Brainstem auditory evoked response at term in preterm infants after perinatal hypoxia-ischaemia

Effect of neonatal asphyxia on the impairment of the auditory pathway by recording auditory brainstem responses in newborn piglets: a new experimentation model to study the perinatal hypoxic-ischemic damage on the auditory system

INTRODUCTION

Hypoxia-ischemia (HI) is a major perinatal problem that results in severe damage to the brain impairing the normal development of the auditory system. The purpose of the present study is to study the effect of perinatal asphyxia on the auditory pathway by recording auditory brain responses in a novel animal experimentation model in newborn piglets.

METHOD

Hypoxia-ischemia was induced to 1.3 day-old piglets by clamping 30 minutes both carotid arteries by vascular occluders and lowering the fraction of inspired oxygen. We compared the Auditory Brain Responses (ABRs) of newborn piglets exposed to acute hypoxia/ischemia (n = 6) and a control group with no such exposure (n = 10). ABRs were recorded for both ears before the start of the experiment (baseline), after 30 minutes of HI injury, and every 30 minutes during 6 h after the HI injury.

RESULTS

Auditory brain responses were altered during the hypoxic-ischemic insult but recovered 30-60 minutes later. Hypoxia/ischemia seemed to induce auditory functional damage by increasing I-V latencies and decreasing wave I, III and V amplitudes, although differences were not significant.

CONCLUSION

The described experimental model of hypoxia-ischemia in newborn piglets may be useful for studying the effect of perinatal asphyxia on the impairment of the auditory pathway.

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.

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.

Changes in brainstem auditory response threshold in preterm babies from birth to late term

CONCLUSION

The hearing threshold in preterm infants was 23 dB above adult hearing level at 30 weeks gestation, and decreased to around 13 dB at term date. There was no major difference in the threshold for infants born at different gestations. At term, 9% had hearing threshold elevation.

OBJECTIVE

To examine changes in hearing threshold from preterm to term in infants born at 30-36 weeks gestation and to detect the prevalence of threshold elevation.

METHODS

The threshold in brainstem auditory evoked response (BAER) was obtained 656 times from postconceptional age (PCA) 30 to 42 weeks in 268 infants born at 30-36 weeks gestation.

RESULTS

The BAER threshold was 23 dB nHL at the youngest age (PCA 30 weeks), and then decreased to around 13 dB nHL at later preterm and term dates (PCA 35-42 weeks). The threshold was decreased with increasing age at a rate of 1.24 dB per week from PCA 30 to 36 weeks and 0.65 dB per week from PCA 30 to 42 weeks. At PCA 33-42 weeks, there were no significant differences in BAER threshold between the infants born at gestational age (GA) 30-32 weeks and those at GA 33-36 weeks. At term, 9% had threshold elevation (>20 dB nHL).

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.

Impairment of perinatal hypoxia-ischemia to the preterm brainstem

Hypoxia-ischemia is a major perinatal problem that results in severe damage to the newborn brain. This study assessed functional integrity of the brainstem at term in preterm infants after perinatal hypoxia-ischemia to shed light on the influence of hypoxia-ischemia on the preterm brainstem. We recruited sixty-eight preterm infants after perinatal hypoxia-ischemia, ranging in gestation 28-35 weeks. Brainstem evoked response was studied at term age (37-42 weeks postconceptional age) with 91-910/s clicks using the maximum length sequence technique. Compared with healthy preterm infants, the preterm infants after perinatal hypoxia-ischemia showed a significant increase in I-V interval at very high rates 455 and 910/s of clicks (P<0.05, 0.05). III-V interval and III-V/I-III interval ratio also increased significantly at 455 and 910/s (P<0.05-0.01). The slope of III-V interval-rate function was significantly steeper than in the healthy preterm infants (P<0.05). Compared with normal term controls, the preterm infants after hypoxia-ischemia showed similar, but slightly more significant, abnormalities. The differences between the preterm infants after hypoxia-ischemia and the healthy preterm and term infants generally increased with increasing click rate. These results demonstrated that central components of brainstem auditory evoked response were abnormal at very high click rates in the preterm infants after perinatal hypoxia-ischemia. Click rate-dependent change in the more central part of the brainstem is also abnormal. Apparently, functional integrity of the brainstem, mainly in the more central part, is impaired. Hypoxic-ischemic damage to the preterm brainstem is unlikely to completely recover within a relatively short period after the insult, which is of clinical importance.