Normal brainstem responses in moderately preterm infants

Suboptimal postnatal function of brainstem auditory pathway in late preterm infants who do not have major perinatal and postnatal complications

OBJECTIVES

To examine postnatal functional status of the brainstem auditory pathway in late preterm infants and detect any postnatal auditory abnormality.

METHODS

Thirty preterm infants born at 33-36 weeks gestation were studied three months after term. None had major perinatal and postnatal complications to minimize confounding effects. Brainstem auditory evoked responses were recorded with 21-91/s clicks.

RESULTS

Compared with postnatal age-matched normal term infants, the late preterm infants did not manifest any major abnormalities in brainstem auditory evoked responses at conventionally used 21/s clicks. At higher click rates, however, the late preterm infants manifested a moderate prolongation in BAER wave V latency. All interpeak intervals tended to be prolonged at higher click rates. The I-V interval was significantly prolonged at 51/s and particularly at 91/s clicks. Both the I-III and III-V intervals were significantly prolonged at 91/s. The late preterm infants also manifested reduced amplitudes of BAER waves III and V at most click rates.

CONCLUSION

The central components of the brainstem auditory evoked responses were abnormal at higher click rates three months after term in the late preterm infants. Postnatal brainstem auditory function is suboptimal in late preterm infants without major complications. This suboptimal brainstem auditory function may not be clearly shown at term or an earlier stage, but can be shown later. Late preterm infants, although they may not have major complications, should be followed for later auditory development, providing valuable information for improving postnatal care.

The Hearing Status of Preterm Infant’s ≤ 34 Weeks as Revealed by Otoacoustic Emissions (OAE) Screening and Diagnostic Brainstem Evoked Response Audiometry (BERA): A Tertiary Center Experience

To know the prevalence of hearing loss in preterm infants & to evaluate the sensitivity & specificity of otoacoustic emission (OAE) in detecting hearing loss in preterm infants ≤ 34 weeks. A total of 70 preterm babies from 28 to 34 weeks of gestational age were enrolled in the study. Detailed prenatal, perinatal, postnatal & family history and physical examination of the babies were carried out. First OAE was done at discharge or two weeks after birth, whichever was earlier and the second OAE assessment was done at 36-40 weeks of corrected age. Diagnostic brainstem evoked response audiometry (BERA) was done in all infants at 36-40 weeks of corrected age, at the time of second OAE. Neonates with hearing impairment were advised for early hearing aid amplification and were referred to the rehabilitation center for further management. The sensorineural hearing loss (SNHL) in either one of the ears was identified in 13 (18.57%) preterm babies. Bilateral profound SNHL was found in 5 (7.14%) babies. Auditory neuropathy profile was found in 7 (53.8%) out of 13 babies who had hearing loss. The sensitivity, specificity, positive and negative predictive values of second TEOAE compared with diagnostic BERA was 46.15%, 85.96%, 42.85%, and 87.5% respectively. Neonatal jaundice (p = 0.009) and history of exchange transfusion (p = 0.019) were found to be significant risk factors of hearing loss in our study. Other risk factors like mode of delivery, birth asphyxia, low APGAR score, meningitis, ototoxic drugs, and seizures were not associated with hearing loss. The prevalence of hearing loss in preterm infants < 34 weeks is very high. OAE alone is not an ideal screening test for high-risk neonates ≤ 34 weeks because of its low sensitivity. OAE combined with diagnostic BERA should be done in all high-risk infants preterm neonates ≤ 34 weeks to identify cases of auditory neuropathy spectrum disorders.

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.

Developmental heatmaps of brain functional connectivity from newborns to 6-year-olds

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Heatmaps quantify degrees of developmental changes in functional connectivity.

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More changes are observed in the first than second postnatal year, driven by girls.

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Most change is observed from ages 2–4 compared with any other age span.

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Limbic and subcortical areas show more changes than primary sensory regions.

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Consistent trajectories of functional connectivity are found across validations.

Different functional networks exhibit distinct longitudinal trajectories throughout development, but the timeline of the dynamics of functional connectivity across the whole brain remains to be elucidated. Here we used resting-state fMRI to investigate the development of voxel-level changes in functional connectivity across the first six years of life. Globally, we found that developmental changes in functional connectivity are nonlinear with more changes during the first postnatal year than the second, followed by most significant changes from ages 2–4 and from ages 4–6. However, the overall global difference observed between the first and second year appears to have been driven by girls. Limbic and subcortical areas consistently demonstrated the most substantial changes, whereas primary sensory areas were the most stable. These patterns were consistent in full-term and preterm subgroups. Validation on randomly divided subsamples as well as in an independent cross-sectional sample revealed global patterns consistent with the main results. Overall, the derived developmental heatmaps reveal novel dynamics underlying functional circuit development during the first 6 years of life.

Newborn hearing screening at the Neonatal Intensive Care Unit and Auditory Brainstem Maturation in preterm infants

OBJECTIVES

Aim of this study is to report and discuss the results of 4 years of Newborn hearing screening (NHS) program at the Neonatal Intensive Care Unit (NICU), particularly evaluating the clinical ABR results.

METHODS

Retrospective study. NHS data from NICU newborns, admitted for ≥5 days, in the period from January 1st^, 2013 and December 31st^, 2016, were retrieved and analyzed. NHS results were classified as following: (i) "pass" when both ears for both the a-TEOAE (automated Transient-Evoked Otoacoustic Emissions) and the a-ABR (automated Auditory Brainstem Response) protocol resulted as "pass"; (ii) "fail" when one ear, at either one of the two performed tests resulted as "fail"; (iii) "missing" when the newborns were not tested with both protocols. All "fail" and "missing" newborns were retested (with both tests): in the case of a second "fail" result, a clinical ABR was performed within a period of 3 months.

RESULTS

A total of 1191 newborns were screened. From those, 1044/1191 resulted as "pass", 108/1191 as "fail", and 39/1191 as "missing". During the re-testing of these 147 newborns, 43 were assigned as "missing", 63 were assigned as "pass" (showing bilaterally a wave V identifiable within 30 dB nHL) and 25 failed the retest and/or did not present an identifiable wave V within 30 dB nHL. Among the 147 retested infants, we identified a group of 16 subjects who resulted as NHS "refer" and who, during the audiological follow-up, showed either: (i) a unilateral or bilateral wave V identifiable over 30 dB nHL, at the first clinical ABR assessment; or (ii) a bilateral wave V identifiable within 30 dB nHL, in a following clinical ABR test during the first year of life. These 16 subjects were defined to have an 'Auditory Brainstem Maturation' issue.

CONCLUSIONS

A possible "maturation" of the ABR response (and therefore of the auditory pathway) has been hypothesised in 16 out of 1191 infants (1.3%). A delay of the auditory pathway maturation in preterm babies compared to term newborns has already been suggested in the literature. A possible delay of the NHS retest could be considered, in selected cases, with significant savings in economic resources and parental anxiety.

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 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.

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.

Small-for-gestation birth exerts a minor additional effect on functional impairment of the auditory brainstem in high-risk babies born at late preterm

OBJECTIVE

To address if small-for-gestational-age (SGA) significantly affects the developing auditory brainstem in late preterm babies with perinatal problems (i.e. high-risk), providing valuable information for management of such babies.

METHODS

SGA and appropriate-for-gestational age (AGA) babies born at 33-36weeks of gestation were studied at term using maximum length sequence brainstem auditory evoked response in response to 91-910/s clicks.

RESULTS

Compared with AGA late preterm babies without perinatal problems (i.e. low-risk), the high-risk SGA babies manifested a significant increase in wave V latency and I-V interval at all 91-910/s clicks, and III-V interval at 455 and 910/s. The amplitude was smaller for wave I at 227 and 910/s, wave III at 910/s and wave V at 227 and 910/s. Compared with low-risk SGA babies, the high-risk SGA babies showed similarly abnormalities. Compared with high-risk AGA babies, the high-risk SGA babies manifested slightly different abnormalities.

CONCLUSIONS

Brainstem auditory response was abnormal in high-risk SGA late preterm babies. The abnormalities, suggesting brainstem auditory impairment, were slightly different from high-risk AGA late preterm babies.

SIGNIFICANCE

SGA birth exerts a minor additional effect on the impaired auditory brainstem in high-risk babies born at late preterm. For these babies, neuroprotective measures should mainly target at associated perinatal problems, although the relatively minor adverse SGA effect cannot be ignored.

A longitudinal study of brainstem auditory response from birth to late term in late preterm babies and abnormal findings in high-risk babies

OBJECTIVES

The objective of this study was to examine brainstem auditory function in late preterm babies from birth to late term and detect abnormality in high-risk babies.

METHODS

A total of 125 babies born at 33-36 weeks' gestations were studied by longitudinally recording brainstem auditory evoked response from birth to postconceptional age (PCA) 42 weeks. The data were compared between 88 babies who had various perinatal problems (high-risk group) and 37 babies who had no major perinatal problems (healthy group).

RESULTS

As PCA increased from 33 to 42 weeks, all wave latencies and I-V interpeak interval in brainstem auditory evoked response were decreased, while all wave amplitudes were increased in these babies. At PCA 33-34 weeks, wave III and V latencies and I-V interval in the high-risk late preterm babies were significantly longer than those in the healthy late preterm babies (P<0.05-0.01). At PCA 35-36 weeks, both V latency and I-V interval were significantly longer than those in the healthy babies (P<0.05 and 0.01). During the term period (PCA 37-42 weeks), these differences became smaller with increasing age. The wave V latency and I-V interval in the high-risk babies were significantly longer than those in the healthy babies at PCA 37-38 and 39-40 weeks (all P<0.05), though not significantly at PCA 41-42 weeks. The amplitudes of waves I, III, and V all tended to be smaller than those in the healthy babies.

CONCLUSIONS

During early life, brainstem auditory function is abnormal in high-risk late preterm babies. The abnormality is most significant at early preterm, improves with increasing age and approaches normal at late term.

Mild maturational delay of the brainstem at term in late preterm small-for-gestation age babies

AIMS

To detect any functional abnormality in the brainstem auditory pathway in late preterm babies born of small-for-gestational age (SGA) using maximum length sequence brainstem evoked response.

STUDY DESIGN

The response was recorded and analyzed at term in 38 SGA (birthweight <3rd centile) babies born at 33-36 week gestation. The results were compared with 40 age-matched babies born of appropriate-for-gestational age (AGA) (birthweight >10th centile). None of the subjects had major perinatal problems.

RESULTS

All wave latencies and interpeak intervals in the SGA group were slightly longer than those in the AGA group at most click rates. Wave III latency was significantly longer than that in the AGA group at 227/s (P < 0.05), and wave V latency was at 227 and 910/s (P < 0.05 and 0.05). Of the interpeak intervals, only the I-V interval in the SGA group was significantly longer than that in the AGA group at the highest rate 910/s (P < 0.05). The amplitudes of waves I, III and V in the SGA group all tended to be smaller than those in the AGA group at all click rates 91-910/s. The wave V amplitude was significantly smaller at most click rates (227-910/s, all P < 0.05). The slopes of all wave latency-, interval-, and amplitude-rate functions were similar in SGA and AGA groups.

CONCLUSIONS

There were marginal abnormalities in MLS BAER of low-risk late preterm SGA babies, suggesting a mild degree of maturational delay in the brainstem. Intrauterine growth retardation occurring in late preterm babies has a minor effect on neural maturation of the immature brainstem.

Newborn hearing screening and early diagnostic in the NICU

The aim was to describe the outcome of neonatal hearing screening (NHS) and audiological diagnosis in neonates in the NICU. The sample was divided into Group I: neonates who underwent NHS in one step and Group II: neonates who underwent a test and retest NHS. NHS procedure was automated auditory brainstem response. NHS was performed in 82.1% of surviving neonates. For GI, referral rate was 18.6% and false-positive was 62.2% (normal hearing in the diagnostic stage). In GII, with retest, referral rate dropped to 4.1% and false-positive to 12.5%. Sensorineural hearing loss was found in 13.2% of infants and conductive in 26.4% of cases. There was one case of auditory neuropathy spectrum (1.9%). Dropout rate in whole process was 21.7% for GI and 24.03% for GII. We concluded that it was not possible to perform universal NHS in the studied sample or, in many cases, to apply it within the first month of life. Retest reduced failure and false-positive rate and did not increase evasion, indicating that it is a recommendable step in NHS programs in the NICU. The incidence of hearing loss was 2.9%, considering sensorineural hearing loss (0.91%), conductive (1.83%) and auditory neuropathy spectrum (0.19%).

Comparison of brainstem auditory evoked response at different click rates between preterm babies after neonatal necrotizing enterocolitis and healthy preterm babies

BACKGROUND

Neonatal necrotizing enterocolitis (NEC) is associated with an increased incidence of poor neurodevelopment. The knowledge of underlying neurophysiology is very limited, and the influence of NEC on the preterm brainstem is very poorly understood.

OBJECTIVE

To assess the effect of NEC on the immature auditory brainstem by excluding any possible confounding effect of preterm birth.

METHODS

We recorded and analyzed brainstem auditory evoked response (BAER) at different click rates in preterm babies (30-34 weeks gestation) after NEC. The results were compared with those in age-matched healthy preterm babies who had no NEC.

RESULTS

At click rate 21/s, the latencies of BAER waves I and III in the preterm NEC babies were similar to those babies without NEC. However, wave V latency was longer in the NEC babies than in those without NEC. The I-V interpeak interval was also longer in the NEC babies than in those without NEC. These abnormalities were persistent at higher click rates 51 and 91/s. Wave I amplitude in the preterm NEC babies did not differ significantly from that in those without NEC, but wave III and V amplitudes were smaller than in those without NEC at all 21-91/s clicks.

CONCLUSIONS

Compared with healthy preterm babies, preterm babies after NEC showed a major increase in wave V latency and I-V interval at all 21-91/s clicks. Brainstem auditory function is impaired in preterm NEC babies after excluding the possible confounding effect of preterm birth. Neonatal NEC and associated perinatal conditions adversely affect the premature brainstem.

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.

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.

Influence of postconceptional age on universal newborn hearing screening in NICU-babies

The feasibility of universal newborn hearing screening (UNHS) using automated auditory brainstem response (AABR) devices in the neonatal intensive care unit (NICU) is already well demonstrated. The aim of this study was to find out whether the postconceptional age (PCA) of the babies at the time of the AABR measurement has an influence on the measuring results and to determine the earliest time point for a reliable hearing screening in preterm neonates. Hearing screening measurements of 634 neonates (NICU-Babies) were included. We had complete data for 577 of these babies. The babies were born between 24 and 42 weeks of gestation in the years 2007–2008 and were screened in the Neonatal Unit of the Marburg University hospital. In this group, the hearing screening had been performed at or after 32 weeks of PCA. The AABR measurements showed a specificity of 93.9% (babies tested between 32 and 34 weeks of PCA), 95.8% (tested between 35 and 37 weeks), 95.9% (tested between 38 and 40 weeks of PCA) and 92.1% (tested after 40 weeks of PCA). Hearing screening yields reliable results at 32 weeks PCA. Therefore, an UNHS can be already performed before term without risking a higher rate of false positive results. However, individual factors such as cardiorespiratory and temperature stability of the baby should be considered.

Brainstem auditory response findings in late preterm infants in neonatal intensive care unit

AIM

To examine brainstem auditory function at term in late preterm infants admitted to neonatal intensive care unit (NICU).

METHODS

Fifty-two preterm infants, born at 33-36 week gestation, were recruited in an NICU and were studied at term using brainstem auditory evoked response (BAER).

RESULTS

Compared with normal term infants, BAER wave V latency in the NICU preterm infants was increased at 51 and 91/sec (p<0.05, 0.05). Intervals of III-V and I-V were increased at all 21, 51 and 91/sec clicks (p<0.05-0.01), which was more significant at higher than lower rates. Interval ratio of III-V/I-III was increased significantly at 51 and 91/sec (p<0.05 and 0.01). Wave I and III latencies and I-III interval did not differ significantly from normal controls at any click rates. All amplitudes of waves I, III and V amplitude tended to be reduced at higher rates, while wave I amplitude was reduced significantly at 91/sec clicks.

CONCLUSION

There were BAER abnormalities in the NICU late preterm infants, suggesting compromised brainstem auditory function. Compared with a basically normal BAER in low-risk late preterm infants previously reported, the abnormalities suggest that perinatal problems or complications adversely affect the late preterm auditory brainstem.

Maximum length sequence brainstem auditory evoked response in low-risk late preterm babies

OBJECTIVES

Recent research indicates that there is delayed development in the more central part of the auditory brainstem in very preterm babies. We aimed to study whether this is also the case for late preterm babies.

METHODS

The maximum length sequence brainstem auditory evoked response (MLS BAER) was used to study functional status of the auditory brainstem. Babies born at 33-36 week gestation and without any major perinatal complications were recruited. MLS BAER was recorded and analyzed at term age.

RESULTS

No significant correlation was found between most MLS BAER variables and physiological factors (gender, postconceptional age, bodyweight, and head circumference obtained at time of testing). Wave latencies and amplitudes, and I-V and I-III intervals in the preterm babies were essentially similar to those in the term controls at all click rates. However, III-V interval increased significantly at 227-910/s clicks (p<0.05-0.01). All latencies, amplitudes and intervals correlated significantly with click rates (all p<0.001). No differences were found in the slopes of MLS BAER variables-rate functions between the later preterm babies and term controls.

CONCLUSIONS

Babies born at 33-36 weeks gestation without major complications had an increased III-V interval at high-rate stimulation. This suggests that late preterm babies have a mild delay in neural conduction in the more central part of the auditory brainstem.

Presença de microfonismo coclear no peate-clique: diagnóstico diferencial entre espectro da neuropatia auditiva e perdas auditivas cocleares descendentes em crianças

TEMA: diagnóstico diferencial entre espectro da neuropatia auditiva e perdas auditivas cocleares descendentes em crianças com presença de microfonismo coclear no PEATE-clique. PROCEDIMENTOS: este relato de caso descreve os resultados da avaliação audiológica de duas crianças atendidas no Centro "Audição na Criança" da Divisão de Educação e Reabilitação dos Distúrbios da Comunicação da Pontifícia Universidade Católica de São Paulo (CeAC/DERDIC/PUCSP) que apresentaram microfonismo coclear no registro do PEATE-clique. As crianças foram submetidas às avaliações utilizando-se o PEATE-clique, o registro das emissões otoacústicas e a avaliação audiológica tonal, com a técnica da Audiometria de Reforço Visual. RESULTADOS: as avaliações comportamental, eletroacústica e eletrofisiológica revelaram que as crianças apresentam perda auditiva sensorioneural (coclear) com configuração descendente, de modo que a presença do microfonismo coclear no registro do PEATE-clique era provavelmente gerada pela preservação da cóclea nas frequências baixas. CONCLUSÃO: os casos apresentados mostram que na ausência das emissões otoacústicas e presença do microfonismo coclear, não se deve interpretar isoladamente cada exame, para que não ocorram equívocos no diagnóstico, que pode ser confundido com o Espectro da Neuropatia Auditiva. O microfonismo coclear pode aparecer em outras condições, tais como em perdas auditivas cocleares descendentes.

Relative maturation of peripheral and central regions of the human brainstem from preterm to term and the influence of preterm birth

Relative maturation of peripheral and central regions of the neonatal brainstem was studied using brainstem auditory evoked responses in 174 healthy preterm infants (gestational age 30-36 wk). From 30- to 42-wk postconceptional age (PCA), I-III and III-V intervals shortened with increasing age. It was difficult to detect any apparent differences in maturational rate between the two intervals. However, III-V/I-III interval ratio decreased with increasing age, indicating that from preterm to term III-V interval shortens more than I-III interval. During term period (37- to 42-wk PCA), I-III interval was similar to term controls, but III-V interval was significantly longer and III-V/I-III interval ratio was significantly greater than controls at 37- to 38-wk PCA and 39-40 wk PCA and was the same as controls at 41-42 wk. Therefore, from 30- to 42-wk PCA maturation of central regions of the brainstem, reflected by III-V interval, is relatively faster than peripheral regions, reflected by I-III interval which seems to be already more mature than III-V interval before 30 wk. Maturation in central regions in preterm infants is relatively delayed at early term, but "catches-up" later, whereas peripheral regions already reach normal level of maturation at early term. Preterm birth slightly delays early maturation of central brainstem regions.