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

Prevalence and Risk Factors for Cerebral Palsy in Children With Congenital Heart Disease Based on Risk of Surgical Mortality

BACKGROUND

Children with congenital heart disease (CHD) have a higher prevalence of motor impairment secondary to brain injury, resulting in cerebral palsy (CP). The purpose of this study is to determine the prevalence of CP in CHD in a single-center cohort, stratify risk based on surgical mortality using Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) categories and identify risk factors.

METHODS

Retrospective cohort study of pediatric patients registered in the University of Florida (UF) Society of Thoracic Surgeons Congenital Heart Surgery database from 2006 to 2017 with a diagnosis of CHD who continued follow-up for more than two years at UF.

RESULTS

A total of 701 children with CHD met inclusion criteria. Children identified to have CP were 54 (7.7%). Most common presentation was spastic hemiplegic CP with a Gross Motor Function Classification System of level 2. Analysis of surgical and intensive care factors between the two groups showed that children with CHD and CP had longer time from admission to surgery (P = 0.003), higher STAT categories 4 and 5 (P = 0.038), and higher frequency of brain injury and seizures (P < 0.001). Developmental disabilities and rehabilitation needs were significantly greater for children with CHD and CP when compared with those with CHD alone (P < 0.001).

CONCLUSIONS

In our cohort, 7.7% children with CHD develop CP; this is significantly higher than the 2010 US population estimate of 0.3%. Our study suggests higher STAT categories, brain injury, and seizures are associated with developing CP in children with CHD.

The Association Between Congenital Heart Disease and Autism Spectrum Disorder: A Systematic Review and Meta-Analysis

Congenital heart disease (CHD) is linked to an increased incidence of neurodevelopmental impairments in young patients. Given the number of published studies on this topic, a synthesis of the literature is timely and needed. We performed a systematic review and meta-analysis of the medical literature to assess the evidence linking CHD to incidence of autism spectrum disorder (ASD). A systematic review of studies on CHD and ASD in PubMed, Cochrane and Institute for Scientific Information (ISI) from 1965 to May 2021 was conducted. Quantitative estimates of association between CHD and ASD were extracted from eligible studies for the meta-analysis. Pooled estimates were obtained using a random effect models fit by a generalised linear mixed model. We screened 2709 articles and 24 articles were included in this review. Among the 24 studies, there was a total of 348,771 subjects (12,114 CHD, 9829 ASD and 326,828 controls). Seven of 24 studies were eligible for the meta-analysis, which included information on a total of 250,611 subjects (3984 CHD, 9829 ASD, and 236,798 controls). The summary estimate indicated that having CHD is associated with almost double the odds of ASD compared with patients without CHD (OR 1.99, 95% CI 1.77-2.24, p < 0.01). Early developmental delay, perinatal factors, and genetics were potential risk factors and etiologies for the onset of ASD symptoms in CHD patients. Having CHD is associated with an increased risk of presenting with a diagnosis or symptoms suggestive of ASD.

Neurodevelopmental Outcomes in Children with Congenital Heart Disease: Ten Years After the American Heart Association Statement

Even before birth, children with congenital heart disease (CHD) are at risk for neurodevelopmental concerns, with additional insults occurring as part of their treatment course and from subsequent exposures to socioeconomic stressors. With multiple affected neurodevelopmental domains, individuals with CHD face lifelong cognitive, academic, psychological, and quality-of-life difficulties. Early and repeated neurodevelopmental evaluation is key to receiving appropriate services. However, obstacles at the level of the environment, provider, patient, and family can make the completion of these evaluations difficult. Future neurodevelopmental endeavors should aim to evaluate CHD-specific programs, their effectiveness, and barriers to access.

Neurodevelopmental Assessment in Children With Congenital Heart Disease by Applying the Denver Developmental Screening Test 2: A Prospective Cross-Sectional Study

Background Congenital heart conditions often cause developmental delays and impact neurodevelopment throughout one's lifetime. Hence, it is crucial to analyze the impact that heart defects have on the developing brain of a child. The present cross-sectional study was undertaken given the paucity of studies on the developmental status in children with congenital heart diseases (CHDs) in central India, where we tried to evaluate and compare the prevalence of neurodevelopmental delay in individuals with different congenital cardiac disorders. The objectives of our study were, firstly, to utilize the Denver Developmental Screening Test 2 (DDST-2) to evaluate the neurodevelopmental conditions in children with CHD; secondly, to compare the neurodevelopmental state of children with acyanotic CHD (ACHD) and cyanotic CHD (CCHD); and thirdly, to ascertain the prevalence of developmental delay in children with CHD. Methodology The study population comprised children aged six months to six years with two-dimensional (2D) echocardiography confirmation of CHD; those who were critically ill, had genetic syndromes, and were not willing to participate in the study were excluded. The neurodevelopmental assessment was conducted using the DDST-2. The screening looked at each patient's progress in four areas: personal-social, fine motor-adaptive, language, and gross motor. Based on these observations, results were obtained and interpreted. Result Out of 82 children with CHD, the prevalence rate of developmental delay according to the DDST-2 was found to be maximum in the gross motor domain and the least affected in the social domain, which was similar to the analysis of developmental delay by developmental quotient (DQ). The comparative analysis of developmental delay in ACHD and CCHD according to the DDST-2 showed a significant P value only in the gross motor domain. Conclusion The DDST-2 is a straightforward screening tool for determining how well-developed infants with CHD are. The gross motor domain is the most frequently damaged in ACHD and CCHD, followed by the fine motor domain, and the social domain is the least affected. Cyanotic CHD patients are more susceptible to developmental delay than children with ACHD.

Longitudinal Motor-Developmental Outcomes in Infants with a Critical Congenital Heart Defect

Infants with critical congenital heart defects (CCHDs) are at increased risk for neurodevelopmental delays. The early identification of motor delays is clinically relevant to prevent or reduce long-term consequences. The current study aims to describe the motor-developmental pathways of infants with a CCHD. Motor development was assessed in 215 infants and toddlers using the Dutch version of the Bayley-III. At 3 months (n = 165), 9 months (n = 188), and 18 months (n = 171) the motor composite scores were 97, 98, and 104, respectively. A motor composite score of ≤−2 SD was only seen in 2.4%, 0%, and 2.3%, respectively, with gross motor deficits being observed more often than fine motor deficits (12% vs. 0% at 18 months). Over 90% of infants who scored average at 9 months still did so at 18 months. The majority of infants with below-average gross motor scores (≤−1) at 9 months still had a below-average or delayed motor score (≤−2 SD) at 18 months. Abnormal gross motor scores (≤−2 SD) increased with age. Infants with single-ventricle physiology performed significantly (p ≤ 0.05) worse on both fine and gross motor skills at 9 and 18 months compared to infants with other CCHDs.

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.

Transitions from short to long-term outcomes in pediatric critical care: considerations for clinical practice

Most children are surviving critical illness in highly resourced pediatric intensive care units (PICUs). However, in research studies, many of these children survive with multi-domain health sequelae that has the potential to affect development over many years, termed post-intensive care syndrome-pediatrics (PICS-p). Clinically, there are no recommendations for the assessment and follow-up of children with critical illness as exists for the premature neonatal and congenital heart disease populations. In research studies, primary and secondary outcomes are largely assessed at or prior to hospital discharge, disregarding post-hospital outcomes important to PICU stakeholders. Incorporating longer term outcomes into clinical and research programs, however, can no longer be overlooked. Barriers to outcomes assessments are varied and generalized vs. individualized, but some PICU centers are discovering how to overcome them and are providing this service to families-sometimes specific populations-in need. Research programs and funders are increasingly recognizing the value and need to assess long-term outcomes post-PICU. Finally, we should seek the strong backing of the PICU community and families to insist that long-term outcomes become our new clinical standard of care. PICUs should consider development of a multicenter, multinational collaborative to assess clinical outcomes and optimize care delivery and patient and family outcomes. The aim of this review is to present the potential considerations of implementing long-term clinical follow-up following pediatric critical illness.

Prenatal markers of atypical neurodevelopment in children with congenital heart defects

BACKGROUND

A growing body of literature demonstrates that survivors of congenital heart defects (CHD) are at increased risk of neurodevelopmental delay, which frequently manifests as motor delay during the first year of life.

OBJECTIVE

The aim of this study was to determine prenatal predictors of an early atypical neurodevelopment. This information could help assist decision-making during prenatal counseling.

STUDY DESIGN

In this retrospective cohort study, we evaluated the records of 75 children with CHD followed at the Clinique d'Investigation Neuro-Cardiaque (CINC) of the CHU Ste-Justine born between 2013 and 2016. The neurodevelopmental outcome was determined using the Alberta Infant Motor Scale (AIMS) at 4 months. Associations between prenatal factors and atypical neurodevelopment (AIMS < 10th percentile) were assessed using bivariate and multivariate analyses.

RESULTS

Forty-four infants (58.7%) had atypical neurodevelopment. When there was no extra cardiac anomaly seen on prenatal ultrasound, a head to abdominal ratio (HC/AC) below 1.1 was associated with a four-fold increased risk of atypical neurodevelopment (OR = 4.54; 95% CI = 1.24-16.64 p = .023). There was no difference in identified genetic anomaly in both groups. However, there was a trend toward more extra cardiac anomalies in infants with atypical neurodevelopment (27.3%) compared to 9.7% in those with typical neurodevelopment (p = .061).

CONCLUSION

Our study shows that early atypical neurodevelopment affects the majority of children with CHD and highlights the importance of post-natal monitoring by a specialized team. A thorough prenatal ultrasound is important to screen for those at higher risk i.e. those with extra cardiac anomaly and HC/AC below 1.1. A larger cohort is needed to validate those results.

Neurodevelopmental outcomes in children with isolated congenital diaphragmatic hernia: A systematic review and meta-analysis

BACKGROUND

Congenital diaphragmatic hernia (CDH) reportedly has neurologic consequences in childhood however little is known about the impact in isolated CDH.

AIMS

Herein we aimed to describe the risk of neurodevelopmental complications in children born with isolated CDH.

MATERIALS & METHODS

We systematically reviewed literature for reports on the neurological outcome of infants born with isolated CDH. The primary outcome was neurodevelopmental delay. Secondary outcomes included, motor skills, intelligence, vision, hearing, language and behavior abnormalities.

RESULTS

Thirteen out of 87 (15%) studies reported on isolated CDH, including 2624 out of 24,146 children. Neurodevelopmental delay was investigated in four studies and found to be present in 16% (3-34%) of children. This was mainly attributed to motor problems in 13% (2-30%), whereas cognitive dysfunction only in 5% (0-20%) and hearing in 3% (1-7%). One study assessed the effect of fetal surgery. When both isolated and non-isolated children were included, these numbers were higher.

DISCUSSION

This systematic review demonstrates that only a minority of studies focused on isolated CDH, with neurodevelopmental delay present in 16% of children born with CDH.

CONCLUSION

To accurately counsel patients, more research should focus on isolated CDH cases and examine children that underwent fetal surgery.

Variants of significance: medical genetics and surgical outcomes in congenital heart disease

PURPOSE OF REVIEW

This article reviews the current understanding and limitations in knowledge of the effect genetics and genetic diagnoses have on perioperative and postoperative surgical outcomes in patients with congenital heart disease (CHD).

RECENT FINDINGS

Presence of a known genetic diagnosis seems to effect multiple significant outcome metrics in CHD surgery including length of stay, need for extracorporeal membrane oxygenation, mortality, bleeding, and heart failure. Data regarding the effects of genetics in CHD is complicated by lack of standard genetic assessment resulting in inaccurate risk stratification of patients when analyzing data. Only 30% of variation in CHD surgical outcomes are explained by currently measured variables, with 2.5% being attributed to diagnosed genetic disorders, it is thought a significant amount of the remaining outcome variation is because of unmeasured genetic factors.

SUMMARY

Genetic diagnoses clearly have a significant effect on surgical outcomes in patients with CHD. Our current understanding is limited by lack of consistent genetic evaluation and assessment as well as evolving knowledge and discovery regarding the genetics of CHD. Standardizing genetic assessment of patients with CHD will allow for the best risk stratification and ultimate understanding of these effects.

Neurodevelopmental evaluation strategies for children with congenital heart disease aged birth through 5 years: recommendations from the cardiac neurodevelopmental outcome collaborative

This paper provides specific guidelines for the neurodevelopmental evaluation of children aged birth through 5 years with complex congenital heart disease. There is wide recognition that children with congenital heart disease are at high risk for neurodevelopmental impairments that are first apparent in infancy and often persist as children mature. Impairments among children with complex congenital heart disease cross developmental domains and affect multiple functional abilities. The guidelines provided are derived from the substantial body of research generated over the past 30 years describing the characteristic developmental profiles and the long-term trajectories of children surviving with complex congenital heart conditions. The content and the timing of the guidelines are consistent with the 2012 American Heart Association and the American Academy of Pediatrics scientific statement documenting the need for ongoing developmental monitoring and assessment from infancy through adolescence. The specific guidelines offered in this article were developed by a multidisciplinary clinical research team affiliated with the Cardiac Neurodevelopmental Outcome Collaborative, a not-for-profit organisation established to determine and implement best neurodevelopmental practices for children with congenital heart disease. The guidelines are designed for use in clinical and research applications and offer an abbreviated core protocol and an extended version that expands the scope of the evaluation. The guidelines emphasise the value of early risk identification, use of evidence-based assessment instruments, consideration of family and cultural preferences, and the importance of providing multidimensional community-based services to remediate risk.

The origins and development of the cardiac neurodevelopment outcome collaborative: creating innovative clinical, quality improvement, and research opportunities

Compared to the general population, individuals with complex congenital heart disease are at increased risk for deficits in cognitive, neurodevelopmental, psychosocial, and physical functioning, resulting in a diminished health-related quality of life. These deficits have been well described over the past 25 years, but significant gaps remain in our understanding of the best practices to improve neurodevelopmental and psychosocial outcomes and health-related quality of life for individuals with paediatric and congenital heart disease. Innovative clinical, quality improvement, and research opportunities with collaboration across multiple disciplines and institutions were needed to address these gaps. The Cardiac Neurodevelopmental Outcome Collaborative was founded in 2016 with a described mission to determine and implement best practices of neurodevelopmental and psychosocial services for individuals and their families with paediatric and congenital heart disease through clinical, quality improvement, and research initiatives. The vision is to be a multi-centre, multi-national, multi-disciplinary group of healthcare professionals committed to working together and partnering with families to optimise neurodevelopmental outcomes for individuals with paediatric and congenital heart disease through clinical, quality, and research initiatives, intending to maximise quality of life for every individual across the lifespan. This manuscript describes the development and organisation of the Cardiac Neurodevelopmental Outcome Collaborative.

Variations in practice in cardiac neurodevelopmental follow-up programs

Over the last two decades, heart centres have developed strategies to meet the neurodevelopmental needs of children with congenital heart disease. Since the publication of guidelines in 2012, cardiac neurodevelopmental follow-up programmes have become more widespread. Local neurodevelopmental programmes, however, have been developed independently in widely varying environments. We sought to characterise variation in structure and personnel in cardiac neurodevelopmental programmes. A 31-item survey was sent to all member institutions of the Cardiac Neurodevelopmental Outcome Collaborative. Multidisciplinary teams at each centre completed the survey. Responses were compiled in a descriptive fashion. Of the 29 invited centres, 23 responded to the survey (79%). Centres reported more anticipated neurodevelopment visits between birth and 5 years of age (median 5, range 2-8) than 5-18 years (median 2, range 0-10) with 53% of centres lacking any standard for routine neurodevelopment evaluations after 5 years of age. Estimated annual neurodevelopment clinic volume ranged from 85 to 428 visits with a median of 16% of visits involving children >5 years of age. Among responding centres, the Bayley Scales of Infant and Toddler Development and Wechsler Preschool and Primary Scale of Intelligence were the most routinely used tests. Neonatal clinical assessment was more common (64%) than routine neonatal brain imaging (23%) during hospitalisation. In response to clinical need and published guidelines, centres have established formal cardiac neurodevelopment follow-up programmes. Centres vary considerably in their approaches to routine screening and objective testing, with many centres currently focussing their resources on evaluating younger patients.

Genetics in congenital heart disease. Are we ready for it?

Genetics has rightly acquired an important place in almost all medical disciplines in recent years and this is certainly the case in the field of congenital cardiology. Not only has this led to greater insight into the pathophysiology of congenital heart defects but it also has a beneficial impact on patient management. Integration of clinical genetics in multidisciplinary centers of expertise for CHD is therefore a clear recommendation. Adult and pediatric cardiologists play a crucial role in the process of genetic evaluation of patients and families and should have be familiar with red flags for referral for further clinical genetic elaboration, counseling, and eventual testing. Some basic knowledge is also important for the correct interpretation of genetic testing results. In this review article, we provide a practical overview of what genetic evaluation entails, which type of genetic tests are possible today, and how this can be used in practice for the individual patient.

Educational and learning morbidity in pediatric heart transplant recipients: A pediatric heart transplant society study

Educational development is an important component of quality of life for children with heart transplant. Aims include determining prevalence of and risk factors for modified education placement in a large representative sample of pediatric heart transplant recipients. Participants included 1495 patients (age 6-18 years) from the PHTS database. Data on education placement and clinical predictors were collected at listing and at 1 and 3 years post-transplant. At listing, 88% of patients were in typical education placement, while 12% were in modified education. Males (P = .02), those with CHD (P < .0001), those with non-private insurance (P < .0001), and those with longer hospital stay (P = .001) were more likely to be in a modified education placement at time of listing. Age, race, listing status, mechanical support, and waitlist time were not significantly associated with placement. The prevalence of typical education placement was similar (87% at 1-year and 86% at 3-year) post-transplant. Predictors of modified education placement at 3-year follow-up included placement at listing (OR = 12.9 [95% CI 7.6-21.9], P < .0001), non-private insurance (OR = 2.0 [95% CI 1.3-3.2], P = .001), CHD (OR = 1.8 [95% CI 1.1-2.7, P = .01), history of post-transplant infection (OR = 1.9 [95% CI 1.2-2.9, P = .007), and number of post-transplant infections (OR = 1.3 [95% CI 1.1-1.5, P = .002). Among pediatric heart transplant recipients, males, those with non-private insurance, those with CHD, and those who experience post-transplant infections are at greatest risk for modified academic placement, which persists for several years post-transplant and deserves targeted intervention.

Role of cilia in the pathogenesis of congenital heart disease

An essential role for cilia in the pathogenesis of congenital heart disease (CHD) has emerged from findings of a large-scale mouse forward genetic screen. High throughput screening with fetal ultrasound imaging followed by whole exome sequencing analysis recovered a preponderance of cilia related genes and cilia transduced cell signaling genes among mutations identified to cause CHD. The perturbation of left-right patterning in CHD pathogenesis is suggested by the association of CHD with heterotaxy, but also by the finding of the co-occurrence of laterality defects with CHD in birth defect registries. Many of the cilia and cilia cell signaling genes recovered were found to be related to Hedgehog signaling. Studies in mice showed cilia transduced hedgehog signaling coordinates left-right patterning with heart looping and differentiation of the heart tube. Cilia transduced Shh signaling also regulates later events in heart development, including outflow tract septation and formation of the atrioventricular septum. More recent work has shown mutations in cilia related genes may also contribute to valve disease that largely manifest in adult life. Overall, these and other findings show cilia play an important role in CHD and also in more common valve diseases.

Recent advances in our understanding of neurodevelopmental outcomes in congenital heart disease

PURPOSE OF REVIEW

Patients with congenital heart disease (CHD) suffer from a pattern of neurodevelopmental abnormalities including deficits in language and executive function. In this review, we summarize recent studies that examine these outcomes, their risk factors, possible biomarkers, and attempts to develop therapeutic interventions.

RECENT FINDINGS

The latest literature has highlighted the role of genetics in determining neurologic prognosis, as we have increased our understanding of potentially modifiable perioperative risk factors. The role of potentially neurotoxic medical therapies has become more salient. One recent focus has been how neurodevelopment affects quality of life and leads to a high prevalence of mental illness. Neuroimaging advances have provided new insights into the pathogenesis of deficits.

SUMMARY

Although many risk factors in CHD are not modifiable, there is promise for interventions to improve neurodevelopmental outcomes in patients with CHD. Biomarkers are needed to better understand the timing and prognosis of injury and to direct therapy. Research into psychosocial interventions is urgently needed to benefit the many survivors with CHD.

Fetal cardiac abnormalities: Genetic etiologies to be considered

Congenital heart diseases are a common prenatal finding. The prenatal identification of an associated genetic syndrome or a major extracardiac anomaly helps to understand the etiopathogenic diagnosis. Besides, it also assesses the prognosis, management, and familial recurrence risk while strongly influences parental decision to choose termination of pregnancy or postnatal care. This review article describes the most common genetic diagnoses associated with a prenatal finding of a congenital heart disease and a suggested diagnostic process.

'Big issues' in neurodevelopment for children and adults with congenital heart disease

It is established that neurodevelopmental disability (NDD) is common in neonates undergoing complex surgery for congenital heart disease (CHD); however, the trajectory of disability over the lifetime of individuals with CHD is unknown. Several ‘big issues’ remain undetermined and further research is needed in order to optimise patient care and service delivery, to assess the efficacy of intervention strategies and to promote best outcomes in individuals of all ages with CHD. This review article discusses ‘gaps’ in our knowledge of NDD in CHD and proposes future directions.

Gestational Age, Birth Weight, and Outcomes Six Years After the Norwood Procedure

BACKGROUND

Preterm delivery and low birth weight (LBW) are generally associated with worse outcomes in hypoplastic left heart syndrome (HLHS), but an individual preterm or small neonate may do well. We sought to explore the interactions between gestational age, birth weight, and birth weight for gestational age with intermediate outcomes in HLHS.

METHODS

We analyzed survival, growth, neurodevelopment, length of stay, and complications to age 6 years in subjects with HLHS from the Single Ventricle Reconstruction trial. Univariate and multivariable survival and regression analyses examined the effects and interactions of LBW (<2500 g), weight for gestational age, and gestational age category.

RESULTS

Early-term delivery (n = 234) was more common than term (n = 219) delivery. Small for gestational age (SGA) was present in 41% of subjects, but only 14% had LBW. Preterm, compared with term, delivery was associated with an increased risk of death or transplant at age 6 years (all: hazard ratio = 2.58, confidence interval = 1.43-4.67; Norwood survivors: hazard ratio = 1.96, confidence interval = 1.10-3.49) independent of LBW and weight for gestational age. Preterm delivery, early-term delivery, LBW, and SGA were each associated with lower weight at 6 years. Neurodevelopmental outcomes were worst in the LBW cohort.

CONCLUSIONS

Preterm delivery in HLHS was associated with worse survival, even beyond Norwood hospitalization. LBW, SGA, and early-term delivery were associated with worse growth but not survival. LBW was associated with worse neurodevelopment, despite similar length of stay and complications. These data suggest that preterm birth and LBW (although often concomitant) are not equivalent, impacting clinical outcomes through mechanisms independent of perioperative course complexity.

Monitoring and management of brain hemodynamics and oxygenation

While cardiorespiratory monitoring is standard for newborns in the NICU, monitoring of brain hemodynamics and oxygenation is usually sporadic and targeted to newborns with suspected or confirmed neurologic disorders. This is unfortunate, since critically ill newborns, both preterm and term-born, are at high risk of brain injury and would benefit from improved techniques for continuous monitoring of brain hemodynamics and oxygenation, in addition to monitoring of systemic hemodynamics and oxygenation. Near-infrared spectroscopy (NIRS) and, to a lesser extent, Doppler ultrasound are techniques that have been used in research and increasingly for clinical purposes to measure and monitor brain hemodynamics and oxygenation in newborns. NIRS monitoring can be useful for detection of diverse pathologic conditions that occur frequently in very preterm newborns and in selected populations of term newborns at risk for brain injury related to disturbances of systemic hemodynamics. This chapter reviews the current state of the art with regard to brain-monitoring techniques and the research directed at this important area, and it concludes with suggestions for the use of currently available tools to manage newborns at high risk of neurologic injury from disturbances in brain hemodynamics and oxygenation.

Cellular and Molecular Mechanisms of Recessive Hereditary Methaemoglobinaemia Type II

Cytochrome b5 reductase 3 (CYB5R3) is a membrane-bound NADH-dependent redox enzyme anchored to the mitochondrial outer membrane, endoplasmic reticulum, and plasma membrane. Recessive hereditary methaemoglobinaemia (RHM) type II is caused by CYB5R3 deficiency and is an incurable disease characterized by severe encephalopathy with mental retardation, microcephaly, generalized dystonia, and movement disorders. Currently, the etiology of type II RHM is poorly understood and there is no treatment for encephalopathy associated with this disease. Defective CYB5R3 leads to defects in the elongation and desaturation of fatty acids and cholesterol biosynthesis, which are conventionally linked with neurological disorders of type II RHM. Nevertheless, this abnormal lipid metabolism cannot explain all manifestations observed in patients. Current molecular and cellular studies indicate that CYB5R3 deficiency has pleiotropic tissue effects. Its localization in lipid rafts of neurons indicates its role in interneuronal contacts and its presence in caveolae of the vascular endothelial membrane suggests a role in the modulation of nitric oxide diffusion. Its role in aerobic metabolism and oxidative stress in fibroblasts, neurons, and cardiomyocytes has been reported to be due to its ability to modulate the intracellular ratio of NAD⁺/NADH. Based on the new molecular and cellular functions discovered for CYB5R3 linked to the plasma membrane and mitochondria, the conventional conception that the cause of type II RHM is a lipid metabolism disorder should be revised. We hypothesized that neurological symptoms of the disease could be caused by disorders in the synapse, aerobic metabolism, and/or vascular homeostasis rather than in disturbances of lipid metabolism.