between groups ( p  > 0.05) in all the variables described.

Conclusion  In the first evaluation preterm had higher thresholds in ASSR. There was no difference at 18 months of age, showing the auditory maturation of preterm infants throughout their development.

Brainstem auditory evoked responses in foals: reference values, effect of age, rate of acoustic stimulation, and neurologic deficits

Background

Age and rate of acoustic stimulation affect peak latencies in brainstem auditory evoked responses (BAER) in humans. Those effects are unknown in foals.

Hypothesis/Objectives

Our goals were to (1) establish reference values for BAER in foals by using 3 different stimulation protocols, (2) evaluate the effects of age and stimulation frequencies on BAER tracing in foals up to 6 months old, and (3) compare the data with BAER obtained from foals with central nervous system (CNS) disorders.

Animals

Thirty‐nine neurologically normal foals and 16 foals with neurologic diseases.

Methods

Prospective observational clinical study. BAER recorded by using 3 protocols of stimulation (11.33 repetitions per second [Hz]/70 decibel normal hearing level [dBNHL]; 11.33 Hz/90 dBNHL; 90 Hz/70 dBNHL).

Results

No effect of age was observed in normal foals (P > .005). No significant difference was observed for latencies and interpeak latencies (IPL) when comparing foals with neurologic diseases and normal foals (P > .05), but 78.6% of foals with neurologic diseases had an asymmetry in their tracing, reflecting a difference in conduction time between the left and right side of the brainstem. Increasing the stimulation rate did not improve detection of CNS disorders.

Conclusions and Clinical Importance

We propose BAER reference values for foals up to 6 months of age by using 3 protocols. Most foals with neurologic deficits had abnormal BAER tracing.

Acoustic reflex on newborns: the influence of the 226 and 1,000 Hz probes

PURPOSE

To analyze the occurrence of acoustic reflex and its threshold on newborns using the 226 and 1,000 Hz probes.

METHODS

Thirty-six newborns with "PASS" results in newborn hearing screening and tympanogram with one or two peaks for both probe tones were included. Group I comprised 20 full-term newborns without risk indicator for hearing loss, and Group II comprised 16 newborns with at least one risk indicator. The study about ipsilateral acoustic reflex thresholds was conducted in 500, 1,000, 2,000, and 4,000 Hz.

RESULTS

The groups presented the acoustic reflex thresholds between 50 and 100 dB for both probe tones. In the comparison between the probes, there were differences in all frequencies evaluated in Group I, with the lowest threshold mean for the 1,000 Hz probe. In Group II, differences were detected at 2,000 Hz. The mean acoustic reflex thresholds were similar in both groups for the 226 Hz probe. There was a difference for the 1,000 Hz probe in all tested frequencies. The percentage of response was higher in both groups for the 1,000 Hz probe. The kappa test showed extremely poor agreement in the comparison of results between both probes.

CONCLUSION

The occurrence of acoustic reflex was higher in newborns and its thresholds were lower with the 1,000 Hz probe both for healthy newborns and for newborns at risk.

Auditory brainstem response in term and preterm infants with neonatal complications: the importance of the sequential evaluation

Introduction Literature data are not conclusive as to the influence of neonatal complications in the maturational process of the auditory system observed by auditory brainstem response (ABR) in infants at term and preterm.

Objectives Check the real influence of the neonatal complications in infants by the sequential auditory evaluation.

Methods Historical cohort study in a tertiary referral center. A total of 114 neonates met inclusion criteria: treatment at the Universal Neonatal Hearing Screening Program of the local hospital; at least one risk indicator for hearing loss; presence in both evaluations (the first one after hospital discharge from the neonatal unit and the second one at 6 months old); all latencies in ABR and transient otoacoustic emissions present in both ears.

Results The complications that most influenced the ABR findings were Apgar scores less than 6 at 5 minutes, gestational age, intensive care unit stay, peri-intraventricular hemorrhage, and mechanical ventilation.

Conclusion Sequential auditory evaluation is necessary in premature and term newborns with risk indicators for hearing loss to correctly identify injuries in the auditory pathway.

Abnormal auditory pathways in PHOX2B mutation positive congenital central hypoventilation syndrome

Background

Congenital central hypoventilation syndrome (CCHS) is a rare disease characterized by severe central hypoventilation due to abnormal autonomic control of breathing. The PHOX2B gene, mutations of which define the disease, is expressed in a group of nuclei located in brainstem areas. Pathways controlling breathing and auditory pathways traverse very similar anatomic structures. In the present study, we measure brainstem auditory evoked potentials (BAEP) to assess auditory pathways in CCHS and investigate to which extent brainstem auditory pathways are also affected.

Methods

BAEPs were measured in 15 patients with PHOX2B mutations positive CCHS (8 boys and 7 girls. mean age 6.3 yrs ± 5) as part of their regular follow-up in the Centre of reference for central hypoventilation (Robert Debré University Hospital. Paris. France).

Results

BAEP responses were found normal in nine patients (60% of the study group) and abnormal in the other six (40%). Abnormal BAEPs which resulted from brainstem dysfunction were found in three patients (20%).

Conclusion

Dysfunction of brainstem auditory pathways can be observed in CCHS. However, auditory evoked responses can be normal in the disease, therefore suggesting much more complex yet-to-be determined interactions between pathways and functions of central control of breathing and of control of hearing.

[The hearing function in the premature infants]

The present review of the literature is focused on the morphological and functional aspects of antenatal ontogenesis of the hearing system with special reference to the peculiar features of its formation during the post-natal period in the premature infants. In this context, the results of the objective psychoacoustic investigation s are considered (including those obtained by such methods as threshold audiometry, verbal and non-verbal tests, evaluation of central auditory processing of the sound information). Also presented are the results of the objective methods of hearing investigations (acoustic impedancometry, registration of optoacoustic emission and auditory evoked potentials). The underdevelopment of the hearing system in the premature infants manifests itself as the specific functional features of all its components. Their parameters are presented with reference to dynamics of their formation. In addition, the problem of central auditory processing of the disorders that are very likely to be present in the premature infants are discussed.

Correlation of the findings of auditory steady-state evoked potential and of behavioral hearing assessment in infants with sensorineural hearing loss

PURPOSE

To correlate the findings of an open-field audiometry with the thresholds of steady-state auditory-evoked potentials (SSAEPs) found in infants of up to 6 months of age with sensorineural hearing loss.

METHODS

This study included 19 infants with sensorineural hearing loss (8 males and 11 females), with minimum age of 2 months and maximum age of 6 months. The SSAEPs were assessed at 500 and 2000 Hz, and the audiometry was performed in open field through observation of behavioral responses to sound stimuli, at the same frequencies.

RESULTS

We observed a significant correlation between the findings of both tests conducted at 500 and 2000 Hz, with p-values of 0.002 and 0.013, respectively. There was no statistical difference between ears (p=0.532) and genders (p=0.615).

CONCLUSION

We conclude that there was a significant correlation between the SSAEP thresholds and the findings of the open-field audiometry. Therefore, we can affirm that the SSAEPs are a viable examination, able to predict the degree and configuration of hearing loss in infants of up to 6 months of age, and that they can be included in the clinical routine of hearing assessments conducted in children.

Auditory Brainstem Response: reference-values for age

PURPOSE: To study the absolute latencies of waves I , III and V and interpeak I-III , III-V and I-V of Auditory brainstem responses obtained in preterm newborns in relation to post-conceptual age, term newborns and six months of age infants, establishing reference values for each age group. METHODS: Retrospective study realized through the analysis of tests performed on 80 infants divided into four groups, being the group one composed per newborns assessed between 35 and 36 weeks post-conceptual age; group two by newborns assessed between 37 and 38 weeks; group three with newborns reviewed between 39 to 40 weeks; and group four with infants evaluated with six months. RESULTS: The wave I absolute latency in the group one was 1.81 ms, decreasing to 1.79 ms in groups two and three, and to 1.70 ms in group four. The wave III latency in group one was 4.74 ms, decreasing to 4.62 ms in group two, to 4.56 ms in the group three and to 4.37 ms in the group four. The wave V latency in group one was 7.14 ms, in the group two it was 7.05 ms, in the group three 6.90 ms; and in the group four it was 6.50 ms. Interpeak latencies were also decreased in all groups. CONCLUSION: The latencies studied decreased with the increasing age and were similar values with the international literature.

Auditory brainstem response in neonates: influence of gender and weight/gestational age ratio

OBJECTIVE

To investigate the influence of gender and weight/gestational age ratio on the Auditory Brainstem Response (ABR) in preterm (PT) and term (T) newborns.

METHODS

176 newborns were evaluated by ABR; 88 were preterm infants - 44 females (22 small and 22 appropriate for gestational age) and 44 males (22 small and 22 appropriate for gestational age). The preterm infants were compared to 88 term infants - 44 females (22 small and 22 appropriate for gestational age) and 44 males (22 small and 22 appropriate for gestational age). All newborns had bilateral presence of transient otoacoustic emissions and type A tympanometry.

RESULTS

No interaural differences were found. ABR response did not differentiate newborns regarding weight/gestational age in males and females. Term newborn females showed statistically shorter absolute latencies (except on wave I) than males. This finding did not occur in preterm infants, who had longer latencies than term newborns, regardless of gender.

CONCLUSIONS

Gender and gestational age influence term infants' ABR, with lower responses in females. The weight/gestational age ratio did not influence ABR response in either groups.

Normatização do potencial evocado auditivo de tronco encefálico em recém-nascidos

OBJETIVO: normatizar os achados do equipamento de PEATE da Clínica de Fonoaudiologia da instituição de origem, em recém-nascidos. MÉTODOS: trata-se de um estudo transversal, exploratório não experimental do qual participaram quarenta recém-nascidos, sem indicadores de risco para a deficiência auditiva, que passaram na triagem auditiva neonatal, divididos de acordo com a idade, em semanas (G1, G2, G3 e G4). Para a coleta de dados foi utilizado o equipamento Smart EP-Intelligent Hearing Systems com estímulo clique. RESULTADOS: a média dos valores das latências absolutas das ondas I, III e V de acordo com a idade são, respectivamente: G1=1,62ms, 4,39ms, 6,8ms; G2=1,62ms, 4,4ms, 6,79ms; G3=1,56ms, 4,39ms, 6,74ms; G4=1,54ms, 4,2ms, 6,53ms. Na mesma ordem, a média dos valores das latências interpico I-III, III-V e I-V foram: 2,77ms, 2,42ms e 5,19ms; 2,78ms, 2,39ms e 5,17ms; 2,83ms, 2,35ms e 5,18ms; 2,66ms, 2,33ms e 4,99ms. CONCLUSÃO: as latências absolutas diminuíram com o aumento da idade tendo média de 1,58ms para a onda I, 4,34ms para a onda III e 6,71ms para a onda V. Da mesma forma, as médias dos interpicos I-III, III-V e I-V foram menores no G4 e obteve-se médias, no primeiro mês, de 2,76ms, 2,37ms e 5,13ms.

Caracterização eletrofisiológica da audição em prematuros nascidos pequenos para a idade gestacional

OBJETIVO: Caracterizar as respostas do Potencial Evocado Auditivo de Tronco Encefálico em recém-nascidos pré-termo pequenos para idade gestacional, comparando-as às de recém-nascidos pré-termo adequados para idade gestacional, verificando se a condição de pequeno para a idade gestacional é indicador de risco para alteração auditiva retrococlear. MÉTODOS: Estudo multicêntrico transversal prospectivo. Avaliou-se 72 recém-nascidos pré-termo, 35 pequenos e 37 adequados para idade gestacional de ambos os gêneros, com idade gestacional de 30 a 36 semanas e avaliados na pré-alta hospitalar, com presença de emissões otoacústicas evocadas por estímulo transiente e timpanometria tipo A. A análise quantitativa dos dados foi feita baseada na média e desvio-padrão das latências das ondas I, III, V e interpicos I-III, III-V, I-V para cada grupo. Para análise qualitativa, os resultados dos potenciais evocados auditivos foram classificados em alterado ou normal mediante a análise das latências absolutas das ondas I, III, V e dos interpicos I-III, III-V, I-V, considerando-se a faixa etária no momento do exame. RESULTADOS: Evidenciaram-se alterações em 32 crianças (44,44% do total), sendo 15 recém-nascidos pequenos (43%) e 17 adequados (46%), não havendo diferença entre os grupos. Dos 15 recém-nascidos pequenos com potencial evocado auditivo alterado, seis tiveram como risco auditivo apenas o fato de ser pequeno para a idade gestacional. No grupo adequado para idade gestacional, houve maior ocorrência de alterações no gênero masculino. CONCLUSÃO: Não houve diferença nas respostas do potencial evocado auditivo entre os recém-nascidos pré-termo pequenos e adequados, de forma que a condição pequeno não se revelou risco para alteração retrococlear.

Sex and gestational age effects on auditory brainstem responses in preterm and term infants

BACKGROUND

Some studies find delayed development of the auditory brainstem in preterm infants, but others do not.

AIM

To compare auditory brainstem responses (ABRs) in healthy preterm and term infants depending on sex and gestational age (GA).

METHODS

Participants were 111 preterm (27-36weeks GA) and 92 term (37-41weeks GA) infants. ABR tests were conducted at 6weeks (corrected age if preterm).

RESULTS

There were no overall differences between term and preterm groups in ABRs. However, males showed longer latencies for waves III, V, and I-III, III-V, and I-V intervals and smaller amplitudes for wave III and V than females in both preterm and term groups (all p values≤.01). A 3-way interaction between group, sex, and GA (p<.05) showed that preterm males with later GA had longer wave I-V interval, whereas term females with later GA showed shorter wave I-V interval. Growth velocity predicted wave I-V interval in preterm infants, controlling for other factors (male: p=.07, female: p<.05).

CONCLUSION

ABRs in preterm and term infants were similar at 6weeks (corrected age if preterm), but males had less advanced ABRs than females. More rapid growth predicted less mature ABR in later GA preterm infants in this setting where they were unlikely to receive extra iron. The roles of GA, growth, and iron balance in ABR development warrant further study.

Impact of gestational age on neonatal hearing screening in vaginally-born late-preterm and early-term infants

BACKGROUND

Late-preterm and early-term (LP-ET) infants, defined herein as 35(0)-37(6) weeks' gestation, often fail on 1st otoacoustic emissions (OAE) test.

HYPOTHESIS

LP-ET infants fail more than term infants (38(0)-42 weeks' gestation) on the 1st OAE test. Aim : To evaluate the effect of gestational age on the 1st OAE test.

METHODS

We studied 1,572 vaginally-delivered (VD) infants ≥35 weeks' gestation (1.1.2011-30.9.2011). Perinatal and neonatal variables and results of OAE tests were recorded.

RESULTS

LP-ET infants, compared to full-term infants, had a significantly 2-fold higher need for repeated hearing tests: 80.2 versus 43.3 tests/1,000 neonates, respectively (p = 0.026). Univariate analysis showed that late prematurity and age at 1st OAE were significantly associated with failure on 1st OAE. At age 24-42 h, failure on 1st OAE was 2-fold higher in the LP-ET infants than in full-term infants: 9.4 versus 4.7% (p = 0.02). Risk for failure on 1st OAE was age-dependent: 9-fold higher when 1st OAE was performed at 24-42 h of age (5.3%) versus 0.6% after age 42 h. Multivariate analysis showed that variables that were independently significantly associated with failure on 1st OAE included late prematurity (OR 2.0 (1.1-3.7)) and age at 1st OAE (OR 9.2 (1.2-70.7)).

CONCLUSIONS

Compared to term infants, VD LP-ET infants had 2-fold higher rates of failure on 1st OAE (up to 42 h of life) and needed repeated hearing tests. Failure rates after 42 h become negligible in both groups. In VD LP-ET infants, 1st OAE is better performed after 42 h of age.

Brainstem auditory response findings in term neonates in intensive care unit

OBJECTIVES

Whether term infants in neonatal intensive care unit (NICU) have brainstem auditory abnormalities remains to be determined. This study aimed to detect any abnormality in brainstem auditory function in term neonates who are admitted to NICU.

METHODS

From a NICU, we recruited 55 term neonates with various perinatal problems. They were studied during the first week after birth using brainstem auditory evoked response (BAER), and the results were compared with normal term controls.

RESULTS

Wave I and III latencies and I-III interpeak interval of the evoked response in the NICU term neonates were similar to those in the controls. Wave V latency and I-V and III-V interpeak intervals tended to be increased at 21/s clicks. The increase was more obvious at higher rates 51 and 91/s. Analysis of variance revealed that at 21/s clicks only III-V interval was significantly increased (p < 0.05). At 51 and 91/s clicks, wave V latency and III-V and I-V intervals were significantly increased (p < 0.05-0.01). The rates of the abnormalities were seen more at higher than at lower click rates. The amplitudes of waves I, III, and V in the NICU neonates were all slightly reduced, but none differed significantly from the controls.

CONCLUSIONS

There are some abnormalities in BAER in term neonates in NICU, suggesting functional abnormality in the auditory brainstem in NICU infants.

Potencial evocado auditivo de tronco encefálico em crianças encaminhadas de um programa de triagem auditiva neonatal

OBJETIVOS: descrever os achados do exame de potencial evocado auditivo de tronco encefálico (PEATE) de crianças de um programa de triagem auditiva neonatal e analisar a diferença de gênero e a interferência da idade nas medidas da latência das ondas do PEATE. MÉTODOS: para tal foram avaliadas 41 crianças com idade entre um a nove meses, referenciadas de um Programa de Triagem Municipal ao Centro de Estudos de Educação e Saúde (CEES) na cidade de Marília, SP no ano de 2010. RESULTADOS: foi observado resultado normal em 31 (75,6%) e alterado em 10 (24,4%) pacientes. Nesses últimos foram observadas alterações principalmente do tipo condutiva unilateral e bilateral. Observou-se também que a medida que a idade aumenta a latência das ondas diminui numa correlação inversa. CONCLUSÕES: o diagnóstico das crianças deste Programa de Triagem Auditiva Neonatal foi precoce. Os resultados do PEATE poderão servir de referência para outros estudos deste âmbito. O PEATE nesta população permite um melhor direcionamento da conduta e intervenção e aconselhamento específico aos familiares.

Electrophysiological study of hearing in full-term small-for-gestational-age newborns

PURPOSE: To describe the Brainstem Auditory Evoked Potential (BAEP) results of full-term small-for-gestational-age newborns, comparing them to the results of full-term appropriate-for-gestational-age newborns, in order to verify whether the small-for-gestational-age condition is a risk indicator for retrocochlear hearing impairment. METHODS: This multicentric prospective cross-sectional study assessed 86 full-term newborns - 47 small- (Study Group) and 39 appropriate-for-gestational-age (Control Group - of both genders, with ages between 2 and 12 days. Newborns with presence of transient evoked otoacoustic emissions and type A tympanometry were included in the study. Quantitative analysis was based on the mean and standard deviation of the absolute latencies of waves I, III and V and interpeak intervals I-III, III-V and I-V, for each group. For qualitative analysis, the BAEP results were classified as normal or altered by analyzing these data considering the age range of the newborn at the time of testing. RESULTS: In the Study Group, nine of the 18 (38%) subjects with altered BAEP results had the condition of small-for-gestational-age as the only risk factor for hearing impairments. In the Control Group, seven (18%) had altered results. Female subjects from the Study Group tended to present more central alterations. In the Control Group, the male group tended to have more alterations. CONCLUSION: Full-term children born small or appropriate for gestational age might present transitory or permanent central hearing impairments, regardless of the presence of risk indicators.

Modifications of auditory brainstem responses (ABR): observations in full-term and pre-term newborns

OBJECTIVE

In this study, we have evaluated by means of auditory brainstem responses (ABR), in a population derived from a newborn hearing screening protocol, some aspects of maturation of the auditory pathways in the first months after birth, and the possible repercussions on early treatment.

MATERIALS AND METHODS

In this retrospective study newborns were recruited through our hearing screening program, and an ABR evaluation was performed on 339 newborns, that had risk factors or had failed the screening, or both. Such population was divided in two groups for statistical analysis purposes: full-term and pre-term. The initial ABR was pathological in 70 infants.

RESULTS

We observed an improvement over time of the estimated hearing threshold in follow-up ABRs in 43 newborns (26 in the full-term group, mean improvement 27.9 dB SPL, and 17 in the pre-term group, mean improvement 34.6 dB SPL); such an improvement might be related to a maturation of the auditory pathways that was not complete at birth.

CONCLUSIONS

The auditory system might not be completely developed at birth, and might require some months to complete; hence any early clinical approach should consider the possibility of an overtreatment, and any therapeutic strategy should only be considered once the diagnosis is certain and definitive.

The maturational process of the auditory system in the first year of life characterized by brainstem auditory evoked potentials

The study of brainstem auditory evoked potentials (BAEP) allows obtaining the electrophysiological activity generated in the cochlear nerve to the inferior colliculus. In the first months of life, a period of greater neuronal plasticity, important changes are observed in the absolute latency and inter-peak intervals of BAEP, which occur up to the completion of the maturational process, around 18 months of life in full-term newborns, when the response is similar to that of adults.

OBJECTIVE

The goal of this study was to establish normal values of absolute latencies for waves I, III and V and inter-peak intervals I-III, III-V and I-V of the BAEP performed in full-term infants attending the Infant Hearing Health Program of the Speech-Language Pathology and Audiology Course at Bauru School of Dentistry, Brazil, with no risk history for hearing impairment.

MATERIAL AND METHODS

The stimulation parameters were: rarefaction click stimulus presented by the 3ª insertion phone, intensity of 80 dBnHL and a rate of 21.1 c/s, band-pass filter of 30 and 3,000 Hz and average of 2,000 stimuli. A sample of 86 infants was first divided according to their gestational age in preterm (n=12) and full-term (n=74), and then according to their chronological age in three periods: P1: 0 to 29 days (n=46), P2: 30 days to 5 months 29 days (n=28) and P3: above 6 months (n= 12).

RESULTS

The absolute latency of wave I was similar to that of adults, generally in the 1st month of life, demonstrating a complete process maturity of the auditory nerve. For waves III and V, there was a gradual decrease of absolute latencies with age, characterizing the maturation of axons and synaptic mechanisms in the brainstem level.

CONCLUSION

Age proved to be a determining factor in the absolute latency of the BAEP components, especially those generated in the brainstem, in the first year of life.

Incidence and clinical value of prolonged I-V interval in NICU infants after failing neonatal hearing screening

Infants admitted to neonatal intensive care units (NICUs) have a higher incidence of perinatal complications and delayed maturational processes. Parameters of the auditory brainstem response (ABR) were analyzed to study the prevalence of delayed auditory maturation or neural pathology. The prevalence of prolonged I–V interval as a measure of delayed maturation and the correlation with ABR thresholds were investigated. All infants admitted to the NICU Sophia Children’s Hospital between 2004 and 2009 who had been referred for ABR measurement after failing neonatal hearing screening with automated auditory brainstem response (AABR) were included. The ABR parameters were retrospectively analyzed. Between 2004 and 2009, 103 infants were included: 46 girls and 57 boys. In 58.3% (60 infants) of our population, the I–V interval was recordable in at least one ear at first diagnostic ABR measurement. In 4.9%, the I–V interval was severely prolonged. The median ABR threshold of infants with a normal or mildly prolonged I–V interval was 50 dB. The median ABR threshold of infants with a severely prolonged I–V interval was 30 dB. In conclusion, in case both peak I and V were measurable, we found only a limited (4.9%) incidence of severely prolonged I–V interval (≥0.8 ms) in this high-risk NICU population. A mild delay in maturation is a more probable explanation than major audiologic or neural pathology, as ABR thresholds were near normal in these infants.

Risk factors for elevation of ABR threshold in NICU-treated infants

OBJECTIVE

Several risk factors for hearing impairment among infants treated in the neonatal intensive care unit (NICU) have been reported, but there have been few studies that show the correlation strength between the risk factors in NICU-treated infants and hearing impairment in childhood. The aim of this study was to clarify the relationship between risk factors in NICU-treated infants and a deteriolation of auditory brainstem response (ABR) threshold in their childhood.

METHODS

One hundred one NICU-treated infants with ABR threshold of 50 dBnHL or more underwent 2nd ABR test at 20 months after delivery. Multiple regression analysis was performed with ABR threshold change as an objective variable and risk factors as explanatory variables.

RESULTS

Two ABR tests of the 101 infants resulted in that 7 showed an elevation of ABR threshold by 20 dB, 70 showed a drop of ABR threshold by 20 dB, and 24 showed no significant change. Multiple regression analysis revealed that the factors contributing to the elevation of ABR threshold were congenital diaphragmatic hernia, severe respiratory disease, and a high C-reactive protein (CRP) level.

CONCLUSIONS

In the infants treated in NICU, an incidence of ABR threshold of 50 dBnHL or more was 9.0%, and 6.9% of the infants with the ABR threshold abnormality showed a significant elevation of ABR threshold in their childhood. Factors significantly related to an elevation of ABR threshold were a history of congenital diaphragmatic hernia, severe respiratory disease, and elevation of CRP. In infants with such factors, periodical examination of hearing is required.

Fitting model of ABR age dependency in a clinical population of normal hearing children

The purpose of this study was to present a simple and powerful fitting model that describes age-dependent changes of auditory brainstem responses (ABR) in a clinical population of normal hearing children. A total of 175 children (younger than 200 weeks postconceptional age) were referred for audiologic assessment with normal ABR results. ABR parameters of normal hearing children between 2003 and 2008 were included. The results of the right ears recorded at 90 dB nHL were analyzed. A simple and accurate fitting model was formulated based on these data. A very similar age-dependent effect was found for peaks III and V, and I–III and I–V intervals; latencies decrease as postconceptional age increases. It shows that the total age-dependent effect will be completed after 1.5–2 years. The age-dependent effect can be modeled by a relatively simple and accurate exponential function. This fitting model can be easily implemented to analyze ABR results of infants in daily clinical practice. We speculate about the underlying physiological processes.