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Ventriculomegaly

Introduction Ventriculomegaly (VM) is a nonspecific term, describing dilatation of the lateral cerebral ventricles, usually defined as greater than 10 mm at the level of the atria. VM is the most frequent abnormal central nervous system (CNS) finding detected with prenatal imaging techniques. It is not a disease, but rather a sign that represents a common endpoint of various pathologic processes with different outcomes and prognosis; it…

Vascular Cerebral Anomalies

Introduction Cerebral vascular malformations are rare but potentially disastrous abnormalities. Aneurysm of the vein of Galen is the most common abnormality described in prenatal series. Other types of intracranial vascular malformations are diagnosed prenatally only rarely. In the neonatal period, the clinical features include cyanosis, systolic murmur secondary to hyperdynamic circulation, cardiomegaly, and increased intracranial pressure. Before the availability of ultrasound (US) diagnosis, most cerebral vascular…

Neural Tube Defects

Introduction Neural tube defects (NTD) are the consequence of a failure in the closure of the neural tube, and differ depending on their localization and extent. The term “neural tube defects” includes defects of the cranial vault, including the spectrum of acrania, exencephaly, and anencephaly, and encephaloceles, spinal defects (“spina bifida” or myelomeningocele), and combined cranial and spinal defects such as craniorachischisis. These defects, as well…

Intracranial Hemorrhage, Cysts, Tumors, and Destructive Lesions

Introduction Destructive cerebral lesions are not embryonic malformations, but rather the result of an insult to a normally developed fetal brain. The most common causes are hemorrhage, hypoxia-ischemia, and infections, but the pathophysiology is unclear in many cases. The prognosis is usually poor. This chapter describes the main features of fetal intracranial destructive lesions, including intracranial hemorrhages, porencephaly, hydranencephaly, and schizencephaly. Other intracranial lesions that develop…

Holoprosencephaly

Introduction Holoprosencephaly (HPE) has been known since antiquity through the figure of the cyclopean shepherd Polyphemos in Homer's Odyssey (circa 800 bc ). Until the 17th century, a cyclopic newborn, whether it was a human or an animal, was associated with mystic and fabulous narrations. In the 18th century, HPE and other anomalies were recognized as congenital conditions, and cases of HPE were collected and described…

Walker-Warburg Syndrome

Introduction Walker-Warburg syndrome (WWS) is a rare, lethal congenital diffuse neurodysplasia, characterized by variable ocular and cerebral abnormalities. Cerebral findings include ventriculomegaly, encephalocele, and Dandy-Walker malformation. Ocular findings are varied, may occur in the posterior or anterior segments of the eye, or both, and include microphthalmia, congenital cataracts, corneal opacities, nonreactive pupils, iris synechiae, optic disk colobomas, and retinal dysplasia or detachment. Disease Definition The principal…

Cerebellar Anomalies

Introduction The fetal cerebellum develops throughout pregnancy and may be visualized starting from the first trimester. By the seventh week of gestation, the rhombencephalic vesicle, the precursor of the fourth ventricle and cisterna magna, is the most prominent structure of the brain. By the eighth week, the cerebellar hemispheres may be seen lateral to the fourth ventricle; the choroid plexus of the fourth ventricle is also…

Cortical Development and Disorders

Introduction Cortical neuronal cell development starts at about 7 weeks' gestation from stem cells in the germinal matrix that line the ventricles. The stem cells proliferate and differentiate into glial cells and neurons. The glial cells migrate radially to the brain surface and create a scaffold for the neurons to follow to the outer cortex, where the neurons organize connections and commissures. Other neurons derived from…

Septooptic Dysplasia

Introduction Septooptic dysplasia (SOD), also known as de Morsier syndrome, is a rare heterogeneous disorder. It is characterized by optic nerve hypoplasia and midline forebrain abnormalities, such as agenesis of the corpus callosum, absence of the cavum septi pellucidi, and pituitary hypoplasia with consequent panhypopituitarism. It has been proposed that the terms SOD and de Morsier syndrome should be abandoned, as they are not independent entities.…

Corpus Callosum and Septum Pellucidum Anomalies

Introduction Anomalies of the corpus callosum and septum pellucidum are disorders of prosencephalic midline development. Midline prosencephalic development peaks at 7 to 12 weeks' gestation and includes the formation of the chiasmatic, commissural, and hypothalamic plates, enabling formation of the corpus callosum (12 to 20 weeks) and septum pellucidum. Corpus callosum and septum pellucidum anomalies are often associated with other brain abnormalities. Corpus Callosum Anomalies Definition…

Choroid Plexus Anomalies: Cysts and Papillomas

Introduction The choroid plexus is a vascular convolute, consisting of epithelial cells (a type of microglia), fenestrated blood vessels, and stroma, which lie in the ventricular system of the brain. It is the main source of cerebrospinal fluid (CSF) and actively regulates the constituents in CSF. The choroid plexus epithelial cells and the tanycytes, special ependymal cells located in the floor of the third ventricle, constitute…

Fetal Spleen

Introduction The fetal spleen is an important center of hematopoiesis until the late fetal period. In postnatal life, the function of the spleen is mainly as an immune organ, with lymphocyte and monocyte production continuing throughout adult life. During fetal development, the spleen appears between the fifth and eighth gestational weeks as an aggregation of reticular mesenchymal cells in the dorsal epigastrium of the stomach. The…

Sacrococcygeal Teratoma and Fetus in Fetu

Introduction Sacrococcygeal teratoma (SCT) is the most common tumor in newborns. Fetal SCT diagnosed in utero is associated with a 50% risk of preterm delivery, a mortality rate of 15% to 35%, and a morbidity rate of 12% to 68%. Perinatal mortality and morbidity are high because of high-output cardiac failure, fetal hydrops, preterm delivery, anemia, dystocia, and tumor rupture. The intrapelvic and intraabdominal extent of…

Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome

Introduction Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is a rare and severe condition that is characterized by functional intestinal obstruction with dilated small intestine, microcolon, malrotation, decreased or absent bowel movement, and, prenatally, a massively enlarged nonobstructive urinary bladder often associated with hydroureteronephrosis. The anomaly was first described by Berdon et al. in 1976 and is also termed neonatal hollow visceral myopathy . Female fetuses are affected four to…

Intraabdominal Masses

Introduction Intraabdominal solid masses and cystic lesions are not commonly identified during the routine 20-week anomaly ultrasound (US) scan and are uncommon findings at later gestations. However, intraabdominal masses occasionally are seen as an incidental finding during a third-trimester US scan assessing fetal growth and wellbeing. Potential differential diagnoses are numerous, but the differential diagnosis typically can be restricted through a detailed assessment of the site…

Hepatic Anomalies

Introduction Structural fetal hepatic anomalies include tumors (usually primary, rarely metastatic), calcifications, cysts, hepatomegaly, and biliary anomalies. Fetal biliary anomalies are discussed in Chapter 25 . Many of these conditions can be diagnosed prenatally by ultrasound (US). Hepatic Tumors, Calcifications, and Cysts Solid hepatic tumors are rare, accounting for approximately 5% of perinatal neoplasms. They include benign and malignant primary neoplasms and metastases of nonhepatic cancers.…

Congenital Diaphragmatic Hernia

Introduction Incomplete formation of the fetal diaphragm early in gestation results in a diaphragmatic defect allowing abdominal organs to herniate into the chest. These organs compete for space with the growing lungs, leading to inadequate pulmonary development and to respiratory failure and pulmonary hypertension at birth. Even with the advances made in the neonatal management of congenital diaphragmatic hernia (CDH), the postnatal mortality of this condition…

Intestinal Obstruction

Introduction The fetal intestinal tract can be altered by numerous pathologic processes. Typical ultrasound (US) findings of bowel obstruction are dilated bowel loops in the fetal abdomen proximal to the obstruction. Although large bowel dilatation occasionally can be observed, most cases of bowel dilatation are in the small intestine. Early diagnosis is possible for some proximal obstructions, such as duodenal atresia and esophageal atresia. In this…

Biliary Anomalies

Introduction The diagnosis and detection of some forms of bile duct disease have become possible with routine prenatal ultrasound. However, it remains difficult to offer a specific diagnosis or even prognosis in most cases. The most common finding is probably cystic dilatation of the biliary tree, mainly because of choledochal cysts or biliary atresia. In this chapter, biliary atresia, choledochal cysts, and gallstones will be discussed,…

Abdominal Cysts

Introduction Different organ systems can give rise to abdominal cysts that can be detected on prenatal ultrasound (US) ( Table 24.1 ). Depending on the location, gestational age, gender, and US appearance of the cyst, a limited differential diagnosis or the correct diagnosis can often be achieved. Intraabdominal cysts may develop from many organs. The most frequent origins are the urinary system (hydronephrosis, multicystic dysplastic kidneys,…