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Magnetic resonance imaging in the prenatal diagnosis of neural tube defects

Authors:
Ander Zugazaga Cortazar at Parc de Salut Mar
Ander Zugazaga Cortazar
C Martín Martinez
C Martín Martinez
C Martín Martinez
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Carmina Duran at Corporació Sanitària Parc Taulí
Carmina Duran
Maria Rosa Bella-Cueto at Corporació Sanitària Parc Taulí
Maria Rosa Bella-Cueto
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Abstract and Figures

Objective: To assess the role of magnetic resonance imaging (MRI) in the prenatal diagnosis of neural tube defects (NTDs). Background: NTDs comprise a heterogeneous group of congenital anomalies that derive from the failure of the neural tube to close. Advances in ultrasonography and MRI have considerably improved the diagnosis and treatment of NTDs both before and after birth. Ultrasonography is the first technique in the morphological study of the fetus, and it often makes it possible to detect or suspect NTDs. Fetal MRI is a complementary technique that makes it possible to clear up uncertain ultrasonographic findings and to detect associated anomalies that might go undetected at ultrasonography. The progressive incorporation of intrauterine treatments makes an accurate diagnosis of NTDs essential to ensure optimal perinatal management. The ability of fetal MRI to detect complex anomalies that affect different organs has been widely reported, and it can be undertaken whenever NTDs are suspected. Conclusion: We describe the normal appearance of fetal neural tube on MRI, and we discuss the most common anomalies involving the structures and the role of fetal MRI in their assessment. Key points: • To learn about the normal anatomy of the neural tube on MRI • To recognise the MR appearance of neural tube defects • To understand the value of MRI in assessing NTDs.
Neural tube defects
Neural tube defects
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Complex closed spinal dysraphism: lipomyelocele and diastematomyelia. Fetus at 22 weeks' gestation. a Sagittal T2-weighted HASTE image shows a deformity of the spinal canal completely covered by soft tissues (arrows). b Coronal image showing the widening of the spinal canal at the lumbar level (white arrows) and abnormally low termination of the medullary cone (black arrow) below the kidneys. c CT study after birth shows the deformed, widened spinal canal (arrowheads) and soft
Complex closed spinal dysraphism: lipomyelocele and diastematomyelia. Fetus at 22 weeks' gestation. a Sagittal T2-weighted HASTE image shows a deformity of the spinal canal completely covered by soft tissues (arrows). b Coronal image showing the widening of the spinal canal at the lumbar level (white arrows) and abnormally low termination of the medullary cone (black arrow) below the kidneys. c CT study after birth shows the deformed, widened spinal canal (arrowheads) and soft
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a, b Normal anatomy of the neural tube. Normal cranial bone structures. Fetus at 24 weeks’ gestation. a Sagittal and b coronal T2-weighted HASTE images of the fetal head show the osseous structures of the base of the skull (arrows in a) and bones of the cranial vault (arrows in b). c–f Normal fetal spine. Fetus at 27 weeks’ gestation. c Sagittal T2-weighted HASTE image of the spinal canal. The vertebral bodies are hypointense with a band of higher intensity in the centre (white arrows), the intervertebral spaces are hyperintense (black arrows). The ellipse marks the medullary cone. d Coronal T2-weighted HASTE image shows the vertebral pedicles as hypointense rounded structures on both sides of the spinal canal (arrowheads). The interpedicular distance in the lumbar spine is slightly increased (arrows); this is a normal finding that should not be confused with spina bifida. A false cervicothoracic scoliosis is also seen (black arrow). e Axial image at the level of L1–L2 shows the medullary cone (white arrow) inside the spinal canal (the asterisks mark the kidneys). f The medullary cone is no longer seen in this axial image of the spinal canal below the kidneys; sometimes the nerve roots can be identified (white arrows)
a, b Normal anatomy of the neural tube. Normal cranial bone structures. Fetus at 24 weeks’ gestation. a Sagittal and b coronal T2-weighted HASTE images of the fetal head show the osseous structures of the base of the skull (arrows in a) and bones of the cranial vault (arrows in b). c–f Normal fetal spine. Fetus at 27 weeks’ gestation. c Sagittal T2-weighted HASTE image of the spinal canal. The vertebral bodies are hypointense with a band of higher intensity in the centre (white arrows), the intervertebral spaces are hyperintense (black arrows). The ellipse marks the medullary cone. d Coronal T2-weighted HASTE image shows the vertebral pedicles as hypointense rounded structures on both sides of the spinal canal (arrowheads). The interpedicular distance in the lumbar spine is slightly increased (arrows); this is a normal finding that should not be confused with spina bifida. A false cervicothoracic scoliosis is also seen (black arrow). e Axial image at the level of L1–L2 shows the medullary cone (white arrow) inside the spinal canal (the asterisks mark the kidneys). f The medullary cone is no longer seen in this axial image of the spinal canal below the kidneys; sometimes the nerve roots can be identified (white arrows)
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Neural tube defects
Neural tube defects
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Encephalocele. Fetus at 21 weeks’ gestation. a Sagittal and b axial T2-weighted HASTE images show the protrusion of the occipital lobe and occipital horn of the ventricular system (black arrows in a and b) through a defect in the bone and soft tissues (white arrows in a). c Ultrasound image also shows the protrusion of the occipital lobe (white arrows). d, e Images of the same fetus at 31 weeks’ gestation show a decrease in the extruded encephalic component (arrow in e) and an increase in the associated meningeal component (arrow in d)
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Encephalocele. Fetus at 21 weeks’ gestation. a Sagittal and b axial T2-weighted HASTE images show the protrusion of the occipital lobe and occipital horn of the ventricular system (black arrows in a and b) through a defect in the bone and soft tissues (white arrows in a). c Ultrasound image also shows the protrusion of the occipital lobe (white arrows). d, e Images of the same fetus at 31 weeks’ gestation show a decrease in the extruded encephalic component (arrow in e) and an increase in the associated meningeal component (arrow in d)
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... The rate of Chiari type II malformation in the current study (44.7%) was lower than what has been reported elsewhere (>75%). [4,8] The literature reports that MRI is superior to cranial ultrasound for evaluation of the posterior fossa. [8,17] Owing to limited availability and long waiting times for MRI, patients admitted to the UAH neonatal unit with MMC receive a cranial sonar to expedite intracranial visualisation. ...
... [4,8] The literature reports that MRI is superior to cranial ultrasound for evaluation of the posterior fossa. [8,17] Owing to limited availability and long waiting times for MRI, patients admitted to the UAH neonatal unit with MMC receive a cranial sonar to expedite intracranial visualisation. MRI is performed on an outpatient basis. ...
... In the absence of access to antenatal sonars, evidence indicates that the sensitivity of serum AFP retains viability for antenatal MMC detection. [4,5,8] The current study demonstrates no usage of serum AFP or amniocentesis during antenatal assessments. This represents a modifiable factor that could improve antenatal MMC detection, which in turn would allow delivery of affected neonates in a tertiary institution to further decrease the delay to repair. ...
Profiles of patients with myelomeningocele admitted to the neonatal unit at Universitas Academic Hospital in Bloemfontein, South Africa
Article
Full-text available
  • Oct 2023
Background. Myelomeningocele (MMC) is a common neural tube defect with significant sequelae. There are limited recent data on the mortality and morbidity of MMC in South Africa (SA). Objective. To describe the outcomes and characteristics of patients with MMC admitted to the neonatal unit at Universitas Academic Hospital (UAH) in Bloemfontein, SA. Methods. A retrospective, descriptive study which included 53 patients with MMC admitted to the neonatal unit between 1 January 2017 and 31 December 2019 was conducted. Electronic patient records were reviewed. Data included outcomes, length of stay, complications and maternal and infant characteristics. Results. The inpatient mortality rate was 11.3% (n=6/53). The median length of stay was 18 days. Notable MMC complications included hydrocephalus (88.7%; n=47/53), Chiari malformation type II (44.7%; n=21/47), lower-limb paralysis (84.9%; n=45/53), lower-limb deformities (60.4%; n=32/53), meningitis (52.8%; n=28/53), neuropathic bladder (37.7%; n=20/53) and loss of anal tone (41.5%; n=22/53). MMC repair was performed in 62.2% (n=33/53) and 27.3% (n=9/33) developed complications. Wound sepsis and breakdown were the most common complications (18.2%, n=6/33), with a median 8 days to complications. Antenatal sonar was not performed in 62% (n=31/50) of cases. MMC was detected antenatally in 20% of cases. Conclusion. The inpatient mortality rate in thisstudy was lower than the mortality rates reported in other low- and middle-income countries although significant morbidity was identified. A lack of quality antenatal care and access to antenatal sonars were barriers to early detection of MMC. Other healthcare system infrastructural failures may be contributory, which highlights the need for ongoing inter- sectoral collaboration for prevention, early detection and management of MMC to improve patient outcomes.
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... Another possible differential diagnosis is the sinus pericranii, a low-flow venous malformation characterized by the presence of an extracranial soft-tissue mass, usually located in the midline, caused by an abnormal communication between intracranial dural sinuses and extracranial veins via transcalvarial emissary veins [17]. The torcular pseudomass may also resemble a simple occipital meningocele (herniation of meninges and cerebrospinal fluid through a cranial defect) given its homogeneous T2 hyperintensity [18]. However, the torcular pseudomass, although located in the posterior midline, is a strictly intracranial structure and is not associated with calvarial defects. ...
... However, the torcular pseudomass, although located in the posterior midline, is a strictly intracranial structure and is not associated with calvarial defects. More complex meningoencephaloceles involve additional herniation of cerebral parenchyma through the bony defect and are commonly associated with other intracranial anomalies [18]. Last, benign inclusion cysts, such as dermoid or epidermoid cysts, present with distinct signal on T1-and T2-weighted imaging as well as restricted diffusion in the latter [19]. ...
Torcular pseudomass is frequently detected on fetal magnetic resonance imaging and reduces with gestational age
Article
Full-text available
  • Nov 2022
  • PEDIATR RADIOL
Background The torcular pseudomass is an incidental extra-axial midline mass located between the venous sinuses and the occipital squama in the pediatric population. Although this structure is presumed to be a developmental feature, it has not been characterized on fetal MRI. Objective To determine the frequency, imaging features and longitudinal in utero evolution of torcular pseudomass using fetal MRI. Materials and methods We present a single-center retrospective study of fetal MRI performed at a tertiary hospital. Two independent reviewers first ordinally scored torcular pseudomass as absent, focal, crescentic or bulky based on morphology. We reviewed available follow-up fetal and postnatal MRI and further classified torcular pseudomass as stable, involuted or progressive. We also collected clinical and demographic data from electronic charts and compared them among categories, corrected for multiple comparisons. Results This study included a total of 219 fetuses with median gestational age of 28 weeks (interquartile range [IQR]: 23–32 weeks). Torcular pseudomass was absent in 8% (n=17) and present as a focal mass in 15% (n=33), crescentic in 45% (n=98) and bulky in 32% (n=71) of the cases. Median gestational age was statistically different among torcular pseudomass categories and inversely associated with size. Follow-up fetal MRI was available in 9.6% (n=21) of cases (median interval 4 weeks; IQR: 2–9 weeks) and torcular pseudomass in these cases was classified as stable in 67% (n=14), involuted in 29% (n=6) and progressive in 5% (n=1). Postnatal MRI was available in 5% (n=12) of fetuses (median interval 11.5 months, IQR: 3–17 months), and among these cases torcular pseudomass was classified as stable in 33% (n=4) and involuted in 67% (n=8). Conclusion Torcular pseudomass is highly prevalent in the fetal population and shows a natural tendency to involute, even in utero, although it sometimes persists during early infanthood.
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... Failure of neural tube closure during development results in a variety of neural tube defects, causing spinal anomalies in cases of spinal dysraphism like spina bifida; or cranial anomalies like with anencephaly, characterized by absence of a major portion of the cranium. Though, anencephaly is less indicated for MRI [45]. Distinguishing characteristics of common types of spina bifida are shown in Figure 2. Worldwide incidence varies geographically, but estimated on average about 0.1-1% of live births, with anticonvulsants correlating with increased risk, and folic acid associated with reduced risk of neural tube defects [45]. ...
... Though, anencephaly is less indicated for MRI [45]. Distinguishing characteristics of common types of spina bifida are shown in Figure 2. Worldwide incidence varies geographically, but estimated on average about 0.1-1% of live births, with anticonvulsants correlating with increased risk, and folic acid associated with reduced risk of neural tube defects [45]. Spinal dysraphism occurs from improper closure of the spinal cord and surrounding membranes during fetal development, and can be classified by open or closed. ...
Common Indications and Techniques in Prenatal MRI
Chapter
Full-text available
  • Jul 2022
Fetal and perinatal diagnostic imaging with MRI has evolved and expanded during recent times, allowing more widespread use and availability. Common indications are for neurodevelopmental conditions that are inconclusive with ultrasonography. The modality is pivotal in treatment planning for in utero interventions, such as repair of neural tube defects, and for particular obstetrical complications. The technique is also useful for identifying neurological sequelae from conditions like congenital heart defects and maternal viral infections. Many other applications are not indicated for routine use, particularly due to the high cost, but show much promise in research applications. Recently, complications associated with COVID-19 have been an area of interest, with prenatal MRI cohorts and case studies reporting obstetrical complications and neurodevelopmental effects. This review is aimed at highlighting common indications for the use of MRI in maternal-fetal medicine, including the MRI sequences and physics often implemented. Also, an in-depth analysis of the SARS-CoV-2 virus is discussed; in addition to pregnancy-related complications and the role of prenatal MRI in diagnosis and treatment.
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... Despite nearly 100% of neonates born with an open myelomeningocele having evidence of hydrocephalus at the time of birth, but only 70% will develop hydrocephalus during fetal life [14,15]. The use of three-dimensional ultrasound may be more accurate for the localisation of lesion level compared with two-dimensional ultrasound, but a discrepancy exists with the clinical significance of the improved accuracy, which is generally in the region of one spinal level compared with postnatal findings [16,17]. ...
Prenatal Diagnosis and Pregnancy Management of MMC
Article
Full-text available
  • Feb 2022
Open spina bifida (myelomeningocele) is a specific kind of neural tube defect (NTD) resulting from a trouble of closure of the caudal region of the neural tube early in embryogenesis. The diagnosis and management of open spina bifida has changed significantly over the past century. Significant advances in the prevention, diagnosis and treatment of open spina bifida have been made over the last years. The most significant strategy for the prevention of open spina bifida has been with folic acid supplementation. Although progress in the field of myelomeningocele diagnosis and treatment has revolutionised the medical treatment of open spina bifida, the postnatal treatment of myelomeningocele evolved significantly and is now complicated by issues surrounding prenatal diagnosis, including availability, economic feasibility, and selection for invasive fetal surgery and management of pregnancy.
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... Ultrasound is commonly used in the prenatal diagnosis of congenital CNS anomalies, to help clinicians to counsel patients and their families [24,29,32], as was evident from our study. Advances in foetal MRI have progressed over the past decades from an experimental procedure to an important technique routine practice in confirming congenital defects in many centers globally [18,19,[33][34][35][36][37][38]. The present study presents results for comparison of two of the diagnostic methods: one before and the other after the birth of the baby. ...
Evaluation of the Significance of MRI in the Prenatal Diagnosis of Neural Tube Defects
Article
  • Sep 2021
PurposeCongenital anomalies, also known as birth defects have been the primary focus of a number of studies globally. Our primary objective is to evaluate the significance of MRI in the prenatal diagnosis of congenital central nervous system (CNS) anomalies and explore the role of autopsy techniques in the postnatal phase as a verification tool. Additionally, we are focused on proving the MRI-specific diagnostic capabilities in comparison to the current gold standard based on autopsy.Methods The study is based on a thorough analysis of incidences of congenital CNS anomalies in four women and their foetuses. Primary in-vivo MRI diagnostics and subsequent verification via autopsy (postmortem) have been performed.ResultsWe described the foetal CNS anomalies based on MRI diagnostics and additionally verified the results by autopsy to confirm the findings and improve the services offered to patients and their families.Conclusion The findings of the study confirmed the role of the MRI as a reliable tool for unequivocal diagnosis of congenital CNS anomalies and malformations.
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... An initial step for the quantification of fetal brain morphology and volumetry is image segmentation. It is clinically relevant to analyse information such as shape or volume of the developing cortex, cerebellum, brainstem, white matter and cerebrospinal fluid spaces, as many congenital disorders cause subtle changes to these tissue compartments 6,15,16 . Existing growth data is mainly based on normally developing brains [17][18][19] , and we lack growth data for many pathologies and congenital disorders. ...
An automatic multi-tissue human fetal brain segmentation benchmark using the Fetal Tissue Annotation Dataset
Article
Full-text available
  • Jul 2021
It is critical to quantitatively analyse the developing human fetal brain in order to fully understand neurodevelopment in both normal fetuses and those with congenital disorders. To facilitate this analysis, automatic multi-tissue fetal brain segmentation algorithms are needed, which in turn requires open datasets of segmented fetal brains. Here we introduce a publicly available dataset of 50 manually segmented pathological and non-pathological fetal magnetic resonance brain volume reconstructions across a range of gestational ages (20 to 33 weeks) into 7 different tissue categories (external cerebrospinal fluid, grey matter, white matter, ventricles, cerebellum, deep grey matter, brainstem/spinal cord). In addition, we quantitatively evaluate the accuracy of several automatic multi-tissue segmentation algorithms of the developing human fetal brain. Four research groups participated, submitting a total of 10 algorithms, demonstrating the benefits the dataset for the development of automatic algorithms.
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ExSwin-Unet: An Unbalanced Weighted Unet with Shifted Window and External Attentions for Fetal Brain MRI Image Segmentation
Chapter
  • Feb 2023
Accurate fetal brain MRI image segmentation is essential for fetal disease diagnosis and treatment. While manual segmentation is laborious, time-consuming, and error-prone, automated segmentation is a challenging task owing to (1) the variations in shape and size of brain structures among patients, (2) the subtle changes caused by congenital diseases, and (3) the complicated anatomy of brain. It is critical to effectively capture the long-range dependencies and correlations among training samples to yield satisfactory results. Recently, some transformer-based models have been proposed and achieved good performance in segmentation tasks. However, the self-attention blocks embedded in transformers often neglect the latent relationships among different samples. Model may have biased results due to the unbalanced data distribution in the training dataset. We propose a novel unbalanced weighted Unet equipped with a new ExSwin transformer block to comprehensively address the above concerns by effectively capturing long-range dependencies and correlations among different samples. We design a deeper encoder to facilitate features extracting and preserving more semantic details. In addition, an adaptive weight adjusting method is implemented to dynamically adjust the loss weight of different classes to optimize learning direction and extract more features from under-learning classes. Extensive experiments on a FeTA dataset demonstrate the effectiveness of our model, achieving better results than state-of-the-art approaches.
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Neural Tube Development and Defects: Meningocele, Encephalocele, Hydrocephalus
Chapter
  • Jan 2023
Neural tube defects (NTD’s) are common congenital anomalies, with incidence of 300,000 births per year worldwide, being highest in Southeast Asian countries. The incidence from major cities in India is reported as 3.9–8.8 per 1000 births (live and dead) (2005), and 6.57–8.21 per 1000 live births from rural India. Most NTD’s are preventable. The incidence has reduced over the past 20 years with antenatal Folic acid supplementation in early gestation. These defects are significant as they can give rise to paralysis or death and should be diagnosed well in time and managed, so as to support the United Nations Millennium Development Goal 4 of reducing the burden of child mortality.The neural tube is a primordial structure extending along the entire length of the embryo and gives rise to the brain and the spinal cord. In-utero, CNS developments starts at 3 weeks by primary neurulation. NTD’s occur due to defect in the midline fusion of neural tube resulting in cranial or spinal dysraphism, and may involve nerve roots, spinal cord, or bony vertebrae. They can be open or closed types. Sporadically, the same neonate may have more than one defect, suggesting multisite closure of the neural tube. Diagnosis is best using radiological imaging. Treatment is surgical closure. Open NTD can also be repaired antenatally, in utero. Anesthetic management for repair of NTD in neonates demands thorough preoperative evaluation, essential investigations and imaging studies, meticulous planning, experienced team, and a well-equipped set-up with a multidisciplinary approach.This chapter will discuss the types of NTD’s, neuro-embryology, etiopathogenesis, diagnostic modalities, and anesthetic concerns and management of these babies when they present for repair of NTD, in the neonatal period.KeywordsNeonateNeural tube defectsNeuro-embryologyOpen defectsClosed defectsNeuroporesAnencephalySpina bifidaRachischisisMeningomyeloceleOccult spinal dysraphismSplit cord malformationTethered cord syndromeEncephaloceleHydrocephalusEndoscopic third ventriculostomyAnesthetic management
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Maternal serum alpha-fetoprotein level and the relationship to ventriculomegaly in fetal neural tube defect: A retrospective cohort study
Article
  • Feb 2021
  • EUR J OBSTET GYN R B
Objective To estimate the significance of the association between mid-trimester maternal serum alpha-fetoprotein (MSAFP) level and fetal neuroanatomic findings in cases of open neural tube defect (ONTD). Methods Retrospective study of patients referred for prenatal ONTD repair between 2012 and 2018. Cases were classified into three groups based on their MSAFP level: 1)High MSAFP (>3.8MoM – n = 22), 2)Moderately high MSAFP (≤3.8 and ≥2.5MoM – n = 28), 3)Normal MSAFP (<2.5MoM – n = 18). MRI scans at the time of referral were used to assess the relationship between MSAFP and: A)Type of ONTD; B) Ventriculomegaly; C) Size of the myeloschisis lesion; D) Volume of myelomeningocele; E) Anatomical level of the lesion (LL). Results Having a high MSAFP level was more likely to be associated ventriculomegaly at mid-gestation than a moderately high or normal MSAFP level (OR = 8.4;CI95[0.9-73.4];p = 0.05 and OR = 2.8;CI95[0.9-8.8];p = 0.07). There were no differences between the three groups regarding type of lesion, size of the myeloschisis lesion, anatomic LL, or volume of the myelomeningocele sac. Myeloschisis cases with normal MSAFP had a larger surface area when compared to myeloschisis cases with moderately high MSAFP (219.8[104.4-551] vs 155.4[38.5-502.4] mm², p = 0.04). Conclusion A 2nd trimester MSAFP level >3.8MoM in a fetus with ONTD is associated with mid-gestation ventriculomegaly.
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Pediatric neuroimaging: Fifth edition
Book
  • Feb 2012
The thoroughly updated Fifth Edition of Pediatric Neuroimaging is a highly illustrated text-reference that describes and illustrates the full range of pediatric disorders diagnosable by modern neuroimaging. Covering the diagnosis of brain, spinal, and head and neck disorders in the pediatric patient, the text is rooted in the principle that the proper interpretation of studies requires the acquisition of high-quality images and an understanding of the basic concepts of neuroembryology, normal development, and pathophysiology. Much coverage is given to the disorders seen in everyday practice. The emphasis is on CT and MRI, which are the optimal imaging modalities in children. The first two chapters describe useful imaging techniques in this patient population and the imaging manifestations of normal development, to distinguish that from manifestations of disease. The final ten chapters of the book are divided by groups of diseases, with numerous drawings and images that illuminate the underlying pathologic and embryologic/genetic bases of each disorder. The goal is provide a basic approach to groups of diseases, then offer detailed information about the clinical manifestations, underlying biochemistry, molecular biology, genetics and/or pathology of specific disorders. The book incorporates the essential concepts for obtaining good images and understanding normal development, which helps the reader to distinguish normal developmental changes from disease. © 2012 by Lippincott Williams & Wilkins, a Wolters Kluwer business. All rights reserved.
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Diagnostic Imaging of Fetal Anomalies
Article
  • Jun 2006
  • AUSTRALAS RADIOL
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BIRTHMARKS TO WORRY ABOUT
Article
  • Jul 1998
  • DERMATOL CLIN
Most birthmarks are benign lesions of little concern. Rarely, congenital cutaneous lesions may indicate an underlying systemic disorder. This article will focus on birthmarks that are markers of neural tube dysraphism. The term dysraphia is defined as incomplete fusion of a raphe. The skin and the nervous system are both derived from the ectoderm. Separation of the neural ectoderm from the epithelial ectoderm occurs during the third to fifth weeks of gestation. This cleavage occurs concurrently with the formation and closure of the neural tube. This embryologic association may explain why apparently trivial, cutaneous lesions are often present over occult neural tube dysraphia. The discussion in this article will be divided into cutaneous markers of cranial dysraphism (calvarial defects) and those of spinal dysraphism.
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