Magnetic resonance imaging of bilirubin encephalopathy: current limitations and future promise

Molecular events in brain bilirubin toxicity revisited

The mechanisms involved in bilirubin neurotoxicity are still far from being fully elucidated. Several different events concur to damage mainly the neurons among which inflammation and alteration of the redox state play a major role. An imbalance of cellular calcium homeostasis has been recently described to be associated with toxic concentrations of bilirubin, and this disequilibrium may in turn elicit an inflammatory reaction. The different and age-dependent sensitivity to bilirubin damage must also be considered in describing the dramatic clinical picture of bilirubin-induced neurological damage (BIND) formerly known as kernicterus spectrum disorder (KSD). This review aims to critically address what is known and what is not in the molecular events of bilirubin neurotoxicity to provide hints for a better diagnosis and more successful treatments. Part of these concepts have been presented at the 38th Annual Audrey K. Brown Kernicterus Symposium of Pediatric American Society, Washington DC, May 1, 2023.

Magnetic resonance spectroscopy and auditory brain-stem response audiometry as predictors of bilirubin-induced neurologic dysfunction in full-term jaundiced neonates

The purpose of this research was to define the functions of MRS and ABR as predictors of bilirubin-induced neurologic dysfunction (BIND) in full-term neonates who required intervention (phototherapy and/or exchange transfusion). This prospective cohort study was done at the NICU of Tanta University Hospitals over a 2-year duration. Fifty-six full-term neonates with pathological unconjugated hyperbilirubinemia were divided according to MRS and ABR findings into 2 groups: group (1) included 26 cases with mild acute bilirubin encephalopathy (BIND-M score 1-4). Group (2) included 30 cases with neonatal hyperbilirubinemia only. In addition, 20 healthy neonates with similar ages were employed as the controls. When compared to group 2 and the control group, group 1's peak-area ratios of NAA/Cr and NAA/Cho were found to be significantly reduced (P < 0.05). As compared to group 2 and the control group, group 1's Lac/Cr ratio was significantly greater (P < 0.05), but the differences were not significant for group 2 when compared to the control group. Waves III and V peak latencies, I-III, and I-V interpeak intervals were significantly prolonged in group 1 in comparison to group 2 and controls (P < 0.05) with no significant difference between group 2 and control group.   Conclusion: When the symptoms of ABE are mild and MRI does not show any evident abnormalities, MRS and ABR are helpful in differentiating individuals with ABE from patients with neonatal hyperbilirubinemia.    Trial registration:  ClinicalTrials.gov , Identifier: NCT06018012. What is Known: • MRS can be used as a diagnostic and prognostic tool for the differential diagnosis of patients with acute bilirubin encephalopathy, from patients with neonatal hyperbilirubinemia What is New: • ABR is a useful diagnostic and prognostic tool in the care and management of neonates with significantly raised bilirubin. It can be used as early predictor of acute bilirubin encephalopathy in the earliest stage of auditory damage caused by bilirubin.

Predictive and diagnostic measures for kernicterus spectrum disorder: a prospective cohort study

BACKGROUND

Kernicterus spectrum disorder (KSD) resulting from neonatal hyperbilirubinemia remains a common cause of cerebral palsy worldwide. This 12-month prospective cohort study followed neonates with hyperbilirubinemia to determine which clinical measures best predict KSD.

METHODS

The study enrolled neonates ≥35 weeks gestation with total serum bilirubin (TSB) ≥ 20 mg/dl admitted to Aminu Kano Hospital, Nigeria. Clinical measures included brain MRI, TSB, modified bilirubin-induced neurologic dysfunction (BIND-M), Barry-Albright Dystonia scale (BAD), auditory brainstem response (ABR), and the modified KSD toolkit. MRI signal alteration of the globus pallidus was scored using the Hyperbilirubinemia Imaging Rating Tool (HIRT).

RESULTS

Of 25 neonates enrolled, 13/25 completed 12-month follow-up and six developed KSD. Neonatal BIND-M ≥ 3 was 100% sensitive and 83% specific for KSD. Neonatal ABR was 83% specific and sensitive for KSD. Neonatal HIRT score of 2 was 67% sensitive and 75% specific for KSD; this increased to 100% specificity and sensitivity at 12 months. BAD ≥ 2 was 100% specific for KSD at 3-12 months, with 50-100% sensitivity.

CONCLUSIONS

Neonatal MRIs do not reliably predict KSD. BIND-M is an excellent screening tool for KSD, while the BAD or HIRT score at 3 or 12 months can confirm KSD, allowing for early diagnosis and intervention.

IMPACT

The first prospective study of children with acute bilirubin encephalopathy evaluating brain MRI findings over the first year of life. Neonatal MRI is not a reliable predictor of kernicterus spectrum disorders (KSD). Brain MRI at 3 or 12 months can confirm KSD. The modified BIND scale obtained at admission for neonatal hyperbilirubinemia is a valuable screening tool to assess risk for developing KSD. The Barry Albright Dystonia scale and brain MRI can be used to establish a diagnosis of KSD in at-risk infants as early as 3 months.

Second nationwide survey of bilirubin encephalopathy in preterm infants in Japan

OBJECTIVES

To determine the clinical features of bilirubin encephalopathy in preterm infants (pBE) in Japan.

METHODS

We performed a retrospective, nationwide questionnaire-based survey. The initial survey determined the number of children with pBE who were born after 2000. Using a structured questionnaire, the second survey clarified the clinical manifestations and characteristics of children with pBE, including demographic data, neurological symptoms, and MRI and auditory brainstem response (ABR) findings.

RESULTS

The initial survey identified 41 pBE infants from 18 institutions. After exclusion of patients included in previous studies, clinical information was collected from 30 patients (21 boys and 9 girls) during the secondary survey. The median gestational age was 26 weeks and the median birthweight was 846 g. Chronic lung disease and symptomatic patent ductus arteriosus were common neonatal complications. Head control was observed in 63% and functional gait in 17% of patients. Purposeful hand use was seen in 57% and verbal communication in 50% of patients. MRI showed T2 hyperintensities in the globus pallidus of 29 of 30 patients. ABR abnormalities were present in 11 of 15 patients. None of the variables were significantly different between the 2017 and 2021 surveys.

CONCLUSIONS

The pBE infants had severely impaired gross motor function and relatively preserved manual function and verbal communication. MRI and ABR findings aid in the diagnosis of pBE.

Unconjugated bilirubin is correlated with the severeness and neurodevelopmental outcomes in neonatal hypoxic-ischemic encephalopathy

Unconjugated bilirubin (UB) levels during the first week after birth are related to outcomes in neonatal hypoxic-ischemic encephalopathy (HIE). Clinical Sarnat staging of HIE, brain magnetic resonance imaging (MRI), hearing outcomes, and neurodevelopmental outcomes ≥ 1 year were used to correlate UB in 82 HIE patients. The initial UB level was significantly correlated with lactic acid levels. The peak UB was higher (p < 0.001) in stage I (10.13 ± 4.03 mg/dL, n = 34) than in stages II and III (6.11 ± 2.88 mg/dL, n = 48). Among the 48 patients receiving hypothermia treatment, a higher peak UB was significantly (p < 0.001) correlated with unremarkable brain MRI scans and unremarkable neurodevelopmental outcomes at age ≥ 1 year. The peak UB were higher (P = 0.015) in patients free of seizures until 1 year of age (6.63 ± 2.91 mg/dL) than in patients with seizures (4.17 ± 1.77 mg/dL). Regarding hearing outcomes, there were no significant differences between patients with and without hearing loss. The UB level in the first week after birth is an important biomarker for clinical staging, MRI findings, seizures after discharge before 1 year of age, and neurodevelopmental outcomes at ≥ 1 year of age.

Mildly Elevated Bilirubin Levels are Associated with Increased Magnetic Resonance Imaging Signal Intensity in the Basal Ganglia of Preterm Neonates

OBJECTIVE

This study aimed to test whether mildly elevated bilirubin levels in preterm infants are associated with increased signal intensity (SI) on magnetic resonance imaging (MRI) of the basal ganglia (BG).

STUDY DESIGN

MRI was performed at term equivalent age in 55 postpreterm infants using a neonatal MRI 1-T scanner. SI of the BG was correlated with mild hyperbilirubinemia.

RESULTS

BG MRI SI was significantly increased in infants with mild hyperbilirubinemia on T1-weighted image (T1; p = 0.0393) and T2-weighted image (T2; p = 0.0309). We found no effect of gestational age or sepsis on BG MRI intensity; however, there was a significant effect of acidosis on T1 (p = 0.0223) but not on T2 (p = 0.2316). Infants with combined hyperbilirubinemia and acidosis had the most significant increase in SI on both T1 and T2 respectively (p = 0.0072 and 0.0195, respectively).

CONCLUSION

We found a positive association between increased BG MRI SI and mildly elevated bilirubin levels. The effect was greatly strengthened when hyperbilirubinemia was associated with acidosis.

KEY POINTS

· Excessive bilirubin is neurotoxic to the neonatal brain. It is deposited in the BG.. · BG MRI SI is increased with bilirubin deposition.. · The premature brain is more vulnerable to bilirubin associated MRI changes..

Acute and Chronic Kernicterus: MR Imaging Evolution of Globus Pallidus Signal Change during Childhood

BACKGROUND AND PURPOSE

Despite its rarity in Western countries, kernicterus resulting from severe neonatal hyperbilirubinemia and its associated neurologic consequences still persists. Subtle MR imaging patterns may be overlooked, leading to diagnostic and prognostic uncertainties. The study systematically analyzes MR imaging pattern over time.

MATERIALS AND METHODS

A retrospective MR imaging study was conducted in Departments of Pediatric Neurology at the University Children's Hospitals in Leipzig, Germany, or Tübingen, Germany, between 2012 and 2022 in patients who presented beyond the neonatal period suspected of having chronic kernicterus.

RESULTS

Eight patients with a total of 15 MR images were identified. The clinical diagnosis of kernicterus was confirmed in all cases on the basis of typical MR imaging findings: Bilateral, diffuse hyperintensity of the globus pallidus was observed in the neonatal period on T1WI (1 MR imaging, at 2 weeks), in infancy on T2WI (4 MR images, at 9-26 months). In children 2 years of age and older, bilateral hyperintensity on T2WI was limited to the borders of the globus pallidus (8 MR images, at 20 months -13 years). Notably, 2 children exhibited normal initial MR imaging findings at 2 months of age. Hence, MR imaging depiction of kernicterus pathology evolves with time, first evident on T1WI, subsequently on T2WI, with a "blind window" during early infancy. The T2WI signal change initially involves the entire globus pallidus and later is limited to the borders. Kernicterus had not been diagnosed in any except 2 patients by previous investigators.

CONCLUSIONS

All patients presented with a characteristic clinical history and signs and an evolving MR imaging pattern. Nonetheless, the diagnosis of kernicterus was frequently missed. Abnormalities on later MR images appear to be underrecognized.

The differential value of radiomics based on traditional T1-weighted sequences in newborns with hyperbilirubinemia

BACKGROUND

On the basis of visual-dependent reading method, radiological recognition and assessment of neonatal hyperbilirubinemia (NH) or acute bilirubin encephalopathy (ABE) on conventional magnetic resonance imaging (MRI) sequences are challenging. Prior studies had shown that radiomics was possible to characterize ABE-induced intensity and morphological changes on MRI sequences, and it has emerged as a desirable and promising future in quantitative and objective MRI data extraction. To investigate the utility of radiomics based on T1-weighted sequences for identifying neonatal ABE in patients with hyperbilirubinemia and differentiating between those with NH and the normal controls.

METHODS

A total of 88 patients with NH were enrolled, including 50 patients with ABE and 38 ABE-negative individuals, and 70 age-matched normal neonates were included as controls. All participants were divided into training and validation cohorts in a 7:3 ratio. Radiomics features extracted from the basal ganglia of T1-weighted sequences on magnetic resonance imaging were evaluated and selected to set up the prediction model using the K-nearest neighbour-based bagging algorithm. A receiver operating characteristic curve was plotted to assess the differentiating performance of the radiomics-based model.

RESULTS

Four of 744 radiomics features were selected for the diagnostic model of ABE. The radiomics model yielded an area under the curve (AUC) of 0.81 and 0.82 in the training and test cohorts, with accuracy, precision, sensitivity, and specificity of 0.82, 0.80, 0.91, and 0.69 and 0.78, 0.8, 0.8, and 0.75, respectively. Six radiomics features were selected in this model to distinguish those with NH from the normal controls. The AUC for the training cohort was 0.97, with an accuracy of 0.92, a precision of 0.92, a sensitivity of 0.93, and a specificity of 0.90. The performance of the radiomics model was confirmed by testing the test cohort, and the AUC, accuracy, precision, sensitivity, and specificity were 0.97, 0.92, 0.96, 0.89, and 0.95, respectively.

CONCLUSIONS

The proposed radiomics model based on traditional TI-weighted sequences may be used effectively for identifying ABE and even differentiating patients with NH from the normal controls, which can provide microcosmic information beyond experience-dependent vision and potentially assist in clinical diagnosis and treatment.

Bilirubin-Induced Transcriptomic Imprinting in Neonatal Hyperbilirubinemia

Recent findings indicated aberrant epigenetic control of the central nervous system (CNS) development in hyperbilirubinemic Gunn rats as an additional cause of cerebellar hypoplasia, the landmark of bilirubin neurotoxicity in rodents. Because the symptoms in severely hyperbilirubinemic human neonates suggest other regions as privileged targets of bilirubin neurotoxicity, we expanded the study of the potential impact of bilirubin on the control of postnatal brain development to regions correlating with human symptoms. Histology, transcriptomic, gene correlation, and behavioral studies were performed. The histology revealed widespread perturbation 9 days after birth, restoring in adulthood. At the genetic level, regional differences were noticed. Bilirubin affected synaptogenesis, repair, differentiation, energy, extracellular matrix development, etc., with transient alterations in the hippocampus (memory, learning, and cognition) and inferior colliculi (auditory functions) but permanent changes in the parietal cortex. Behavioral tests confirmed the presence of a permanent motor disability. The data correlate well both with the clinic description of neonatal bilirubin-induced neurotoxicity, as well as with the neurologic syndromes reported in adults that suffered neonatal hyperbilirubinemia. The results pave the way for better deciphering the neurotoxic features of bilirubin and evaluating deeply the efficacy of new therapeutic approaches against the acute and long-lasting sequels of bilirubin neurotoxicity.

Deep Learning Network with Spatial Attention Module for Detecting Acute Bilirubin Encephalopathy in Newborns Based on Multimodal MRI

BACKGROUND

Acute bilirubin encephalopathy (ABE) is a significant cause of neonatal mortality and disability. Early detection and treatment of ABE can prevent the further development of ABE and its long-term complications. Due to the limited classification ability of single-modal magnetic resonance imaging (MRI), this study aimed to validate the classification performance of a new deep learning model based on multimodal MRI images. Additionally, the study evaluated the effect of a spatial attention module (SAM) on improving the model's diagnostic performance in distinguishing ABE.

METHODS

This study enrolled a total of 97 neonates diagnosed with ABE and 80 neonates diagnosed with hyperbilirubinemia (HB, non-ABE). Each patient underwent three types of multimodal imaging, which included T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), and an apparent diffusion coefficient (ADC) map. A multimodal MRI classification model based on the ResNet18 network with spatial attention modules was built to distinguish ABE from non-ABE. All combinations of the three types of images were used as inputs to test the model's classification performance, and we also analyzed the prediction performance of models with SAMs through comparative experiments.

RESULTS

The results indicated that the diagnostic performance of the multimodal image combination was better than any single-modal image, and the combination of T1WI and T2WI achieved the best classification performance (accuracy = 0.808 ± 0.069, area under the curve = 0.808 ± 0.057). The ADC images performed the worst among the three modalities' images. Adding spatial attention modules significantly improved the model's classification performance.

CONCLUSION

Our experiment showed that a multimodal image classification network with spatial attention modules significantly improved the accuracy of ABE classification.

Imaging of nerve injury in neonatal acute bilirubin encephalopathy using 1H-MRS and Glu-CEST techniques

Objectives

To investigate the significance of proton magnetic resonance spectroscopy (1H-MRS) and glutamate chemical exchange saturation transfer (Glu-CEST) techniques in assessing the condition and prognosis of acute bilirubin encephalopathy patients and to understand the mechanism of nerve injury in this disease.

Materials and methods

From September 2019 to February 2021, 31 neonates with acute bilirubin encephalopathy and 16 healthy neonates were enrolled in this study. All the quantitative results of 1H-MRS, Glu-CEST, and conventional magnetic resonance imaging (MRI) of all neonates were analyzed. The associations between statistically significant indicators of imaging and developmental quotients (DQ) were analyzed.

Results

The 31 cases were assigned to the mild subgroup (n = 21) and moderate and severe subgroup (n = 10) according to the bilirubin-induced neurologic dysfunction (BIND) scores. The case group had elevated Cho and GABA absolute concentrations compared to the normal control group (all p &lt; 0.05). Compared with the normal control group, the absolute concentration of GABA of the moderate and severe subgroup was significantly larger (p &lt; 0.05). Compared with the normal control group, the Glu-CEST% values in the left basal ganglia, right thalamus, left frontal cortex and bilateral medial geniculate body of the case group was significantly larger (all p &lt; 0.05). The moderate and severe subgroup had higher Glu-CEST% values in the left basal ganglia, right thalamus, and bilateral medial geniculate body than the normal control group (all p &lt; 0.05). A negative association was revealed between the DQ scores and the Glu-CEST% values in the left basal ganglia (r = −0.888, p &lt; 0.05).

Conclusion

The combination of 1H-MRS and Glu-CEST techniques can monitor the intracerebral metabolite level of acute bilirubin encephalopathy and evaluate the illness severity.

The added value of brain MR spectroscopy in children with Crigler-Najjar syndrome type-I: correlation with demographic, neurodevelopmental, and laboratory findings

OBJECTIVE

The aim of this study is to demonstrate the role of proton magnetic resonance spectroscopy (1H-MRS) in the detection of brain microstructural changes in patients with Crigler-Najjar syndrome type-I (CNs-I), and its correlation with demographic, neurodevelopmental and laboratory findings.

METHODS

Prospective study was conducted on 25 children with CNs-I and 25 age and sex-matched children, who served as control. They underwent multivoxel 1H-MRS of basal ganglion at echo time 135-144 ms. N-acetyl aspartate/Creatine (NAA/Cr) and Choline (Ch)/Cr were calculated and correlated with demographic, clinical, and laboratory findings of patients with CNs-I.

RESULTS

There was a significant difference in NAA/Cr and Ch/Cr between patients and controls. The cut-off value for NAA/Cr and Ch/Cr used to differentiate patients from controls were 1.8 and 1.2 with an area under the curve (AUC) of 0.91 and 0.84 respectively. There was a significant difference in MRS ratios between patients with neurodevelopmental delay (NDD) and patients without NDD. The cut-off values for NAA/Cr and Ch/Cr used to differentiate between patients with NDD and patients without NDD were 1.47 and 0.99, with AUC of 0.87 and 0.8 respectively. The NAA/Cr and Ch/Cr were well correlated with family history (p = 0.006 and p < 0.001) respectively, consanguinity (p < 0.001 and p = 0.001), neurodevelopmental delay (p = 0.001 and p = 0.004), serum bilirubin level (r = -0.77, p < 0.001), (r = -0.49, p = 0.014), phototherapy (p < 0.001 and p = 0.32), blood transfusion (p < 0.001 and p = 0.001) respectively.

CONCLUSION

1H-MRS can be a useful tool in the detection of neurological changes in patients with CNs-I; NAA/Cr and Ch/Cr parameters are well correlated with demographic, clinical, and laboratory findings.

ADVANCES IN KNOWLEDGE

Our study is the first report on using MRS in assessing neurological manifestations in CNs. 1H-MRS can be a useful tool in the detection of neurological changes in patients with CNs-I.

Development and evaluation clinical-radiomics analysis based on T1-weighted imaging for diagnosing neonatal acute bilirubin encephalopathy

Purpose

To investigate the value of clinical-radiomics analysis based on T1-weighted imaging (T1WI) for predicting acute bilirubin encephalopathy (ABE) in neonates.

Methods

In this retrospective study, sixty-one neonates with clinically confirmed ABE and 50 healthy control neonates were recruited between October 2014 and March 2019. Two radiologists' visual diagnoses for all subjects were independently based on T1WI. Eleven clinical and 216 radiomics features were obtained and analyzed. Seventy percent of samples were randomly selected as the training group and were used to establish a clinical-radiomics model to predict ABE; the remaining samples were used to validate the performance of the models. The discrimination performance was assessed by receiver operating characteristic (ROC) curve analysis.

Results

Seventy-eight neonates were selected for training (median age, 9 days; interquartile range, 7-20 days; 49 males) and 33 neonates for validation (median age, 10 days; interquartile range, 6-13 days; 24 males). Two clinical features and ten radiomics features were finally selected to construct the clinical-radiomics model. In the training group, the area under the ROC curve (AUC) was 0.90 (sensitivity: 0.814; specificity: 0.914); in the validation group, the AUC was 0.93 (sensitivity: 0.944; specificity: 0.800). The AUCs of two radiologists' and the radiologists' final visual diagnosis results based on T1WI were 0.57, 0.63, and 0.66, respectively. The discriminative performance of the clinical-radiomics model in the training and validation groups was increased compared to the radiologists' visual diagnosis (P < 0.001).

Conclusions

A combined clinical-radiomics model based on T1WI has the potential to predict ABE. The application of the nomogram could potentially provide a visualized and precise clinical support tool.

Investigation of EEG changes before and after phototherapy in infants with severe hyperbilirubinemia

BACKGROUND

Despite the known effect of hyperbilirubinemia in neonates, the effect of phototherapy on electroencephalography (EEG) remains unknown. Therefore, we aimed to determine the alteration of electroencephalography in infants with hyperbilirubinemia before and after phototherapy.

METHODS

This cross-sectional study was performed on infants of≥35 weeks of gestation with hyperbilirubinemia. Information including age, sex, birth weight, hemoglobin levels, and treatment measures was recorded. In all studied infants, an EEG was performed before (in the first eight hours of hospitalization) and after treatment (after phototherapy or blood transfusion). The required duration of phototherapy, hospitalization and adverse effects were assessed then EEG of the neonates was compared before and after treatment.

RESULTS

A total of 52 infants (44% female and 56% male) were included in this study. Mean gestational age, weight, and bilirubin were 38.6±1.53 weeks, 3150±625 g, and 23.87±4.36 mg/dl, respectively. The most common findings before phototherapy were Frontal Theta (21 patients, 40.4 percent) and Delta Brush (14 patients, 26.9%), while the most common findings after phototherapy were Frontal Theta (20 patients, 38.5%) and Delta Brush (19 patients, 36.5%). Mean±SD of bilirubin in infants with and without Delta Brush was 21.30±1.67 mg/dl and 19.95±0.94 mg/dl, respectively.

CONCLUSIONS

Hyperbilirubinemia in newborns may be linked to altered EEG findings. After phototherapy, the Frontal theta was reduced, but the Delta brush was intensified. Bilirubin levels were higher in infants with Delta Brush in their EEG compared to infants without this finding.

Brain structure correlates with auditory function in children diagnosed with auditory neuropathy spectrum disorder

INTRODUCTION

Auditory neuropathy spectrum disorder (ANSD) is a term for a collection of test results which indicate disruption of the auditory signal at some point along the neural pathway. This results in a spectrum of functional outcomes, ranging from reasonably normal hearing to profound hearing loss. This study assessed brain structure changes and behavioral correlates in children diagnosed with ANSD.

METHODS

Seventeen children who had previously been diagnosed with ANSD were recruited to the study and underwent a battery of behavioral measures of hearing, language, and communication, along with structural MR imaging. Analysis of cortical thickness of temporal lobe structures was carried out using FreeSurfer. Tract-based spatial statistics were performed on standard diffusion parameters of fractional anisotropy and diffusivity metrics. The control group comprised imaging data taken from a library of MRI scans from neurologically normal children. Control images were matched as closely as possible to the ANSD group for age and sex.

RESULTS

Reductions in right temporal lobe cortical thickness were observed in children with ANSD compared to controls. Increases in medial diffusivity in areas including the corpus callosum and in the right occipital white matter were also seen in the group with ANSD compared to controls. Speech perception abilities, both in quiet and in noise, were correlated with cortical thickness measurements for several temporal lobe structures in children with ANSD, and relationships were also seen between diffusion metrics and measures of auditory function.

CONCLUSION

This study shows that children with ANSD have structural brain differences compared to healthy controls. It also demonstrates associations between brain structure and behavioral hearing abilities in children diagnosed with ANSD. These results show that there is a potential for structural imaging to be used as a biomarker in this population with the possibility of predicting functional hearing outcome.

Models of bilirubin neurological damage: lessons learned and new challenges

OBJECTIVE

Jaundice (icterus) is the visible manifestation of the accumulation of bilirubin in the tissue and is indicative of potential toxicity to the brain. Since its very first description more than 2000 years ago, many efforts have been undertaken to understand the molecular determinants of bilirubin toxicity to neuronal cells to reduce the risk of neurological sequelae through the use of available chemicals and in vitro, ex vivo, in vivo, and clinical models. Although several studies have been performed, important questions remain unanswered, such as the reasons for regional sensitivity and the interplay with brain development. The number of new molecular effects identified has increased further, which has added even more complexity to the understanding of the condition. As new research challenges emerged, so does the need to establish solid models of prematurity.

METHODS

This review critically summarizes the key mechanisms of severe neonatal hyperbilirubinemia and the use of the available models and technologies for translational research.

IMPACT

We critically review the conceptual dogmas and models used for studying bilirubin-induced neurotoxicity. We point out the pitfalls and translational gaps, and suggest new clinical research challenges. We hope to inform researchers on the pro and cons of the models used, and to help direct their experimental focus in a most translational research.

Bilirubin Encephalopathy

PURPOSE OF REVIEW

Hyperbilirubinemia is commonly seen in neonates. Though hyperbilirubinemia is typically asymptomatic, severe elevation of bilirubin levels can lead to acute bilirubin encephalopathy and progress to kernicterus spectrum disorder, a chronic condition characterized by hearing loss, extrapyramidal dysfunction, ophthalmoplegia, and enamel hypoplasia. Epidemiological data show that the implementation of universal pre-discharge bilirubin screening programs has reduced the rates of hyperbilirubinemia-associated complications. However, acute bilirubin encephalopathy and kernicterus spectrum disorder are still particularly common in low- and middle-income countries.

RECENT FINDINGS

The understanding of the genetic and biochemical processes that increase the susceptibility of defined anatomical areas of the central nervous system to the deleterious effects of bilirubin may facilitate the development of effective treatments for acute bilirubin encephalopathy and kernicterus spectrum disorder. Scoring systems are available for the diagnosis and severity grading of these conditions. The treatment of hyperbilirubinemia in newborns relies on the use of phototherapy and exchange transfusion. However, novel therapeutic options including deep brain stimulation, brain-computer interface, and stem cell transplantation may alleviate the heavy disease burden associated with kernicterus spectrum disorder. Despite improved screening and treatment options, the prevalence of acute bilirubin encephalopathy and kernicterus spectrum disorder remains elevated in low- and middle-income countries. The continued presence and associated long-term disability of these conditions warrant further research to improve their prevention and management.

Detecting acute bilirubin encephalopathy in neonates based on multimodal MRI with deep learning

BACKGROUND

Differentiating acute bilirubin encephalopathy (ABE) from non-ABE in neonates with hyperbilirubinemia (HB) from routine magnetic resonance imaging (MRI) is extremely challenging since both conditions demonstrate similar T1 hyperintensities. To this end, we investigated whether the integration of multimodal MRI from routine clinical scans with deep-learning approaches could improve diagnostic performance.

METHODS

A total of 75 neonates with ABE and 75 neonates with HB (non-ABE) were included in the study. Each patient had three types of multimodal images taken, i.e., a T1-weighted image (T1WI), a T2-weighted image (T2WI), and an apparent diffusion coefficient (ADC) map. The three types of MRI contrasts and their combination were fed into two deep convolutional neural networks (CNNs), i.e., ResNet18 and DenseNet201. The performance of CNNs was compared with a traditional statistical method named logistic regression.

RESULTS

We demonstrated that diagnostic methods with the multimodal data were better than any of the single-modal data. Both CNN models outperformed the logistic regression method. The best performance was achieved by DenseNet201 with the combination of three modalities of T1WI, T2WI, and ADC, with an accuracy of 0.929 ± 0.042 and an area under the curve (AUC) of 0.991 ± 0.007.

CONCLUSIONS

Our study demonstrated that CNN models with multimodal MRI significantly improve the accuracy of diagnosing ABE.

IMPACT

We proposed an efficient strategy of detecting ABE in neonates based on multimodal MRI with deep learning, which achieved an accuracy of 0.929 ± 0.042 and an AUC of 0.991 ± 0.007. We demonstrated the advantage of integrating multimodal MRI in detecting ABE in neonates with HB, using deep-learning models. Our strategy of diagnosing ABE using deep-learning techniques with multimodal MRI from routine clinical scans is potentially applicable to clinical practice.

Diffusion tensor magnetic resonance imaging: is it valuable in the detection of brain microstructural changes in patients having migraine without aura?

Purpose

The aim of this study is to assess the diagnostic value of diffusion tensor magnetic resonance imaging (MRI) in the detection of brain microstructural changes in patients having migraine without aura.

Material and methods

Our prospective study included 33 patients having migraine without aura and 15 volunteers with matched age and sex, who underwent brain MRI with diffusion tensor imaging (DTI). The fractional anisotropy (FA) and mean diffusivity (MD) of selected grey and white matter regions on both sides were measured and correlated with the neurological clinical examination.

Results

Significant differences were detected in MD values in the thalamus, globus pallidus, and hippocampus head on the right side of patients versus controls. Also, significant differences of the FA values were detected in the thalamus, globus pallidus, and hippocampus head on the right side of patients versus controls. Regarding the FA values of the same regions on the left side, a significant difference in the FA value was detected only in the hippocampus head. There was a statistically significant difference in the FA values on both sides of the white matter of the frontal lobes, posterior limbs of the internal capsules, and cerebellar hemispheres in patients compared to controls. There was a statistically significant difference in MD values in the white matter of both frontal lobes, posterior limb of the right internal capsule, and both cerebellar hemispheres in patients compared to controls.

Conclusions

DTI can detect microstructural changes of the grey and white matter in patients having migraine without aura that could not be detected by conventional MRI.

Magnetic Resonance Image of Neonatal Acute Bilirubin Encephalopathy: A Diffusion Kurtosis Imaging Study

Background and Objective: The abnormal T1-weighted imaging of MRI can be used to characterize neonatal acute bilirubin encephalopathy (ABE) in newborns, but has limited use in evaluating the severity and prognosis of ABE. This study aims to assess the value of diffusion kurtosis imaging (DKI) in detecting ABE and understanding its pathogenesis.

Method: Seventy-six newborns with hyperbilirubinemia were grouped into three groups (mild group, moderate group, and severe group) based on serum bilirubin levels. All the patients underwent conventional MRI and DKI serial, as well as 40 healthy full-term infants (control group). The regions of interest (ROIs) were the bilateral globus pallidus, dorsal thalamus, frontal lobe, auditory radiation, superior temporal gyrus, substantia nigra, hippocampus, putamen, and inferior olivary nucleus. The values of mean diffusivity (MD), axial kurtosis (AK), radial kurtosis (RK), and mean kurtosis (MK), and fractional anisotropy (FA), radial diffusivity (RD), and axis diffusivity (AD) of the ROIs were evaluated. All newborns were followed up and evaluated using the Denver Development Screening Test (DDST). According to the follow-up results, the patients were divided into the normal group, the suspicious abnormal group, and the abnormal group.

Result: Compared with the control group, significant differences were observed with the increased MK of dorsal thalamus, AD of globus pallidus in the moderate group, and increased RD, MK, AK, and RK value of globus pallidus, dorsal thalamus, auditory radiation, superior temporal gyrus, and hippocampus in the severe group. The peak value of total serum bilirubin was moderately correlated with the MK of globus pallidus, dorsal thalamus, and auditory radiation and was positively correlated with the other kurtosis value. Out of 76 patients, 40 finished the DDST, and only 9 patients showed an abnormality. Compared with the normal group, the AK value of inferior olivary nucleus showed significant differences (p < 0.05) in the suspicious abnormal group, and the MK of globus pallidus, temporal gyrus, and auditory radiation; RK of globus pallidus, dorsal thalamus, and auditory radiation; and MD of globus pallidus showed significant differences (p < 0.05) in the abnormal group.

Conclusion: DKI can reflect the subtle structural changes of neonatal ABE, and MK is a sensitive indicator to indicate the severity of brain damage.

Magnetic Resonance Imaging Findings in Preterm Infants With Bilirubin Encephalopathy Beyond Three Years Corrected Age

BACKGROUND

Magnetic resonance imaging (MRI) abnormalities in preterm infants with bilirubin encephalopathy (BE) become less clear as the infants age. We assessed MRI findings in children with preterm BE older than 36 months corrected age (CA).

METHODS

In a previous questionnaire survey, hospitals were asked to provide head MRI data of patients older than 36 months CA. MRI findings were reviewed by three pediatric neurology specialists and classified as no abnormalities, partial globus pallidus (GP) lesions, or diffuse GP lesions.

RESULTS

In total, 33 MRI scans were available from 28 patients. The median gestational age and birth weight were 26 weeks and 824 g, respectively. The prevalence of MRI abnormalities was 100% in patients at 37 to 48 months CA, 71% in those at 49 to 60 months CA, 50% in those at 61 to 72 months CA, 67% in those at 73 to 84 months CA, and 38% in those at 85 months CA or older. Partial GP lesions were more common than diffuse GP lesions at all ages. No significant differences in sex, gestational age, birth weight, or gross motor function impairment were observed among lesion groups.

CONCLUSIONS

GP lesions were detected on MRI in most children with preterm BE when studied after 36 months CA, although MRI abnormalities became less apparent along with age. Partial GP lesions may be a characteristic of older children with preterm BE.

Detecting neonatal acute bilirubin encephalopathy based on T1-weighted MRI images and learning-based approaches

Background

Neonatal hyperbilirubinemia is a common clinical condition that requires medical attention in newborns, which may develop into acute bilirubin encephalopathy with a significant risk of long-term neurological deficits. The current clinical challenge lies in the separation of acute bilirubin encephalopathy and non-acute bilirubin encephalopathy neonates both with hyperbilirubinemia condition since both of them demonstrated similar T1 hyperintensity and lead to difficulties in clinical diagnosis based on the conventional radiological reading. This study aims to investigate the utility of T1-weighted MRI images for differentiating acute bilirubin encephalopathy and non-acute bilirubin encephalopathy neonates with hyperbilirubinemia.

Methods

3 diagnostic approaches, including a visual inspection, a semi-quantitative method based on normalized the T1-weighted intensities of the globus pallidus and subthalamic nuclei, and a deep learning method with ResNet18 framework were applied to classify 47 acute bilirubin encephalopathy neonates and 32 non-acute bilirubin encephalopathy neonates with hyperbilirubinemia based on T1-weighted images. Chi-squared test and t-test were used to test the significant difference of clinical features between the 2 groups.

Results

The visual inspection got a poor diagnostic accuracy of 53.58 ± 5.71% indicating the difficulty of the challenge in real clinical practice. However, the semi-quantitative approach and ResNet18 achieved a classification accuracy of 62.11 ± 8.03% and 72.15%, respectively, which outperformed visual inspection significantly.

Conclusion

Our study indicates that it is not sufficient to only use T1-weighted MRI images to detect neonates with acute bilirubin encephalopathy. Other more MRI multimodal images combined with T1-weighted MRI images are expected to use to improve the accuracy in future work. However, this study demonstrates that the semi-quantitative measurement based on T1-weighted MRI images is a simple and compromised way to discriminate acute bilirubin encephalopathy and non-acute bilirubin encephalopathy neonates with hyperbilirubinemia, which may be helpful in improving the current manual diagnosis.

Amplitude of low-frequency fluctuation may be an early predictor of delayed motor development due to neonatal hyperbilirubinemia: a fMRI study

BACKGROUND

Acute bilirubin encephalopathy or kernicterus is the worst consequence of brain damage caused by the elevation of total unbound serum bilirubin (TSB) in neonates. The present study aimed to visualize the characteristic brain regions of neonates with hyperbilirubinemia (HB) using functional magnetic resonance imaging (fMRI) and to measure the amplitude of low-frequency fluctuation (ALFF) values.

METHODS

This was a prospective cohort study, which included newborns with HB who were hospitalized at the Children's Hospital of Fudan University. The control group included neonates admitted with neonatal simple wet lung or pneumonia without neurological disease or brain injury. Newborns were divided into a severe hyperbilirubinemia group (SHB), moderate HB group, and control group based on TSB levels. The newborns completed routine MRI combined with fMRI scans and brainstem auditory evoked potentials (BAEPs) during their hospitalization.

RESULTS

A total of 251 newborns were included in this study. There were 45 patients in the SHB group, 65 in the HB group, and 141 in the control group. The average ALFF value in the basal ganglia region in the SHB group was the highest, which was greater than that in the HB and control groups (P<0.001). The ALFF increased with an increase in TSB concentration. Based on the results of the Bayley Scales of infant development assessment, we further found that the most significant difference in ALFF remained in the basal ganglia region between newborns with motor development scores above 70 (including 70) and below 70. Correlation analysis revealed a strong negative correlation between motor development scores and ALFF (r=-0.691, P<0.001). When ALFF alone was used to predict motor development, the sensitivity was 89%. When ALFF was combined with TSB and BEAP results, the area under the ROC curve was the largest (AUC =0.85). The sensitivity and specificity of the model were 67.86% and 90.77%, respectively.

CONCLUSIONS

The ALFF value may be able to serve as an early imaging biomarker and has a greater sensitivity than TSB or BAEP results in predicting long-term motor development (18 m) in HB.

Neonatal Encephalopathy: Beyond Hypoxic-Ischemic Encephalopathy

Neonatal encephalopathy is a clinical syndrome of neurologic dysfunction that encompasses a broad spectrum of symptoms and severity, from mild irritability and feeding difficulties to coma and seizures. It is vital for providers to understand that the term "neonatal encephalopathy" is simply a description of the neonate's neurologic status that is agnostic to the underlying etiology. Unfortunately, hypoxic-ischemic encephalopathy (HIE) has become common vernacular to describe any neonate with encephalopathy, but this can be misleading. The term should not be used unless there is evidence of perinatal asphyxia as the primary cause of encephalopathy. HIE is a common cause of neonatal encephalopathy; the differential diagnosis also includes conditions with infectious, vascular, epileptic, genetic/congenital, metabolic, and toxic causes. Because neonatal encephalopathy is estimated to affect 2 to 6 per 1,000 term births, of which HIE accounts for approximately 1.5 per 1,000 term births, (1)(2)(3)(4)(5)(6) neonatologists and child neurologists should familiarize themselves with the evaluation, diagnosis, and treatment of the diverse causes of neonatal encephalopathy. This review begins by discussing HIE, but also helps practitioners extend the differential to consider the broad array of other causes of neonatal encephalopathy, emphasizing the epidemiology, neurologic presentations, diagnostics, imaging findings, and therapeutic strategies for each potential category.

Amplitude-integrated electroencephalography improves the predictive ability of acute bilirubin encephalopathy

BACKGROUND

To establish a clinical prediction model of acute bilirubin encephalopathy (ABE) using amplitude-integrated electroencephalography (aEEG).

METHODS

A total of 114 neonatal hyperbilirubinemia patients in the Beijing Chaoyang Hospital from August 2015 to October 2018 were enrolled in this study. There were 62 (54.38%) males, and the age of patients undergoing aEEG examination was 2-23 days, with an average of 7.61±4.08 days. Participant clinical information, peak bilirubin value, albumin value, hyperbilirubinemia, and the graphic indicators of aEEG were extracted from medical records, and ABE was diagnosed according to a bilirubin-induced neurological dysfunction (BIND) score >0. Multivariable logistic regression was used to establish a clinical prediction model of ABE. Furthermore, decision curve analysis (DCA) was performed to evaluate the model's predictive value.

RESULTS

According to the BIND score, there were a total of 23 (20.18%) ABE cases. The multivariable logistic regression analysis showed that the value of bilirubin/albumin (B/A), presence of hyperbilirubinemia risk factors, number of sleep-wake cycling (SWC) within 3 hours, widest bandwidth, duration of SWC, and type of SWC were significantly associated with ABE. A clinical prediction model was developed as: p=ex/ (1+ex), X=0.278+0.713*B/A+2.602*with risk factors (with risk factors equals 1) - 1.500*SWC number within 3 hours + 0.219*the widest bandwidth-0.065*the duration of one SWC + 1.491* SWC (mature SWC equals 0, immature SWC equals 1). The area under the curve (AUC) was 0.85 [95% confidence interval (CI): 0.75-0.94], which was significantly higher than the AUC only based on conventional clinical information of B/A (AUC: 0.58, 95% CI: 0.45-0.72). The DCA also showed good predictive ability compared to B/A.

CONCLUSIONS

A clinical prediction model can be established based on the patients' B/A, presence of risk factors for hyperbilirubinemia, number of SWC within 3 hours, widest bandwidth, duration of 1 SWC, and the type of SWC. It has good predictive ability and may improve the diagnostic accuracy of ABE.

Analysis on the MRI and BAEP Results of Neonatal Brain With Different Levels of Bilirubin

BACKGROUND

To explore whether there is abnormality of neonatal brains' MRI and BAEP with different bilirubin levels, and to provide an objective basis for early diagnosis on the bilirubin induced subclinical damage on brains.

METHODS

To retrospectively analyze the clinical data of 103 neonatal patients, to conduct routine brain MRI examination and BAEP testing, and to analyze BAEP and MRI image results of the neonatal patients, who were divided into three groups based on the levels of total serum bilirubin concentration (TSB): 16 cases in mild group (TSB: 0.0-229.0 ěmol/L), 49 cases in moderate group (TSB: 229.0-342.0 ěmol/L), and 38 cases in severe group (TSB ≥ 342.0 ěmol/L).

RESULTS

We found the following: A. Comparison of the bilirubin value of the different group: The bilirubin value of the mild group is 171.99 ± 33.50 ěmol/L, the moderate group is 293.98 ± 32.09 ěmol/L, and the severe group is 375.59 ± 34.25 ěmol/L. The comparison of bilirubin values of the three groups of neonates (p < 0.01) indicates the difference is statistically significant (p < 0.01). B. The weight value of the <2,500 g group is 2.04 ± 0.21 and the ≥2,500 g group is 3.39 ± 0.46; the weight comparison of the two groups indicates that the difference is statistically significant (p < 0.01). C. Comparison of the abnormal MRI of the different groups: The brain MRI result's abnormal ratio of the mild group is 31.25%, the moderate group is 16.33%, and the severe group is 21.05%, but the comparison of brain MRI results of the three neonates groups indicates that the difference is not statistically significant (p > 0.05). D. Comparison of abnormal MRI signal values of globus pallidus on T1WI in different groups: 1. The comparison of normal group signal values with that of mild group (p < 0.05), with that of moderate group, and with that of severe group (p < 0.01) indicates that the difference is statistically significant.

CONCLUSION

At low level of bilirubin, central nervous system damage may also occur and can be detected as abnormality by MRI and BAEP. Meanwhile, MRI and BAEP can also provide early abnormal information for the judgment of central nervous system damage of the children with NHB who have no acute bilirubin encephalopathy (ABE) clinical features, and provide clues for early treatment and early intervention.

A nationwide survey of bilirubin encephalopathy in preterm infants in Japan

OBJECTIVES

To examine the clinical characteristics of bilirubin encephalopathy in preterm infants (pBE) in Japan.

METHODS

We performed a two-step nationwide questionnaire survey. The initial survey determined the number of children with pBE. Using a structured questionnaire, the second survey clarified the clinical manifestations and characteristics of children with pBE, including the perinatal history, neonatal complications, neurological features, verbal communication, diet, and magnetic resonance imaging (MRI) and auditory brainstem response (ABR) findings.

RESULTS

The initial survey included 190 pBE infants, indicating an incidence of approximately 10 per year. Clinical information was available for 142 of them. The median gestational age was 26 weeks and the median birthweight was 883 g. As to neonatal complications, 20% had none, 25% had one complication, 54% had two or more. Head control was observed in 45% and functional gait in 8%. Purposeful hand use was seen in 41% of patients and verbal communication in 40%. MRI showed T2 hyperintensities in the globi pallidi in 111 of 136 patients, especially between 7 and 18 months of corrected age. ABR abnormalities were present in 88 of 117 patients.

CONCLUSIONS

pBE was infrequent but constantly observed during the study period, especially in very preterm infants, even in those with no severe neonatal complications. Severely impaired gross motor function and relatively preserved manual function and verbal communication were characteristic. MRI and ABR abnormalities will facilitate diagnosis.

Diagnostic value of combination of cranial MRI, serum homocysteine and procalcitonin for hyperbilirubinemia complicated with brain injury in neonates

The present study aimed to explore the diagnostic value of the combination of cranial magnetic resonance imaging (MRI), serum homocysteine (HCY) and procalcitonin (PCT) for hyperbilirubinemia complicated with brain injury in neonates. One hundred and forty-nine children with hyperbilirubinemia admitted to Shandong Medical Imaging Research Institute from January 2014 to April 2016 were collected as research subjects, and were divided into a brain injury group (n=67) and a non-brain injury group (n=82) according to whether children suffered from brain injury. PCT levels were detected by electrochemiluminescence (ECL), and HCY levels by enzymatic cycling assay (ECA). The combination of cranial MRI, HCY and PCT was used to diagnose hyperbilirubinemia complicated with brain injury in neonates. The concentrations of HCY and PCT in the brain injury group were significantly higher than those in the non-brain injury group (P<0.001). According to the MRI examination results, the patients were divided into an MRI normal group and an MRI abnormal group. In the brain injury group, the serum HCY and PCT levels of the MRI abnormal group were significantly higher than those of the MRI normal group, with a statistically significant difference (P<0.05). In the non-brain injury group, the serum HCY and PCT levels of the MRI abnormal group were significantly higher than those of the MRI normal group, with a statistically significant difference (P<0.05). The sensitivity of the combined detection was significantly higher than that of single detection (P<0.05); the specificity was significantly higher than that of HCY detection (P<0.05), and the accuracy was significantly higher than that of MRI and HCY single detection (P<0.05). In conclusion, the combination of cranial MRI, HCY and PCT, which has a high diagnostic value for hyperbilirubinemia complicated with brain injury in neonates, is conducive to the early diagnosis and timely treatment of the disease and the reduction of sequelae.

Bilateral lesions of the basal ganglia and thalami (central grey matter)-pictorial review

The basal ganglia and thalami are paired deep grey matter structures with extensive metabolic activity that renders them susceptible to injury by various diseases. Most pathological processes lead to bilateral lesions, which may be symmetric or asymmetric, frequently showing characteristic patterns on imaging studies. In this comprehensive pictorial review, the most common and/or typical genetic, acquired metabolic/toxic, infectious, inflammatory, vascular and neoplastic pathologies affecting the central grey matter are subdivided according to the preferential location of the lesions: in the basal ganglia, in the thalami or both. The characteristic imaging findings are described with emphasis on the differential diagnosis and clinical context.

Long-term Effects of Indirect Hyperbilirubinemia on Auditory and Neurological Functions in Term Newborns

Objective:

The aim of this study was to investigate the long-term effects of hyperbilirubinemia on neurological and hearing function in otherwise healthy term newborns with neonatal indirect hyperbilirubinemia.

Method:

This study was performed prospectively in 41 term newborns hospitalized for indirect hyperbilirubinemia. Patients with no signs of hemolysis were categorized in 3 groups based on stabil levels as sTB <20 mg/dl, 20-24.9 mg/dl, and =>25 mg/dl. Patients with total bilirubin level =>20 mg/dl and hemolytic disease were classified as the fourth group. The relationship between maximum sTB level, duration of exposure to sTB levels >20 mg/dl and etiology of jaundice with neurological and auditory functions was investigated. Detailed neurological examination, Denver II developmental screening test and hearing tests (otoacoustic emissions, OAE and auditory brainstem responses, ABR) were performed to all patients between 18-24 months of age.

Results:

Neurodevelopmental disorder was found in 5 (12.2%) patients. Hemolytic disease was detected in two of these patients. Hearing loss was found in 4 (9.8%) of the patients. Two of these patients had auditory neuropathy spectrum disorder and the other two had cochlear hearing loss. The sTB levels of all these patients were above 25 mg/dl. No neurological disorder or hearing loss was found in the patients who had stabil of <25 mg/dl. Exposure time to sTB levels above 20 mg/dl was significantly longer in patients with neurological dysfunction and pathologic ABR results (p:0.007, p:0.007; p<0.05).

Conclusion:

This study demonstrates that kernicterus may develop in term newborns with severe hyperbilirubinemia (sTB>25 mg/dl) without any finding of significant hemolysis. Not only the bilirubin level but also the duration of exposure to high bilirubin levels may be effective in the development of bilirubin neurotoxicity. The high rate of hearing loss in our patients emphasizes the importance of screening for infants with severe hyperbilirubinemia using comprehensive auditory evaluation for early diagnosis of possible hearing loss.

[Application of magnetic resonance diffusion tensor imaging in bilirubin-induced neurological dysfunction in neonates]

OBJECTIVE

To study the value of fractional anisotropy (FA) of regions of interest (ROI) on magnetic resonance diffusion tensor imaging (DTI) in bilirubin-induced neurological dysfunction in neonates.

METHODS

A total of 91 neonates with hyperbilirubinemia who were hospitalized from January 2017 to January 2018 were enrolled. According to the peak level of total serum bilirubin, they were divided into three groups: mild/moderate increase (n=45), severe increase (n=35), and extremely severe increase (n=11). According to the presence or absence of abnormal neurological manifestations, they were divided into two groups: neurological dysfunction (n=20) and non-neurological dysfunction (n=71). Ten healthy full-term infants were enrolled as the control group. Head DTI was performed for all neonates to measure the FA values of the bilateral globus pallidus, the anterior limb of the internal capsule, the posterior limb of the internal capsule, and the cerebellar dentate nucleus.

RESULTS

The extremely severe increase group had significantly lower FA values of the globus pallidus than the control, mild/moderate increase, and severe increase groups (P<0.05). The severe increase group had significantly lower FA values of the globus pallidus than the control group (P<0.05). The extremely severe increase group had significantly lower FA values of the posterior limb of the internal capsule than the control, mild/moderate increase, and severe increase groups (P<0.05). The neurological dysfunction group had significantly lower FA values of the globus pallidus and the posterior limb of the internal capsule than the non-neurological dysfunction group (P<0.05).

CONCLUSIONS

Serum bilirubin level combined with the changes in the DTI FA values of the globus pallidus and the posterior limb of the internal capsule can be used to predict the injury of cerebral nuclei and white matter fibers.

[Application of magnetic resonance diffusion tensor imaging in bilirubin-induced neurological dysfunction in neonates]

OBJECTIVE

To study the value of fractional anisotropy (FA) of regions of interest (ROI) on magnetic resonance diffusion tensor imaging (DTI) in bilirubin-induced neurological dysfunction in neonates.

METHODS

A total of 91 neonates with hyperbilirubinemia who were hospitalized from January 2017 to January 2018 were enrolled. According to the peak level of total serum bilirubin, they were divided into three groups: mild/moderate increase (n=45), severe increase (n=35), and extremely severe increase (n=11). According to the presence or absence of abnormal neurological manifestations, they were divided into two groups: neurological dysfunction (n=20) and non-neurological dysfunction (n=71). Ten healthy full-term infants were enrolled as the control group. Head DTI was performed for all neonates to measure the FA values of the bilateral globus pallidus, the anterior limb of the internal capsule, the posterior limb of the internal capsule, and the cerebellar dentate nucleus.

RESULTS

The extremely severe increase group had significantly lower FA values of the globus pallidus than the control, mild/moderate increase, and severe increase groups (P<0.05). The severe increase group had significantly lower FA values of the globus pallidus than the control group (P<0.05). The extremely severe increase group had significantly lower FA values of the posterior limb of the internal capsule than the control, mild/moderate increase, and severe increase groups (P<0.05). The neurological dysfunction group had significantly lower FA values of the globus pallidus and the posterior limb of the internal capsule than the non-neurological dysfunction group (P<0.05).

CONCLUSIONS

Serum bilirubin level combined with the changes in the DTI FA values of the globus pallidus and the posterior limb of the internal capsule can be used to predict the injury of cerebral nuclei and white matter fibers.

Early prediction of adverse outcomes in infants with acute bilirubin encephalopathy

OBJECTIVE

Acute bilirubin encephalopathy (ABE) remains one of the important causes of neonatal mortality and child disability, early identification, and intervention which could improve outcomes. The purpose of this study was to evaluate early predictors of adverse outcomes in infants with ABE.

METHODS

Newborns of gestational age ≥ 35 weeks and diagnosed with ABE were included in the study. Bilirubin-induced neurological dysfunction (BIND) score, total serum bilirubin (TSB) peak value, and serum albumin levels were determined. Adverse outcomes were defined as death or survival with auditory dysfunction and/or cerebral palsy.

RESULTS

Eighty-two infants were eligible for recruitment in the study. The outcome data from 76 ABE infants (92%) were used for analysis, of which 25 infants got adverse outcomes and 51 live a normal life. Univariate analysis for BIND score, TSB peak value, bilirubin-albumin ratio (B/A), albumin level, abnormal AABR, and neonatal sepsis was performed to elucidate the association with adverse outcomes. Bivariate logistic regression analysis showed B/A (OR 10.48, 95%CI: 1.55-70.81, P = 0.02) and BIND score (OR 3.68, 95%CI: 1.39-9.72, P = 0.01) were correlated with adverse outcomes. ROC curve analysis showed that B/A (≥8.9 mg/g), BIND score (≥6) could predict adverse outcomes of ABE separately; B/A in conjunction with BIND score could increase prediction sensitivity to 100%.

INTERPRETATION

Both B/A and BIND score can be used to predict adverse outcomes of ABE, and the combination of the two parameters can increase prediction sensitivity significantly.

Diffusion Tensor Imaging of Microstructural Changes in the Gray and White Matter in Patients With Crigler-Najjar Syndrome Type I

PURPOSE

This study aimed to evaluate the role of diffusion tensor imaging of microstructural changes in gray and white matter in Crigler-Najjar syndrome type I.

PATIENT AND METHODS

A prospective study was conducted on 10 patients with Crigler-Najjar syndrome type I and 10 age- and sex-matched children who underwent diffusion tensor imaging of the brain. Mean diffusivity (MD) and fractional anisotropy (FA) of gray and white matter were measured.

RESULTS

There was a significantly higher MD of the gray matter regions including the globus pallidus, thalamus, caudate head, substantia nigra, and dentate nucleus in patients versus controls (P = 0.007, 0.001, 0.014, 0.003, and 0.002), respectively. The areas under the curve (AUC) of MD of the globus pallidus and thalamus used to differentiate patients from controls were 0.93 and 0.925, respectively. There was a significant difference in MD of the frontal white matter and posterior limb of the internal capsule in patients versus controls (P = 0.001 and 0.02), respectively. The AUCs of MD of these regions used to differentiate patients from controls were 0.82 and 0.8. There was a significant difference in FA of the frontal white matter and posterior limb of the internal capsule in patients versus controls (P = 0.006 and 0.006), respectively. The AUCs of FA of these regions were 0.83 and 0.85, respectively. The MD of the globus pallidus correlated with serum bilirubin (r = 0.87 and P = 0.001).

CONCLUSION

Diffusion tensor imaging can detect microstructural changes of deep gray matter and some regions of white matter in Crigler-Najjar syndrome type I.

Bilirubin Induced Encephalopathy

Hyperbilirubinemia is one of the most common neonatal disorders. Delayed diagnosis and treatment of the pathologic and progressive indirect hyperbilirubinemia lead to neurological deficits, defined as bilirubin induced encephalopathy (BIE) (2). The incidence of this disorder in underdeveloped countries is much more than developed areas. All neonates with the risk factors for increased the blood level of indirect bilirubin are at risk for BIE, especially preterm neonates which are prone to low bilirubin kernicterus . BIE can be transient and acute (with early, intermediate and advanced phases)or be permanent, chronic and lifelong ( with tetrad of symptoms including visual (upward gaze palsy), auditory (sensory neural hearing loss), dental dysplasia abnormalities, and extrapyramidal disturbances (choreoathetosis cerebral palsy).Beside the abnormal neurologic manifestations of the jaundiced neonates ,brain MRI is the best imaging modality for the confirmation of the diagnosis. Although early treatment of extreme hyperbilirubinemia by phototherapy and exchange transfusion can prevent the BIE, unfortunately the chronic bilirubin encephalopathy does not have definitive treatment.

Machine Learning Assisted MRI Characterization for Diagnosis of Neonatal Acute Bilirubin Encephalopathy

Background: The use of magnetic resonance imaging (MRI) in diagnosis of neonatal acute bilirubin encephalopathy (ABE) in newborns has been limited by its difficulty in differentiating confounding image contrast changes associated with normal myelination. This study aims to demonstrate the feasibility of building a machine learning prediction model based on radiomics features derived from MRI to better characterize and distinguish ABE from normal myelination. Methods: In this retrospective study, we included 32 neonates with clinically confirmed ABE and 29 age-matched controls with normal myelination. Radiomics features were extracted from the manually segmented region of interest (ROI) on T1-weighted spin echo images, followed by the feature selection using two-sample independent t-test, least absolute shrinkage and selection operator (Lasso) regression, and Pearson's correlation matrix. Additional feature quantifying the relative mean intensity of ROI was defined and calculated. A prediction model based on the selected features was built to classify ABE and normal myelination using multiple machine learning classifiers and a leave-one-out cross-validation scheme. Receiver operating characteristics (ROC) analysis was used to evaluate the prediction performance with the area under the curve (AUC) and feature importance ranked based on the Fisher score. Results: Among 1319 radiomics features, one radiologist-defined intensity-based feature and 12 texture features were selected as the most discriminative features. Based on these features, decision trees had the best classification performance with the largest AUC of 0.946, followed by support vector machine (SVM), tree-bagger, logistic regression, Naïve Bayes, discriminant analysis, and k-nearest neighborhood (KNN), which have an AUC of 0.931, 0.925, 0.905, 0.891, 0.883, and 0.817, respectively. The relative mean intensity outperformed other 12 texture features in differentiating ABE from controls. Conclusions: The results from this study demonstrated a new strategy of characterizing ABE-induced intensity and morphological changes in MRI, which are difficult to be recognized, interpreted, or quantified by the routine experience and visual-based reading strategy. With more quantitative and objective measurements, the reported machine learning assisted radiomics features-based approach can improve the diagnosis and support clinical decision-making.

Neonatal Jaundice

Hyperbilirubinemia is a common occurrence in neonates; it may be physiological or pathological. Conjugated hyperbilirubinemia may result from medical or surgical causes, and can result in irreversible liver damage if untreated. The aim of imaging is the timely diagnosis of surgical conditions like biliary atresia and choledochal cysts. Abdominal ultrasound is the first line imaging modality, and Magnetic resonance cholangiopancreatography (MRCP) also has a role, especially in pre-operative assessment of choledochal cysts (CDCs). For biliary atresia, the triangular cord sign and gallbladder abnormalities are the two most useful ultrasound features, with a combined sensitivity of 95%. Liver biopsy has an important role in pre-operative evaluation; however, the gold standard for diagnosis of biliary atresia remains an intra-operative cholangiogram. Choledochal cysts are classified into types according to the number, location, extent and morphology of the areas of cystic dilatation. They are often associated with an abnormal pancreaticobiliary junction, which is best assessed on MRCP. Caroli's disease or type 5 CDC comprises of multiple intrahepatic cysts. CDCs, though benign, require surgery as they may be associated with complications like cholelithiasis, cholangitis and development of malignancy. Severe unconjugated hyperbilirubinemia puts neonates at high risk of developing bilirubin induced brain injury, which may be acute or chronic. Magnetic resonance imaging of the brain is the preferred modality for evaluation, and shows characteristic involvement of the globus pallidi, subthalamic nuclei and cerebellum - in acute cases, these areas show T1 hyperintensity, while chronic cases typically show hyperintensity on T2 weighted images.

Early Amplitude-Integrated Electroencephalography Predicts Long-Term Outcomes in Term and Near-Term Newborns With Severe Hyperbilirubinemia

BACKGROUND

We aimed to determine the predictive neurological prognostic value of early amplitude-integrated electroencephalography (aEEG) in term and near-term neonates with severe hyperbilirubinemia compared with cranial magnetic resonance imaging (MRI) and auditory brainstem response (ABR).

METHODS

Infants of ≥35 weeks of gestation with severe hyperbilirubinemia (total serum bilirubin [TSB] ≥340 μmol/L) or with hyperbilirubinemia (TSB ≥257 μmol/L) in association with bilirubin-induced neurological dysfunction were recruited. All the subjects had an aEEG after being admitted to the neonatal intensive care unit, whereas cranial MRI and ABR were performed when TSB had come down to the normal range. All the infants were followed up to 12 months.

RESULTS

During the study period, 77 of 83 infants were eligible, of which 71 had severe hyperbilirubinemia and six had hyperbilirubinemia in association with bilirubin-induced neurological dysfunction. Thirty-three infants were diagnosed with acute bilirubin encephalopathy (ABE), two of whom died of ABE, and 62 completed the follow-up, of which 12 infants had adverse outcomes. Sixty-four infants underwent aEEG, 40 infants had cranial MRI, and 39 infants had ABR. Logistic regression and the receiver-operator characteristic curve analysis showed that the ability of severely abnormal aEEG to predict adverse neurological outcomes in severe hyperbilirubinemia was no better than abnormal ABR, with a sensitivity of 35.7% versus 83.3%, a specificity of 92.0% versus 74.1%, a positive predictive value of 55.6% versus 58.8%, and a negative predictive value of 83.6% versus 90.9%.

CONCLUSIONS

Early aEEG could predict adverse neurodevelopmental outcomes in neonates with severe hyperbilirubinemia, although the sensitivity was lower than ABR.

Clinicopathological Spectrum of Bilirubin Encephalopathy/Kernicterus

Bilirubin encephalopathy/kernicterus is relatively rare, but continues to occur despite universal newborn screening. What is more interesting is the spectrum of clinical and even neuropathological findings that have been reported in the literature to be associated with bilirubin encephalopathy and kernicterus. In this review, the authors discuss the array of clinicopathological findings reported in the context of bilirubin encephalopathy and kernicterus, as well as the types of diagnostic testing used in patients suspected of having bilirubin encephalopathy or kernicterus. The authors aim to raise the awareness of these features among both pediatric neurologists and neuropathologists.

High unbound bilirubin for age: a neurotoxin with major effects on the developing brain

Neonatal hyperbilirubinemia is one of the most frequent diagnoses made in neonates. A high level of unconjugated bilirubin that is unbound to albumin is neurotoxic when the level exceeds age-specific thresholds or at lower levels in neonates with neurotoxic risk factors. Lower range of unbound bilirubin results in apoptosis, while moderate-to-high levels result in neuronal necrosis. Basal ganglia and various brain stem nuclei are more susceptible to bilirubin toxicity. Proposed mechanisms of bilirubin-induced neurotoxicity include excessive release of glutamate, mitochondrial energy failure, release of proinflammatory cytokines, and increased intracellular calcium concentration. These mechanisms are similar to the events that occur following hypoxic-ischemic insult in neonates. Severe hyperbilirubinemia in term neonates has been shown to be associated with increased risk for autism spectrum disorders. The neuropathological finding of bilirubin-induced neurotoxicity also includes cerebellar injury with a decreased number of Purkinje cells, and disruption of multisensory feedback loop between cerebellum and cortical neurons which may explain the clinical characteristics of autism spectrum disorders. Severe hyperbilirubinemia occurs more frequently in infants from low- and middle-income countries (LMIC). Simple devices to measure bilirubin, and timely treatment are essential to reduce neurotoxicity, and improve outcomes for thousands of neonates around the world.

Neurometabolic Disorders of the Newborn

There is an extensive and diverse set of medical conditions affecting the neonatal brain within the spectrum of neurometabolic disorders. As such, their clinical presentations can be rather nonspecific, and can often mimic acquired entities such as hypoxic-ischemic encephalopathy and sepsis. Similarly, the radiological findings in these entities can also be frequently nonspecific, but a more detailed analysis of imaging findings (especially magnetic resonance imaging) alongside the relevant clinical details can be a rewarding experience, thus enabling a timely and targeted diagnosis. Early diagnosis of an underlying neurometabolic disorder is vital, as some of these entities are potentially treatable, and laboratory and genetic testing can be precisely targeted. Further, their detection helps with counselling families for future pregnancies. We present a review of neurometabolic disorders specific to the newborns with a focus on how neuroimaging findings match their clinical presentation patterns.

Toxic-Metabolic Neurologic Disorders in Children: A Neuroimaging Review

There are multiple causes of neurotoxicity in children including medications, extrinsic toxins and insults, illicit drugs, built up of toxic metabolites due to genetic or acquired disorders, and metabolic abnormalities. The review is centered on causes of neurotoxicity affecting the pediatric brain and producing typical and easily recognized imaging manifestations. Early identification of common and less common imaging findings may point toward the correct direction, and may facilitate early diagnosis and institution of appropriate treatment to reverse or at least limit the injury to the developing brain. Two common imaging patterns of neurotoxicity in children are the posterior reversible encephalopathy syndrome and acute toxic leukoencephalopathy that are usually related to chemotherapy and immunosuppression for common pediatric malignancies. Another well-described imaging pattern of injury in children involves reversible splenial lesions with or without associated white matter abnormalities. Multiple additional extrinsic causes of neurotoxicity are presented including radiation and chemoradiation, various medications and treatment regimens, poisoning, illicit drug use or accidental exposure, and the respective characteristic neuroimaging findings are highlighted. Intrinsic neurotoxicity may occur in the setting of inborn errors of metabolism or acquired progressive organ failure leading to build up of toxic metabolites. Additional intrinsic causes of neurotoxicity include metabolic derangements and characteristic imaging findings in all instances are reviewed. The goal of the article is to enhance familiarity of neurologists and neuroradiologists with the imaging appearance of common and less common toxic insults to the pediatric brain.

Imaging the term neonatal brain

Brain imaging is important for the diagnosis and management of sick term neonates. Although ultrasound and computed tomography may provide some information, magnetic resonance imaging is now the brain imaging modality of choice because it is the most sensitive technique for detecting and quantifying brain abnormalities and does not expose infants to radiation. This statement describes the principles, roles and limitations of these three imaging modalities and makes recommendations for appropriate use in term neonates. The primary focus is the brain of term infants with neonatal encephalopathy, many of whom are diagnosed with hypoxic-ischemic encephalopathy.

Diagnostic value of conventional MRI combined with DTI for neonatal hyperbilirubinemia

BACKGROUND

Neonatal hyperbilirubinemia (NHB) is a common clinical disease and can cause bilirubin encephalopathy in severe cases. It is now widely accepted that increased signal intensity in the globus pallidus on MR T1WI is an important sign of neonatal bilirubin encephalopathy. And brain diffusion tensor imaging (DTI) has not been used extensively to study hyperbilirubinemia (HB). So we compared newborns with different hyperbilirubinemia of different severities and healthy newborns in order to determine the relationships among MRI signal intensities, serum bilirubin levels, and the molecular changes in brain water diffusion in hyperbilirubinemia.

METHODS

Seventy-three newborns with hyperbilirubinemia were grouped into three groups: the mild increase group (M, 27 cases), the moderate increase group (O, 28 cases), and the severe group (S, 18 cases). The groups were based on serum bilirubin levels. We performed cranial MRI in these newborns, as well as 29 healthy full-term infants (group N). We compared and analyzed the mean signal values for the globus pallidus and the relationship between the bilirubin level and the score on the neonatal behavioral neurological assessment. Fifteen, 10, and 10 patients in groups M, O + S, and N were successfully examined using diffusion tensor imaging (DTI). We assessed the relationships among the signal from the globus pallidus, fractional anisotropy (FA), and average diffusion coefficient (DCav) of the posterior limb of the internal capsule (PLIC).

RESULTS

There were significant differences in the mean signal value of bilateral globus pallidus between group O/S and group N [p = 0.029 and 0.000 (left), 0.038 and 0.000 (right)]. There were no significant differences in bilateral FA or DCav values between the patient groups and group N. The bilateral PLIC-FA and DCav values were significantly different between the patient groups and group N (P = 0.014 and 0.047, respectively).

CONCLUSIONS

Increased signal intensity in the globus pallidus on T1-weighted imaging can be used as an objective index to evaluate neonatal bilirubin encephalopathy. Globus pallidus and PLIC injuries are likely to occur when the total serum bilirubin level is ≥20 mg/dl.

Magnetic Resonance Imaging Abnormalities in Advanced Acute Bilirubin Encephalopathy Highlight Dentato-Thalamo-Cortical Pathways

A distinct pattern of acute restricted diffusion on magnetic resonance imaging localized to key regions within the dentato-thalamo-cortical pathway was observed early in a term newborn during advanced stages of acute bilirubin encephalopathy. These findings demonstrate that vulnerability to bilirubin toxicity extends across specific neuroanatomic tracts.

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.