Normal development of the fetal brain by MRI

Cat-Ear-Line: A Sonographic Sign of Cortical Development?

OBJECTIVES

Diagonal echogenic lines outside the lateral ventricle have often been observed in the anterior coronal planes of the normal fetal brain by neurosonography. We have observed abnormal shapes of these echogenic lines in cases of malformation of cortical development (MCD). We named the ultrasound finding "cat-ear-line" (CEL). This study aimed to examine how and when CEL develops in normal cases compared with MCD cases.

METHODS

We retrospectively examined the fetal brain volume dataset acquired through transvaginal 3D neurosonography of 575 control cases and 39 MCD cases from 2014 to 2020. We defined CEL as the hyperechogenic continuous lines through subplate (SP) and intermediate zone (IZ), pre-CEL as the lines that existed only within the SP, and abnormal CEL as a mass-like or mosaic shadow-like structure that existed across the SP and IZ. All fetuses in the MCD group had some neurosonographic abnormalities and were ultimately diagnosed with MCD.

RESULTS

The CEL was detected in 97.9% (369/377) of the control group from 19 to 30 weeks. The CEL visualization rate of the MCD group in the same period was 40.0% (14/35) which was significantly lower than that of the control group (P < .001).

CONCLUSIONS

From this study, it appears that the CEL is an ultrasound finding observed at and beyond 19 weeks in a normally developing fetus. In some MCD cases, pre-CEL at and beyond 19 weeks or abnormal CEL was observed. Maldeveloped CEL at mid-trimester may help identify cases at-risk of subsequent MCD.

Brain cortical maturation assessed by magnetic resonance imaging in unaffected or mildly affected fetuses with cytomegalovirus infection

OBJECTIVES

To assess by magnetic resonance imaging (MRI) the cortical maturation pattern in fetuses with cytomegalovirus (CMV) infection with mild or no abnormalities on ultrasound (US) and MRI, and to establish possible differences compared with healthy controls.

METHODS

This was a retrospective case-control study of consecutive pregnancies with a CMV-infected fetus undergoing prenatal MRI as a complementary diagnostic tool in two centers, and a control group of singleton low-risk pregnancies without fetal structural abnormalities, with normal fetal growth and with healthy newborns. CMV infection was confirmed by extraction of CMV-DNA from fetal and neonatal samples. Only fetuses with mild (mildly affected) or no (unaffected) neuroimaging abnormalities on US and MRI were included. MRI measurements of fetal parieto-occipital sulcus, cingulate sulcus and calcarine sulcus depth, Sylvian fissure depth and Sylvian fissure angles were performed and cortical development grading of specific cortical areas and sulci were assessed by one operator who was blinded to CMV infection status. Data were compared between controls and fetuses with CMV infection, using linear regression and non-parametric trend analysis.

RESULTS

Twenty-four CMV-infected fetuses (seven unaffected and 17 mildly affected) and 24 healthy controls that underwent fetal MRI between 27 and 36 weeks' gestation were included. Compared with controls, CMV-infected fetuses showed significantly larger median lateral ventricular width (right side, 7.8 (interquartile range (IQR), 5.9-9.9) mm vs 3.9 (IQR, 2.6-5.3) mm; left side, 7.5 (IQR, 6.0-10.9) mm vs 4.2 (IQR, 3.2-5.3) mm), significantly decreased parieto-occipital sulcus depth (right side, 12.6 (IQR, 11.3-13.5) mm vs 15.9 (IQR, 13.5-17.3) mm; left side, 12.3 (IQR, 10.6-13.5) mm vs 16.0 (IQR, 13.3-17.5) mm) and calcarine sulcus depth (right side, 15.4 (IQR, 14.4-16.3) mm vs 17.5 (IQR, 16.1-18.7) mm; left side, 14.6 (IQR, 14.1-15.6) mm vs 16.7 (IQR, 15.6-18.9) mm) (P < 0.001 for all). Compared with controls, CMV-infected fetuses also had significantly smaller upper (right side, 42.8° (IQR, 35.8-45.8°) vs 48.9° (IQR, 38.4-64.7°); left side, 40.9° (IQR, 34.2-45.8°) vs 48.2° (IQR, 41.9-60.7°)) and lower (right side, 41.6° (IQR, 34.4-49.2°) vs 48.9° (IQR, 40.6-60.9°); left side, 42.2° (IQR, 38.8-46.9°) vs 48.9° (IQR, 39.5-57.5°)) Sylvian fissure angles (P < 0.05 for all). In addition, the mildly affected CMV-infected fetuses had a significantly lower cortical development grading in the temporal and parietal areas, and the parieto-occipital and calcarine sulci compared with healthy fetuses (P < 0.05). These differences persisted when adjusting for gestational age, ipsilateral atrium width, fetal gender and when considering small-for-gestational age as a confounding factor.

CONCLUSIONS

Unaffected and mildly affected CMV-infected fetuses showed delayed cortical maturation compared with healthy controls. These results suggest that congenital CMV infection, even in non-severely affected fetuses that are typically considered of good prognosis, could be associated with altered brain cortical structure. Further research is warranted to better elucidate the correlation of these findings with neurodevelopmental outcomes. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal Brain Anatomy

"Fetal brain development has been well studied, allowing for an ample knowledge of the normal changes that occur during gestation. Imaging modalities used to evaluate the fetal central nervous system (CNS) include ultrasound and MRI. MRI is the most accurate imaging modality for parenchymal evaluation and depiction of developmental CNS anomalies. The depiction of CNS abnormalities in a fetus can only be accurately made when there is an understanding of its normal development. This article reviews the expected normal fetal brain anatomy and development during gestation. Additional anatomic structures seen on brain imaging sequences are also reviewed."

Is fetal MRI ready for neuroimaging prime time? An examination of progress and remaining areas for development

A major challenge in designing large-scale, multi-site studies is developing a core, scalable protocol that retains the innovation of scientific advances while also lending itself to the variability in experience and resources across sites. In the development of a common Healthy Brain and Child Development (HBCD) protocol, one of the chief questions is "is fetal MRI ready for prime-time?" While there is agreement about the value of prenatal data obtained non-invasively through MRI, questions about practicality abound. There has been rapid progress over the past years in fetal and placental MRI methodology but there is uncertainty about whether the gains afforded outweigh the challenges in supporting fetal MRI protocols at scale. Here, we will define challenges inherent in building a common protocol across sites with variable expertise and will propose a tentative framework for evaluation of design decisions. We will compare and contrast various design considerations for both normative and high-risk populations, in the setting of the post-COVID era. We will conclude with articulation of the benefits of overcoming these challenges and would lend to the primary questions articulated in the HBCD initiative.

Age-specific structural fetal brain atlases construction and cortical development quantification for chinese population

In magnetic resonance imaging (MRI) studies of fetal brain development, structural brain atlases usually serve as essential references for the fetal population. Individual images are usually normalized into a common or standard space for analysis. However, the existing fetal brain atlases are mostly based on MR images obtained from Caucasian populations and thus are not ideal for the characterization of the fetal Chinese population due to neuroanatomical differences related to genetic factors. In this paper, we use an unbiased template construction algorithm to create a set of age-specific Chinese fetal atlases between 21-35 weeks of gestation from 115 normal fetal brains. Based on the 4D spatiotemporal atlas, the morphological development patterns, e.g., cortical thickness, cortical surface area, sulcal and gyral patterns, were quantified. The fetal brain abnormalities were detected when referencing the age-specific template. Additionally, a direct comparison of the Chinese fetal atlases and Caucasian fetal atlases reveals dramatic anatomical differences, mainly in the medial frontal and temporal regions. After applying the Chinese and Caucasian fetal atlases separately to an independent Chinese fetal brain dataset, we find that the Chinese fetal atlases result in significantly higher accuracy than the Caucasian fetal atlases in guiding brain tissue segmentation. These results suggest that the Chinese fetal brain atlases are necessary for quantitative analysis of the typical and atypical development of the Chinese fetal population in the future. The atlases with their parcellations are now publicly available at https://github.com/DeepBMI/FBA-Chinese.

Fetal Brain Magnetic Resonance Imaging Findings Predict Neurodevelopment in Children with Tuberous Sclerosis Complex

OBJECTIVE

To correlate fetal brain magnetic resonance imaging (MRI) findings with epilepsy characteristics and neurodevelopment at 2 years of age in children with tuberous sclerosis complex (TSC) to improve prenatal counseling.

STUDY DESIGN

This retrospective cohort study was performed in a collaboration between centers of the EPISTOP consortium. We included children with definite TSC, fetal MRIs, and available follow-up data at 2 years of age. A pediatric neuroradiologist masked to the patient's clinical characteristics evaluated all fetal MRIs. MRIs were categorized for each of the 10 brain lobes as score 0: no (sub)cortical lesions or doubt; score 1: a single small lesion; score 2: more than one small lesion or at least one large lesion (>5 mm). Neurologic manifestations were correlated to lesion sum scores.

RESULTS

Forty-one children were included. Median gestational age at MRI was 33.3 weeks; (sub)cortical lesions were detected in 97.6%. Mean lesion sum score was 4.5. At 2 years, 58.5% of patients had epilepsy and 22% had drug-resistant epilepsy. Cognitive, language, and motor development were delayed in 38%, 81%, and 50% of patients, respectively. Autism spectrum disorder (ASD) was diagnosed in 20.5%. Fetal MRI lesion sum scores were significantly associated with cognitive and motor development, and with ASD diagnosis, but not with epilepsy characteristics.

CONCLUSIONS

Fetal cerebral lesion scores correlate with neurodevelopment and ASD at 2 years in children with TSC.

Fetal MRI assessment of posterior fossa anomalies: A review

Prenatal ultrasound (US) is the first prenatal imaging tool for screening and evaluation of posterior fossa malformations since it is noninvasive, widely available, and safe for both mother and child. Fetal MRI is a widely used secondary technique to confirm, correct, or complement questionable US findings and plays an essential role in evaluating fetuses with suspected US findings and /or positive family history. The main sequences of fetal MRI consist of T2-weighted (T2w) ultrafast, single-shot sequences. Axial, coronal, and sagittal images are typically acquired allowing for a detailed evaluation of the posterior fossa contents. Also, various complimentary sequences, such as T1w, T2*w gradient sequences, or advanced techniques, including diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy, may provide additional information based on the studied malformation. Inclusion of these techniques should be done with careful risk-benefit analysis. The use of fetal MRI also aims to evaluate for associated anomalies. In addition, prenatal diagnosis of posterior fossa malformations is still a challenge but advances in knowledge in human developmental anatomy, genetic, and imaging recognition patterns have enabled us to shed some light on prognostic information that will help with the counseling of families. Finally, high-resolution late third trimester fetal MRI offers a safe alternative to early postnatal MR imaging, basically taking advantage of the uterine environment as a kind of "maternal incubator." Our goal is to discuss the spectrum of prenatal posterior fossa pathologies that can be studied by fetal MRI and their key neuroimaging features.

Prenatal findings of cataract and arthrogryposis: recurrence of cerebro-oculo-facio-skeletal syndrome and review of differential diagnosis

BACKGROUND

Cerebro-oculo-facio-skeletal syndrome (COFS) is a severe and progressive neurologic condition characterized by prenatal onset of arthrogryposis, cataract, microcephaly and growth failure. The aim of this study was to present a case of recurrence of the COFS syndrome and to propose a differential diagnosis flow-chart in case of prenatal findings of arthrogryposis and cataract.

CASE PRESENTATION

We report a case of recurrence of COFS3 syndrome within the same family, with similar diagnostic features. In the first case the COFS syndrome remained undiagnosed, while in the second case, due to prenatal findings of arthrogryposis and cataract, genetic investigation focusing on responsible genes of COFS (ERCC5, ERCC6 and FKTN genes) was carried out. The fetus was found to be compound heterozygous for two different ERCC5 mutations, confirming the clinical suspect of COFS syndrome. A review of the literature on possible causative genes of prenatal cataract and arthrogryposis was performed and we present a flow-chart to guide differential diagnosis and possible genetic testing in case of these findings.

CONCLUSION

COFS syndrome is a rare autosomic recessive condition. However, it can be suspected and diagnosed prenatally. The flow-chart illustrates a pathway to guide differential diagnosis according to the prenatal findings. Main syndromes, key testing and specific genes are included. Targeted molecular testing should be offered to the couple in order to reach a diagnosis and assess the recurrence risk for future pregnancies.

A Sparse Volume Reconstruction Method for Fetal Brain MRI Using Adaptive Kernel Regression

Slice-to-volume reconstruction (SVR) method can deal well with motion artifacts and provide high-quality 3D image data for fetal brain MRI. However, the problem of sparse sampling is not well addressed in the SVR method. In this paper, we mainly focus on the sparse volume reconstruction of fetal brain MRI from multiple stacks corrupted with motion artifacts. Based on the SVR framework, our approach includes the slice-to-volume 2D/3D registration, the point spread function- (PSF-) based volume update, and the adaptive kernel regression-based volume update. The adaptive kernel regression can deal well with the sparse sampling data and enhance the detailed preservation by capturing the local structure through covariance matrix. Experimental results performed on clinical data show that kernel regression results in statistical improvement of image quality for sparse sampling data with the parameter setting of the structure sensitivity 0.4, the steering kernel size of 7 × 7 × 7 and steering smoothing bandwidth of 0.5. The computational performance of the proposed GPU-based method can be over 90 times faster than that on CPU.

Early development of human ganglionic eminences assessed in vitro by using 7.04 Tesla micro-MRI - a pilot study

Background and aims

Ganglionic eminences are temporary structures which appear during the 5^th week post-fertilization on the floor of telencephalic vesicles and disappear until the 35^th week of gestation. The aim of this descriptive study of morphological research is to depict the ganglionic eminences within the embryonic and early fetal brains by using micro-MRI.

Methods

Six human embryos and fetuses ranging from 21 mm crown-rump length CRL (9 gestational week GW) to 85 mm CRL (14 GW) were examined in vitro by micro-MRI. The investigation was performed with a Bruker BioSpec 70/16USR scanner (Bruker BioSpin MRI GmbH, Ettlingen, Germany) operating at 7.04 Tesla.

Results

We describe the morphological characteristics of the ganglionic eminences at different gestational ages. The acquisition parameters were modified for each subject in order to obtain an increased spatial resolution. The remarkable spatial resolution of 27 μm/voxel allows visualization of millimetric structures of the developing brain on high quality micro-MR images.

Conclusion

In our study we give the description of the ganglionic eminences within the embryonic and early fetal brains by using micro-MRI, which, to the best of our knowledge, have not been previously documented in literature. Micro-MRI provides accurate images, which are comparable with the histological slices.

Growth trajectories of the human fetal brain in healthy and complicated pregnancies and associations with neurodevelopmental outcome in the early life course

BACKGROUND

There is a need for non-invasive prenatal markers of the brain to assess fetuses at risk for poor postnatal neurodevelopmental outcome. Periconceptional maternal conditions and pregnancy complications impact prenatal brain development.

AIMS

To investigate associations between growth trajectories of fetal brain structures and neurodevelopmental outcome in children in the early life course.

STUDY DESIGN

Periconceptional prospective observational cohort.

SUBJECTS

Singleton pregnancies were included in the Rotterdam periconception cohort. Two- and three-dimensional ultrasound scans at 22, 26 and 32 weeks gestational age were analysed.

OUTCOME MEASURES

Head circumference (HC), cerebellum, corpus callosum (CC), Sylvian fissure, insula and parieto-occipital fissure (POF) were measured. Neurodevelopment was evaluated using the Age-and-Stages-questionnaire-3 (ASQ-3) and the Child-Behaviour-Checklist (CBCL) at 2 years of age. Linear mixed models, used to estimate the prenatal brain growth trajectories, and linear regression models, used to evaluate the associations between prenatal brain structures and neurodevelopmental outcomes, were applied in the total study population, and in subgroups: fetal growth restriction (FGR), preterm birth (PTB), fetal congenital heart disease (CHD), and uncomplicated controls.

RESULTS

Consent for participation was received from parents on behalf of their child 138/203 (68%). ASQ-3 was completed in 128/203 children (63%) and CBCL in 93/203 children (46%). Significant smaller subject-specific growth trajectories (growth rate of CC, HC, left insula, left POF and right POF and the baseline size of CC, HC, left POF and right POF) were found in the FGR subgroup, compared to the other subgroups (all p-values <0.05). In the total group (n = 138), the growth rate of the left insula was associated with poorer ASQ-3 score (β = -869.51; p < 0.05). Healthy controls (n = 106) showed a comparable association (β = -1209.87; p < 0.01). FGR (n = 10) showed a larger baseline size of the right Sylvian fissure in association with poorer CBCL-score (β = 4.13; p < 0.01). In CHD (n = 12) the baseline size of the left Sylvian fissure and its growth rate were associated with respectively poorer and better CBCL-scores (β = 3.11; p < 0.01); (β = -171.99; p < 0.01). In PTB (n = 10) no associations were found.

CONCLUSIONS

This explorative study suggests associations between ultrasound measurements of fetal brain growth and neurodevelopmental outcome at 2 years of age. In future, this non-invasive technique may improve early identification of fetuses at risk for neurodevelopmental outcome and follow-up postnatal clinical care.

Intrauterine versus post-mortem magnetic resonance in second trimester termination of pregnancy for central nervous system abnormalities

OBJECTIVE

To evaluate if limiting factors of intrauterine magnetic resonance imaging (iuMRI) performed in the early second trimester of pregnancy (19-23 weeks) affect its accuracy in comparison to post-mortem MRI (pmMRI) in fetuses that underwent termination of pregnancy (TOP) for central nervous system (CNS) defects.

STUDY DESIGN

This is a secondary analysis of a 10 years prospective observational study. Cases of TOP < 23 weeks for CNS malformation that had undergone neurosonography (NSG), iuMRI, pmMRI and autopsy were included. The agreement between iuMRI and pmMRI was calculated. The autopsy represented the gold-standard.

RESULTS

Overall, 143 TOPs for fetal congenital anomaly underwent the post-mortem diagnostic protocol. Of these, 31 cases underwent iuMRI and pmMRI for CNS abnormality. Three cases were excluded due to brain autolysis at autopsy. Corpus callosum defects were the most represented (16/28; 57 %). In only one case of posterior fossa defect, pmMRI identified the presence of vermian hypoplasia not diagnosed at iuMRI. In 2 cases (7%), iuMRI added clinically relevant additional findings to NSG, that were posteriorly confirmed by pmMRI.

CONCLUSIONS

The study shows that, at 19-23 weeks and for CNS defects, limiting factors that might influence the performance of iuMRI have little influence on iuMRI accuracy. This finding is particularly important for professionals who work in countries with legal bound for TOP in the early second trimester.

The use of image fusion in prenatal medicine

Fusion imaging (FI), the simultaneous display of the same anatomical region using two imaging modalities, has been used in other areas of medicine for both diagnosis and guiding interventions. Examples include positron emission tomography-computed tomography (PET-CT) imaging in oncology and ultrasound-magnetic resonance imaging (US-MRI) fusion in biopsies of the prostate gland. The underlying principle is to take advantage of the complementary information in each modality to improve accuracy, be it diagnostic accuracy or targeting accuracy in biopsies. For example, PET-CT overlays the metabolic activity of lesions on the superb spatial and anatomical detail of CT. While the historical mainstay of fetal imaging has been ultrasound, advances in ultrafast MR imaging together with advances in fetal MRI over the past two decades, have resulted in the opportunity to explore fusion imaging in fetal medicine. We present an overview of the principles of US-MRI fusion imaging in prenatal medicine, report our local experience, and review the literature in this emerging area. We share our perspective on how FI can improve diagnostic confidence, be used as an educational tool, and potentially enhance guidance in certain fetal procedures.

Three-dimensional ultrasound imaging of fetal brain fissures in the growth restricted fetus

Objectives

To examine differences in growth trajectories of fetal brain fissures in the growth restricted fetus (FGR) compared to controls.

Methods

We selected a subgroup of 227 women with a singleton pregnancy from the Rotterdam Periconceptional Cohort. Participants received three-dimensional ultrasound (3D-US) examinations of the fetal brain at 22, 26 and 32 weeks of gestational age (GA). The left and right Sylvian, insula and parieto-occipital fissures (POF) were measured in standardized planes. Linear mixed models with adjustment for potential confounders were applied to estimate differences between the trajectories of brain fissure depth measurements of FGR and controls.

Results

22 FGR and 172 controls provided 31 and 504 3D-US respectively for longitudinal brain fissure depth measurements. Success rates for the Sylvian and insula depth measurements were over 80% and for POF over 62% at all GA. In FGR compared to controls, the trajectory of the right Sylvian fissure depth was significantly decreased (ß = -4.30, 95%CI = -8.03;-0.56, p = 0.024) while its growth rate was slightly increased (ß = 0.02, 95%CI = 0.00;0.04, p = 0.04), after adjustment for GA, head circumference, gender, educational level and parity.

Conclusions

The small differences in brain fissure measurements between 22 and 32 weeks GA in FGR warrant further investigation in larger cohorts with postnatal follow-up.

The Role of the Subplate in Schizophrenia and Autism: A Systematic Review

The subplate (SP) represents a transitory cytoarchitectural fetal compartment containing most subcortical and cortico-cortical afferents, and has a fundamental role in the structural development of the healthy adult brain. There is evidence that schizophrenia and autism may be determined by developmental defects in the cortex or cortical circuitry during the earliest stages of pregnancy. This article provides an overview on fetal SP development, considering its role in schizophrenia and autism, as supported by a systematic review of the main databases. The SP has been described as a cortical amplifier with a role in the coordination of cortical activity, and sensitive growth and migration windows have crucial consequences with respect to cognitive functioning. Although there are not enough studies to draw final conclusions, improved knowledge of the SP's role in schizophrenia and autism spectrum disorders may help to elucidate and possibly prevent the onset of these two severe disorders.

Fetal neurology: Principles and practice with a life-course perspective

Clinical service, educational, and research components of a fetal/neonatal neurology program are anchored by the disciplines of developmental origins of health and disease and life-course science as programmatic principles. Prenatal participation provides perspectives on maternal, fetal, and placental contributions to health or disease for fetal and subsequent neonatal neurology consultations. This program also provides an early-life diagnostic perspective for neurologic specialties concerned with brain health and disease throughout childhood and adulthood. Animal models and birth cohort studies have demonstrated how the science of epigenetics helps to understand gene-environment interactions to better predict brain health or disease. Fetal neurology consultations provide important diagnostic contributions during critical or sensitive periods of brain development when future neurotherapeutic interventions will maximize adaptive neuroplasticity. Age-specific normative neuroinformatics databases that employ computer-based strategies to integrate clinical/demographic, neuroimaging, neurophysiologic, and genetic datasets will more accurately identify either symptomatic patients or those at risk for brain disorders who would benefit from preventive, rescue, or reparative treatment choices throughout the life span.

Fetal cerebellar disorders

The embryologic development of the cerebellum extends over a long time period, thus making it vulnerable to a broad spectrum of malformations and disruptions. Knowledge of the main steps of fetal posterior fossa development; the normal imaging patterns at different stages of embryogenesis; the large spectrum of cerebellar malformations; and their clinical presentations enables diagnosis and precise counseling of parents. Sonography is the most important imaging method for the screening of cerebellar malformations since it is noninvasive, widely available, and safe for both mother and child. The ultrasonographic approach for the evaluation of the fetal posterior fossa is based on the classic transabdominal visualization of axial planes with addition when indicated of a more comprehensive, multiplanar transvaginal or transfundal approach, including coronal and sagittal imaging planes. Fetal magnetic resonance imaging (MRI) has become an adjunct to prenatal ultrasound since the 1980s. Good-quality images have been obtained thanks to the implementation of fast and ultrafast MRI sequences. Fetal MRI has higher-contrast resolution than prenatal sonography and may contribute to the differentiation of normal from abnormal tissue. Both prenatal neurosonography and fetal MRI enable accurate prenatal diagnosis of most posterior fossa anomalies.

Malformations of Cortical Development: From Postnatal to Fetal Imaging

Abnormal fetal corticogenesis results in malformations of cortical development (MCD). Abnormal cell proliferation leads to microcephaly or megalencephaly, incomplete neuronal migration results in heterotopia and lissencephaly, neuronal overmigration manifests as cobblestone malformations, and anomalous postmigrational cortical organization is responsible for polymicrogyria and focal cortical dysplasias. MCD comprises various congenital brain disorders, caused by different genetic, infectious, or vascular etiologies and is associated with significant neurological morbidity. Although MCD are rarely diagnosed prenatally, both dedicated multiplanar neurosonography and magnetic resonance imaging enable good demonstration of fetal cortical development. The imaging signs of fetal MCD are: delayed or absent cerebral sulcation; premature abnormal sulci; thin and irregular hemispheric parenchyma; wide abnormal overdeveloped gyri; wide opening of isolated sulci; nodular bulging into the lateral ventricles; cortical clefts; intraparenchymal echogenic nodules; and cortical thickening. The postnatal and prenatal imaging features of four main malformations of cortical development—lissencephaly, cobblestone malformations, periventricular nodular heterotopia, and polymicrogyria—are described.

MYSTERIES OF THE HUMAN FETUS REVEALED

The impressive program of research from the DiPietro laboratory succeeds in its aim to document the ontogeny of human fetal neurobehavioral development. From studies of great depth and breadth, and wielding creative methods of assessment, DiPietro et al. open a window into the largely inaccessible developing human fetal brain. This commentary, with reference to the seminal cardiovascular studies of the Laceys, supports the measures of the fetal heart to index fetal well-being and to provide evidence of stimulus processing. A separate case is made that the DiPietro program provides unique and invaluable information for assessing the influential Developmental Origins of Health and Disease or Fetal Programming Models. The goal of these models, to predict or understand the influences of early experience or response patterns on later postnatal life, is identical to the ultimate goal of the DiPietro program. Because human fetal behavior is uncontaminated by socialization or parenting or peers, it may be the best reflection of fetal exposures. The remarkable neurobehavioral profiles generated by the DiPietro program can make a critical contribution to the Fetal Programming Model in terms of sensitive and critical periods of nervous system vulnerability and to specify gestational periods of neurobehavioral risk.

Patch-based augmentation of Expectation-Maximization for brain MRI tissue segmentation at arbitrary age after premature birth

Accurate automated tissue segmentation of premature neonatal magnetic resonance images is a crucial task for quantification of brain injury and its impact on early postnatal growth and later cognitive development. In such studies it is common for scans to be acquired shortly after birth or later during the hospital stay and therefore occur at arbitrary gestational ages during a period of rapid developmental change. It is important to be able to segment any of these scans with comparable accuracy. Previous work on brain tissue segmentation in premature neonates has focused on segmentation at specific ages. Here we look at solving the more general problem using adaptations of age specific atlas based methods and evaluate this using a unique manually traced database of high resolution images spanning 20 gestational weeks of development. We examine the complimentary strengths of age specific atlas-based Expectation-Maximization approaches and patch-based methods for this problem and explore the development of two new hybrid techniques, patch-based augmentation of Expectation-Maximization with weighted fusion and a spatial variability constrained patch search. The former approach seeks to combine the advantages of both atlas- and patch-based methods by learning from the performance of the two techniques across the brain anatomy at different developmental ages, while the latter technique aims to use anatomical variability maps learnt from atlas training data to locally constrain the patch-based search range. The proposed approaches were evaluated using leave-one-out cross-validation. Compared with the conventional age specific atlas-based segmentation and direct patch based segmentation, both new approaches demonstrate improved accuracy in the automated labeling of cortical gray matter, white matter, ventricles and sulcal cortical-spinal fluid regions, while maintaining comparable results in deep gray matter.

Normal development

Numerous events are involved in brain development, some of which are detected by neuroimaging. Major changes in brain morphology are depicted by brain imaging during the fetal period while changes in brain composition can be demonstrated in both pre- and postnatal periods. Although ultrasonography and computed tomography can show changes in brain morphology, these techniques are insensitive to myelination that is one of the most important events occurring during brain maturation. Magnetic resonance imaging (MRI) is therefore the method of choice to evaluate brain maturation. MRI also gives insight into the microstructure of brain tissue through diffusion-weighted imaging and diffusion tensor imaging. Metabolic changes are also part of brain maturation and are assessed by proton magnetic resonance spectroscopy. Understanding and knowledge of the different steps in brain development are required to be able to detect morphologic and structural changes on neuroimaging. Consequently alterations in normal development can be depicted.

Assessment of MRI-Based Automated Fetal Cerebral Cortical Folding Measures in Prediction of Gestational Age in the Third Trimester

BACKGROUND AND PURPOSE

Traditional methods of dating a pregnancy based on history or sonographic assessment have a large variation in the third trimester. We aimed to assess the ability of various quantitative measures of brain cortical folding on MR imaging in determining fetal gestational age in the third trimester.

MATERIALS AND METHODS

We evaluated 8 different quantitative cortical folding measures to predict gestational age in 33 healthy fetuses by using T2-weighted fetal MR imaging. We compared the accuracy of the prediction of gestational age by these cortical folding measures with the accuracy of prediction by brain volume measurement and by a previously reported semiquantitative visual scale of brain maturity. Regression models were constructed, and measurement biases and variances were determined via a cross-validation procedure.

RESULTS

The cortical folding measures are accurate in the estimation and prediction of gestational age (mean of the absolute error, 0.43 ± 0.45 weeks) and perform better than (P = .024) brain volume (mean of the absolute error, 0.72 ± 0.61 weeks) or sonography measures (SDs approximately 1.5 weeks, as reported in literature). Prediction accuracy is comparable with that of the semiquantitative visual assessment score (mean, 0.57 ± 0.41 weeks).

CONCLUSIONS

Quantitative cortical folding measures such as global average curvedness can be an accurate and reliable estimator of gestational age and brain maturity for healthy fetuses in the third trimester and have the potential to be an indicator of brain-growth delays for at-risk fetuses and preterm neonates.

A case of Norman-Roberts syndrome identified from postnatal diagnosis of microlissencephaly

Lissencephaly is a rare brain malformation. What differentiates microlissencephaly from classical lissencephaly and other variants is the presence of severe microcephaly. Very few postnatal cases of Norman-Roberts syndrome are described in the literature. We report a case of microlissencephaly with a polymalformative syndrome that prompted postnatal diagnosis of Norman-Roberts syndrome.

Non-central nervous system fetal magnetic resonance imaging

Fetal magnetic resonance imaging (MRI) is currently offered in a limited number of centers but is predominantly used for suspected fetal central nervous system abnormalities. This article concentrates on the role of the different imaging sequences and their value to clinical practice. It also discusses the future of fetal MRI.

Morphological features and length measurements of fetal lateral ventricles at 16-25 weeks of gestation by magnetic resonance imaging

Normal growth of the lateral ventricles (LVs) was characterized three-dimensionally using magnetic resonance imaging (MRI) data from 16 human fetuses at 16-25 weeks of gestation. The LV was differentiated into four primary regions, the anterior horn, central parts, posterior horn, and inferior horn, at 16 weeks of gestation. The LV changed shape mainly by elongation and narrowing, which corresponded to the external and internal growth of the surrounding cerebrum. Six length parameters measured in the LV correlated with biparietal diameter by simple regression analysis (R(2) range, 0.56-0.93), which may be valuable for establishing a standardized prenatal protocol to assess fetal well-being and development across intrauterine periods. No correlation was found between biparietal diameter and LV volume (R(2) = 0.13).

Statistical analysis of relative pose of the thalamus in preterm neonates

Preterm neonates are at higher risk of neurocognitive and neurosensory abnormalities. While numerous studies have looked at the effect of prematurity on brain anatomy, none to date have attempted to understand the relative pose of subcortical structures and to assess its potential as a biomarker of abnormal growth. Here, we perform the first relative pose analysis on a point distribution model (PDM) of the thalamus between 17 preterm and 19 term-born healthy neonates. Initially, linear registration and constrained harmonic registration were computed to remove the irrelevant global pose information and obtain correspondence in vertices. All the parameters for the relative pose were then obtained through similarity transformation. Subsequently, all the pose parameters (scale, rotation and translation) were projected into a log-Euclidean space, where univariate and multivariate statistics were performed. Our method detected relative pose differences in the preterm birth for the left thalamus. Our results suggest that relative pose in subcortical structures is a useful indicator of brain injury, particularly along the anterior surface and the posterior surface. Our study supports the concept that there are regional thalamic asymmetries in the preterm that may be related to subtle white matter injury, have prognostic significance, or be related to preterm birth itself.

Fetal magnetic resonance imaging at 3.0 T

Magnetic resonance imaging (MRI) has been used to image the in utero fetus for the past 3 decades. Although not as commonplace as other patient-oriented MRI, it is a growing field and demonstrating a role in the clinical care of the fetus. Indeed, the body of literature involving fetal MRI exceeds 3000 published articles. Indeed, there is interest in accessing even the healthy fetus with MRI to further understand the development of humans during the fetal stage. On the horizon is fetal imaging using 3.0-T clinical systems. Although a clear path is not necessarily determined, experiments, theoretical calculations, advances in pulse sequence design, new hardware, and experience from imaging at 1.5 T help define the path.

Prematurity and congenital heart disease

Significant advances in technology and therapy have led to dramatic improvements in the survival of preterm babies over the last 2 decades. Similarly, improvements in surgical and cardiac intensive care techniques have increased the feasibility of supporting even very small babies to the point of surgical repair, leading some to adopt an approach of early and complete surgical repair in preterm infants, with the aim of minimizing potential preoperative morbidity associated with extended medical management or surgical palliation. (1,2) However, multiple diagnostic and therapeutic challenges complicate the care of premature infants. Major errors in echocardiography are more common in neonates weighing less than 2.5 kg, (3) and the ideal timing and type of surgical intervention in premature infants remains unknown. These problems are compounded by the need for critical care practices that optimize management of immature cardiopulmonary, gastrointestinal, and neurological systems. This review will summarize some of the recent advances in neonatal and perinatal medicine, which have the potential to contribute to improved management of preterm infants with critical cardiac disease.

Single-ventricle anatomy predicts delayed microstructural brain development

BACKGROUND

Term newborns with congenital heart disease (CHD) show delayed brain development as early as the third trimester, especially in single-ventricle physiology (SVP). Mechanisms causing delayed brain development in CHD are uncertain but may include impaired fetal brain blood flow. Our objective was to determine if cardiac anatomy associated with obstruction to antegrade flow in the ascending aorta is predictive of delayed brain development as measured by diffusion tensor imaging and magnetic resonance spectroscopic (MRS) imaging.

METHODS

Echocardiograms from 36 term newborns with SVP were reviewed for the presence of aortic atresia and the diameter of the ascending aorta. Quantitative magnetic resonance imaging parameters measuring brain microstructural (fractional anisotropy (FA) and average diffusivity (Dav)) or metabolic development (N-acetylaspartate (NAA) and lactate/choline (Lac/Cho)) were recorded.

RESULTS

Increasing NAA/Cho and white matter (WM) FA, and decreasing Dav and Lac/Cho characterize normal brain development. Consistent with the hypothesis that delayed brain development is related to impaired brain perfusion, smaller ascending aortic diameter and aortic atresia were associated with higher Dav and lower WM FA. Echocardiogram variables were not associated with brain metabolic measures.

CONCLUSIONS

These observations support the hypothesis that obstruction to fetal cerebral blood flow impairs brain microstructural development.

Functional plasticity before the cradle: a review of neural functional imaging in the human fetus

The organization of the brain is highly plastic in fetal life. Establishment of healthy neural functional systems during the fetal period is essential to normal growth and development. Across the last several decades, remarkable progress has been made in understanding the development of human fetal functional brain systems. This is largely due to advances in imaging methodologies. Fetal neuroimaging began in the 1950-1970's with fetal electroencephalography (EEG) applied during labor. Later, in the 1980's, magnetoencephalography (MEG) emerged as an effective approach for investigating fetal brain function. Most recently, functional magnetic resonance imaging (fMRI) has arisen as an additional powerful approach for examining fetal brain function. This review will discuss major developmental findings from fetal imaging studies such as the maturation of prenatal sensory system functions, functional hemispheric asymmetry, and sensory-driven neurodevelopment. We describe how with improved imaging and analysis techniques, functional imaging of the fetus has the potential to assess the earliest point of neural maturation and provide insight into the patterning and sequence of normal and abnormal brain development.

Identification of fetal precentral gyrus on diffusion weighted MRI

To investigate the association of the diffusion-weighted MR imaging characteristics of fetal preCG and gestational age. Forty-four fetuses with normal brain MRI findings were included in the study. Gestational ages ranged from 18 to 36 weeks (mean 25.2 weeks). All exams were performed with a 1.5-T scanner using a body array coil during free maternal breathing without sedation. Precentral gyrus was defined as the hyperintense strip anterior to the central sulcus, on the superior section of axial brain images at the level of superior frontal cortex. The presence of preCG hyperintensity was noted as observed/subtle/not observed at different b values (500, 1000 s/mm(2)) and on apparent diffusion coefficient (ADC) maps and compared to the imaging characteristics of the superior frontal cortex. Precentral gyrus was first detected at 25 weeks as a hyperintense strip on DWI and hypointense strip on ADC maps. Display of preCG b 1000 s/mm(2) images were better than b 500 s/mm(2). Between 25 and 27 weeks, in 40% of fetuses preCG was observed on one hemisphere, and it was evident bilaterally in 60% of cases. Starting from the 28th week, preCG was observed on both hemispheres in 100% of cases. Diffusion weighted imaging helps better understanding of the evolution of fetal preCG. The hyperintense preCG strip starts to appear at 25 weeks, and when interpreting fetal DWI after 28 weeks this may be a sign to be sought for in all fetuses and an indicator for normal development.

Lessons about neurodevelopment from anatomical magnetic resonance imaging

The arrival of magnetic resonance imaging (MRI) has offered major advances in our understanding of both normal and abnormal neurodevelopment. This review is a broad overview of the key findings that anatomical MRI research has provided in regard to the normal developing brain and presents key issues and consideration in pediatric imaging. Volumetric MRI studies, using various methods, have reliably found that gray-matter volume increases and peaks in late childhood, followed by a slow but continued loss, whereas white matter increases rapidly until age 10 years with continued development well beyond adolescence. The introduction of analysis techniques, such as voxel-based morphometry, cortical thickness measures, and cortical pattern mapping, have begun to answer more regionally specific questions. Pediatric neuroimaging studies carry specific requirements, given not only the high degree of variability between individuals, ages, and sexes but also issues of behavioral compliance, MR signal, and postprocessing methodologies such as appropriate normalization. Considerations in future pediatric imaging studies are presented. Ultimately, the promise of computational analysis of structural MRI data is to understand how changes in cerebral morphology relate to acquisition and enhancement of skills and behaviors in typical and atypical development.

Magnetic resonance imaging of the fetus

Fetal magnetic resonance imaging (MRI) has become established as part of clinical practice in many centres worldwide especially when visualization of the central nervous system pathology is required. In this review we summarize the recent literature and provide an overview of fetal development and the commonly encountered fetal pathologies visualized with MRI and illustrated with numerous MR images. We aim to convey the role of fetal MRI in clinical practice and its value as an additional investigation alongside ultrasound yet emphasize the need for caution when interpreting fetal MR images especially where experience is limited.

3D global and regional patterns of human fetal subplate growth determined in utero

The waiting period of subplate evolution is a critical phase for the proper formation of neural connections in the brain. During this time, which corresponds to 15 to 24 postconceptual weeks (PCW) in the human fetus, thalamocortical and cortico-cortical afferents wait in and are in part guided by molecules embedded in the extracellular matrix of the subplate. Recent advances in fetal MRI techniques now allow us to study the developing brain anatomy in 3D from in utero imaging. We describe a reliable segmentation protocol to delineate the boundaries of the subplate from T2-W MRI. The reliability of the protocol was evaluated in terms of intra-rater reproducibility on a subset of the subjects. We also present the first 3D quantitative analyses of temporal changes in subplate volume, thickness, and contrast from 18 to 24 PCW. Our analysis shows that firstly, global subplate volume increases in proportion with the supratentorial volume; the subplate remained approximately one-third of supratentorial volume. Secondly, we found both global and regional growth in subplate thickness and a linear increase in the median and maximum subplate thickness through the waiting period. Furthermore, we found that posterior regions--specifically the occipital pole, ventral occipito-temporal region, and planum temporale--of the developing brain underwent the most statistically significant increases in subplate thickness. During this period, the thickest region was the developing somatosensory/motor cortex. The subplate growth patterns reported here may be used as a baseline for comparison to abnormal fetal brain development.

MR imaging of the fetal brain

Fetal MRI is clinically performed to evaluate the brain in cases where an abnormality is detected by prenatal sonography. These most commonly include ventriculomegaly, abnormalities of the corpus callosum, and abnormalities of the posterior fossa. Fetal MRI is also increasingly performed to evaluate fetuses who have normal brain findings on prenatal sonogram but who are at increased risk for neurodevelopmental abnormalities, such as complicated monochorionic twin pregnancies. This paper will briefly discuss the common clinical conditions imaged by fetal MRI as well as recent advances in fetal MRI research.