Auditory neural myelination is associated with early childhood language development in premature infants

Ambient sound stimulation tunes axonal conduction velocity by regulating radial growth of myelin on an individual, axon-by-axon basis

Adaptive myelination is the emerging concept of tuning axonal conduction velocity to the activity within specific neural circuits over time. Sound processing circuits exhibit structural and functional specifications to process signals with microsecond precision: a time scale that is amenable to adjustment in length and thickness of myelin. Increasing activity of auditory axons by introducing sound-evoked responses during postnatal development enhances myelin thickness, while sensory deprivation prevents such radial growth during development. When deprivation occurs during adulthood, myelin thickness was reduced. However, it is unclear whether sensory stimulation adjusts myelination in a global fashion (whole fiber bundles) or whether such adaptation occurs at the level of individual fibers. Using temporary monaural deprivation in mice provided an internal control for a) differentially tracing structural changes in active and deprived fibers and b) for monitoring neural activity in response to acoustic stimulation of the control and the deprived ear within the same animal. The data show that sound-evoked activity increased the number of myelin layers around individual active axons, even when located in mixed bundles of active and deprived fibers. Thicker myelination correlated with faster axonal conduction velocity and caused shorter auditory brainstem response wave VI-I delays, providing a physiologically relevant readout. The lack of global compensation emphasizes the importance of balanced sensory experience in both ears throughout the lifespan of an individual.

Long-term neurodevelopmental follow-up of children exposed to pravastatin in utero

BACKGROUND

Preeclampsia, especially before term, increases the risk of child neurodevelopmental adverse outcomes. Biological plausibility, preclinical studies, and pilot clinical trials conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Obstetric-Fetal Pharmacology Research Centers Network support the safety and use of pravastatin to prevent preeclampsia.

OBJECTIVE

This study aimed to determine the effect of antenatal pravastatin treatment in high-risk pregnant individuals on their child's health, growth, and neurodevelopment.

STUDY DESIGN

This was an ancillary follow-up cohort study of children born to mothers who participated in the Obstetric-Fetal Pharmacology Research Centers Network pilot trials of pravastatin vs placebo in individuals at high risk of preeclampsia (ClinicalTrials.gov; identifier NCT01717586). After obtaining written informed consent (and assent as appropriate), the parent was instructed to complete the Child Behavior Checklist. To assess the child's motor, cognitive, and developmental outcomes, a certified and blinded study psychologist completed child motor, cognitive, emotional, and behavioral assessments using validated tools. Given the small number of individuals in the studies, the 10- and 20-mg pravastatin groups were combined into 1 group, and the results of the pravastatin group were compared with that of the placebo group.

RESULTS

Of 40 children born to mothers in the original trial, 30 (15 exposed in utero to pravastatin and 15 to placebo) were enrolled in this follow-up study. The time of follow-up, which was 4.7 years (interquartile range, 2.5-6.9), was not different between children in the pravastatin group and children in the placebo group. There was no difference in the child's body mass index percentiles per sex and corrected age, the rates of extremes of body mass index percentiles, or the report of any other medical or developmental complications between the 2 groups. No child born in the pravastatin group had any limitation in motor assessment compared with 2 children (13.3%) who walked with difficulty and 4 children (26.7%) who had reduced manual abilities in the placebo group. Moreover, children born to mothers who received pravastatin had a higher general mean conceptual ability score (98.2±16.7 vs 89.7±11.0; P=.13) and a lower frequency (15.4% vs 35.7%; P=.38) of having a score of <85 (ie, 1 standard deviation lower than the mean) compared with those in the placebo group. Finally, there was no difference in the parents' report on the Child Behavior Checklist between the 2 groups.

CONCLUSION

This study reported on the long-term neuromotor, cognitive, and behavioral outcomes among children exposed to pravastatin in utero during the second and third trimesters of pregnancy. Although the data were limited by the original trial's sample size, no identifiable long-term neurodevelopmental safety signal was evident with the use of pravastatin during pregnancy. This favorable neonatal risk-benefit analysis justifies continued research using pravastatin in clinical trials.

Normal reference values of low frequency specific air-conducted auditory brainstem responses among normal hearing children of different ages: A retrospective observational study

OBJECTIVES

To explore and compare the normal reference values (NRV) for low frequency specific air-conducted tone-burst auditory brainstem response (tb-ABR) among children of different ages and with normal hearing, because tb-ABR is often used to supplement the lack of click-evoked ABR (click-ABR) frequency but the NRV of this response threshold in different populations remain inconclusive.

METHODS

This retrospective observational study included children younger than 5 years of age with normal hearing in Hubei Province between November 2020 and September 2021. These children came to center of audiology for audiological examination including click-ABR due to different purposes and had accepted suggestion of tb-ABR test (0.5 kHz, 1 kHz). The children were divided into 5 groups according to age (0-12, 13-24, 25-36, 37-48, and 49-60 months of age), and 20 children (40 ears) met the inclusion criteria were selected from each group. The responding thresholds, peak latencies (PL), and inter-peak latencies (IPL) of the major waves were counted and compared in each group.

RESULTS

NRV of responding thresholds (dBnHL) in children aged 0-12, 13-24, 25-36, 37-48, and 49-60 months were 27.25 ± 9.47, 22.63 ± 5.31, 21.5 ± 5.33, 18.25 ± 5.83, and 21.63 ± 6.24 at 0.5 kHz, and 23.63 ± 7.16, 20.88 ± 7.06, 22 ± 4.21, 17.75 ± 6.09, and 21.38 ± 4.53 at 1 kHz, respectively. The response thresholds of children aged 0-12 months were significantly higher compared to children in other age groups at 0.5 kHz (all P < 0.05) and significantly higher than in children aged 37-48 months at 1 kHz (P < 0.05). There were significant differences among children of different ages in Wave III (P < 0.001) and Wave V (P < 0.001) in the peak latencies, and Waves I-III (P = 0.003) and Waves I-V (P < 0.001) in the inter-peak latencies at 0.5 kHz. Also, there were significant differences among children of different ages in Wave III and Wave V in the PL, and Waves I-III, Waves III-V, and Waves I-V in the IPL at 1 kHz (all P < 0.001).

CONCLUSION

The NRV of tb-ABR at 0.5 kHz and 1 kHz might differ among children of different ages. Newborn infants (<12 months old) might have a higher response threshold, while children aged 37-48 months might have a lower response threshold. However, it was a retrospective analysis with a small sample size, prospective contrast studies with larger samples are needed in the future.

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.

A randomized pilot clinical trial of pravastatin versus placebo in pregnant patients at high risk of preeclampsia

BACKGROUND

Preeclampsia remains a major cause of maternal and neonatal morbidity and mortality. Biologic plausibility, compelling preliminary data, and a pilot clinical trial support the safety and utility of pravastatin for the prevention of preeclampsia.

OBJECTIVE

We previously reported the results of a phase I clinical trial using a low dose (10 mg) of pravastatin in high-risk pregnant women. Here, we report a follow-up, randomized trial of 20 mg pravastatin versus placebo among pregnant women with previous preeclampsia who required delivery before 34+6 weeks' gestation with the objective of evaluating the safety and pharmacokinetic parameters of pravastatin.

STUDY DESIGN

This was a pilot, multicenter, blinded, placebo-controlled, randomized trial of women with singleton, nonanomalous pregnancies at high risk for preeclampsia. Women between 12+0 and 16+6 weeks of gestation were assigned to receive a daily pravastatin dose of 20 mg or placebo orally until delivery. In addition, steady-state pravastatin pharmacokinetic studies were conducted in the second and third trimesters of pregnancy and at 4 to 6 months postpartum. Primary outcomes included maternal-fetal safety and pharmacokinetic parameters of pravastatin during pregnancy. Secondary outcomes included maternal and umbilical cord blood chemistries and maternal and neonatal outcomes, including rates of preeclampsia and preterm delivery, gestational age at delivery, and birthweight.

RESULTS

Of note, 10 women assigned to receive pravastatin and 10 assigned to receive the placebo completed the trial. No significant differences were observed between the 2 groups in the rates of adverse or serious adverse events, congenital anomalies, or maternal and umbilical cord blood chemistries. Headache followed by heartburn and musculoskeletal pain were the most common side effects. We report the pravastatin pharmacokinetic parameters including pravastatin area under the curve (total drug exposure over a dosing interval), apparent oral clearance, half-life, and others during pregnancy and compare it with those values measured during the postpartum period. In the majority of the umbilical cord and maternal samples at the time of delivery, pravastatin concentrations were below the limit of quantification of the assay. The pregnancy and neonatal outcomes were more favorable in the pravastatin group. All newborns passed their brainstem auditory evoked response potential or similar hearing screening tests. The average maximum concentration and area under the curve values were more than 2-fold higher following a daily 20 mg dose compared with a 10 mg daily pravastatin dose, but the apparent oral clearance, half-life, and time to reach maximum concentration were similar, which is consistent with the previously reported linear, dose-independent pharmacokinetics of pravastatin in nonpregnant subjects.

CONCLUSION

This study confirmed the overall safety and favorable pregnancy outcomes for pravastatin in women at high risk for preeclampsia. This favorable risk-benefit analysis justifies a larger clinical trial to evaluate the efficacy of pravastatin for the prevention of preeclampsia. Until then, pravastatin use during pregnancy remains investigational.

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.

[Psychoacoustic methods in diagnosis of central auditory processing disorders in prematurely born children]

INTRODUCTION

The presence of numerous perinatal risk factors and comorbid pathology in prematurely born children, even in the absence of peripheral auditory deficit, can lead to disruptions in the processes of higher nervous sound information processing with the formation of central auditory disorders.

OBJECTIVE

Audiological assessment of the functional state of auditory system central parts in prematurely born children.

MATERIAL AND METHODS

The study involved 54 deeply premature born infants, which were divided into 3 groups depending on age (6-7, 8-9, and 10-11 years), 18 subjects in each group, and 70 healthy, term-born children of the corresponding age. In addition to the traditional audiological examination, all children underwent an assessment of functional state of the central parts of auditory system through a pause detection test (Random Gap Detection Test, RGDT); the perception of fast rhythmic sequences of stimuli, monaural low excess speech testing, binaural interaction test in alternating binaural speech format (ABS ), dichotic presentation of pairs of single digits, single digits and monosyllables, two-digit numerals, Russian matrix phrasal test in noise (RUMatrix) were studied.

RESULTS

Prematurely born infants of all age groups were significantly worse compared to control group (p<0.01) while having RGDT, a test for assessing the perception of fast rhythmic sequences of stimuli and dichotic binaural integration tests. Monaural intelligibility of monosyllabic words in silence in children of all three groups did not differ from normal values, but it suffered from contralateral use of noise interference in children aged 6-7. According to the RUMatrix test, legibility of phrases in noise was impaired in 65% of subjects. Test results in the ABS format revealed a significant violation of speech intelligibility (p<0.01) only in children of the younger age group.

CONCLUSION

In prematurely born children, there is a dysfunction of the central parts of the auditory system, which is multilevel in nature, partially leveling as children grow older. Moreover, the processes of temporary processing of acoustic information suffer to the greatest extent, not being compensated up to adolescence.

Neonatal brainstem auditory function associates with early receptive language development in preterm children

AIM

To study whether auditory function measured with brainstem auditory evoked potential and brainstem audiometry recordings in the neonatal period associates with language development 1 year later in preterm infants.

METHODS

This retrospective study included 155 preterm infants (birthweight ≤1500 g and/or birth ≤32 gestational weeks) born between 2007 and 2012 at the Turku University Hospital. Auditory function was recorded in neonatal period. Information of language development was gathered at the mean corrected age of 1 year by using the Finnish version of the MacArthur Communicative Development Inventory.

RESULTS

Slower auditory processing (longer interpeak interval, IPI I-V) in the right ear in the neonatal brainstem auditory evoked potential recording associated with smaller receptive lexicon size at 1 year (P = .043). Infants with longer IPI I-V were more likely to have a deviant (≤17 words) receptive lexicon size (P = .033). The absence of a contralateral response with right ear stimulation increased the risk for deviant lexicon size (P = .049).

CONCLUSION

The results suggest that impaired auditory function in the neonatal period in preterm infants may lead to a poorer receptive language outcome 1 year later. Auditory pathway function assessment provides information for the identification of preterm children at risk for weak language development.

Auditory Processing Differences in Toddlers With Autism Spectrum Disorder

Purpose Auditory processing measures have been used in an attempt to understand the relationship between neurological mechanisms and autism spectrum disorder (ASD) symptomatology in school-age children. The focus of the current study was to understand neural auditory processing in 2- to 3-year-olds with ASD. Method Auditory processing measures (click auditory brainstem responses and speech-evoked frequency-following responses) were hypothesized to differ between typically developing children (n = 18) and children with ASD (n = 18). Auditory processing measures were hypothesized to relate to language development in children with ASD. Results The current study found limited differences in auditory processing measures between the two groups. No relationships were found between auditory processing measures and language development measures. Conclusions Future research is necessary to characterize auditory processing in toddlers with ASD. Longitudinal approaches should be considered when studying auditory processing in children with ASD in order to explore its developmental relationship with ASD symptomatology.

Auditory and speech function after cochlear implantation in prelingually deaf children with white matter lesions

AIM

To explore how auditory and speech function developed post-cochlear implantation (pCI) in prelingually deaf children with white matter lesions (WML).

METHOD

Patients (41 males, 29 females; mean age at implantation 2y 11mo [SD 7.5mo], range 1y 8mo-5y) were divided into the following groups according to preoperative brain magnetic resonance imaging evaluation: mild WML, moderate WML, severe WML, and control. We assessed auditory and speech performance at baseline, 6 months, 12 months, and 24 months pCI. As well as auditory event-related potentials, topographic maps and electroencephalography source imaging were recorded and analysed at 24 months pCI.

RESULTS

For children with WML (any level), postoperative auditory or speech performance at 6 months was significantly below that of control participants. After stratification, auditory and speech performance was highly related to WML grading. Auditory or speech performance in mild WML or control groups was comparatively better than the moderate WML and severe WML groups. The recovery rate of speech performance fell behind that of the auditory perception. With the increasing severity of WML, N1 amplitude was significantly smaller with a consistent presentation in the topographic map, which was similar in the mild WML and control group. The dominant auditory centre was activated in the control or mild WML groups, but not in the moderate WML and severe WML groups.

INTERPRETATION

WML gradually affect auditory and speech development, and electrophysiological performance pCI in prelingually deaf children.

WHAT THIS PAPER ADDS

Auditory and speech performance in prelingually deaf children with white matter lesions (WML) was significantly worse than those without WML. Postoperative auditory and speech performance in children with WML was highly related to WML grading. Grand N1 amplitude in auditory event-related potentials was negatively related to the severity of WML. Non-dominant areas close to the auditory cortex were potentially activated in severe WML.

Developmental influence of unconjugated hyperbilirubinemia and neurobehavioral disorders

Bilirubin-induced brain injury in the neonatal period has detrimental effects on neurodevelopment that persist into childhood and adulthood, contributing to childhood developmental disorders. Unconjugated bilirubin is a potent antioxidant that may be useful for protecting against oxidative injuries, but it becomes a potent neurotoxin once it crosses the blood brain barrier. Because bilirubin toxicity involves a myriad of pathological mechanisms, can damage most types of brain cells, and affects brain circuits or loops that influence cognition, learning, behavior, sensory, and language, the clinical effects of bilirubin-induced neurotoxicity are likely to be manifold. One possible effect that several experts have identified is bilirubin-induced neurological dysfunction (subtle kernicterus). However, the underlying biological mechanisms or pathways by which subtle kernicterus could lead to developmental disorders has not been elucidated previously. Our aim in this review is to describe a spectrum of developmental disorders that may reflect subtle kernicterus and outline plausible biological mechanisms for this possible association. We review existing evidence that support or refute the association between unconjugated hyperbilirubinemia and developmental disorders, and limitations associated with these studies.

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.

Auditory brainstem response in full-term neonates born to mothers with iron deficiency anemia: relation to disease severity

Background: Iron is crucial for fetal brain development; however, there are insufficient data regarding the effects of maternal iron deficiency anemia (IDA) on auditory neural maturation.Aim: We evaluated the effect of maternal IDA on auditory brainstem response (ABR) in full-term neonates.Methods: Out of 223 pregnant women, 50 were diagnosed as having IDA and 50 healthy mothers were enrolled as controls. ABR test was done for the studied neonates within 48 hours after birth and at 3 months.Results: We found that hemoglobin and iron profile were lower in neonates born to anemic mothers compared with controls. Of 100 neonates screened for ABR, 25 failed the test (all of them were born to anemic mothers). The majority of neonates who failed the screening ABR test (88%) had latent iron deficiency (cord blood ferritin 11-75 µg/L). After 3 months, 85 neonates underwent diagnostic ABR test which revealed significantly prolonged interpeak latencies I-III, III-V, and I-V among neonates born to IDA mothers compared with the control group. Within the IDA group, all interpeak latencies were more prolonged in neonates with latent iron deficiency and in those born to mothers with serum ferritin <15 µg/L. Logistic regression analysis showed that maternal hemoglobin and mean corpuscular volume could predict neonatal ABR results.Conclusions: IDA during late pregnancy adversely affects cord blood iron and hearing status. ABR results are closely related to the severity of maternal and neonatal iron status. Antenatal screening of pregnant mothers is needed to improve fetal iron status and prevent abnormal auditory maturation.

Delayed myelination and neurodevelopment in male seizure-prone versus seizure-resistant rats

OBJECTIVE

Aberrant myelination and developmental delay have been reported in epilepsy. However, it is unclear whether these are linked to intrinsic mechanisms that support a predisposition toward seizures and the development of epilepsy. Thus, we compared rates of myelination and neurodevelopment in male rats selectively bred for enhanced susceptibility to kindling epileptogenesis (FAST) with male rats bred for resistance (SLOW).

METHODS

Myelin-specific gene expression was compared in the brainstem, cerebellum, and cerebral hemisphere of FAST and SLOW rats on postnatal days (PNDs) 5, 11, 17, 23, and 90 to determine strain-specific myelination rates. Myelin protein levels were also compared at PNDs 5 and 23 in the brainstem. Relative rates of neurodevelopment were evaluated between PNDs 5 and 21 using physical growth landmarks and neuromotor tests including righting reflex, cliff avoidance, negative geotaxis, and locomotor activity.

RESULTS

Myelin-specific mRNA expression was significantly down-regulated in FAST rats on PNDs 5 and 11 in all 3 brain structures, indicating relatively delayed myelination. Likewise, corresponding protein levels were significantly lower in FAST brainstem on PND 5. Developmental delay was evident in the FAST strain such that only 9% of FAST pups, compared to 81% of SLOW, had open eyes by PND 13, locomotor activity was significantly reduced between PNDs 12 and 16, and neuromotor task acquisition was delayed between PNDs 5 and 10.

SIGNIFICANCE

Relative delays in myelination and neurodevelopment co-occurred in the seizure-prone FAST strain in the absence of seizures. These findings suggest these symptoms are not seizure-induced and may be mechanistically linked to an underlying pathophysiology supporting a predisposition toward developing epilepsy.

Short-term outcome of brainstem auditory function in term infants after discharge from the neonatal intensive care unit

OBJECTIVES

To examine short-term outcome of brainstem auditory function in term infants after discharge from the neonatal intensive care unit (NICU).

METHODS

Brainstem auditory evoked response (BAER) was recorded and analysed at various click rates at 2-4 months of age in 43 term NICU graduates. The data were compared with those in age-matched normal controls.

RESULTS

The threshold of BAER in the NICU graduates was marginally elevated. The graduates also showed an increase in wave III latency at 91/s and wave V latency at all 21-91/s. The I-V interval was increased at 51 and 91/s, whereas the I-III and III-V intervals were slightly increased, with no significant differences from normal controls at any click rates. The amplitudes of waves I and V in the NICU graduates were moderately reduced at all click rates. Wave III amplitudes were reduced at 51 and 91/s. None of the slopes of BAER variables-rate functions in the NICU graduates differed significantly from normal controls.

CONCLUSIONS

The BAER was moderately abnormal in the NICU graduates, suggesting that brainstem auditory function is moderately impaired at 2-4 months of age after discharge. There is a need to monitor postnatal auditory and neural development for NICU graduates.

Reading ability reflects individual differences in auditory brainstem function, even into adulthood

Research with developmental populations suggests that the maturational state of auditory brainstem encoding is linked to reading ability. Specifically, children with poor reading skills resemble biologically younger children with respect to their auditory brainstem responses (ABRs) to speech stimulation. Because ABR development continues into adolescence, it is possible that the link between ABRs and reading ability changes or resolves as the brainstem matures. To examine these possibilities, ABRs were recorded at varying presentation rates in adults with diverse, yet unimpaired reading levels. We found that reading ability in adulthood related to ABR Wave V latency, with more juvenile response morphology linked to less proficient reading ability, as has been observed for children. These data add to the evidence indicating that auditory brainstem responses serve as an index of the sound-based skills that underlie reading, even into adulthood.

Bilirubin-Induced Audiologic Injury in Preterm Infants

Although hyperbilirubinemia is extremely common among neonates and is usually mild and transient, it sometimes leads to bilirubin-induced neurologic damage (BIND). The auditory pathway is highly sensitive to the effects of elevated total serum/plasma bilirubin (TB) levels, with damage manifesting clinically as auditory neuropathy spectrum disorder. Compared to full-term neonates, preterm neonates are more susceptible to BIND and suffer adverse effects at lower TB levels with worse long-term outcomes. Furthermore, although standardized guidelines for management of hyperbilirubinemia exist for term and late preterm neonates, similar guidelines for neonates less than 35 weeks gestational age are limited.

Socioeconomic (SES) differences in language are evident in female infants at 7months of age

BACKGROUND

Language skills, strongly linked to academic success, are known to differ by socioeconomic status (SES), with lower SES individuals performing less well than higher SES.

AIMS

To examine the effect of SES on infant language at 7months of age and the relationship between maternal vocabulary skills and infant language function. To determine if the relationships between SES and infant language are mediated by maternal vocabulary skills.

STUDY DESIGN

Longitudinal follow-up of healthy term female African American infants born to mothers in two SES groups: Low SES (income-to-needs≤1, no education beyond high school) and Higher SES (Income-to-Needs >1, at least a high school diploma).

SUBJECTS

54 infants tested at 7months of age; 54 mothers tested at infant age 7months.

OUTCOME MEASURES

Preschool Language Scale-5 (PLS-5), Vocabulary and Matrix Reasoning subtests of the Wechsler Adult Intelligence Scale-IV.

RESULTS

Low SES infants (n=29) performed less well than Higher SES (n=25) on PLS-5 Total Language, Auditory Comprehension, and Expressive Communication (p≤0.012). Maternal Vocabulary subtest scores were lower in Low SES than Higher SES (p=0.002), but not related to infant PLS Language scores (p≥0.17). Maternal vocabulary did not mediate the relationship between SES and infant language skills at age 7months.

CONCLUSIONS

In this single sex and race cohort of healthy, term, female infants, lower SES exerted negative effects on infant language by 7months of age. While maternal vocabulary scores showed no relation with infant language skills at 7months, continued study of the relations between SES, infant outcomes and maternal characteristics is needed to determine how low SES conditions impact early language. These findings underscore the importance of early interventions, as well as policies designed to improve socioeconomic conditions for infants and families.

Bilirubin-induced neural impairment: a special focus on myelination, age-related windows of susceptibility and associated co-morbidities

Bilirubin-induced neurologic dysfunction (BIND) and classical kernicterus are clinical manifestations of moderate to severe hyperbilirubinemia whenever bilirubin levels exceed the capacity of the brain defensive mechanisms in preventing its entrance and cytotoxicity. In such circumstances and depending on the associated co-morbidities, bilirubin accumulation may lead to short- or long-term neurodevelopmental disabilities, which may include deficits in auditory, cognitive, and motor processing. Neuronal cell death, astrocytic reactivity, and microglia activation are part of the bilirubin-induced pathogenesis. Less understood is how abnormal growth and maturation of oligodendrocytes may impact on brain development, affecting the formation of myelin tracts. Based on in-vitro and in-vivo models, as well as in clinical cases presented here, we propose the existence of impaired myelination by bilirubin with long-term sequelae, mainly in pre-term infants. Sensitive time-windows are highlighted and centered on the different developmental-dependent impairments determined by bilirubin, and the influence of sepsis and hypoxia is reviewed.