Cortical folding is altered before surgery in infants with congenital heart disease

Unique model of chronic hypoxia in fetal lambs demonstrates abnormal contrast-enhanced ultrasound brain perfusion

BACKGROUND

Children with congenital heart disease (CHD) demonstrate long-term neurodevelopmental impairments. We investigated contrast-enhanced ultrasound (CEUS) cerebral perfusion in a fetal animal model exposed to sub-physiologic oxygen at equivalent levels observed in human fetuses with CHD.

METHODS

Fifteen fetal lambs [hypoxic animals (n = 9) and normoxic controls (n = 6)] maintained in an extrauterine environment underwent periodic brain CEUS. Perfusion parameters including microvascular flow velocity (MFV), transit time, and microvascular blood flow (MBF) were extrapolated from a standardized plane; regions of interest (ROI) included whole brain, central/thalami, and peripheral parenchymal analyses. Daily echocardiographic parameters and middle cerebral artery (MCA) pulsatility indices (PIs) were obtained.

RESULTS

Hypoxic lambs demonstrated decreased MFV, increased transit time, and decreased MBF (p = 0.026, p = 0.016, and p < 0.001, respectively) by whole brain analyses. MFV and transit time were relatively preserved in the central/thalami (p = 0.11, p = 0.08, p = 0.012, respectively) with differences in the peripheral parenchyma (all p < 0.001). In general, cardiac variables did not correlate with cerebral CEUS perfusion parameters. Hypoxic animals demonstrated decreased MCA PI compared to controls (0.65 vs. 0.78, respectively; p = 0.027).

CONCLUSION

Aberrations in CEUS perfusion parameters suggest that in environments of prolonged hypoxia, there are regional microvascular differences incompletely characterized by MCA interrogation offering insights into fetal conditions which may contribute to patient outcomes.

IMPACT

This work utilizes CEUS to study cerebral microvascular perfusion in a unique fetal animal model subjected to chronic hypoxic conditions equal to fetuses with congenital heart disease. CEUS demonstrates altered parameters with regional differences that are incompletely characterized by MCA Doppler values. These findings show that routine MCA Doppler interrogation may be inadequate in assessing microvascular perfusion differences. To our knowledge, this study is the first to utilize CEUS to assess microvascular perfusion in this model. The results offer insight into underlying conditions and physiological changes which may contribute to known neurodevelopmental impairments in those with congenital heart disease.

Meta-regression of sulcal patterns, clinical and environmental factors on neurodevelopmental outcomes in participants with multiple CHD types

Congenital heart disease affects 1% of infants and is associated with impaired neurodevelopment. Right- or left-sided sulcal features correlate with executive function among people with Tetralogy of Fallot or single ventricle congenital heart disease. Studies of multiple congenital heart disease types are needed to understand regional differences. Further, sulcal pattern has not been studied in people with d-transposition of the great arteries. Therefore, we assessed the relationship between sulcal pattern and executive function, general memory, and processing speed in a meta-regression of 247 participants with three congenital heart disease types (114 single ventricle, 92 d-transposition of the great arteries, and 41 Tetralogy of Fallot) and 94 participants without congenital heart disease. Higher right hemisphere sulcal pattern similarity was associated with improved executive function (Pearson r = 0.19, false discovery rate-adjusted P = 0.005), general memory (r = 0.15, false discovery rate P = 0.02), and processing speed (r = 0.17, false discovery rate P = 0.01) scores. These positive associations remained significant in for the d-transposition of the great arteries and Tetralogy of Fallot cohorts only in multivariable linear regression (estimated change β = 0.7, false discovery rate P = 0.004; β = 4.1, false discovery rate P = 0.03; and β = 5.4, false discovery rate P = 0.003, respectively). Duration of deep hypothermic circulatory arrest was also associated with outcomes in the multivariate model and regression tree analysis. This suggests that sulcal pattern may provide an early biomarker for prediction of later neurocognitive challenges among people with congenital heart disease.

Association of genetic and sulcal traits with executive function in congenital heart disease

OBJECTIVE

Persons with congenital heart disease (CHD) are at increased risk of neurodevelopmental disabilities, including impairments to executive function. Sulcal pattern features correlate with executive function in adolescents with single-ventricle heart disease and tetralogy of Fallot. However, the interaction of sulcal pattern features with genetic and participant factors in predicting executive dysfunction is unknown.

METHODS

We studied sulcal pattern features, participant factors, and genetic risk for executive function impairment in a cohort with multiple CHD types using stepwise linear regression and machine learning.

RESULTS

Genetic factors, including predicted damaging de novo or rare inherited variants in neurodevelopmental disabilities risk genes, apolipoprotein E genotype, and principal components of sulcal pattern features were associated with executive function measures after adjusting for age at testing, sex, mother's education, and biventricular versus single-ventricle CHD in a linear regression model. Using regression trees and bootstrap validation, younger participant age and larger alterations in sulcal pattern features were consistently identified as important predictors of decreased cognitive flexibility with left hemisphere graph topology often selected as the most important predictor. Inclusion of both sulcal pattern and genetic factors improved model fit compared to either alone.

INTERPRETATION

We conclude that sulcal measures remain important predictors of cognitive flexibility, and the model predicting executive outcomes is improved by inclusion of potential genetic sources of neurodevelopmental risk. If confirmed, measures of sulcal patterning may serve as early imaging biomarkers to identify those at heightened risk for future neurodevelopmental disabilities.

Functional brain connectivity after corrective cardiac surgery for critical congenital heart disease: a preliminary near-infrared spectroscopy (NIRS) report

Patients with congenital heart disease (CHD) requiring cardiac surgery in infancy are at high risk for neurodevelopmental impairments. Neonatal imaging studies have reported disruptions of brain functional organization before surgery. Yet, the extent to which functional network alterations are present after cardiac repair remains unexplored. This preliminary study aimed at investigating cortical functional connectivity in 4-month-old infants with repaired CHD, using resting-state functional near-infrared spectroscopy (fNIRS). After fNIRS signal frequency decomposition, we compared values of magnitude-squared coherence as a measure of connectivity strength, between 21 infants with corrected CHD and 31 healthy controls. We identified a subset of connections with differences between groups at an uncorrected statistical level of p < .05 while controlling for sex and maternal socioeconomic status, with most of these connections showing reduced connectivity in infants with CHD. Although none of these differences reach statistical significance after FDR correction, likely due to the small sample size, moderate to large effect sizes were found for group-differences. If replicated, these results would therefore suggest preliminary evidence that alterations of brain functional connectivity are present in the months after cardiac surgery. Additional studies involving larger sample size are needed to replicate our data, and comparisons between pre- and postoperative findings would allow to further delineate alterations of functional brain connectivity in this population.

Individual Assessment of Perioperative Brain Growth Trajectories in Infants With Congenital Heart Disease: Correlation With Clinical and Surgical Risk Factors

Background Infants with congenital heart disease (CHD) are at risk of neurodevelopmental impairments, which may be associated with impaired brain growth. We characterized how perioperative brain growth in infants with CHD deviates from typical trajectories and assessed the relationship between individualized perioperative brain growth and clinical risk factors. Methods and Results A total of 36 infants with CHD underwent preoperative and postoperative brain magnetic resonance imaging. Regional brain volumes were extracted. Normative volumetric development curves were generated using data from 219 healthy infants. Z-scores, representing the degree of positive or negative deviation from the normative mean for age and sex, were calculated for regional brain volumes from each infant with CHD before and after surgery. The degree of Z-score change was correlated with clinical risk factors. Perioperative growth was impaired across the brain, and it was associated with longer postoperative intensive care stay (false discovery rate P<0.05). Higher preoperative creatinine levels were associated with impaired brainstem, caudate nuclei, and right thalamus growth (all false discovery rate P=0.033). Older postnatal age at surgery was associated with impaired brainstem and right lentiform growth (both false discovery rate P=0.042). Longer cardiopulmonary bypass duration was associated with impaired brainstem and right caudate growth (false discovery rate P<0.027). Conclusions Infants with CHD can have impaired brain growth in the immediate postoperative period, the degree of which associates with postoperative intensive care duration. Brainstem growth appears particularly vulnerable to perioperative clinical course, whereas impaired deep gray matter growth was associated with multiple clinical risk factors, possibly reflecting vulnerability of these regions to short- and long-term hypoxic injury.

Optimizing Neurodevelopmental Outcomes in Neonates With Congenital Heart Disease

Neurodevelopmental impairment is a common and important long-term morbidity among infants with congenital heart disease (CHD). More than half of those with complex CHD will demonstrate some form of neurodevelopmental, neurocognitive, and/or psychosocial dysfunction requiring specialized care and impacting long-term quality of life. Preventing brain injury and treating long-term neurologic sequelae in this high-risk clinical population is imperative for improving neurodevelopmental and psychosocial outcomes. Thus, cardiac neurodevelopmental care is now at the forefront of clinical and research efforts. Initial research primarily focused on neurocritical care and operative strategies to mitigate brain injury. As the field has evolved, investigations have shifted to understanding the prenatal, genetic, and environmental contributions to impaired neurodevelopment. This article summarizes the recent literature detailing the brain abnormalities affecting neurodevelopment in children with CHD, the impact of genetics on neurodevelopmental outcomes, and the best practices for neonatal neurocritical care, focusing on developmental care and parental support as new areas of importance. A framework is also provided for the infrastructure and resources needed to support CHD families across the continuum of care settings.

Impact of Comorbid Prematurity and Congenital Anomalies: A Review

Preterm infants are more likely to be born with congenital anomalies than those who are born at full-term. Conversely, neonates born with congenital anomalies are also more likely to be born preterm than those without congenital anomalies. Moreover, the comorbid impact of prematurity and congenital anomalies is more than cumulative. Multiple common factors increase the risk of brain injury and neurodevelopmental impairment in both preterm babies and those born with congenital anomalies. These include prolonged hospital length of stay, feeding difficulties, nutritional deficits, pain exposure and administration of medications including sedatives and analgesics. Congenital heart disease provides a well-studied example of the impact of comorbid disease with prematurity. Impaired brain growth and maturity is well described in the third trimester in this population; the immature brain is subsequently more vulnerable to further injury. There is a colinear relationship between degree of prematurity and outcome both in terms of mortality and neurological morbidity. Both prematurity and relative brain immaturity independently increase the risk of subsequent neurodevelopmental impairment in infants with CHD. Non-cardiac surgery also poses a greater risk to preterm infants despite the expectation of normal in utero brain growth. Esophageal atresia, diaphragmatic hernia and abdominal wall defects provide examples of congenital anomalies which have been shown to have poorer neurodevelopmental outcomes in the face of prematurity, with associated increased surgical complexity, higher relative cumulative doses of medications, longer hospital and intensive care stay and increased rates of feeding difficulties, compared with infants who experience either prematurity or congenital anomalies alone.

In Utero MRI Identifies Impaired Second Trimester Subplate Growth in Fetuses with Congenital Heart Disease

The subplate is a transient brain structure which plays a key role in the maturation of the cerebral cortex. Altered brain growth and cortical development have been suggested in fetuses with complex congenital heart disease (CHD) in the third trimester. However, at an earlier gestation, the putative role of the subplate in altered brain development in CHD fetuses is poorly understood. This study aims to examine subplate growth (i.e., volume and thickness) and its relationship to cortical sulcal development in CHD fetuses compared with healthy fetuses by using 3D reconstructed fetal magnetic resonance imaging. We studied 260 fetuses, including 100 CHD fetuses (22.3-32 gestational weeks) and 160 healthy fetuses (19.6-31.9 gestational weeks). Compared with healthy fetuses, CHD fetuses had 1) decreased global and regional subplate volumes and 2) decreased subplate thickness in the right hemisphere overall, in frontal and temporal lobes, and insula. Compared with fetuses with two-ventricle CHD, those with single-ventricle CHD had reduced subplate volume and thickness in right occipital and temporal lobes. Finally, impaired subplate growth was associated with disturbances in cortical sulcal development in CHD fetuses. These findings suggested a potential mechanistic pathway and early biomarker for the third-trimester failure of brain development in fetuses with complex CHD.

SIGNIFICANCE STATEMENT

Our findings provide an early biomarker for brain maturational failure in fetuses with congenital heart disease, which may guide the development of future prenatal interventions aimed at reducing neurological compromise of prenatal origin in this high-risk population.

How does the convergence of prematurity and congenital heart disease impact the developing brain?

Prematurity and congenital heart disease (CHD) are individually associated with increased risk of brain injury and adverse neurodevelopmental outcomes. Delayed brain development in newborns with CHD has been documented to begin in utero and predisposes newborns with CHD to brain injury. Little is known about the combined risks when prematurity and CHD co-occur. The purpose of this review is to highlight the unique vulnerability of preterm newborns with CHD to brain dysmaturation and brain injury, and the urgent need for prospective research.

Motor Developmental Delay After Cardiac Surgery in Children With a Critical Congenital Heart Defect: A Systematic Literature Review and Meta-analysis

PURPOSE

To systematically review evidence regarding the severity and prevalence of motor development in children with a critical congenital heart defect (CCHD) without underlying genetic anomalies.

SUMMARY OF KEY POINTS

Twelve percent of all included studies reported abnormal mean motor developmental scores, and 38% reported below average motor scores. Children with single-ventricle physiology, especially those with hypoplastic left heart syndrome, had the highest severity and prevalence of motor delay, particularly at 0 to 12 months. Most included studies did not differentiate between gross and fine motor development, yet gross motor development was more affected.

RECOMMENDATIONS FOR CLINICAL PRACTICE

We recommend clinicians differentiate between the type of heart defect, fine and gross motor development, and the presence of genetic anomalies. Furthermore, increased knowledge about severity and prevalence will enable clinicians to tailor their interventions to prevent motor development delays in CCHD.

Serial neurosonography in fetuses with congenital heart defects shows mild delays in cortical development

INTRODUCTION

Neurodevelopmental delay is more common in children born with congenital heart defects (CHD), even with optimal perinatal and peri-operative care. It is hypothesized that fetuses with CHD are prone to neurological impairment in utero due to their cardiac defect, possibly leading to delayed cortical development.

METHODS

Cerebral cortical maturation was assessed with advanced neurosonographic examinations every 4 weeks in fetuses with CHD and compared to control fetuses. Five different primary fissures and four areas were scored (ranging 0-5) by blinded examiners using a cortical maturation scheme.

RESULTS

Cortical staging was assessed in 574 ultrasound examinations in 85 CHD fetuses and 61 controls. Small differences in grading were seen in Sylvian and cingulate fissures. (Sylvian fissure: -0.12 grade, 95% CI (-0.23; -0.01) p = 0.05, cingulate fissure: -0.24 grade, 95% CI (-0.38; -0.10) p = <0.001. Other cortical areas showed normal maturation as compared to control fetuses.

CONCLUSION

Small differences were seen in three of the nine analyzed cortical areas in CHD fetuses, in contrast to previous reports on progressive third-trimester delay. The clinical implications of the small differences however, remain unknown.

Abnormal Left-Hemispheric Sulcal Patterns in Adults With Simple Congenital Heart Defects Repaired in Childhood

Background

Children operated on for a simple congenital heart defect (CHD) are at risk of neurodevelopmental abnormalities. Abnormal cortical development and folding have been observed in fetuses with CHD. We examined whether sulcal folding patterns in adults operated on for simple CHD in childhood differ from those of healthy controls, and whether such differences are associated with neuropsychological outcomes.

Methods and Results

Patients (mean age, 24.5 years) who underwent childhood surgery for isolated atrial septal defect (ASD; n=33) or ventricular septal defect (VSD; n=30) and healthy controls (n=37) were enrolled. Sulcal pattern similarity to healthy controls was determined using magnetic resonance imaging and looking at features of sulcal folds, their intersulcal relationships, and sulcal graph topology. The sulcal pattern similarity values were tested for associations with comprehensive neuropsychological scores. Patients with both ASD and VSD had decreased sulcal pattern similarity in the left hemisphere compared with controls. The differences were found in the left temporal lobe in the ASD group and in the whole left hemisphere in the VSD group (P=0.033 and P=0.039, respectively). The extent of abnormal left hemispheric sulcal pattern similarity was associated with worse neuropsychological scores (intelligence, executive function, and visuospatial abilities) in the VSD group, and special educational support in the ASD group.

Conclusions

Adults who underwent surgery for simple CHD in childhood display altered left hemisphere sulcal folding patterns, commensurate with neuropsychological scores for patients with VSD and special educational support for ASD. This may indicate that simple CHD affects early brain development.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03871881.

Investigating altered brain development in infants with congenital heart disease using tensor-based morphometry

Magnetic resonance (MR) imaging studies have demonstrated reduced global and regional brain volumes in infants with congenital heart disease (CHD). This study aimed to provide a more detailed evaluation of altered structural brain development in newborn infants with CHD compared to healthy controls using tensor-based morphometry (TBM). We compared brain development in 64 infants with CHD to 192 age- and sex-matched healthy controls. T2-weighted MR images obtained prior to surgery were analysed to compare voxel-wise differences in structure across the whole brain between groups. Cerebral oxygen delivery (CDO₂) was measured in infants with CHD (n = 49) using phase contrast MR imaging and the relationship between CDO₂ and voxel-wise brain structure was assessed using TBM. After correcting for global scaling differences, clusters of significant volume reduction in infants with CHD were demonstrated bilaterally within the basal ganglia, thalami, corpus callosum, occipital, temporal, parietal and frontal lobes, and right hippocampus (p < 0.025 after family-wise error correction). Clusters of significant volume expansion in infants with CHD were identified in cerebrospinal fluid spaces (p < 0.025). After correcting for global brain size, there was no significant association between voxel-wise brain structure and CDO₂. This study localizes abnormal brain development in infants with CHD, identifying areas of particular vulnerability.

Early-Emerging Sulcal Patterns Are Atypical in Fetuses with Congenital Heart Disease

Fetuses with congenital heart disease (CHD) have third trimester alterations in cortical development on brain magnetic resonance imaging (MRI). However, the intersulcal relationships contributing to global sulcal pattern remain unknown. This study applied a novel method for examining the geometric and topological relationships between sulci to fetal brain MRIs from 21-30 gestational weeks in CHD fetuses (n = 19) and typically developing (TD) fetuses (n = 17). Sulcal pattern similarity index (SI) to template fetal brain MRIs was determined for the position, area, and depth for corresponding sulcal basins and intersulcal relationships for each subject. CHD fetuses demonstrated altered global sulcal patterns in the left hemisphere compared with TD fetuses (TD [SI, mean ± SD]: 0.822 ± 0.023, CHD: 0.795 ± 0.030, P = 0.002). These differences were present in the earliest emerging sulci and were driven by differences in the position of corresponding sulcal basins (TD: 0.897 ± 0.024, CHD: 0.878 ± 0.019, P = 0.006) and intersulcal relationships (TD: 0.876 ± 0.031, CHD: 0.857 ± 0.018, P = 0.033). No differences in cortical gyrification index, mean curvature, or surface area were present. These data suggest our methods may be more sensitive than traditional measures for evaluating cortical developmental alterations early in gestation.

Abnormal Microstructural Development of the Cerebral Cortex in Neonates With Congenital Heart Disease Is Associated With Impaired Cerebral Oxygen Delivery

Background Abnormal macrostructural development of the cerebral cortex has been associated with hypoxia in infants with congenital heart disease ( CHD ). Animal studies have suggested that hypoxia results in cortical dysmaturation at the cellular level. New magnetic resonance imaging techniques offer the potential to investigate the relationship between cerebral oxygen delivery and cortical microstructural development in newborn infants with CHD . Methods and Results We measured cortical macrostructural and microstructural properties in 48 newborn infants with serious or critical CHD and 48 age-matched healthy controls. Cortical volume and gyrification index were calculated from high-resolution structural magnetic resonance imaging. Neurite density and orientation dispersion indices were modeled using high-angular-resolution diffusion magnetic resonance imaging. Cerebral oxygen delivery was estimated in infants with CHD using phase contrast magnetic resonance imaging and preductal pulse oximetry. We used gray matter-based spatial statistics to examine voxel-wise group differences in cortical microstructure. Microstructural development of the cortex was abnormal in 48 infants with CHD , with regions of increased fractional anisotropy and reduced orientation dispersion index compared with 48 healthy controls, correcting for gestational age at birth and scan (family-wise error corrected for multiple comparisons at P<0.05). Regions of reduced cortical orientation dispersion index in infants with CHD were related to impaired cerebral oxygen delivery ( R²=0.637; n=39). Cortical orientation dispersion index was associated with the gyrification index ( R²=0.589; P<0.001; n=48). Conclusions This study suggests that the primary component of cerebral cortex dysmaturation in CHD is impaired dendritic arborization, which may underlie abnormal macrostructural findings reported in this population, and that the degree of impairment is related to reduced cerebral oxygen delivery.

The Congenital Heart Disease Brain: Prenatal Considerations for Perioperative Neurocritical Care

Altered brain development has been highlighted as an important contributor to adverse neurodevelopmental outcomes in children with congenital heart disease. Abnormalities begin prenatally and include micro- and macrostructural disturbances that lead to an altered trajectory of brain growth throughout gestation. Recent progress in fetal imaging has improved understanding of the neurobiological mechanisms and risk factors for impaired fetal brain development. The impact of the prenatal environment on postnatal neurological care has also gained increased focus. This review summarizes current data on the timing and pattern of altered prenatal brain development in congenital heart disease, the potential mechanisms of these abnormalities, and the association with perioperative neurological complications.

Abnormal Left-Hemispheric Sulcal Patterns Correlate with Neurodevelopmental Outcomes in Subjects with Single Ventricular Congenital Heart Disease

Neurodevelopmental abnormalities are the most common noncardiac complications in patients with congenital heart disease (CHD). Prenatal brain abnormalities may be due to reduced oxygenation, genetic factors, or less commonly, teratogens. Understanding the contribution of these factors is essential to improve outcomes. Because primary sulcal patterns are prenatally determined and under strong genetic control, we hypothesized that they are influenced by genetic variants in CHD. In this study, we reveal significant alterations in sulcal patterns among subjects with single ventricle CHD (n = 115, 14.7 ± 2.9 years [mean ± standard deviation]) compared with controls (n = 45, 15.5 ± 2.4 years) using a graph-based pattern-analysis technique. Among patients with CHD, the left hemisphere demonstrated decreased sulcal pattern similarity to controls in the left temporal and parietal lobes, as well as the bilateral frontal lobes. Temporal and parietal lobes demonstrated an abnormally asymmetric left-right pattern of sulcal basin area in CHD subjects. Sulcal pattern similarity to control was positively correlated with working memory, processing speed, and executive function. Exome analysis identified damaging de novo variants only in CHD subjects with more atypical sulcal patterns. Together, these findings suggest that sulcal pattern analysis may be useful in characterizing genetically influenced, atypical early brain development and neurodevelopmental risk in subjects with CHD.

Quantitative MRI study of infant regional brain size following surgery for long-gap esophageal atresia requiring prolonged critical care

INTRODUCTION

Little is known regarding the impact of concurrent critical illness and thoracic noncardiac perioperative critical care on postnatal brain development. Previously, we reported smaller total brain volumes in both critically ill full-term and premature patients following complex perioperative critical care for long-gap esophageal atresia (LGEA). Our current report assessed trends in regional brain sizes during infancy, and probed for any group differences.

METHODS

Full-term (n = 13) and preterm (n = 13) patients without any previously known neurological concerns, and control infants (n = 16), underwent non-sedated 3 T MRI in infancy (<1 year old). T2-weighted images underwent semi-automated brain segmentation using Morphologically Adaptive Neonatal Tissue Segmentation (MANTiS). Regional tissue volumes of the forebrain, deep gray matter (DGM), cerebellum, and brainstem are presented as absolute (cm3) and normalized (% total brain volume (%TBV)) values. Group differences were assessed using a general linear model univariate analysis with corrected age at scan as a covariate.

RESULTS

Absolute volumes of regions analyzed increased with advancing age, paralleling total brain size, but were significantly smaller in both full-term and premature patients compared to controls. Normalized volumes (%TBV) of forebrain, DGM, and cerebellum were not different between subject groups analyzed. Normalized brainstem volumes showed group differences that warrant future studies to confirm the same finding.

DISCUSSION

Both full-term and premature critically ill infants undergoing life-saving surgery for LGEA are at risk of smaller total and regional brain sizes. Normalized volumes support globally delayed or diminished brain growth in patients. Future research should look into neurodevelopmental outcomes of infants born with LGEA.

Cortical Dysmaturation in Congenital Heart Disease

Congenital heart disease (CHD) is among the most common birth defects. Children with CHD frequently display long-term intellectual and behavioral disability. Emerging evidence indicates that cardiac anomalies lead to a reduction in cerebral oxygenation, which appears to profoundly impact on the maturation of cerebral regions responsible for higher-order cognitive functions. In this review we focus on the potential mechanisms by which dysregulation of cortical neuronal development during early life may lead to the significant cognitive impairments that commonly occur in children with CHD. Further understanding of the mechanisms underlying cortical dysmaturation due to CHD will be necessary to identify strategies for neonatal neuroprotection and for mitigating developmental delays in this patient population.

Fetal and neonatal neuroimaging

Magnetic resonance imaging (MRI) can provide detail of the soft tissues of the fetal and neonatal brain that cannot be obtained by any other imaging modality. Conventional T1 and T2 weighted sequences provide anatomic detail of the normally developing brain and can demonstrate lesions, including those associated with preterm birth, hypoxic ischemic encephalopathy, perinatal arterial stroke, infections, and congenital malformations. Specialized imaging techniques can be used to assess cerebral vasculature (magnetic resonance angiography and venography), cerebral metabolism (magnetic resonance spectroscopy), cerebral perfusion (arterial spin labeling), and function (functional MRI). A wealth of quantitative tools, most of which were originally developed for the adult brain, can be applied to study the developing brain in utero and postnatally including measures of tissue microstructure obtained from diffusion MRI, morphometric studies to measure whole brain and regional tissue volumes, and automated approaches to study cortical folding. In this chapter, we aim to describe different imaging approaches for the fetal and neonatal brain, and to discuss their use in a range of clinical applications.

Neurodevelopmental outcome of children with congenital heart disease

Congenital heart disease (CHD) constitutes the most common congenital malformation, with moderate or severe CHD occurring in around 6 in 1000 live births. Due to advances in medical care, survival rates have increased significantly. Thus, the majority of children with CHD survive until adolescence and adulthood. Children with CHD requiring cardiopulmonary bypass surgery are at risk for neurodevelopmental impairments in various domains, including mild impairments in cognitive and neuromotor functions, difficulties with social interaction, inattention, emotional symptoms, and impaired executive function. The prevalence for these impairments ranges from 20% to 60% depending on age and domain ("high prevalence-low severity"). Domains are often affected simultaneously, leading to school problems with the need for learning support and special interventions. The etiology of neurodevelopmental impairments is complex, consisting of a combination of delayed intrauterine brain development and newly occurring perioperative brain injuries. Mechanisms include altered intrauterine hemodynamic flow as well as neonatal hypoxia and reduced cerebral blood flow. The surgical procedure and postoperative phase add to this cascade of factors interfering with normal brain development. Early identification of children at high risk through structured follow-up programs is mandated to provide individually tailored early interventions and counseling to improve developmental health.

Structural brain abnormalities in adolescents and young adults with congenital heart defect: a systematic review

AIM

The primary objective of this systematic review is to define and quantify brain structural abnormalities present in adolescents and young adults with complex congenital heart defect (CHD). We also aim to evaluate the extent to which these structural abnormalities are associated with functional outcomes.

METHOD

A search of studies examining brain structure by magnetic resonance imaging in adolescents and young adults with complex CHD was performed in Embase, MEDLINE, and Web of Science. A meta-analysis was conducted to determine the odds of brain abnormalities in young people with CHD. Results not included in the meta-analysis were collated using descriptive statistics.

RESULTS

Two hundred and fifty-four studies were identified through the literature search. Among these, 14 original studies were included in the review. The odds of brain abnormalities in young people with CHD were 7.9 times higher (p<0.001) than in typically developing comparison individuals. Focal and multifocal lesions were the most common types of abnormality (odds ratio 22.5 [p<0.001]). Preliminary evidence from volumetric, cortical, and microstructural integrity measurements suggests that brain abnormalities are associated with poorer neurocognitive outcomes.

INTERPRETATION

This review provides strong evidence that adolescents and young adults with CHD are at increased risk of presenting with structural brain abnormalities and highlights the contribution of advanced quantitative magnetic resonance imaging techniques to identify the subtle but frequent brain alterations in this population. However, more studies are needed to clarify how these abnormalities relate to function.

WHAT THIS PAPER ADDS

There is a high prevalence of brain abnormalities in young people with congenital heart defect (CHD). Brain volumes, cortical measurements, and white matter microstructure are altered in young people with CHD. Brain abnormalities are associated with poorer function in young people with CHD.

A computational method for longitudinal mapping of orientation-specific expansion of cortical surface in infants

The cortical surface of the human brain expands dynamically and regionally heterogeneously during the first postnatal year. As all primary and secondary cortical folds as well as many tertiary cortical folds are well established at term birth, the cortical surface area expansion during this stage is largely driven by the increase of surface area in two orthogonal orientations in the tangent plane: 1) the expansion parallel to the folding orientation (i.e., increasing the lengths of folds) and 2) the expansion perpendicular to the folding orientation (i.e., increasing the depths of folds). This information would help us better understand the mechanisms of cortical development and provide important insights into neurodevelopmental disorders, but still remains largely unknown due to lack of dedicated computational methods. To address this issue, we propose a novel method for longitudinal mapping of orientation-specific expansion of cortical surface area in these two orthogonal orientations during early infancy. First, to derive the two orientation fields perpendicular and parallel to cortical folds, we propose to adaptively and smoothly fuse the gradient field of sulcal depth and also the maximum principal direction field, by leveraging their region-specific reliability. Specifically, we formulate this task as a discrete labeling problem, in which each vertex is assigned to an orientation label, and solve it by graph cuts. Then, based on the computed longitudinal deformation of the cortical surface, we estimate the Jacobian matrix at each vertex by solving a least-squares problem and derive its corresponding stretch tensor. Finally, to obtain the orientation-specific cortical surface expansion, we project the stretch tensor into the two orthogonal orientations separately. We have applied the proposed method to 30 healthy infants, and for the first time we revealed the orientation-specific longitudinal cortical surface expansion maps during the first postnatal year.

Structural network topology correlates of microstructural brain dysmaturation in term infants with congenital heart disease

Neonates with complex congenital heart disease (CHD) demonstrate microstructural brain dysmaturation, but the relationship with structural network topology is unknown. We performed diffusion tensor imaging (DTI) in term neonates with CHD preoperatively (N = 61) and postoperatively (N = 50) compared with healthy term controls (N = 91). We used network topology (graph) analyses incorporating different weighted and unweighted approaches and subject-specific white matter segmentation to investigate structural topology differences, as well as a voxel-based analysis (VBA) to confirm the presence of microstructural dysmaturation. We demonstrate cost-dependent network inefficiencies in neonatal CHD in the pre- and postoperative period compared with controls, related to microstructural differences. Controlling for cost, we show the presence of increased small-worldness (hierarchical fiber organization) in CHD infants preoperatively, that persists in the postoperative period compared with controls, suggesting the early presence of brain reorganization. Taken together, topological microstructural dysmaturation in CHD infants is accompanied by hierarchical fiber organization during a protracted critical period of early brain development. Our methodology also provides a pipeline for quantitation of network topology changes in neonates and infants with microstructural brain dysmaturation at risk for perinatal brain injury.

The neonatal brain in critical congenital heart disease: Insights and future directions

Neurodevelopmental outcomes are impaired in survivors of critical congenital heart disease (CHD) in several developmental domains including motor, cognitive and sensory outcomes. These deficits can extend into the adolescent and early adulthood years. The cause of these neurodevelopmental impairments is multi-factorial and includes patient specific risk factors, cardiac anatomy and physiology as well as brain changes seen on MRI. Advances in imaging techniques have identified delayed brain development in the neonate with critical CHD as well as acquired brain injury. These abnormalities are seen even before corrective neonatal cardiac surgery. This review focuses on describing brain changes seen on MRI in neonates with CHD, risk factors for these changes and the association with neurodevelopmental outcome. There is an emerging focus on the impact of cardiovascular physiology on brain health and the complex heart-brain interplay that influences ultimate neurodevelopmental outcome in these patients.

Abnormal neurogenesis and cortical growth in congenital heart disease

Long-term neurological deficits due to immature cortical development are emerging as a major challenge in congenital heart disease (CHD). However, cellular mechanisms underlying dysregulation of perinatal corticogenesis in CHD remain elusive. The subventricular zone (SVZ) represents the largest postnatal niche of neural stem/progenitor cells (NSPCs). We show that the piglet SVZ resembles its human counterpart and displays robust postnatal neurogenesis. We present evidence that SVZ NSPCs migrate to the frontal cortex and differentiate into interneurons in a region-specific manner. Hypoxic exposure of the gyrencephalic piglet brain recapitulates CHD-induced impaired cortical development. Hypoxia reduces proliferation and neurogenesis in the SVZ, which is accompanied by reduced cortical growth. We demonstrate a similar reduction in neuroblasts within the SVZ of human infants born with CHD. Our findings demonstrate that SVZ NSPCs contribute to perinatal corticogenesis and suggest that restoration of SVZ NSPCs' neurogenic potential is a candidate therapeutic target for improving cortical growth in CHD.

Intraventricular Hemorrhage in Moderate to Severe Congenital Heart Disease

OBJECTIVES

Determine the prevalence of intraventricular hemorrhage in infants with moderate to severe congenital heart disease, investigate the impact of gestational age, cardiac diagnosis, and cardiac intervention on intraventricular hemorrhage, and compare intraventricular hemorrhage rates in preterm infants with and without congenital heart disease.

DESIGN

A single-center retrospective review.

SETTING

A tertiary care children's hospital.

PATIENTS

All infants admitted to St. Louis Children's Hospital from 2007 to 2012 with moderate to severe congenital heart disease requiring cardiac intervention in the first 90 days of life and all preterm infants without congenital heart disease or congenital anomalies/known genetic diagnoses admitted during the same time period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cranial ultrasound data were reviewed for presence/severity of intraventricular hemorrhage. Head CT and brain MRI data were also reviewed in the congenital heart disease infants. Univariate analyses were undertaken to determine associations with intraventricular hemorrhage, and a final multivariate logistic regression model was performed. There were 339 infants with congenital heart disease who met inclusion criteria and 25.4% were born preterm. Intraventricular hemorrhage was identified on cranial ultrasound in 13.3% of infants, with the majority of intraventricular hemorrhage being low-grade (grade I/II). The incidence increased as gestational age decreased such that intraventricular hemorrhage was present in 8.7% of term infants, 19.2% of late preterm infants, 26.3% of moderately preterm infants, and 53.3% of very preterm infants. There was no difference in intraventricular hemorrhage rates between cardiac diagnoses. Additionally, the rate of intraventricular hemorrhage did not increase after cardiac intervention, with only three infants demonstrating new/worsening high-grade (grade III/IV) intraventricular hemorrhage after surgery. In a multivariate model, only gestational age at birth and African-American race were predictors of intraventricular hemorrhage. In the subset of infants with CT/MRI data, there was good sensitivity and specificity of cranial ultrasound for presence of intraventricular hemorrhage.

CONCLUSIONS

Infants with congenital heart disease commonly develop intraventricular hemorrhage, particularly when born preterm. However, the vast majority of intraventricular hemorrhage is low-grade and is associated with gestational age and African-American race.

Impaired development of the cerebral cortex in infants with congenital heart disease is correlated to reduced cerebral oxygen delivery

Neurodevelopmental impairment is the most common comorbidity associated with complex congenital heart disease (CHD), while the underlying biological mechanism remains unclear. We hypothesised that impaired cerebral oxygen delivery in infants with CHD is a cause of impaired cortical development, and predicted that cardiac lesions most associated with reduced cerebral oxygen delivery would demonstrate the greatest impairment of cortical development. We compared 30 newborns with complex CHD prior to surgery and 30 age-matched healthy controls using brain MRI. The cortex was assessed using high resolution, motion-corrected T2-weighted images in natural sleep, analysed using an automated pipeline. Cerebral oxygen delivery was calculated using phase contrast angiography and pre-ductal pulse oximetry, while regional cerebral oxygen saturation was estimated using near-infrared spectroscopy. We found that impaired cortical grey matter volume and gyrification index in newborns with complex CHD was linearly related to reduced cerebral oxygen delivery, and that cardiac lesions associated with the lowest cerebral oxygen delivery were associated with the greatest impairment of cortical development. These findings suggest that strategies to improve cerebral oxygen delivery may help reduce brain dysmaturation in newborns with CHD, and may be most relevant for children with CHD whose cardiac defects remain unrepaired for prolonged periods after birth.

Genetic contribution to neurodevelopmental outcomes in congenital heart disease: are some patients predetermined to have developmental delay?

PURPOSE OF REVIEW

Neurodevelopmental impairment is common in children with moderate to severe congenital heart disease (CHD). As children live longer and healthier lives, research has focused on identifying causes of neurodevelopmental morbidity that significantly impact long-term quality of life. This review will address the role of genetic factors in predicting neurodevelopmental outcome in CHD.

RECENT FINDINGS

A robust literature suggests that among children with various forms of CHD, those with known genetic/extracardiac anomalies are at highest risk of neurodevelopmental impairment. Advances in genetic technology have identified genetic causes of CHD in an increasing percentage of patients. Further, emerging data suggest substantial overlap between mutations in children with CHD and those that have previously been associated with neurodevelopmental disorders.

SUMMARY

Innate and patient factors appear to be more important in predicting neurodevelopmental outcome than medical/surgical variables. Future research is needed to establish a broader understanding of the mutations that contribute to neurodevelopmental disorders and the variations in expressivity and penetrance.

Prenatal influence of congenital heart defects on trajectories of cortical folding of the fetal brain using three-dimensional ultrasound

OBJECTIVE

The objective of the study is to investigate the prenatal influence of congenital heart defects (CHD) on trajectories of fetal cortical folding using three-dimensional ultrasound (3D US).

METHOD

We included 20 CHD fetuses and 193 controls for studying the fetal brain at 22, 26 and 32 weeks' gestational age (GA). The Sylvian, insula and parieto-occipital fissure (POF) depths were measured using 3D US, and reliability was evaluated. Doppler indices of the umbilical artery and middle cerebral artery were measured to calculate the cerebro-placental ratio. Associations between CHD and cortical folding were estimated using linear mixed models.

RESULTS

Brain fissure measurements were successful in over 80% of 3D US scans, except for the POF at 32 weeks' GA (65%). All measurements showed a good reliability (intraclass correlation coefficients > 0.84). Growth trajectories of the left insula depth (ß = -2.753, 95% CI = -5.375; -0.130, p = 0.040) and right POF (ß = -3.762, 95% CI = -7.178; -0.346, p = 0.031) were decreased in CHD compared with controls, whereas growth rates were increased (ß = 0.014, 95% CI = 0.001; 0.027, p = 0.036 and ß = 0.024, 95% CI = 0.007; 0.041, p = 0.006). In contrast to controls, we found no associations between cerebro-placental ratio and cortical folding in CHD.

CONCLUSION

Fetal cortical folding can be evaluated reliably by measuring brain fissure depths. Trajectories of cortical folding between 22 and 32 weeks' GA seem to be influenced by CHD. © 2017 John Wiley & Sons, Ltd.

Neuroimaging, cardiovascular physiology, and functional outcomes in infants with congenital heart disease

This review integrates data on brain dysmaturation and acquired brain injury using fetal and neonatal magnetic resonance imaging (MRI), including the contribution of cardiovascular physiology to differences in brain development, and the relationship between brain abnormalities and subsequent neurological impairments in infants with congenital heart disease (CHD). The antenatal and neonatal period are critical for optimal brain development; the developing brain is particularly vulnerable to haemodynamic disturbances during this time. Altered cerebral perfusion and decreased cerebral oxygen delivery in the antenatal period can affect functional and structural brain development, while postnatal haemodynamic fluctuations may cause additional injury. In critical CHD, brain dysmaturation and acquired brain injury result from a combination of underlying cardiovascular pathology and surgery performed in the neonatal period. MRI findings in infants with CHD can be used to evaluate potential clinical risk factors for brain abnormalities, and aid prediction of functional outcomes at an early stage. In addition, information on timing of brain dysmaturation and acquired brain injury in CHD has the potential to be used when developing strategies to optimize neurodevelopment.

Brain Injury and Neurodevelopmental Outcome in Congenital Heart Disease: A Systematic Review

CONTEXT

Brain injury during prenatal and preoperative postnatal life might play a major role in neurodevelopmental impairment in infants with congenital heart disease (CHD) who require corrective or palliative surgery during infancy. A systematic review of cerebral findings during this period in relation to neurodevelopmental outcome (NDO), however, is lacking.

OBJECTIVE

To assess the association between prenatal and postnatal preoperative cerebral findings and NDO in infants with CHD who require corrective or palliative surgery during infancy.

DATA SOURCES

PubMed, Embase, reference lists.

STUDY SELECTION

We conducted 3 different searches for English literature between 2000 and 2016; 1 for prenatal cerebral findings, 1 for postnatal preoperative cerebral findings, and 1 for the association between brain injury and NDO.

DATA EXTRACTION

Two reviewers independently screened sources and extracted data on cerebral findings and neurodevelopmental outcome. Quality of studies was assessed using the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

Abnormal cerebral findings are common during the prenatal and postnatal preoperative periods. Prenatally, a delay of cerebral development was most common; postnatally, white matter injury, periventricular leukomalacia, and stroke were frequently observed. Abnormal Doppler measurements, brain immaturity, cerebral oxygenation, and abnormal EEG or amplitude-integrated EEG were all associated with NDO.

LIMITATIONS

Observational studies, different types of CHD with different pathophysiological effects, and different reference values.

CONCLUSIONS

Prenatal and postnatal preoperative abnormal cerebral findings might play an important role in neurodevelopmental impairment in infants with CHD. Increased awareness of the vulnerability of the young developing brain of an infant with CHD among caregivers is essential.

[A prenatal ultrasound study of cerebral sulci and gyrus development in fetuses with tetralogy of Fallot]

OBJECTIVE

To evaluate the development of the cerebral sulci and gyrus and cerebral blood flow in fetuses with tetralogy of Fallot (ToF) in the second and third trimesters using ultrasound imaging.

METHODS

Forty fetuses (23-33⁺⁶ weeks) with ToF diagnosed using ultrasound imaging between December, 2015 and September, 2016 were analyzed in this study. The development of the cerebral sulci and gyrus was evaluated by measuring the parietal-occipital fissure (POF) depth, POF angle, sylvian fissure (SF) depth, SF width, uncovered insular width, calcarine fissure (CF) depth, hemisphere depth on the views of POF, SF and CF, uncovered insular ratio, biparietal diameter (BPD), and head circumference (HC). Cerebral hemodynamics were assessed by measuring the umbilical artery resistance index, umbilical artery pulsation index, middle cerebral artery pulsation index (MCA-PI), middle cerebral artery resistance index, the cerebral-to-placental resistance ratio, and the cerebroplacental ratio.

RESULTS

In ToF fetuses, the POF depth, SF depth, CF depth, BPD, HC and hemisphere depth on the views of parietal-occipital sulcus and calcarine sulcus were significantly smaller than those in the control group (P<0.05). The middle cerebral artery resistance index, middle cerebral artery pulsation index, the cerebral-to-placental resistance ratio and the cerebroplacental ratio were also significantly lower in ToF fetuses than in the control group (P<0.05).

CONCLUSION

The cerebral sulci and gyrus in ToF fetuses in second and third trimesters show underdevelopment compared with those in normal fetuses, and the changes in hemodynamics caused by abnormal cardiac structure might be one of the reasons for cerebral sulci and gyrus underdevelopment in fetuses with ToF.

Clinical Factors Associated with Cerebral Metabolism in Term Neonates with Congenital Heart Disease

OBJECTIVE

To determine associations between patient and clinical factors with postnatal brain metabolism in term neonates with congenital heart disease (CHD) via the use of quantitative magnetic resonance spectroscopy.

STUDY DESIGN

Neonates with CHD were enrolled prospectively to undergo pre- and postoperative 3T brain magnetic resonance imaging. Short-echo single-voxel magnetic resonance spectroscopy of parietal white matter was used to quantify metabolites related to brain maturation (n-acetyl aspartate, choline, myo- inositol), neurotransmitters (glutamate and gamma-aminobutyric acid), energy metabolism (glutamine, citrate, glucose, and phosphocreatine), and injury/apoptosis (lactate and lipids). Multivariable regression was performed to search for associations between (1) patient-specific/prenatal/preoperative factors with concurrent brain metabolism and (2) intraoperative and postoperative factors with postoperative brain metabolism.

RESULTS

A total of 83 magnetic resonance images were obtained on 55 subjects. No patient-specific, prenatal, or preoperative factors associated with concurrent metabolic brain dysmaturation or elevated lactate could be identified. Chromosome 22q11 microdeletion and age at surgery were predictive of altered concurrent white matter phosphocreatine (P < .0055). The only significant intraoperative association found was increased deep hypothermic circulatory arrest time with reduced postoperative white matter glutamate and gamma-aminobutyric acid (P < .0072). Multiple postoperative factors, including increased number of extracorporeal membrane oxygenation days (P < .0067), intensive care unit, length of stay (P < .0047), seizures in the intensive care unit (P < .0009), and home antiepileptic use (P < .0002), were associated with reduced postoperative white matter n-acetyl aspartate.

CONCLUSION

Multiple postoperative factors were found to be associated with altered brain metabolism in term infants with CHD, but not patient-specific, preoperative, or intraoperative factors.

Synchronous Aberrant Cerebellar and Opercular Development in Fetuses and Neonates with Congenital Heart Disease: Correlation with Early Communicative Neurodevelopmental Outcomes, Initial Experience

Patients with congenital heart disease (CHD) demonstrate multidomain cognitive delays. Cingulo-opercular and cerebellar brain networks are critical to language functions. This is a description of our initial experience aiming to identify an anatomic correlate for CHD patients with expressive language delays. Fetal CHD patients, prospectively enrolled, underwent serial fetal (1.5T), postnatal pre- and postoperative (3T) MRI. Non-CHD patients were enrolled retrospectively from the same epoch. Comparable fetal and neonatal T2 contrast was used for manual linear cross-sectional measurement. Multivariable analysis was used for adjustments and curve fitting. Neurodevelopment was assessed with Battelle Developmental Inventory, 2nd ed. between 9 and 36 months of age. This interim analysis included patients from our longitudinal CHD study who had fetal, postnatal imaging and neurodevelopmental data-yielding a total of 62 mothers (11 CHD fetuses and 51 non-CHD fetuses). Altered brain trajectories were seen in selected cerebellar and opercular measurements in CHD patients compared with the non-CHD group. Smaller inferior cerebellar vermis measurements were associated with multiple communication-related abnormalities. Altered early structural development of the cerebellum and operculum is present in patients with CHD, which correlates with specific neurodevelopmental abnormalities.

Delayed cortical gray matter development in neonates with severe congenital heart disease

BACKGROUND

This study aimed to assess cortical gray matter growth and maturation in neonates with congenital heart disease (CHD).

METHODS

Thirty-one (near) term neonates with severe CHD (8 univentricular heart malformation (UVH), 21 d-transposition of great arteries (d-TGA) and 2 aortic coarctation) underwent cerebral MRI before (postnatal-day 7) and after (postnatal-day 24) surgery. Eighteen controls with similar gestational age had one MRI (postnatal-day 23). Cortical gray matter volume (CGM), inner cortical surface (iCS), and median cortical thickness were extracted as measures of volumetric growth, and gyrification index (GI) as measure of maturation.

RESULTS

Over a median of 18 d, CGM increased by 21%, iCS by 17%, thickness and GI both by 9%. Decreased postoperative CGM and iCS were seen for CHD compared to controls (P values < 0.01), however with similar thickness and GI. UVH showed lower postoperative iCS, thickness (P values < 0.05) and GI (P value < 0.01) than d-TGA and controls. Infants requiring preoperative balloon-atrioseptostomy (BAS, 61%) had reduced postoperative CGM, iCS, and GI (P values < 0.05).

CONCLUSION

Infants with severe CHD show reduced cortical volumes compared to controls with gyrification being delayed in UVH, but not in d-TGA. Infants requiring BAS show higher risk of impaired cortical volume and gyrification.

Factors Influencing Neurodevelopment after Cardiac Surgery during Infancy

Short- and long-term neurodevelopmental (ND) disabilities with negative impact on psychosocial and academic performance, quality of life, and independence in adulthood are known to be the most common sequelae for surviving children after surgery for congenital heart disease (CHD). This article reviews influences and risk factors for ND impairment. For a long time, the search for independent risk factors was focused on the perioperative period and modalities of cardiopulmonary bypass (CPB). CPB operations to ensure intraoperative vital organ perfusion and oxygen supply with or without circulatory arrest or regional cerebral perfusion bear specific risks. Examples of such risks are embolization, deep hypothermia, flow rate, hemodilution, blood gas management, postoperative hyperthermia, systemic inflammatory response, and capillary leak syndrome. However, influences of these procedure-specific risk factors on ND outcome have not been found as strong as expected. Furthermore, modifications have not been found to support the effectiveness of the currently used neuroprotective strategies. Postoperative factors, such as need for extracorporal membrane oxygenation or assist device support and duration of hospital stay, significantly influence ND parameters. On the other hand, the so-called "innate," less modifiable patient-specific risk factors have been found to exert significant influences on ND outcomes. Examples are type and severity of CHD, genetic or syndromic abnormalities, as well as prematurity and low birth weight. Structural and hemodynamic characteristics of different CHDs are assumed to result in impaired brain growth and delayed maturation with respect to the white matter. Beginning in the fetal period, this so-called "encephalopathy of CHD" is suggested a major innate risk factor for pre-, peri-, and postoperative additional hypoxic or ischemic brain injury and subsequent ND impairment. Furthermore, MRI studies on brain volume, structure, and function in adolescents have been found correlated with cognitive, motor, and executive dysfunctions. Finally, family and environmental factors independently moderate against ND outcomes. In conclusion, the different mediating factors may exert independent effects on ND and interactive influences. Implications for the future comprise modifying clinical risk factors, such as perioperative cerebral oxygen delivery, conducting brain MRI studies in correlation to ND outcomes, and extending psychosocial interventions leading to adequate resilience.

Neuroprotective strategies--what do we really need to know?

While preliminary data are encouraging, definitive data are lacking to conclusively demonstrate the benefit of perioperative neurologic monitoring in improving neurodevelopmental outcomes in children who require surgery for congenital heart disease. Nonetheless, in the current era, some form of perioperative neurologic monitoring is important. Strategies include bicortical near infrared spectroscopy monitoring in the pre- and postoperative periods along with bicortical near infrared spectroscopy and transcranial Doppler intraoperatively. These monitors provide real-time information concerning cerebral oxygen delivery and blood flow. These strategies will allow us to refine treatments to optimize neurodevelopmental potential in children with congenital heart disease.

New imaging approaches to evaluate newborn brain injury and their role in predicting developmental disorders

PURPOSE OF REVIEW

This review highlights recent work using advanced imaging approaches that have improved our understanding of the underlying neural mechanisms associated with disrupted brain development or demonstrated the potential of MRI to provide objective biomarkers of cerebral injury that relate to subsequent neurodevelopmental performance.

RECENT FINDINGS

Preterm birth impacts on the development of thalamocortical connections to inferior frontal and medial temporal cortex, and cingulate gyri. Impairments to cortical development in these regions are evident in early adulthood and associated with lower intelligence quotient scores. Disruptions to microstructural development of cortical gray matter are prevalent in survivors of preterm birth and related to immaturity at birth, postnatal growth and neurodevelopmental performance. Brain dysmaturation is also evident in infants with congenital heart disease and is detectable prior to surgery, highlighting the influence of adverse conditions on in-utero brain development. In infants with hypoxic-ischemic encephalopathy who have undergone therapeutic hypothermia, quantitative magnetic resonance measures in the neonatal period are related to performance at 2 years.

SUMMARY

Advanced MRI approaches offer the opportunity to assess objectively brain structure and function, and a number of studies, spanning different patient groups, demonstrate their utility as early biomarkers of altered neurological outcome.