Neurodevelopment after moderate hyperbilirubinemia at term

A Study of General Movement Assessment and Its Association With Neurodevelopmental Outcome at Age 12 to 15 Months Among Term Neonates With Hyperbilirubinemia

BACKGROUND

To determine the association between optimality score at term age and age three to five months and neurodevelopmental outcome among neonates with hyperbilirubinemia.

METHODS

Fifty infants with and without hyperbilirubinemia were enrolled. The motor repertoires of the infants were evaluated through general movement assessment (GMA) at term age and three to five months post-term. The association between the General Movement Optimality Score (GMOS), Motor Optimality Score (MOS), and Development Assessment Scale for Indian Infants (DASII) at age 12 to 15 months was also assessed.

RESULTS

During term age, the median GMOS was significantly lower among infants in the study group when compared with the control group (40 [29 to 42] vs 42 [42 to 42], P < 0.001). However, at age three to five months, there was no significant difference between the groups. Significantly higher number of neonates had abnormal motor repertoire at term age and age three to five months in the study group when compared with the control group (18 [36%] vs 2 [4%], P = 0.001, at term age and 6 [12.2%] vs 1 [2%], P =0.04, at age three to five months). Among neonates with hyperbilirubinemia, the median GMOS and MOS were significantly lower at term age and age three to five months in infants with motor and mental developmental quotient scores <85 when compared with ≥85.

CONCLUSIONS

GMA including GMOS and MOS performed in neonates with hyperbilirubinemia during the neonatal period and early infancy is associated with neurodevelopmental outcomes in the first year of life. GMA can help initiate early intervention in such neonates.

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.

The Relationship between General Movements and Risk Factors in Moderate-Late Preterm Infants: A Prospective Cohort Study

INTRODUCTION

Moderate-late preterm infants constitute the largest segment of preterm births globally. While previously considered to have a low neurological risk, recent research has uncovered an elevated incidence of neurodevelopmental conditions in this group. This study aimed to assess the relationship between the general movement assessment and birth-related risk factor-based tools in moderate-late preterm infants.

METHODS

A prospective cohort study of 65 moderate-late preterm infants in a neonatal intensive care unit involved the evaluation of general movements, the Nursery Neurobiologic Risk Score, and the Perinatal Risk Inventory. Associations were analyzed using Fisher's exact test, Spearman's correlation was used for ordinal variables, and backward stepwise logistic regression was used to identify predictor variables for the assessments.

RESULTS

The findings indicated a high prevalence of normal (41%) and poor (52%) repertoire patterns during the writhing period. While no significant associations were found between the three assessments, a slight approximation emerged between dysmorphic traits and patterns (p = 0.053). Furthermore, an extended period of ventilation correlated with a higher likelihood of developing a cramped synchronized pattern and there was a correlation between both risk factor-based tools (p < 0.001).

CONCLUSIONS

This research enhances our understanding of the early impact on general movement assessments in moderate-late preterm infants. While no clear relationship emerged between general movement assessment and risk factor-based tools, there was a subtle connection noted with dysmorphic traits. A longer ventilation duration was linked to a higher risk of developing cramped synchronized patterns.

Prospective cohort study of neurodevelopmental outcomes following extreme neonatal hyperbilirubinaemia in Australia

AIM

This study aimed to establish the incidence and nature of neurodevelopmental outcomes following extreme neonatal hyperbilirubinaemia in an Australian cohort.

METHODS

A prospective cohort study of neurodevelopmental outcomes up to 3 years of age of infants born between 2010 and 2013 at ≥34 weeks gestation, with total serum bilirubin ≥450 μmol/L and/or clinical signs of acute bilirubin encephalopathy. Outcome measures comprised neurological examination, Bayley Scales of Infant and Toddler Development, 3rd edition and Ages and Stages Questionnaire, 3rd edition.

RESULTS

The Australian estimated incidence of kernicterus is 0.35 per 100 000 live births. Within the follow-up cohort of 26, three children have clinical neurodevelopmental impairment: one has gross motor function classification system level 4 cerebral palsy, audiological deficiency and visual impairment; the second has gross motor function classification system level 1 cerebral palsy and the third has global developmental delay with autism spectrum disorder. Mean Bayley Scales of Infant and Toddler Development, 3rd edition scores were: cognition 10.3 (SD 1.5), receptive communication 9.4 (SD 1.8), expressive communication 9.2 (SD 2.4), fine motor 10.4 (SD 2.6) and gross motor 9.2 (SD 2.3).

CONCLUSION

The Australian national rate of kernicterus compares favourably with global estimates. Future preventative strategies in this context include universal neonatal hyperbilirubinaemia assessment and mandated adverse outcome reporting and investigation.

An investigation of motor development and sensory processing skills in infants with a history of hyperbilirubinemia

BACKGROUND

Hyperbilirubinemia is a clinical picture frequently occurring in the neonatal period and may negatively affect the development of infants.

AIMS

To evaluate term infants with hyperbilirubinemia in terms of both motor development and sensory processing skills and to compare them with their healthy peers without hyperbilirubinemia.

STUDY DESIGN

A cross-sectional study.

SUBJECTS

Children born at term, aged 10-18 months, with and without a history of hyperbilirubinemia were included in the study.

OUTCOME MEASURES

After demographic information was recorded, motor development was evaluated with the Peabody Motor Development Scale-2 and sensory processing skills were evaluated with the Test of Sensory Function in Infant.

RESULTS

A total of 42 children (mean ± SD age of the children 13.07 ± 1.47 months, 22 with hyperbilirubinemia and 20 without hyperbilirubinemia) were included in the study. A statistically significant difference was found in the gross motor (p = 0.02), fine motor (p = 0.03), and total motor (p = 0.017) development scores of the Peabody Motor Development Scale-2 and in the adaptive motor functions (p = 0.004), visual tactile integration (p < 0.001), and total scores (p = 0.004) of The Test of Sensory Function in Infant in favor of the control group.

CONCLUSIONS

The motor and sensory processing skills of children born at term with hyperbilirubinemia may be negatively affected. Infants with hyperbilirubinemia should be evaluated from the early period not only in terms of motor but also sensory processing skills and should be supported with appropriate intervention programs.

Identification of risk factors in pre-term infants with abnormal general movements

INTRODUCTION

This study aimed to investigate the relationship between prenatal, perinatal, and postnatal risk factors for neurodevelopmental impairment (NDI) with the outcomes of General Movement (GM) Assessment (GMA) in pre-term infants at 3-5 months of age. We sought to identify the risk factors associated with the predictors of psychomotor development in pre-term newborns, such as normal fidgety movements (FMs), absent FMs, or abnormal FMs, assessed during the fidgety period of motor development.

METHODS

The SYNAGIS program (prophylactic of Respiratory Syncytial Virus Infection) was used to identify risk factors for the development of neuromotor deficits in 164 pre-term infants who were at high risk of developing these deficits. Based on the GMA, all participants were divided into three groups of infants who presented: (1) normal FMs; (2) absent FMs; and (3) abnormal FMs.

RESULTS

The results of the current study suggest that abnormal GMs not only indicate commonly known factors like birth asphyxia (BA), respiratory distress syndrome (RDS), periventricular leukomalacia (PVL), intraventricular hemorrhage (IVH) grades 3-4, but also predict the development of motor impairments. In the present study, several specific risk factors including bronchopulmonary dysplasia (BPD), infertility treatments, maternal acute viral/bacterial infections during pregnancy, and elevated bilirubin levels were identified as attributes of an atypical fidgety movement pattern.

CONCLUSIONS

Additional clinical data, such as risk factors for NDI associated with early predictors of psychomotor development in pre-term newborns, i.e., absent or abnormal FMs, may be helpful in predicting neurological outcomes in pre-term infants with developmental concerns in the 1st month of life.

The effect of hyperbilirubinemia on motor repertoire of infants between 3 and 5 months of age

Jaundice is a common problem and occurs as a result of the increase in bilirubin level in infants. Infants may be adversely affected by this situation. The aim of this study is to determine whether neonatal jaundice affects the movements and postures of 3- to 5-month-old infants with hyperbilirubinemia and the correlation of motor repertoire at the same age with bilirubin levels. The study group included 30 infants (9 girls, 21 boys) with hyperbilirubinemia and a control group of 30 infants (11 girls, 19 boys) with typical development without hyperbilirubinemia. The motor repertoires of the infants were evaluated through detailed general movement (GM) analysis using video recordings made at 9-17 weeks post-term. The infants with hyperbilirubinemia had lower motor optimality score and subcategory scores (including observed movement patterns, age-adequate movement repertoire, observed postural patterns, and movement character) compared with the control group. The fidgety movement scores decreased as bilirubin value increased in infants.Conclusion: Infants with hyperbilirubinemia had poorer motor repertoire when compared to a control group. For this reason, detailed GM analysis of these infants will predict probable neurodevelopmental problems and infants with needs can begin individualized early intervention suitable for movement repertoire and posture at the earliest time. What is Known: • GMs of infants with hyperbilirubinemia were previously described. • However, the motor repertoires of infants with hyperbilirubinemia were not described in detail. What is New: • Infants with hyperbilirubinemia had poorer motor repertoire when compared to peers. • This is important in determining the need for individualized early intervention.

Early Neurodevelopmental Outcome of Neonates with Gestation 35 Weeks or More with Serum Bilirubin in Exchange Range Without Encephalopathy: A Prospective Observational Study

OBJECTIVE

To describe early neurodevelopment outcomes of neonates with severe hyperbilirubinemia without acute bilirubin encephalopathy (ABE).

METHODS

Neonates born at gestation ≥35 weeks, admitted to NICU with total serum bilirubin (TSB) in exchange range with no features of ABE, were followed up until the age of 6 months. Infants were assessed for impaired hearing and neurodevelopment at 3 months and 6 months of age.

RESULTS

A total of 59 neonates were enrolled in the study. At 3 months of age, 7.6 percent of neonates were found to have hypotonia and motor delay, whereas 42.3 percent had abnormal brainstem evoked response audiometery. At 6 months, 6.4 percent of neonates were found to have persistent neurodevelopmental impairment.

CONCLUSION

Severe hyperbilirubinemia is associated with impaired neurodevelopment and hearing even in infants without ABE. Peak TSB level strongly correlates with abnormal outcomes.

Perinatal Factors in Newborn Are Insidious Risk Factors for Childhood Autism Spectrum Disorders: A Population-based Study

We analyzed claims data from the Taiwan National Health Insurance database, which contains data of 23.5 million Taiwan residents. We included children born after January 1, 2000 who had received a diagnosis of autism spectrum disorders (ASD). Patients who were not diagnosed with ASD were included in the control group. The ASD prevalence was 517 in 62,051 (0.83%) children. Neonatal jaundice, hypoglycemia, intrauterine growth retardation (IUGR), and craniofacial anomalies (CFA) differed significantly between the ASD and control groups. After logistic regressive analysis, the adjusted odds ratios of IUGR, CFA, neonatal hypoglycemia, and neonatal jaundice were 8.58, 7.37, 3.83, and 1.32, respectively. Those insidiously perinatal risk factors, namely CFA, IUGR, neonatal hypoglycemia, and neonatal jaundice, could increase the risk of ASD.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Long-term neurodevelopmental outcomes of significant neonatal jaundice in Taiwan from 2000-2003: a nationwide, population-based cohort study

Newborns with significant neonatal jaundice (SNJ) would admit for evaluation and/or intervention due to an earlier or more rapid increase in bilirubin level. Bilirubin-induced neurological dysfunction in this population might be underestimated. We aimed to investigate the risk of long-term neurodevelopmental sequelae of SNJ in Taiwan. An SNJ 2000–2003 follow-up cohort consisting of 66,983 neonates was extracted from the nationwide, population-based health insurance database in Taiwan to survey the accumulative incidence of long-term (7-year) neurodevelopmental sequelae in comparison to a reference general-population neonate cohort of 12,579 individuals born in 2000. The SNJ follow-up cohort was furtherly categorized into subgroups according to interventions (phototherapy, intensive phototherapy, and exchange transfusion). The SNJ follow-up cohort exhibited significantly higher cumulative rates of long-term neurodevelopmental sequelae than did the reference cohort (P < 0.05). The risks of infantile cerebral palsy, hearing loss, and developmental delay in the SNJ follow-up cohort were between twice and three times of those in the reference cohort after adjusting for gender, comorbid perinatal disorders and urbanization levels. All intervention subgroups demonstrated higher risks for long-term neurodevelopmental sequelae than the reference cohort (P < 0.05) after adjustment. Patients with SNJ are at risk of developing neurodevelopmental disorders during their growth period. A scheduled follow-up protocol of physical and neurodevelopmental assessment during early childhood for these SNJ patients would potentially be helpful for the early detection of and intervention for neurodevelopmental disorders.

The spectrum of bilirubin neurotoxicity in term and near-term babies with hyperbilirubinemia: Does outcome improve with time?

BACKGROUND

While neonatal jaundice is generally a common benign condition; severe hyperbilirubinemia has a devastating potential for brain injury.

AIM

To detect the impact of severe neonatal hyperbilirubinemia on motor and mental development and its progress over time in the first year of life using the Bayley scales of infant development (BSID) II.

STUDY DESIGN AND PATIENTS

177 term/near-term infants admitted for neonatal hyperbilirubinemia to the NICU of Cairo University Children's Hospital were enrolled. Clinical examination, BIND score and laboratory tests were performed at admission. Neurodevelopmental assessment using BSIDΙΙ was performed at 3 months for 147/177 neonates, and at 6 months and 12 months for 139/177 neonates. Auditory brainstem evoked potential was recorded at 3 months of age and repeated if abnormal.

OUTCOME MEASURES

Psychomotor (PDI) and mental developmental indices (MDI) using BSIDII. Auditory impairment using Auditory Brainstem Response (ABR).

RESULTS

TSB levels ranged from 10 to 63 mg/dL (179.6-1077 μmol/L) with a mean of 25.52 ± 6.5 mg/dL (436 ± 112.9 μmol/L) and BIND scores ranged from 0 to 7. By one year of age, 19/139 patients were affected; 8 had classic kernicterus, 3 had isolated auditory impairment, 1 had severe motor and mild mental delay and 7 had mild motor delay. TSB level and BIND score had positive correlation with auditory impairment and lower scores for PDI (which improved with time) and MDI (which remained stationary). Duration of exposure to hyperbilirubinemia negatively affected neurodevelopmental scores.

CONCLUSION

The impact of severe hyperbilirubinemia is mainly on motor and auditory impairment. Mild mental delay was detected by BSIDII in few patients. Neurodevelopmental outcome improves over time.

Incidence, Risk Factors, and Outcomes of Hyperbilirubinemia in Adult Cardiac Patients Supported by Veno-Arterial ECMO

The aims of this study were to evaluate the incidence, risk factors, and outcomes of hyperbilirubinemia in cardiac patients with veno-arterial (VA) ECMO. Data on 89 adult patients with cardiac diseases who received VA ECMO implantation in our hospital were retrospectively reviewed. All patients were divided into the following three groups: 24 in normal group (N, total bilirubin [TBIL] ≤3 mg/dL), 30 in high bilirubin group (HB, 6 mg/dL ≥ TBIL > 3 mg/dL), and 35 in severe high bilirubin group (SHB, TBIL > 6 mg/dL). lg(variables + 1) was performed for nonnormally distributed variables. The incidence of hyperbilirubinemia (>3 mg/dL) was 73%. In a multiple linear regression analysis, lg(peak TBIL + 1) was significantly associated with lg(peak AST + 1) (b-coefficient 0.188, P = 0.001), lg(peak pFHb + 1) (b-coefficient 0.201, P = 0.003), and basic TBIL (b-coefficient 0.006, P = 0.009). Repeated measurement analysis of variance revealed that the main effect for three groups in pFHb and lg(AST + 1) was significant at first 3 days during ECMO. The patients in SHB had low platelets during ECMO and low in-hospital survival rate. Hyperbilirubinemia remains common in patients with VA ECMO and is associated with low platelets and high in-hospital mortality. Hemolysis and liver dysfunction during ECMO and basic high bilirubin levels are risk factors of hyperbilirubinemia.

Neurological condition assessed with the Hempel examination and cognition and behaviour at 4years

AIM

To investigate associations between neurological condition, assessed with the Hempel examination, in terms of minor neurological dysfunction (MND) and neurological optimality, and cognition and behaviour at 4years.

STUDY DESIGN

Cross-sectional analyses within a prospective, assessor-blinded follow-up study.

SUBJECTS

Four-year-old singletons born to subfertile parents (n=235; 120 boys).

OUTCOME MEASURES

Outcome parameters were complex minor neurological dysfunction (complex MND) and the neurological optimality score (NOS). Cognitive outcome was evaluated with the Kaufman Assessment Battery for Children, resulting in a total intelligence quotient (IQ). Behavioural outcome was evaluated with the Child Behavior Checklist, resulting in a total problem T-score.

RESULTS

Fifty-seven (24.3%) children had complex MND. None of the children showed fine motor dysfunction, suggesting a ceiling effect of the Hempel assessment. Complex MND was not correlated with IQ or total problem T-score. Nevertheless, a higher NOS was correlated with a higher IQ and a lower total problem T-score (adjusted mean estimate [95% confidence interval]: cognition: 0.445 [0.026; 0.865], p=0.038; behaviour: -0.458 [-0.830; -0.087], p=0.016).

INTERPRETATION

At age 4, complex MND assessed with the Hempel assessment was not associated with cognition and behaviour, presumably due to a ceiling effect in the Hempel domain of fine motor function. A more optimal neurological condition was associated with higher IQ and better behaviour.

Predictive value of General Movement Assessment for preterm infants' development at 2 years - implementation in clinical routine in a non-academic setting

BACKGROUND

General movements (GM) are used in academic settings to predict developmental outcome in infants born preterm. However, little is known about the implementation and predictive value of GM in non-academic settings.

AIMS

The aim of this study is twofold: To document the implementation of GM assessment (GMA) in a non-academic setting and to assess its predictive value in infants born preterm.

METHODS AND PROCEDURES

We documented the process of implementing GMA in a non-academic outpatient clinic. In addition, we assessed the predictive value of GMA at 1 and 3 months' corrected age for motor and cognitive development at 2 years in 122 children born <33 weeks' gestation. Outcome at two years was based upon the Bayley Scales of Infant Development-II (mental/psychomotor developmental index (MDI, PDI)) and a neurological examination. The infants' odds of atypical outcome (MDI or PDI ≤70 or diagnosis CP) and the predictive accuracy of abnormal GMA were calculated in a clinical routine scenario, which used all available GM information (primarily at 3 months or at 1 month, when 3 months were not available). In addition, separate analysis was undertaken for the samples of GMA at 1 and 3 months.

OUTCOMES AND RESULTS

Tips to facilitate GMA implementation are described. In our clinical routine scenario, children with definitely abnormal GM were more likely to have an atypical two-year outcome than children with normal GM (OR 13.2 (95% CI 1.56; 112.5); sensitivity 55.6%, specificity 82.1%). Definitely abnormal GM were associated with reduced MDI (-12.0, 95% CI -23.2; -0.87) and identified all children with cerebral palsy (CP) in the sample of GMA at 3 months only.

CONCLUSIONS AND IMPLICATIONS

GMA can be successfully implemented in a non-academic outpatient setting. In our clinical routine scenario, GMA allowed for adequate prediction of neurodevelopment in infants born preterm, thereby allaying concerns about diagnostic accuracy in non-academic settings.

Bilirubin-Induced Neurotoxicity in the Preterm Neonate

Bilirubin-induced neurotoxicity in preterm neonates remains a clinical concern. Multiple cellular and molecular cascades likely underlie bilirubin-induced neuronal injury, including plasma membrane perturbations, excitotoxicity, neuroinflammation, oxidative stress, and cell cycle arrest. Preterm newborns are particularly vulnerable secondary to central nervous system immaturity and concurrent adverse clinical conditions that may potentiate bilirubin toxicity. Acute bilirubin encephalopathy in preterm neonates may be subtle and manifest primarily as recurrent symptomatic apneic events. Low-bilirubin kernicterus continues to be reported in preterm neonates, and although multifactorial in nature, is often associated with marked hypoalbuminemia.

Movement disorders due to bilirubin toxicity

Advances in the care of neonatal hyperbilirubinemia have led to a decreased incidence of kernicterus. However, neonatal exposure to high levels of bilirubin continues to cause severe motor symptoms and cerebral palsy (CP). Exposure to moderate levels of unconjugated bilirubin may also cause damage to the developing central nervous system, specifically the basal ganglia and cerebellum. Brain lesions identified using magnetic resonance imaging following extreme hyperbilirubinemia have been linked to dyskinetic CP. Newer imaging techniques, such as diffusion tensor imaging or single-photon emission computed tomography, allow quantification of more subtle white matter injury following presumed exposure to unbound bilirubin, and may explain more subtle movement disorders. New categories of bilirubin-induced neurologic dysfunction, characterized by subtle bilirubin encephalopathy following moderate hyperbilirubinemia, have been implicated in long-term motor function. Further research is needed to identify subtle impairments resulting from moderate-severe neonatal hyperbilirubinemia, to understand the influence of perinatal risk factors on bilirubin toxicity, and to develop neuroprotective treatment strategies to prevent movement disorders due to bilirubin toxicity.

Are the neuromotor disabilities of bilirubin-induced neurologic dysfunction disorders related to the cerebellum and its connections?

Investigators have hypothesized a range of subcortical neuropathology in the genesis of bilirubin-induced neurologic dysfunction (BIND). The current review builds on this speculation with a specific focus on the cerebellum and its connections in the development of the subtle neuromotor disabilities of BIND. The focus on the cerebellum derives from the following observations: (i) the cerebellum is vulnerable to bilirubin-induced injury; perhaps the most vulnerable region within the central nervous system; (ii) infants with cerebellar injury exhibit a neuromotor phenotype similar to BIND; and (iii) the cerebellum has extensive bidirectional circuitry projections to motor and non-motor regions of the brainstem and cerebral cortex that impact a variety of neurobehaviors. Future study using advanced magnetic resonance neuroimaging techniques have the potential to shed new insights into bilirubin's effect on neural network topology via both structural and functional brain connectivity measurements.

The clinical syndrome of bilirubin-induced neurologic dysfunction

Clinicians have hypothesized a spectrum of minor neurologic manifestations, consistent with neuroanatomical reports and collectively termed as a "syndrome of bilirubin-induced neurologic dysfunction (BIND)," which can occur in the absence of classical kernicterus. The current review builds on these initial reports with a focus on clinical signs and symptoms that are assessed by standardized tools and manifest from neonatal age to childhood. These clinical manifestations are characterized by the following domains: (i) neuromotor signs; (ii) muscle tone abnormalities; (iii) hyperexcitable neonatal reflexes; (iv) variety of neurobehavior manifestations; (v) speech and language abnormalities; and (vi) evolving array of central processing abnormalities, such as sensorineural audiology and visuomotor dysfunctions. Concerns remain that the most vulnerable infants are likely to acquire BIND, either because their exposure to bilirubin is not identified as severe enough to need treatment or is prolonged but slightly below current threshold levels for intervention. Knowing that a total serum/plasma bilirubin (TB) level is not the most precise indicator of neurotoxicity, the role of expanded biomarkers or a "bilirubin panel" has yet to be validated in prospective studies. Future studies that correlate early "toxic" bilirubin exposure to long-term academic potential of children are needed to explore new insights into bilirubin's effect on the structural and functional maturation of an infant's neural network topology.

Subtle bilirubin-induced neurodevelopmental dysfunction (BIND) in the term and late preterm infant: does it exist?

Subtle bilirubin-induced neurological dysfunction (BIND) is defined as disturbances in sensory and sensorimotor integration, central auditory processing, coordination, and muscle tone in the absence of the classical findings of kernicterus. This review is restricted to the (sensori)motor signs of BIND associated with unconjugated hyperbilirubinemia in term and late preterm neonates. The diagnosis of BIND at follow-up requires validated, age-specific techniques that are designed to identify these disturbances in infancy and later childhood. The (sensori)motor signs of BIND are compatible with the pathological substrate of unconjugated hyperbilirubinemia and its known effects on the brain.

Bilirubin-albumin binding, bilirubin/albumin ratios, and free bilirubin levels: where do we stand?

Treatment for unconjugated hyperbilirubinemia is predominantly based on one parameter, i.e., total serum bilirubin (TSB) levels. Yet, overt kernicterus has been reported in preterm infants at relatively low TSB levels, and it has been repeatedly shown that free unconjugated bilirubin (freeUCB) levels, or bilirubin/albumin (B/A) ratios for that matter, are more closely associated with bilirubin neurotoxicity. In this article, we review bilirubin-albumin binding, UCBfree levels, and B/A ratios in addition to TSB levels to individualize and optimize treatment especially in preterm infants. Methods to measure bilirubin-albumin binding or UCBfree are neither routinely performed in Western clinical laboratories nor incorporated in current management guidelines on unconjugated hyperbilirubinemia. For bilirubin-albumin binding, this seems justified because several of these methods have been challenged, and sufficiently powered prospective trials on the clinical benefits are lacking. Technological advances in the measurement of UCBfree may provide a convenient means for integrating UCBfree measurements into routine clinical management of jaundiced infants. A point-of-care method, as well as determination of UCBfree levels in various newborn populations, is desirable to learn more about variations in time and how various clinical pathophysiological conditions affect UCBfree levels. This will improve the estimation of approximate UCBfree levels associated with neurotoxicity. To delineate the role of UCBfree in the management of jaundiced (preterm) infants, trials are needed using UCBfree as treatment parameter. The additional use of the B/A ratio in jaundiced preterms has been evaluated in the Bilirubin Albumin Ratio Trial (BARTrial; Clinical Trials: ISRCTN74465643) but failed to demonstrate better neurodevelopmental outcome in preterm infants <32 weeks assigned to the study group. Awaiting a study in which infants are assigned to be managed solely on the basis of their B/A ratio (with TSB excluded ) versus TSB levels alone-and determining which group does better-the additional use of the B/A ratio in the management of hyperbilirubinemia in preterms is not advised. In conjunction with TSB levels, other parameters possibly allow for more accurate prediction of bilirubin toxicity. Yet, different methodologies for estimating these parameters exist, and sufficiently powered, prospective clinical trials supporting their clinical benefit, i.e., reduced bilirubin neurotoxicity when using these parameters, are lacking. Their use in addition to TSB needs to be prospectively evaluated, especially in preterm neonates, and preferentially in randomized clinical trials, which include specific risk factors and assessment of clinical relevant outcome measures for detecting those infants at risk of bilirubin toxicity.

Jaundice and kernicterus in the moderately preterm infant

Moderate preterm infants remain at increased risk for adverse outcomes, including acute bilirubin encephalopathy (ABE). Evidence-based guidelines for management of hyperbilirubinemia in preterm infants less than 35 weeks' gestational age are not yet optimized. High concentrations of unconjugated bilirubin can cause permanent posticteric neurologic sequelae (kernicterus). Clinical manifestations of ABE in preterm infants are similar to, but often more subtle than, those of term infants. This review outlines clinical strategies to operationalize management of hyperbilirubinemia in moderately preterm infants to meet recently published consensus-based recommendations.