Auditory brainstem responses (ABR) in neonates with hyperbilirubinemia

Neonatal hyperbilirubinemia and repercussions on neurodevelopment: A systematic review

BACKGROUND

Accumulation of bilirubin above normal levels is considered a neurological risk factor for both premature and full-term newborns. This systematic review aimed to determine the effect of neonatal hyperbilirubinemia on neurodevelopment in preterm and full-term newborns.

METHODS

PubMed, EMBASE, Cochrane Library, CINAHL, PsycINFO, Scopus and Lilacs databases were searched for articles published until 1 June 2022. The quality of cohort and case-control studies was assessed with the Newcastle-Ottawa Scale, and the MINCir scale was used to evaluate the methodological quality of therapy studies or the therapeutic procedures. Premature neonates without neurological conditions and those born at term with hyperbilirubinemia as the sole risk factor were included. Studies reporting one or more neurodevelopmental outcomes were included with an inter-group comparison of a hyperbilirubinemia group versus a non-hyperbilirubinemia or non-pathological hyperbilirubinemia group. The main outcomes were auditory function, visual function, cognitive function, motor function, behavior, global development and neurological risk.

RESULTS

The search identified 951 studies, 19 of which (n = 2210 newborns) were finally included. Fifteen of the cohort and case-control studies presented low risk of bias, and six studies showed high methodological quality. Within the preterm population, hyperbilirubinemia as the sole risk factor was not shown to affect neurodevelopment. Auditory, neurological and motor development alterations were found in the population of full-term newborns with hyperbilirubinemia, which were more evident during the first year of life.

CONCLUSIONS

Elevated bilirubin levels may be a trigger for the onset of neurodevelopmental disorders in full-term infants during the first year of life. More studies are warranted in the preterm population with hyperbilirubinemia to draw conclusions about its impact on their neurodevelopment.

Hyperbilirubinemia impact on newborn hearing: a literature review

The increase in bilirubin levels in newborns can cause toxic effects on the auditory system, which can lead to hearing loss. This review aimed to verify the impact of hyperbilirubinemia in the hearing of newborns, relating audiological findings to serum levels of bilirubin. A literature review was conducted during October 2017, using the terms "hyperbilirubinemia", "jaundice", "infant", "newborn" and "hearing loss", on databases CAPES journals, MEDLINE and BIREME (SciELO, BBO). 827 studies were identified and 59 were selected for full-text reading, resulting in the selection of seven articles that met the inclusion criteria and were considered relevant to the sample of this study. All the reviewed studies performed brainstem auditory evoked potential as the main test for audiological evaluation. Changes in the audiological findings of neonates with hyperbilirubinemia were observed in all studies. There was no consensus on the serum bilirubin levels that may cause auditory changes; however, the relationship between hearing disorders and blood levels of bilirubin was positive. We identify the need to establish reference values for bilirubin levels considered critical for the occurrence of hearing disorders as well as the audiological follow-up of neonates with hyperbilirubinemia.

Brainstem Evoked Response Audiometry (BERA) in Neonates with Hyperbillirubinemia

(1) To study the BERA changes in neonates with unconjugated hyperbilirubinemia. (2) To compare the BERA changes in the neonates with unconjugated hyperbilirubinemia before and after therapy. Thirty consecutive term appropriate for gestational age (AGA) neonates presenting to NICU with total serum bilirubin requiring intervention (using the American Academy of Pediatrics guidelines) were included in the study as cases and thirty normal term AGA neonates with uneventful peri-natal period and a maximum measured serum bilirubin <12 mg/dl in case of term baby were included as controls after obtaining informed consent. Initial BERA was done within 3-24 h of hospitalization after obtaining informed consent from parents, at the time of discharge and at 3 month followup. Machine used for recording BERA was intelligent hearing system version 3.3. In our study out of the 30 cases 10 (33.3 %) cases were found to have BERA changes in the form of absent wave forms, raised threshold, prolonged latencies or prolonged inter peak latencies. In our study, it was observed that there was statistically significant correlation (p value < 0.005) between increasing bilirubin level and BERA changes. Correlation of the findings of this study with previous few studies indicates that BERA can be used as a useful non invasive tool to determine auditory functions in the neonate especially changes of early bilirubin toxicity.

Risk of Sensorineural Hearing Loss and Bilirubin Exchange Transfusion Thresholds

BACKGROUND AND OBJECTIVES

High bilirubin levels are associated with sensorineural hearing loss (SNHL). However, few large studies of relative and excess risk exist. We sought to quantify the risk of SNHL in newborns who had bilirubin levels at or above American Academy of Pediatrics exchange transfusion thresholds (ETT).

METHODS

Infants born at ≥35 weeks gestation in 15 Kaiser Permanente Northern California hospitals from 1995-2011 were eligible (N = 525 409). We used a nested double cohort design. The exposed cohort included subjects with ≥1 bilirubin level at or above ETT. The unexposed cohort was a 3.6% random sample of subjects with all bilirubin levels below ETT (10 unexposed per exposed). An audiologist, blinded to bilirubin levels, reviewed the charts of children in whom SNHL had been diagnosed before age 8 years to confirm the diagnosis. We calculated Cox proportional hazard ratios for time to diagnosis of SNHL.

RESULTS

SNHL was confirmed in 11 (0.60%) of the 1834 exposed subjects and in 43 (0.23%) of the 19 004 unexposed. Only bilirubin levels ≥10 mg/dL above ETT were associated with a statistically significant increased risk of SNHL (hazard ratio: 36 [95% confidence interval (CI): 13 to 101]). Likewise, only bilirubin levels ≥35 mg/dL were associated with a statistically significant increased risk of SNHL (hazard ratio: 91 [95% CI: 32 to 255]). For subjects with total serum bilirubin levels 0 to 4.9 mg/dL above ETT, the upper limit of the 95% CI for excess risk was 0.5%.

CONCLUSIONS

Only bilirubin levels well above ETT were associated with SNHL. At lower bilirubin levels, the excess risk of SNHL was low.

Auditory risk of hyperbilirubinemia in term newborns: a systematic review

OBJECTIVES

High levels of unconjugated bilirubin have been associated with neuronal damage. The auditory brain nuclei and the inferior colliculi are often the first part of the brainstem to be involved, often leading to hearing abnormalities. A systematic review of clinical studies was conducted to evaluate the effect of hyperbilirubinemia on hearing in term newborns, to show the relationship between hearing function and bilirubin levels as well as the effect of treatment.

METHODS

Eligible studies were identified through searches of electronic databases Ovid MEDLINE, Ovid MEDLINE In-Process, Embase, PubMed and The Cochrane Library. Articles obtained were independently reviewed by 2 authors using inclusion criteria to identify eligible studies. The search was restricted to articles written in English, French and Spanish and published between 1970 and 2010. Data extracted included study type, number of patients, bilirubin levels, hyperbilirubinemia criteria, hearing assessment methods, time of hearing assessment and outcome measures.

RESULTS

The nineteen articles included showed heterogeneity regarding the time of hearing test and hyperbilirubinemia criteria. The incidence of hearing loss at initial testing ranged between 13.2-83.3% and 6.7-14.3% at 3 months follow-up. Five studies showed a rising incidence of hearing loss with increasing levels of serum bilirubin.

CONCLUSIONS

Hyperbilirubinemia resulted in abnormal hearing assessment in up to 83.3% of term newborns. Greater hearing abnormalities were observed with rising serum bilirubin levels. Treatment of hyperbilirubinemia led to a considerable decrease in the incidence of hearing loss.

Tau and S100B proteins as biochemical markers of bilirubin-induced neurotoxicity in term neonates

We investigated the relationship between total serum bilirubin and serum Tau and S100B protein levels, and predicted a cutoff level of bilirubin-induced neurotoxicity in term newborns. Total serum bilirubin, serum Tau, and S100B levels were measured in 92 jaundiced term newborns. A neurologic examination, electroencephalogram, brainstem auditory-evoked response, and otoacoustic emission were performed in the infants on admission and at age 3 months. Serum Tau (r = 0.921, P < 0.001) and S100B (r = 0.927, P < 0.001) levels were correlated with total serum bilirubin levels in all infants. Serum Tau and S100B protein levels remained at a steady level up to a total serum bilirubin level of 19.1 mg/dL, and then demonstrated a significant increase. Mean total serum bilirubin, serum Tau, and S100B levels of infants who manifested auditory neuropathy, neurologic abnormalities, or electroencephalogram abnormalities were significantly higher than in infants without these abnormalities (P < 0.05). Clinical and laboratory findings of bilirubin-induced neurotoxicity developed after a total serum bilirubin level of 22 mg/dL was reached. Serum levels of Tau and S100B proteins in jaundiced term newborns were strongly correlated with early-phase bilirubin encephalopathy.

Auditory brainstem responses as a clinical evaluation tool in children after perinatal encephalopathy

Auditory brainstem responses (ABR) reveals the neurophysiological status of the neural axis. In this study we compared the ABR of healthy children, under 1-year-old, with children who suffered from perinatal encephalopathy (PE).

OBJECTIVE

The purpose of this study was to characterize the ABR differences between children with PE and healthy children in order to identify groups with specific neurophysiological profiles, associated with their neurological condition.

METHODS

Thirty-six children with perinatal encephalopathy (PE) and 36 healthy children, ages 1-12 months, were studied. The variables considered were: latencies of waves I, II, N1, III, V, and N2; interpeak latency interval (IPL) of waves I-III, III-V, and I-V; as well as amplitudes of waves I, III, and V. The results were analyzed using ANOVA, as well as Ji(2), and Ward's cluster analysis.

RESULTS

The absolute latencies of the ABR showed an inverse correlation with the children's age. Latencies of waves I, II, N1, V, and N2, IPL III-V, and amplitude of waves III and V show significant differences (p<0.05) between healthy and PE children. Children with PE showed greater absolute latencies and larger wave amplitudes than the control group. Ward's cluster analysis, used to define the groups with similar functional characteristics, revealed three groups: fast, intermediate, and slow-responders, depending on their wave latencies and IPL wave amplitudes. These groups were gender- (p<0.03), age- (p<0.0001), and neurological damage- (p<0.01) related.

CONCLUSIONS

Our data clearly show that the ABR obtained from PE children differ from ABR obtained from healthy children. PE infants showed larger wave latencies, intervals amplitudes than the control group. Three functional profiles resulted from the groups established using the Ward's method, and these indicate their neurological functional condition.

Auditory brainstem responses in neonatal hyperbilirubinemia and effect of therapy

Objectives; To determine the effect of neonatal hyperbilirubinemia on auditory brainstem responses (ABRs) and evaluate ABR responses to lowering of bilirubin levels.

STUDY DESIGN

prospective case control trial

SETTING

tertiary referral center.

PATIENTS

60 neonates (40 cases & 20 controls). Term appropriate for date(AFD) neonates with uncomplicated birth history and bilirubin level of ≥ 13 mg/dL were included as cases, those with bilirubin value of < 13 mg/dL were taken as controls.Interventions; First BERA examination was carried out within 24 hrs of the diagnosis of hyperbilirubinemia and repeat examination was done when total serum bilirubin came down to < 13 mg/dL with treatment. Comparisons were made between cases (before & after therapy) and controlResults; No abnormality in neonates with bilirubin < 18 mg/dL. Abnormal ABRs were observed in 24(60%) of the 40 cases studied, with therapy it reverted back to normal in 15(62%). The commonest abnormality noted was prolonged latency of wave V(42.5%), followed by prolonged latency of wave III(35%) and wave I(22.5%). Prolonged latency of wave I was found in only those with bilirubin > 20mg/dL. Inter peak latency of wave IV (Brain stem conduction time) was prolonged in 8 cases; it reverted to normal in all cases. Prolonged inter peak latency of wave I-III was observed in 7 cases, of which it reverted to normal in 6. Absent waves reappeared in 4 out of 5 cases, but abnormal amplitude ratios reverted to normal in only one of the 7 cases in which it was abnormal.Conclusions; about 60% of term A FD neonates with serum bilirubin of > 18mg/dL will demonstrate ABR changes. Most of these changes revert to normal early after therapy, indicating need for aggressive therapy in this subgroup of neonates.

Short- and long-term outcome of severe neonatal nonhemolytic hyperbilirubinemia

We studied the effects of hyperbilirubinemia on brainstem auditory pathways and neurodevelopmental status in 99 full-term neonates with severe nonhemolytic hyperbilirubinemia (total serum bilirubin level = 301 to 500 micromol/L) born between 1995 and 2000. These were divided into three groups: group 1, moderate hyperbilirubinemia (n = 30; mean maximum total serum bilirubin = 320.7 micromol/L or 18.9 mg%); group 2, severe hyperbilirubinemia (n = 63; mean maximum total serum bilirubin = 369.0 micromol/L or 21.7 mg%); and group 3, super hyperbilirubinemia (n = 6; mean maximum total serum bilirubin = 457.2 micromol/L or 26.9 mg%). All received phototherapy, and three neonates also had exchange transfusion. Initial brainstem auditory evoked potentials were recorded in all at the mean age of 3.1 months (range 1-9 months). At initial assessment, only nine neonates (9.1%) had abnormal brainstem auditory evoked potentials. All except two returned to normal at 2 years. These two children had a hearing threshold at 50 nHL. We then compared serial brainstem auditory evoked potentials until 2 years for these nine cases with initial abnormal brainstem auditory evoked potentials, and nine cases with initial normal brainstem auditory evoked potentials were recruited for comparison. All 99 children had regular physical, neurologic, visual, and auditory assessments every 3 to 6 months until the age of 3 years. There was no significant correlation between demographic factors (gender, gestational age, or birthweight), maximum total serum bilirubin, and total serum bilirubin at discharge with an abnormal brainstem auditory evoked potential. There was no significant difference in the rate of brainstem auditory evoked potential abnormalities between the three groups: moderate (10%), severe (7.9%), and super (16.7%). All had normal neurodevelopmental status at 3 years. Only two children had transient mild motor delay and hypotonia, and both had normal brainstem auditory evoked potentials. There was no relationship between the abnormalities of the brainstem auditory evoked potentials and neurodevelopmental status. None of the three children receiving exchange transfusion had abnormal brainstem auditory evoked potentials or neurodevelopmental outcome. With the neurophysiologic and clinical outcomes in our cohort with severe nonhemolytic hyperbilirubinemia, we propose that the toxic effect of hyperbilirubinemia on auditory brainstem pathways might be transient provided that prompt treatment is initiated.

Somatosensory and brainstem auditory evoked potentials in the Gunn rat model of acute bilirubin neurotoxicity

Brainstem auditory evoked potentials (BAEPs) are a sensitive indicator of bilirubin neurotoxicity. Somatosensory evoked potentials (SEPs) have been proposed as another measure of toxicity, though the lemniscal pathways that generate the SEP are not involved in kernicterus. In 16 to 17-d-old jaundiced (jj) Gunn rats, serial BAEPs and SEPs were obtained up to 8 h after acute bilirubin toxicity. jjs were injected with 150 mg/kg sulfadimethoxine to displace bilirubin into brain tissue (n = 8); littermate controls were jjs given saline (n = 4) and nonjaundiced given sulfadimethoxine or saline (n = 7). After anesthesia, BAEP and SEP recordings were obtained at baseline and serially after injection. SEPs to median nerve stimulation were recorded from surface electrodes over the brachial plexus (Erb's) and contralateral parietal cortex, and subtracted to obtain central conduction time (CCT). There were no statistically significant different baseline values between groups. Baseline BAEP I, I-II, and I-III were 1.22 +/- 0.13, 1.11 +/- 0.12, and 2.10 +/- 0.15 ms, and SEP Erb's and CCT were 1.48 +/- 0.20 and 5.59 +/- 0.50 ms, respectively (n = 19). At 6.8 +/- 1.5 h after injection BAEP I, I-II, and I-III increased 0.10 +/- 0.08, 0.18 +/- 0.17, and 0.56 +/- 0.33 ms over baseline, respectively (p = 0.005, 0.01, and 0.001, respectively, paired, 1-tailed t-tests), in experimental but not control groups. SEP Erb's decreased slightly, -0.06 +/- 0.04 ms in experimental and -0.08 +/- 0.08 ms in control groups, while CCT did not change significantly. BAEPs were completely abolished in two jjs with no SEP changes. When injection of sulfonamide induced significant peripheral and central BAEP abnormalities in jaundiced rats, no SEP abnormalities occurred. SEPs assess proprioception but not other somatosensory function or sensory integration. The results demonstrate the selectivity of acute bilirubin toxicity for the auditory nervous system.

Audiologic evaluation of neonates with severe hyperbilirubinemia using transiently evoked otoacoustic emissions and auditory brainstem responses

OBJECTIVES

To audiologically clarify the lesion site and to test the reliability of transiently evoked otoacoustic emissions (TEOAEs) in hearing screening of hyperbilirubinemic neonates.

STUDY DESIGN

Eleven neonates with severe hyperbilirubinemia who had exchange transfusion in the neonatal intensive care unit of an academic hospital over a 3-year period were included in this study. They were tested with auditory brainstem response (ABR) and TEOAEs after exchange transfusion during hospitalization or at an immediate follow-up visit after discharge. Follow-up ABR tests were performed when infants showed significant hearing loss.

METHODS

ABR and TEOAE tests were performed on the 11 neonates with severe hyperbilirubinemia after exchange transfusion. Follow-up ABR tests were carried out in 3-month intervals in the four neonates who showed abnormal or no response on initial ABR.

RESULTS

Four neonates showed abnormal or no response and the other seven demonstrated normal response in ABR. All 11 neonates passed TEOAEs. Two neonates showed improvement in auditory function at 3- or 6-month follow-up ABR.

CONCLUSION

The results of this study indicate that the site of lesion in hearing loss caused by hyperbilirubinemia may be at the retrocochlear location while the cochlea remains intact. TEOAEs may have limitations in evaluation of hearing in the neonates with hyperbilirubinemia.

Glucose 6-phosphate dehydrogenase deficiency with kernicterus: progressive late recovery from profound deafness

In this case report a near-term infant with Glucose 6-Phosphate Dehydrogenase (G6-PD) deficiency had an unconjugated bilirubin level of 703 on the 11th day of life but maintained his haemoglobin levels above 11 gm/dl. At 4 months of age he demonstrated the clinical picture of Kernicterus: profound sensorineural deafness and evidence of encephalopathy. However, by 15 months of age his abnormal cerebral and motor signs had regressed to a near-normal level in parallel with a gradual improvement in hearing, which also reached normal levels, first in the right ear, then in the left. At this age residual mental retardation has not been excluded but his communication skills, though delayed by 4-6 months, were moving towards the level when they would be appropriate for his age.

Brainstem auditory evoked response (BAER) in childhood bacterial meningitis

Brainstem auditory responses were recorded in 50 children of bacterial meningitis and age matched 50 normal children. Abnormal BAER was found in 32 (64%) patients of bacterial meningitis. These abnormalities included prolonged latency (56.2%); unilateral absent response (25%); bilateral absent response (25%) and prolonged interwave interval (25%). Follow-up could be done in 23 patients of 46 survivors. All the patients with prolonged latency either became normal or improved. In majority of the patients having absent response, the abnormality persisted. Abnormal BAER was significantly associated with age < 2 years (p < 0.02), Modified GCS Score < or = 8 (p < 0.001), Seizures (p < 0.02), raised Intracranial Pressure (ICP) (p < 0.02) and CSF sugar < 20 mg% (p < 0.05).