Abnormal cerebral microstructure in premature neonates with congenital heart disease

Postnatal Brain Trajectories and Maternal Intelligence Predict Childhood Outcomes in Complex CHD

Objective: To determine whether early structural brain trajectories predict early childhood neurodevelopmental deficits in complex CHD patients and to assess relative cumulative risk profiles of clinical, genetic, and demographic risk factors across early development. Study Design: Term neonates with complex CHDs were recruited at Texas Children's Hospital from 2005-2011. Ninety-five participants underwent three structural MRI scans and three neurodevelopmental assessments. Brain region volumes and white matter tract fractional anisotropy and radial diffusivity were used to calculate trajectories: perioperative, postsurgical, and overall. Gross cognitive, language, and visuo-motor outcomes were assessed with the Bayley Scales of Infant and Toddler Development and with the Wechsler Preschool and Primary Scale of Intelligence and Beery-Buktenica Developmental Test of Visual-Motor Integration. Multi-variable models incorporated risk factors. Results: Reduced overall period volumetric trajectories predicted poor language outcomes: brainstem ((β, 95% CI) 0.0977, 0.0382-0.1571; p = 0.0022) and white matter (0.0023, 0.0001-0.0046; p = 0.0397) at 5 years; brainstem (0.0711, 0.0157-0.1265; p = 0.0134) and deep grey matter (0.0085, 0.0011-0.0160; p = 0.0258) at 3 years. Maternal IQ was the strongest contributor to language variance, increasing from 37% at 1 year, 62% at 3 years, and 81% at 5 years. Genetic abnormality's contribution to variance decreased from 41% at 1 year to 25% at 3 years and was insignificant at 5 years. Conclusion: Reduced postnatal subcortical-cerebral white matter trajectories predicted poor early childhood neurodevelopmental outcomes, despite high contribution of maternal IQ. Maternal IQ was cumulative over time, exceeding the influence of known cardiac and genetic factors in complex CHD, underscoring the importance of heritable and parent-based environmental factors.

Single Ventricle Reconstruction III: Brain Connectome and Neurodevelopmental Outcomes: Design, Recruitment, and Technical Challenges of a Multicenter, Observational Neuroimaging Study

Patients with hypoplastic left heart syndrome who have been palliated with the Fontan procedure are at risk for adverse neurodevelopmental outcomes, lower quality of life, and reduced employability. We describe the methods (including quality assurance and quality control protocols) and challenges of a multi-center observational ancillary study, SVRIII (Single Ventricle Reconstruction Trial) Brain Connectome. Our original goal was to obtain advanced neuroimaging (Diffusion Tensor Imaging and Resting-BOLD) in 140 SVR III participants and 100 healthy controls for brain connectome analyses. Linear regression and mediation statistical methods will be used to analyze associations of brain connectome measures with neurocognitive measures and clinical risk factors. Initial recruitment challenges occurred that were related to difficulties with: (1) coordinating brain MRI for participants already undergoing extensive testing in the parent study, and (2) recruiting healthy control subjects. The COVID-19 pandemic negatively affected enrollment late in the study. Enrollment challenges were addressed by: (1) adding additional study sites, (2) increasing the frequency of meetings with site coordinators, and (3) developing additional healthy control recruitment strategies, including using research registries and advertising the study to community-based groups. Technical challenges that emerged early in the study were related to the acquisition, harmonization, and transfer of neuroimages. These hurdles were successfully overcome with protocol modifications and frequent site visits that involved human and synthetic phantoms.

Single Ventricle Reconstruction III: Brain Connectome and Neurodevelopmental Outcomes: Design, Recruitment, and Technical Challenges of a Multicenter, Observational Neuroimaging Study

Patients with hypoplastic left heart syndrome who have been palliated with the Fontan procedure are at risk for adverse neurodevelopmental outcomes, lower quality of life, and reduced employability. We describe the methods (including quality assurance and quality control protocols) and challenges of a multi-center observational ancillary study, SVRIII (Single Ventricle Reconstruction Trial) Brain Connectome. Our original goal was to obtain advanced neuroimaging (Diffusion Tensor Imaging and Resting-BOLD) in 140 SVR III participants and 100 healthy controls for brain connectome analyses. Linear regression and mediation statistical methods will be used to analyze associations of brain connectome measures with neurocognitive measures and clinical risk factors. Initial recruitment challenges occurred related to difficulties with: 1) coordinating brain MRI for participants already undergoing extensive testing in the parent study, and 2) recruiting healthy control subjects. The COVID-19 pandemic negatively affected enrollment late in the study. Enrollment challenges were addressed by 1) adding additional study sites, 2) increasing the frequency of meetings with site coordinators and 3) developing additional healthy control recruitment strategies, including using research registries and advertising the study to community-based groups. Technical challenges that emerged early in the study were related to the acquisition, harmonization, and transfer of neuroimages. These hurdles were successfully overcome with protocol modifications and frequent site visits that involved human and synthetic phantoms.

Trial registration number

ClinicalTrials.gov Registration Number: NCT02692443.

Structural Brain Alterations and Their Associations With Function in Children, Adolescents, and Young Adults With Congenital Heart Disease

Most neonates who receive surgery for complex congenital heart disease (CHD) will survive well into adulthood, however, many of them will face functional challenges at one point during their life as a consequence of their atypical neurodevelopment. Recent advances in neuroscience and the increasing accessibility of magnetic resonance imaging have allowed numerous studies to identify the nature and extent of the brain alterations that are particular to survivors with CHD. Nevertheless, and considering that the range of outcomes is broad in this population, the functional consequences of these brain differences is not always evident. In this review, we summarize the present state of knowledge regarding the structure-function relationships evaluated in children, adolescents, and young adults with CHD using structural magnetic resonance imaging. Overall smaller total and regional brain volume, as well as lower fractional anisotropy in numerous brain regions, were frequently associated with lower cognitive outcomes including executive functioning and memory in adolescents and young adults with CHD. However, we identify several gaps in knowledge including the limited number of prospective investigations involving neonatal imaging and follow-up during childhood or adolescence, as well as the need for studies that evaluate a broader range of functional outcomes and not only the cognitive abilities. Future interdisciplinary investigations using multimodal imaging techniques could help address these gaps.

Reduced Cerebellar Volume in Term Infants with Complex Congenital Heart Disease: Correlation with Postnatal Growth Measurements

Aberrant cerebellar development and the associated neurocognitive deficits has been postulated in infants with congenital heart disease (CHD). Our objective is to investigate the effect of postnatal head and somatic growth on cerebellar development in neonates with CHD. We compared term-born neonates with a history of CHD with a cohort of preterm-born neonates, two cohorts at similar risk for neurodevelopment impairment, in order to determine if they are similarly affected in the early developmental period. Study Design: 51 preterms-born healthy neonates, 62 term-born CHD neonates, and 54 term-born healthy neonates underwent a brain MRI with volumetric imaging. Cerebellar volumes were extracted through an automated segmentation pipeline that was developed in-house. Volumes were correlated with clinical growth parameters at both the birth and time of MRI. Results: The CHD cohort showed significantly lower cerebellar volumes when compared with both the control (p < 0.015) and preterm (p < 0.004) groups. Change in weight from birth to time of MRI showed a moderately strong correlation with cerebellar volume at time of MRI (r = 0.437, p < 0.002) in the preterms, but not in the CHD neonates (r = 0.205, p < 0.116). Changes in birth length and head circumference showed no significant correlation with cerebellar volume at time of MRI in either cohort. Conclusions: Cerebellar development in premature-born infants is associated with change in birth weight in the early post-natal period. This association is not observed in term-born neonates with CHD, suggesting differential mechanisms of aberrant cerebellar development in these perinatal at-risk populations.

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.

Cerebral oxygen saturation and cerebrovascular instability in newborn infants with congenital heart disease compared to healthy controls

Objective

Infants with Congenital Heart Disease (CHD) are at risk for developmental delays, though the mechanisms of brain injury that impair development are unknown. Potential causes could include cerebral hypoxia and cerebrovascular instability. We hypothesized that we would detect significantly reduced cerebral oxygen saturation and greater cerebrovascular instability in CHD infants compared to the healthy controls.

Methods

We performed a secondary analysis on a sample of 43 term infants (28 CHD, 15 healthy controls) that assessed prospectively in temporal cross-section before or at 12 days of age. CHD infants were assessed prior to open-heart surgery. Cerebral oxygen saturation levels were estimated using Near-Infrared Spectroscopy, and cerebrovascular stability was assessed with the response of cerebral oxygen saturation after a postural change (supine to sitting).

Results

Cerebral oxygen saturation was 9 points lower in CHD than control infants in both postures (β = -9.3; 95%CI = -17.68, -1.00; p = 0.028), even after controlling for differences in peripheral oxygen saturation. Cerebrovascular stability was significantly impaired in CHD compared to healthy infants (β = -2.4; 95%CI = -4.12, -.61; p = 0.008), and in CHD infants with single ventricle compared with biventricular defects (β = -1.5; 95%CI = -2.95, -0.05; p = 0.04).

Conclusion

CHD infants had cerebral hypoxia and decreased cerebral oxygen saturation values following a postural change, suggesting cerebrovascular instability. Future longitudinal studies should assess the associations of cerebral hypoxia and cerebrovascular instability with long-term neurodevelopmental outcomes in CHD infants.

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.

Benefits of progesterone on brain immaturity and white matter injury induced by chronic hypoxia in neonatal rats

OBJECTIVES

This study aims to evaluate the protective effects of progesterone on white matter injury and brain immaturity in neonatal rats with chronic hypoxia.

METHODS

Three-day old Sprague-Dawley rats were randomly divided into 3 groups: (1) control (n = 48), rats were exposed to normoxia (fraction of inspired oxygen: 21% ± 0%); (2) chronic hypoxia (n = 48), rats were exposed to hypoxia (fraction of inspired oxygen: 10.5% ± 1.0%); and (3) progesterone (n = 48), rats were exposed to hypoxia and administrated with progesterone (8 mg/kg/d). Hematoxylin-eosin staining, immunohistochemistry, real-time quantitative polymerase chain reaction, and Western blot analyses were compared on postnatal day 14 in different groups. Motor skill and coordination abilities of rats were assessed via rotation experiments.

RESULTS

Increased brain weights (P < .05), narrowed ventricular sizes (P < .01), and rotarod experiment scores (P < .01) were better in the progesterone group than in the chronic hypoxia group. The number of mature oligodendrocytes and myelin basic protein expression increased in the progesterone group compared with the chronic hypoxia group (P < .01). The polarization of M1 microglia cells in the corpus callosum of chronic hypoxia-induced hypomyelination rats was significantly increased, whereas there were fewer M2 microglia cells. Conversely, progesterone therapy had an opposite effect and caused an increase in M2 microglia polarization versus a reduction in M1 microglia cells.

CONCLUSIONS

Progesterone could prevent white matter injury and improve brain maturation in a neonatal hypoxic rat model; this may be associated with inducing a switch from M1 to M2 in microglia.

Health-related quality of life for children and adolescents in school age with hypoplastic left heart syndrome: a single-centre study

Data from neurological and radiological research show an abnormal neurological development in patients treated for hypoplastic left heart syndrome. Thus, the aim of this study was to survey the quality of life scores in comparison with healthy children and children with other heart diseases (mild, moderate, and severe heart defects, heart defects in total). Children with hypoplastic left heart syndrome (aged 6.3-16.9 years) under compulsory education requirements, who were treated at the Children's Heart Center Linz between 1997 and 2009 (n = 74), were surveyed. Totally, 41 children and 44 parents were examined prospectively by psychologists according to Pediatric Quality of Life Inventory, a health-related quality of life measurement. The results of the self-assessments of health-related quality of life on a scale of 1-100 showed a wide range, from a minimum of 5.00 (social functioning) to a maximum of 100 (physical health-related summary scores, emotional functioning, school functioning), with a total score of 98.44. The parents' assessments (proxy) were quite similar, showing a range from 10 (social functioning) up to 100. Adolescent hypoplastic left heart syndrome patients rated themselves on the same level as healthy youths and youths with different heart diseases. The results show that patients with hypoplastic left heart syndrome aged 6-16 years can be successfully supported and assisted in their psychosocial development even if they show low varying physical and psychosocial parameters. The finding that adolescent hypoplastic left heart syndrome patients estimated themselves similar to healthy individuals suggests that they learnt to cope with a severe heart defect.

Punctate white-matter lesions in the full-term newborn: Underlying aetiology and outcome

BACKGROUND

Punctate white matter lesions (PWMLs) are small focal patches of increased signal intensity (SI) on T1- and decreased SI on T2-weighted magnetic resonance imaging (MRI). To date, there have been few reports of PWMLs in term born infants.

OBJECTIVE

To identify associated diagnoses and factors predictive of clinical outcome in (near) term infants with PWMLs.

METHODS

MRI studies and clinical records of (near) term infants, with PWMLs on MRI scans performed in two institutions in the first 28 postnatal days were reviewed. The PWMLs were classified according to their number, pattern and distribution. The medical records were examined to assess the associated diagnoses and determine the neurodevelopmental outcome at >12 months of age. Infants with congenital heart defect(s), those who had neonatal surgery, or those with perinatal arterial ischemic stroke were not eligible for the study.

RESULTS

Forty-two (near) term infants with PWMLs were included. The major clinical association was perinatal asphyxia, present in 19/42 (45%). Ten (24%) had a history of seizures unrelated to asphyxia or a genetic diagnosis. Eleven (26%) had pathological genetic mutations. Other diagnoses, without seizures were identified in 2 (5%). The lesion load of PWMLs was high (>6) in 30/42 (71%). Evidence of irreversible white matter injury was present in 5 infants who had follow-up MRI performed between 18 and 24 months of age, because of clinical concerns. Five infants died and 37 had follow-up at a median age of 24 months. Neurodevelopmental outcome was poorest amongst 6 infants (16%) whose PWMLs occurred in the setting of a genetic disorder.

CONCLUSION

PWMLs in (near) term infants represent white matter injury that may evolve into gliosis and/or white matter loss. Infants with PWMLs in the setting of a genetic disorder appeared at most risk of a poor outcome.

Abnormal fetal cerebral and vascular development in hypoplastic left heart syndrome

Objective

To assess the cerebral and vascular development in fetuses with hypoplastic left heart syndrome (HLHS).

Methods

Pregnant women carrying fetuses diagnosed with HLHS who decided to interrupt their pregnancies were included in our study. Aortic size and blood flow were assessed based from fetal echocardiography. Immunohistochemical staining was performed in brain sections obtained from pathology in fetuses with HLHS and control fetuses without heart disease.

Results

Twenty‐seven midgestation fetal HLHS were included (gestational age, 23.3 ± 3.4 weeks). Head circumference z scores were lower in HLHS fetuses. Middle cerebral artery pulsatility index, a measure of cerebrovascular resistance, was inversely correlated with the ascending aortic z score (P < 0.05). Fetuses with HLHS had lower capillary density in the germinal matrix and their capillaries were larger compared with control fetuses with (P < 0.05). The expression of neuronal differentiation marker, FGFR1, and oligodendrocyte precursor, O4, were lower in HLHS brains compared with controls (P < 0.05).

Conclusion

Our study identified abnormalities of vascular flow and structural brain abnormalities in fetal HLHS associated with impaired neuronal and oligodendrocyte differentiation, as well as cerebral growth impairment, early in gestation. These findings may be related in part to early vascular abnormalities.

What's already known about this topic?

Structural brain abnormalities and abnormalities in neurodevelopment have been reported in HLHS.

What does this study add?

Our study describes abnormal vascular development that may account for abnormal neuronal and white matter differentiation in the developing fetus with HLHS.

Association between Subcortical Morphology and Cerebral White Matter Energy Metabolism in Neonates with Congenital Heart Disease

Complex congenital heart disease (CHD) is associated with neurodevelopmental impairment, the mechanism of which is unknown. Cerebral cortical dysmaturation in CHD is linked to white matter abnormalities, including developmental vulnerability of the subplate, in relation to oxygen delivery and metabolism deficits. In this study, we report associations between subcortical morphology and white matter metabolism in neonates with CHD using quantitative magnetic resonance imaging (MRI) and spectroscopy (MRS). Multi-modal brain imaging was performed in three groups of neonates close to term-equivalent age: (1) term CHD (n = 56); (2) preterm CHD (n = 37) and (3) preterm control group (n = 22). Thalamic volume and cerebellar transverse diameter were obtained in relation to cerebral metrics and white matter metabolism. Short echo single-voxel MRS of parietal and frontal white matter was used to quantitate metabolites related to brain maturation (n-acetyl aspartate [NAA], choline, myo-inositol), neurotransmitter (glutamate), and energy metabolism (glutamine, citrate, creatine and lactate). Multi-variate regression was performed to delineate associations between subcortical morphological measurements and white matter metabolism controlling for age and white matter injury. Reduced thalamic volume, most pronounced in the preterm control group, was associated with increased citrate levels in all three group in the parietal white matter. In contrast, reduced cerebellar volume, most pronounced in the preterm CHD group, was associated with reduced glutamine in parietal grey matter in both CHD groups. Single ventricle anatomy, aortic arch obstruction, and cyanotic lesion were predictive of the relationship between reduced subcortical morphometry and reduced GLX (particularly glutamine) in both CHD cohorts (frontal white matter and parietal grey matter). Subcortical morphological associations with brain metabolism were also distinct within each of the three groups, suggesting these relationships in the CHD groups were not directly related to prematurity or white matter injury alone. Taken together, these findings suggest that subplate vulnerability in CHD is likely relevant to understanding the mechanism of both cortical and subcortical dysmaturation in CHD infants. Future work is needed to link this potential pattern of encephalopathy of CHD (including the constellation of grey matter, white matter and brain metabolism deficits) to not only abnormal fetal substrate delivery and oxygen conformance, but also regional deficits in cerebral energy metabolism.

Cerebral Autoregulation in Neonates With and Without Congenital Heart Disease

BACKGROUND

Congenital heart disease (CHD) is a leading birth defect in the United States, affecting about 40 000 neonates each year. Despite efforts to prevent developmental delays, many children with CHD have neurological deficits that last into adulthood, influencing employability, self-care, and quality of life.

OBJECTIVE

To determine if neonates with CHD have impaired cerebral autoregulation and poorer neurodevelopmental outcomes compared with healthy controls.

METHODS

A total of 44 full-term neonates, 28 with CHD and 16 without, were enrolled in the study. Inclusion criteria included confirmed diagnosis of CHD, stable hemodynamic status, and being no more than 12 days old. Exclusion criteria included intraventricular hemorrhage and intubation. Cerebral autoregulation was determined by measuring regional cerebral oxygenation during a postural change. The Einstein Neonatal Neurobehavioral Assessment Scale was used to measure overall neurodevelopmental outcomes (motor, visual, and auditory functions).

RESULTS

Of the 28 neonates with CHD, 8 had single-ventricle physiology. A χ² analysis indicated no significant difference in impaired cerebral autoregulation between neonates with CHD and controls (P = .38). Neonates with CHD had lower regional cerebral oxygenation than did neonates without CHD (P < .001). Regression analyses with adjustments for cerebral autoregulation indicated that neonates with CHD had poorer total neurodevelopmental outcomes scores (β = 9.3; P = .02) and motor scores (β = 7.6; P = .04).

CONCLUSION

Preoperative neonates with CHD have poorer developmental outcomes and more hypoxemia than do controls.

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.

Cognitive Development of School-Age Hypoplastic Left Heart Syndrome Survivors: A Single Center Study

Neurological and radiologic research results show an abnormal cerebral microstructure as well as abnormal neurodevelopment in patients treated for hypoplastic left heart syndrome. The aim of this study was to assess the varying cognitive performance these children have developed in dependence upon prenatal diagnosis, surgical techniques, surgical learning effects, anatomy, perfusion techniques, gender, pedagogic, and sociodemographic parameters in comparison to age-adjusted normative values. School-age children (6.3-16.9 years) with hypoplastic left heart syndrome, who were treated at the Children's heart Center Linz between 1997 and 2009, (n = 74), were surveyed in reference to cognitive achievements. 43 patients were examined prospectively by psychologists using the Wechsler intelligence scale for children IV in order to determine the respective total intelligence quotient index for each child's developmental stage. The mean index was 84.5 (percentile rank 26.4). The statistical spread and standard deviation ranged from a minimum of 40 to a maximum of 134 ± 20.8. The results for verbal comprehension, perceptual reasoning, and processing speed corresponded with total index results and were thus lower than the mean value of the normative values. The assessment of working memory showed results in the average. Prenatal diagnosis, type of lung perfusion, anatomy, and various cerebral perfusion techniques did not significantly affect the cognitive results of the patients. The results show that hypoplastic left heart syndrome patients can be successfully tutored formally as well as personally in cognitive areas, although when compared to healthy children, they showed lower results for intellectual area parameters.

Neurodevelopmental Abnormalities and Congenital Heart Disease: Insights Into Altered Brain Maturation

In the past 2 decades, it has become evident that individuals born with congenital heart disease (CHD) are at risk of developing life-long neurological deficits. Multifactorial risk factors contributing to neurodevelopmental abnormalities associated with CHD have been identified; however, the underlying causes remain largely unknown, and efforts to address this issue have only recently begun. There has been a dramatic shift in focus from newly acquired brain injuries associated with corrective and palliative heart surgery to antenatal and preoperative factors governing altered brain maturation in CHD. In this review, we describe key time windows of development during which the immature brain is vulnerable to injury. Special emphasis is placed on the dynamic nature of cellular events and how CHD may adversely impact the cellular units and networks necessary for proper cognitive and motor function. In addition, we describe current gaps in knowledge and offer perspectives about what can be done to improve our understanding of neurological deficits in CHD. Ultimately, a multidisciplinary approach will be essential to prevent or improve adverse neurodevelopmental outcomes in individuals surviving CHD.

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.

Mapping the critical gestational age at birth that alters brain development in preterm-born infants using multi-modal MRI

Preterm birth adversely affects postnatal brain development. In order to investigate the critical gestational age at birth (GAB) that alters the developmental trajectory of gray and white matter structures in the brain, we investigated diffusion tensor and quantitative T2 mapping data in 43 term-born and 43 preterm-born infants. A novel multivariate linear model-the change point model, was applied to detect change points in fractional anisotropy, mean diffusivity, and T2 relaxation time. Change points captured the "critical" GAB value associated with a change in the linear relation between GAB and MRI measures. The analysis was performed in 126 regions across the whole brain using an atlas-based image quantification approach to investigate the spatial pattern of the critical GAB. Our results demonstrate that the critical GABs are region- and modality-specific, generally following a central-to-peripheral and bottom-to-top order of structural development. This study may offer unique insights into the postnatal neurological development associated with differential degrees of preterm birth.

The Impact of Venoarterial and Venovenous Extracorporeal Membrane Oxygenation on Cerebral Metabolism in the Newborn Brain

Background

Extracorporeal membrane oxygenation (ECMO) is an effective therapy for supporting infants with reversible cardiopulmonary failure. Still, survivors are at risk for long-term neurodevelopmental impairments, the cause of which is not fully understood.

Objective

To elucidate the effects of ECMO on the newborn brain. We hypothesized that the cerebral metabolic profile of neonates who received ECMO would differ from neonates who did not receive ECMO. To address this, we used magnetic resonance spectroscopy (¹H-MRS) to investigate the effects of venoarterial and venovenous ECMO on cerebral metabolism.

Methods

41 neonates treated with ECMO were contrasted to 38 age-matched neonates.

Results

All ¹H-MRS data were acquired from standardized grey matter and white matter regions of interest using a short-echo (TE = 35 milliseconds), point-resolved spectroscopy sequence (PRESS) and quantitated using LCModel. Metabolite concentrations (mmol/kg) were compared across groups using multivariate analysis of covariance. Elevated creatine (p = 0.002) and choline (p = 0.005) concentrations were observed in the grey matter among neonates treated with ECMO relative to the reference group. Likewise, choline concentrations were elevated in the white matter (p = 0.003) while glutamate was reduced (p = 0.03). Contrasts between ECMO groups revealed lower osmolite concentrations (e.g. myoinositol) among the venovenous ECMO group.

Conclusion

Neonates who underwent ECMO were found to have an abnormal cerebral metabolic profile, with the pattern of abnormalities suggestive of an underlying inflammatory process. Additionally, neonates who underwent venovenous ECMO had low cerebral osmolite concentrations as seen in vasogenic edema.

Early-Term Birth in Single-Ventricle Congenital Heart Disease After the Fontan Procedure: Neurodevelopmental and Psychiatric Outcomes

OBJECTIVES

To investigate the long-term impact of early-term birth (37-38 weeks' gestation) relative to full-term birth (≥39 weeks' gestation) on neurodevelopmental and psychiatric outcomes in adolescents with single-ventricle congenital heart disease (CHD).

STUDY DESIGN

This cross-sectional cohort study analyzed retrospective medical records from full term adolescents with single-ventricle CHD who underwent the Fontan procedure. Participants underwent neurodevelopmental and psychiatric evaluations, as well as structural brain magnetic resonance imaging. Early-term born adolescents were compared with full-term born adolescents using regression models with adjustments for family social status, birth weight, and genetic abnormality status. Medical and demographic risk factors were examined as well.

RESULTS

Compared with the full-term group (n = 100), adolescents born early term (n = 33) scored significantly worse on daily-life executive functions, as measured by the Behavior Rating Inventory of Executive Function parent-report (mean scores: early term, 62.0 ± 10.9; full-term, 55.6 ± 12.2; P = .009) and self-report (P = .02) composites. Adolescents born early term were more likely than those born full term to have a lifetime attention-deficit/hyperactivity disorder (ADHD) diagnosis (early term, 55%; full term, 26%; P = .001). The early-term group also displayed greater psychiatric symptom severity, as indicated by the clinician-reported Brief Psychiatric Rating Scale (mean score: early term, 16.1 ± 8.6; full-term, 12.5 ± 8.2; P = .007).

CONCLUSION

Early-term birth is associated with greater prevalence of executive dysfunction, ADHD diagnosis, and psychiatric problems in adolescents with single-ventricle CHD. Early-term birth should be included as a potential risk factor in the algorithm for closer developmental surveillance in CHD.

Probabilistic maps of the white matter tracts with known associated functions on the neonatal brain atlas: Application to evaluate longitudinal developmental trajectories in term-born and preterm-born infants

Diffusion tensor imaging (DTI) has been widely used to investigate the development of the neonatal and infant brain, and deviations related to various diseases or medical conditions like preterm birth. In this study, we created a probabilistic map of fiber pathways with known associated functions, on a published neonatal multimodal atlas. The pathways-of-interest include the superficial white matter (SWM) fibers just beneath the specific cytoarchitectonically defined cortical areas, which were difficult to evaluate with existing DTI analysis methods. The Jülich cytoarchitectonic atlas was applied to define cortical areas related to specific brain functions, and the Dynamic Programming (DP) method was applied to delineate the white matter pathways traversing through the SWM. Probabilistic maps were created for pathways related to motor, somatosensory, auditory, visual, and limbic functions, as well as major white matter tracts, such as the corpus callosum, the inferior fronto-occipital fasciculus, and the middle cerebellar peduncle, by delineating these structures in eleven healthy term-born neonates. In order to characterize maturation-related changes in diffusivity measures of these pathways, the probabilistic maps were then applied to DTIs of 49 healthy infants who were longitudinally scanned at three time-points, approximately five weeks apart. First, we investigated the normal developmental pattern based on 19 term-born infants. Next, we analyzed 30 preterm-born infants to identify developmental patterns related to preterm birth. Last, we investigated the difference in diffusion measures between these groups to evaluate the effects of preterm birth on the development of these functional pathways. Term-born and preterm-born infants both demonstrated a time-dependent decrease in diffusivity, indicating postnatal maturation in these pathways, with laterality seen in the corticospinal tract and the optic radiation. The comparison between term- and preterm-born infants indicated higher diffusivity in the preterm-born infants than in the term-born infants in three of these pathways: the body of the corpus callosum; the left inferior longitudinal fasciculus; and the pathway connecting the left primary/secondary visual cortices and the motion-sensitive area in the occipitotemporal visual cortex (V5/MT+). Probabilistic maps provided an opportunity to investigate developmental changes of each white matter pathway. Whether alterations in white matter pathways can predict functional outcomes will be further investigated in a follow-up study.

Regional vulnerability of longitudinal cortical association connectivity: Associated with structural network topology alterations in preterm children with cerebral palsy

Preterm born children with spastic diplegia type of cerebral palsy and white matter injury or periventricular leukomalacia (PVL), are known to have motor, visual and cognitive impairments. Most diffusion tensor imaging (DTI) studies performed in this group have demonstrated widespread abnormalities using averaged deterministic tractography and voxel-based DTI measurements. Little is known about structural network correlates of white matter topography and reorganization in preterm cerebral palsy, despite the availability of new therapies and the need for brain imaging biomarkers. Here, we combined novel post-processing methodology of probabilistic tractography data in this preterm cohort to improve spatial and regional delineation of longitudinal cortical association tract abnormalities using an along-tract approach, and compared these data to structural DTI cortical network topology analysis. DTI images were acquired on 16 preterm children with cerebral palsy (mean age 5.6 ± 4) and 75 healthy controls (mean age 5.7 ± 3.4). Despite mean tract analysis, Tract-Based Spatial Statistics (TBSS) and voxel-based morphometry (VBM) demonstrating diffusely reduced fractional anisotropy (FA) reduction in all white matter tracts, the along-tract analysis improved the detection of regional tract vulnerability. The along-tract map-structural network topology correlates revealed two associations: (1) reduced regional posterior-anterior gradient in FA of the longitudinal visual cortical association tracts (inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, optic radiation, posterior thalamic radiation) correlated with reduced posterior-anterior gradient of intra-regional (nodal efficiency) metrics with relative sparing of frontal and temporal regions; and (2) reduced regional FA within frontal-thalamic-striatal white matter pathways (anterior limb/anterior thalamic radiation, superior longitudinal fasciculus and cortical spinal tract) correlated with alteration in eigenvector centrality, clustering coefficient (inter-regional) and participation co-efficient (inter-modular) alterations of frontal-striatal and fronto-limbic nodes suggesting re-organization of these pathways. Both along tract and structural topology network measurements correlated strongly with motor and visual clinical outcome scores. This study shows the value of combining along-tract analysis and structural network topology in depicting not only selective parietal occipital regional vulnerability but also reorganization of frontal-striatal and frontal-limbic pathways in preterm children with cerebral palsy. These finding also support the concept that widespread, but selective posterior-anterior neural network connectivity alterations in preterm children with cerebral palsy likely contribute to the pathogenesis of neurosensory and cognitive impairment in this group.

Developmental synergy between thalamic structure and interhemispheric connectivity in the visual system of preterm infants

Thalamic structural co-variation with cortical regions has been demonstrated in preterm infants, but its relationship to cortical function and severity of non-cystic white matter injury (non-cystic WMI) is unclear. The relationship between thalamic morphology and both cortical network synchronization and cortical structural connectivity has not been established. We tested the hypothesis that in preterm neonates, thalamic volume would correlate with primary cortical visual function and microstructural integrity of cortico-cortical visual association pathways. A total of 80 term-equivalent preterm and 44 term-born infants underwent high-resolution structural imaging coupled with visual functional magnetic resonance imaging or diffusion tensor imaging. There was a strong correlation between thalamic volume and primary visual cortical activation in preterms with non-cystic WMI (r = 0.81, p-value = 0.001). Thalamic volume also correlated strongly with interhemispheric cortico-cortical connectivity (splenium) in preterm neonates with a relatively higher severity of non-cystic WMI (p-value < 0.001). In contrast, there was lower correlation between thalamic volume and intrahemispheric cortico-cortical connectivity, including the inferior longitudinal fasciculus and inferior frontal orbital fasciculus. This study shows distinct temporal overlap in the disruption of thalamo-cortical and interhemispheric cortico-cortical connectivity in preterm infants suggesting developmental synergy between thalamic morphology and the emergence of cortical networks in the last trimester.

Congenital cardiac anomalies and white matter injury

Cardiac abnormalities are the most common birth defects. Derangement of circulatory flow affects many vital organs; without proper supply of oxygenated blood, the brain is particularly vulnerable. Although surgical interventions have greatly reduced mortality rates, patients often suffer an array of neurological deficits throughout life. Neuroimaging provides a macroscopic assessment of brain injury and has shown that white matter (WM) is at risk. Oligodendrocytes and myelinated axons have been identified as major targets of WM injury, but still little is known about how congenital heart anomalies affect the brain at the cellular level. Further integration of animal model studies and clinical research will define novel therapeutic targets and new standards of care to prevent developmental delay associated with cardiac abnormalities.

Abnormal development of thalamic microstructure in premature neonates with congenital heart disease

Preterm birth is associated with alteration in corticothalamic development, which underlies poor neurodevelopmental outcomes. Our hypothesis was that preterm neonates with CHD would demonstrate abnormal thalamic microstructure when compared to critically ill neonates without CHD. A secondary aim was to identify any association between thalamic microstructural abnormalities and perioperative clinical variables. We compared thalamic DTI measurements in 21 preterm neonates with CHD to two cohorts of neonates without CHD: 28 term and 27 preterm neonates, identified from the same neonatal intensive care unit. Comparison was made with three other selected white matter regions using ROI manual-based measurements. Correlation was made with post-conceptional age and perioperative clinical variables. In preterm neonates with CHD, there were age-related differences in thalamic diffusivity (axial and radial) compared to the preterm and term non-CHD group, in contrast to no differences in anisotropy. Contrary to our hypothesis, abnormal thalamic and optic radiation microstructure was most strongly associated with an elevated first arterial blood gas pO2 and elevated preoperative arterial blood gas pH (p < 0.05). Age-related thalamic microstructural abnormalities were observed in preterm neonates with CHD. Perinatal hyperoxemia and increased perioperative serum pH were associated with abnormal thalamic microstructure in preterm neonates with CHD. This study emphasizes the vulnerability of thalamocortical development in the preterm neonate with CHD.

Data quality in diffusion tensor imaging studies of the preterm brain: a systematic review

BACKGROUND

To study early neurodevelopment in preterm infants, evaluation of brain maturation and injury is increasingly performed using diffusion tensor imaging, for which the reliability of underlying data is paramount.

OBJECTIVE

To review the literature to evaluate acquisition and processing methodology in diffusion tensor imaging studies of preterm infants.

MATERIALS AND METHODS

We searched the Embase, Medline, Web of Science and Cochrane databases for relevant papers published between 2003 and 2013. The following keywords were included in our search: prematurity, neuroimaging, brain, and diffusion tensor imaging.

RESULTS

We found 74 diffusion tensor imaging studies in preterm infants meeting our inclusion criteria. There was wide variation in acquisition and processing methodology, and we found incomplete reporting of these settings. Nineteen studies (26%) reported the use of neonatal hardware. Data quality assessment was not reported in 13 (18%) studies. Artefacts-correction and data-exclusion was not reported in 33 (45%) and 18 (24%) studies, respectively. Tensor estimation algorithms were reported in 56 (76%) studies but were often suboptimal.

CONCLUSION

Diffusion tensor imaging acquisition and processing settings are incompletely described in current literature, vary considerably, and frequently do not meet the highest standards.

White matter injury in newborns with congenital heart disease: a diffusion tensor imaging study

BACKGROUND

Brain injury is observed on cranial magnetic resonance imaging preoperatively in up to 50% of newborns with congenital heart disease. Newer imaging techniques such as diffusion tensor imaging provide sensitive measures of the white matter integrity. The objective of this study was to evaluate the diffusion tensor imaging analysis technique of tract-based spatial statistics in newborns with congenital heart disease.

METHODS

Term newborns with congenital heart disease who would require surgery at less than 1 month of age were prospectively enrolled (n = 19). Infants underwent preoperative and postoperative brain magnetic resonance imaging with diffusion tensor imaging. Tract-based spatial statistics, an objective whole-brain diffusion tensor imaging analysis technique, was used to determine differences in white matter fractional anisotropy between infant groups. Term control infants were also compared with congenital heart disease infants. Postmenstrual age was equivalent between congenital heart disease infant groups and between congenital heart disease and control infants.

RESULTS

Ten infants had preoperative brain injury, either infarct or white matter injury, by conventional brain magnetic resonance imaging. The technique of tract-based spatial statistics showed significantly lower fractional anisotropy (P < 0.05, corrected) in multiple major white matter tracts in the infants with preoperative brain injury compared with infants without preoperative brain injury. Fractional anisotropy values increased in the white matter tracts from the preoperative to the postoperative brain magnetic resonance imaging correlating with brain maturation. Control infants had higher fractional anisotropy in multiple white matter tracts compared with infants with congenital heart disease.

CONCLUSION

Tract-based spatial statistics is a valuable diffusion tensor imaging analysis technique that may have better sensitivity in detecting white matter injury compared with conventional brain magnetic resonance imaging in term newborns with congenital heart disease.

Characterization of microstructural injury: a novel approach in infant abusive head trauma-initial experience

Abusive head trauma (AHT) is the leading cause of morbidity and mortality among abused children, yet the neuroanatomical underpinnings of AHT outcome is incompletely understood. The aim of this study was to characterize white matter (WM) abnormalities in infants with AHT using diffusion tensor imaging (DTI) and determine which microstructural abnormalities are associated with poor outcome. Retrospective DTI data from 17 infants (>3 months) with a diagnosis of AHT and a comparison cohort of 34 term infants of similar post-conceptual age (PCA) were compared using a voxel-based DTI analysis of cerebral WM. AHT cases were dichotomously classified into mild/moderate versus severe outcome. Clinical variables and conventional imaging findings were also analyzed in relation to outcome. Outcomes were classified in accordance with the Pediatric Cerebral Performance Category Score (PCPCS). Reduced axial diffusivity (AD) was shown in widespread WM regions in the AHT infants compared with controls as well as in the AHT severe outcome group compared with the AHT mild/moderate outcome group. Reduced mean diffusivity (MD) was also associated with severe outcome. Radial diffusivity (RD), conventional magnetic resonance findings, brain metric measurements, and clinical/laboratory variables (with the exception of Glascow Coma Scale) did not differ among AHT outcome groups. Findings support the unique role of DTI techniques, beyond conventional imaging, in the evaluation of microstructural WM injury of AHT. Reduced AD (likely reflecting axonal damage) and MD were associated with poor clinical outcome. DTI abnormalities may uniquely reflect AHT patterns of axonal injury that are not characterized by conventional imaging, which may have both therapeutic and prognostic implications.