Progression of exencephaly to anencephaly in the human fetus--an ultrasound perspective

Discordant exencephaly in case of a twin delivery: a case report

Introduction and importance

Neural tube defect occurs as a result of failure of spontaneous closure of the neural tube between the third and fourth weeks of foetal life. Exencephaly is a rare malformation of the neural tube characterized by a large amount of protruding brain tissue in the absence of the calvarium.

Case presentation

The authors report a 29-year-old female, non-compliant to iron, calcium and folic acid tablets due to nauseating and itchy sensation after intake for 2 weeks, was admitted in ward Obstetrics ward in view of twin pregnancy. After proper counselling, she was advised for caesarean section, which revealed gross malformation in the form of cleft lip, cleft palate and exposed brain tissue covered by thin layer of membrane with incompletely formed cranial vault and multiple-haematoma and ulcerations in the exposed brain tissue suggestive of Exencephaly. The deformed baby survived for 2 days after birth while the other baby was grossly healthy.

Clinical discussion

Exencephaly is said to be the embryological precursor anomaly of anencephaly. Exencephaly is a type of cranial malformation that characteristically involves a large disorganized mass of brain tissue. The flat bones of calvaria are absent and the brain mass is left uncovered. This condition is incompatible with life.

Conclusion

Each and every pregnant lady must be advised to undergo ultrasonography in every trimester, especially second trimester scan (anomaly scan) to diagnose any gross congenital malformations. Each pregnant lady is suggested to take the necessary vitamins (like folic acid) to avoid any Neural tube defects.

Anatomical Considerations of Embryology and Development of the Musculoskeletal System: Basic Notions for Musculoskeletal Radiologists

The musculoskeletal (MSK) system begins to form in the third week of intrauterine development. Multiple genes are involved in the complex different processes to form the skeleton, muscles and joints. The embryonic period, from the third to the eighth week of development, is critical for normal development and therefore the time when most structural defects are induced. Many of these defects have a genetic origin, but environmental factors may also play a very important role. This review summarizes the embryology of the different components of the MSK system and their configuration as an organ-system, analyzes the clinical implications resulting from failures in the process of organogenesis, and describes the first approach to diagnosis of skeletal abnormalities using prenatal ultrasound.

Comparison of inherited neural tube defects in companion animals and livestock

Neural tube defects (NTDs) are congenital malformations resulting from the improper or incomplete closure of the neural tube during embryonic development. A number of similar malformations of the protective coverings surrounding the central nervous system are also often included under this umbrella term, which may not strictly fit this definition. A range of NTD phenotypes exist and have been reported in humans and a wide range of domestic and livestock species. In the veterinary literature, these include cases of anencephaly, encephalocele, dermoid sinus, spina bifida, and craniorachischisis. While environmental factors have a role, genetic predisposition may account for a significant part of the risk of NTDs in these animal cases. Studies of laboratory model species (fish, birds, amphibians, and rodents) have been instrumental in improving our understanding of the neurulation process. In mice, over 200 genes that may be involved in this process have been identified and variant phenotypes investigated. Like laboratory mouse models, domestic animals and livestock species display a wide range of NTD phenotypes. They remain, however, a largely underutilized population and could complement already established laboratory models. Here we review reports of NTDs in companion animals and livestock, and compare these to other animal species and human cases. We aim to highlight the potential of nonlaboratory animal models for mutation discovery as well as general insights into the mechanisms of neurulation and the development of NTDs.

Morphometric characteristics of anencephalic skulls - A comparative study

Anencephaly is the most severe form of a neural tube defect resulting from the incomplete occlusion of the anterior neuropore in the fourth week of development and associated with a severely underdeveloped brain mass. As desmal ossification of the neurocranium is induced by the presence of soft tissues (brain), no bone develops as direct consequence of the missing brain. The cranial base, by contrast, is formed by chondral ossification, which is genetically determined, and thus present also in anencephaly. Morphometric characteristics of anencephalic skulls, however, have not yet been investigated in sufficient detail before. In this study we therefore comparatively assessed macroscopic morphological-anatomical and cephalometric CT data on structures and dimensions of 11 macerated anencephalic and 4 normal neonatal skulls highlighting skeletal morphological differences. The most striking results were the missing skullcap and the greatly changed morphology of the existing skull bones, which were reduced in size. The parameters of the skull base, the transverse orbital diameter and maxillary width were significantly smaller in anencephalic skulls. The morphology of the viscerocranium appeared similar to that of normal neonatal skulls. The results of this study can be used in diagnosis and skeletal classification for anencephaly. This can help identify bones that are incomplete, fragmented and taphonomically altered, which is often the case in historical and forensic studies.

Ultrasound Appearances of the Acrania-Anencephaly Sequence at 10 to 14 Weeks' Gestation

OBJECTIVES

The acrania-anencephaly sequence is a lethal condition with a high detection rate in experienced hands after 10 weeks' gestation. However, earlier in gestation, many cases remain undetected. Different phenotypic appearances have been described and might help increase the detection rate in less experienced hands and also earlier in gestation. The purpose of this study was to assess interobserver reliability in classifying cases of the acrania-anencephaly sequence during first trimester in 6 different subtypes according to their ultrasound appearances.

METHODS

This was a retrospective descriptive cohort study at 3 centers for fetal imaging. Each case was classified according to its phenotypic appearance by 2 independent operators as "bilobular," "cystic," "elongated," "irregular," "foreshortened," or "overhanging." Frequencies of each type are described, and interoperator agreement was assessed with the intraclass correlation coefficient.

RESULTS

From the 88 included cases, the frequencies of the different subtypes classified as overhanging, elongated, bilobular, cystic, foreshortened, and irregular were 31%, 25%, 19%, 11%, 8%, and 6%, respectively. The interoperator reliability was good, with an intraclass correlation coefficient of 0.903 (95% confidence interval, 0.853-0.937; P < .001).

CONCLUSIONS

Using different subtypes may improve the detection of the acrania-anencephaly sequence. An accurate early diagnosis could lead to timely, less traumatic, and safer management of affected pregnancies.

The fundamental building blocks of cortical development are established in human exencephaly

BACKGROUND

The presence and status of progenitor/stem cells in excencephalic brain have not been previously examined.

METHODS

Brain sections of excencephalic 17-week fetus were stained for specific stem and mature cell markers.

RESULTS

The ventricles were open, the developing cerebral cortex was thin in the radial dimension, and the ventricular surface was undulated. There was a decreased ratio of subventricular/ventricular zone radial glia precursor cells (RGCs; PAX6⁺ and HOPX⁺ cells), a decreased number of intermediate progenitor cells (IPCs; TBR2⁺), a decreased number of neurons (MAP2⁺), and an increased number of astrocytes (S100b⁺), compared to the control. MAP2⁺ neurons, S100b⁺ astrocytes, and OLIG2⁺ oligodendrocytes were present within the subventricular zone.

CONCLUSIONS

This indicates that the underlying condition did not initially preclude radial glial cells from undergoing asymmetric divisions that produce IPCs but halted the developmental progression. RGC and IPC presence in the developing cerebral cortex demonstrates that the fundamental building blocks of cortical formation had been established and that a normal sequence of developmental steps had been initiated in this case of exencephaly. These data expand our understanding of exencephaly etiology and highlight the status of cortical progenitor cells that may be linked to the disorder.

Overview on neural tube defects: From development to physical characteristics

Neural tube defects (NTDs) are the second most common congenital malformations in humans affecting the development of the central nervous system. Although NTD pathogenesis has not yet been fully elucidated, many risk factors, both genetic and environmental, have been extensively reported. Classically divided in two main sub-groups (open and closed defects) NTDs present extremely variable prognosis mainly depending on the site of the lesion. Herein, we review the literature on the histological and pathological features, epidemiology, prenatal diagnosis, and prognosis, based on the type of defect, with the aim of providing important information based on NTDs classification for clinicians and scientists.

Acrania-exencephaly-anencephaly sequence phenotypic characterization using two- and three-dimensional ultrasound between 11 and 13 weeks and 6 days of gestation

The study presents a pictorial essay of acrania-exencephaly-anencephaly sequence using two-(2D) and three-dimensional (3D) ultrasonography, documenting the different phenotypic characterization of this rare disease. Normal and abnormal fetuses were evaluated during the first trimester scan. The International Society of Ultrasound in Obstetrics and Gynecology practice guidelines were adopted to standardize first trimester anatomical ultrasound screening. The guidelines outline the importance of systematic fetal head and brain examination including the formation of cranial bones, choroid-plexus and ventricles. Acrania-exencephaly-anencephaly sequence and/or other neural tube defects, such as meningoencephalocele, may be identified during a routine 11–14 week scan. Early first trimester detection of acrania-exencephaly-anencephaly sequence with the characterization of different related phenotypes, 2D and 3D ultrasound imaging as well as differential diagnosis are also presented in this pictorial essay. The main diagnostic ultrasound features of the disease may be characterized by findings of acrania with increased amniotic fluid echogenicity; “Mickey-Mouse” bi-lobular face, cystic, elongated, irregular and overhanging head morphology. Lightening techniques have also been added to 3D ultrasound to enhance anatomical details. Moreover, discordant amniotic fluid echotexture in the setting of twin pregnancies may be the first sign of acrania-exencephaly-anencephaly sequence. Extracranial malformations, aneuploidy and genetic syndromes associated with acrania-exencephaly-anencephaly sequence are also reported and described. First trimester neuroscan by an expert sonographer with appropriate training together with the application of standardized protocol are essential for a high detection rate of this rare type of neural tube defect malformation during a scan performed at 11 and 13 weeks and 6 days.

Pearls and pitfalls of early obstetric ultrasound in the acute setting

First trimester ultrasound is commonly performed to establish dates or evaluate early pregnancy complications. With improvement in ultrasound technology, visualization of fetal structures has improved. While the emergent evaluation does not typically focus on detailed fetal anatomic evaluation (since this is typically performed at 18-20 weeks), various fetal structural abnormalities can now be visualized, especially during the late first trimester and early second trimester. We present a pictorial review of potential pitfalls encountered in early obstetric ultrasound with an emphasis on fetal structural abnormalities as well as normal fetal anatomy that can be confused with developmental abnormalities.

Acrania-anencephaly associated with hypospadias. Prenatal ultrasound and MRI diagnosis and molecular folate metabolism pathway analysis

Acrania may occur as a single isolated malformation or associated with extracranial defects. Hypospadias is one of the most common congenital abnormalities of the genitalia frequently missed on prenatal sonograms. Second trimester two- and three-dimensional ultrasound and MRI diagnosis with necropsy and folate metabolism pathway analysis. The mechanisms leading to closure of both neural and urethral tubes, are far from being demonstrated, and molecular studies of this very rare association are lacking although it might be based on a common genetic mechanism, leading to a disturbed development pathway at the molecular level.

The eyes of anencephalic babies: a morphological and immunohistochemical evaluation

This study studied the eyes of three anencephalic stillborns to evaluate whether brain degeneration affected eye development and/or survival. The study encompassed histology, scanning electronmicroscopy, and immunocytochemistry. The corneae were otherwise normal except for the presence of blood vessels in the stroma and the posterior surface of the cornea demonstrated wrinkles. Synaechia was present and the lens had occasional vacuolated cells. The retinae had normal layers in most regions except the center where fibroblasts infiltration was observed. The optic nerve was atypical and composed of aggregates of disoriented fibroblasts and disoriented nerve fibers. Anti-cleaved caspase 3 immunocytochemistry revealed only few positive dying cells in the visual cell layer. Antineurofilament 200 reactions demonstrated positive ganglion cells even in the anencephalic eyes. The choroids in anencephaly had more VEGF positive sites, indicating vascularization in both control and anencephalic eyes. If the brains degenerate before retinal maturation, then such degenerations may not have an effect on subsequent retinal development except for the degeneration of the nerve fiber layer. If the brains degenerate after retinal maturation, then the survival of the retinae does not appear to rely on its linkage with the brain at birth, again apart from the degeneration of nerve fibers.

Prenatal sonographic diagnosis of acrania associated with amniotic bands

We describe the prenatal sonographic findings in 2 cases of amniotic band sequence-related acrania. In the first case, sonography demonstrated acrania, asymmetric facial clefts, and digital fusion on the hands and feet. In the second case, sonography demonstrated acrania and amniotic bands adhering to the brain, face, and body. This report highlights the importance of a careful search for amniotic bands and a detailed survey of the fetus' face, digits, and body in the sonographic evaluation of fetal acrania.

Abnormal fetal growth: intrauterine growth retardation, small for gestational age, large for gestational age

The two extremes of abnormal fetal growth are restricted growth and excessive growth, both of which originate from alterations in the uterine metabolic milieu. The fetus must adapt to these conditions to survive. In both instances, however, the inciting insult and the subsequent adaptation of the fetus carry long-term health consequences. In some instances, these changes may have generational implications. Counseling and care by pediatricians should be directed at the continuum of age ranges, including the expectant mother, the newborn, the child and adolescent, and future generations.

First-trimester echogenic amniotic fluid in the acrania-anencephaly sequence

OBJECTIVE

To describe the association between echogenic amniotic fluid and first-trimester fetal acrania.

METHODS

Nine fetuses with acrania were examined between 11 weeks' and 13 weeks 6 days' menstrual age for the presence of echogenic free-floating particles in the amniotic fluid. Cases were classified into 3 types according to the echogenicity of the amniotic fluid: similar to (type 0), slightly greater than (type 1), and clearly more echogenic than (type 2) that of the extracelomic fluid.

RESULTS

In 1 pregnancy, no free-floating particles were identified (type 0). In 6 cases, small free-floating particles scattered within the amniotic cavity were identified, making the amniotic fluid slightly more echogenic than the extracelomic fluid (type 1). In the remaining 2 cases, the amniotic fluid was homogeneously and clearly more echogenic than the extracelomic fluid (type 2).

CONCLUSIONS

A high percentage (89%) of fetuses with acrania had echogenic amniotic fluid, suggesting that this finding could potentially be used as a marker of fetal acrania in the first trimester. This finding also supports the hypothesis of the transition from acrania to anencephaly, with the unprotected brain undergoing progressive destruction from the first trimester, leading to the classic finding of anencephaly in the second trimester.

Ultrasound detection of first trimester malformations: a pictorial essay

Knowledge of normal and abnormal anatomy in the first trimester aids in early detection of anomalies and the avoidance of potential pitfalls.

Neural tube defects in missed abortions: embryoscopic and cytogenetic findings

Transcervical embryoscopy, a new technique for direct visualization of the first trimester conceptus was carried out in 116 cases of missed abortion. Embryonic neural tube defects and other localized developmental defects, were diagnosed in 10 out of 99 cases in which a complete embryoscopic evaluation was possible. All eight successfully karyotyped cases had a numerical chromosomal abnormality. A ninth unkaryotyped embryo with open spina bifida showed, on embryoscopy, a malformation pattern highly suggestive of triploidy. Our embryoscopic and cytogenetic findings provide valuable information for genetic counseling in future pregnancies.

Meningeal-cutaneous relationships in anencephaly: evidence for a primary mesenchymal abnormality

The pathogenesis of cranial and spinal dysraphia has been controversial. Studies of spinal dysraphia have shown that the relationships of the pia and dura to the cutaneous layers were best understood as the result of a primary abnormality of mesenchymal structures, with the nervous system lesions occurring as a result of exposure of the bare spinal cord on the body surface. This study was undertaken to determine if the relationship of the cutaneous layers in anencephaly were similar to those found in spinal dysraphia. We reviewed serial histologic sections of the cranial structures of 10 anencephalic fetuses autopsied at The Johns Hopkins Hospital. We found the dura to be continuous with the deep dermis and the pia continuous with the superficial dermis and epidermis, the same arrangement observed in myelomeningocele. The development of eyes and cranial nerves, the absence of a bony calvarium, and the meningeal-cutaneous relationships found in this study support the idea that anencephaly can originate as an abnormality of mesenchymal structures and that the brain is secondarily lost to injury in utero because of its exposed position.

Sonographic markers of exencephaly at 9 + 3 weeks of gestation

Following the introduction of transvaginal sonography, several first trimester diagnoses of the exencephaly anencephaly sequence have been reported, with the earliest being described at 10 weeks of gestation. We report a case with a high index of suspicion for exencephaly at 9 weeks and 3 days because of three sonographic features: the cranial pole of the embryo was smaller than the chest, the cranial pole bulged dorsally and the surface of the cranium was irregular. The diagnosis was confirmed by a repeat ultrasound examination at 11 + 4 weeks and by autopsy after termination of pregnancy.

Sonographic diagnosis of exencephaly: omphalocele at 11 weeks of gestation

This report presents a sonographic diagnosis of exencephaly combined with omphalocele at 11 weeks of gestation. The transvaginal ultrasound showed frog-eye appearance face with no skull, abnormal shape of disorganized brain with covering membrane separated from brain mass by anechoic fluid in some area, and omphalocele of 8 mm diameter. Therapeutic abortion was successfully done with misoprostol. Postabortal macroscopic findings confirmed the prenatal diagnosis. The combination of exencephaly and omphalocele is rare, and this is one of the earliest diagnosis of not only exencephaly but also omphalocele. To our best knowledge, this represents the earliest diagnosis of the combination. In conclusion, transvaginal ultrasound proved highly informative for both exencephaly and omphalocele as early as in first trimester.

Crooked tail (Cd) models human folate-responsive neural tube defects

Genetic correlation of human neural tube defects (NTDs) with NTD genes identified in mouse may unravel predisposing complex traits for assessment of individual risk and treatment in clinical settings. Folic acid (FA) can reduce the recurrence of NTDs in human populations by as much as 50-70%, though the mechanism of this rescue is unknown. We examined whether Crooked tail ( Cd ), a mouse strain prone to exencephaly, could provide a genetic animal model for folate-responsive NTDs. The Cd locus was localized to a 0.2 cM interval of the Mouse Genome Database genetic map, identifying tightly linked markers for genotyping prior to phenotypic expression. In a controlled diet study, Cd was found to mimic closely the clinical response to FA. FA supplementation reduced the recurrence risk of Cd exencephaly by as much as 55%. This rescue was dose dependent and did not require subjects to be inherently folate deficient. Like the female predominance of NTDs in humans, female Cd embryos were most likely to display exencephaly and were more responsive than males to the FA rescue. Importantly, FA supplementation shifted the severity of Cd phenotypic expression from early embryonic lethality to longer survival, and reduced the incidence of NTDs. The Cd locus is distinct from the known genes associated with neurulation defects, and isolation of this gene will assist identification of biochemical, genetic and gender-dependent factors contributing to folate-responsive NTDs.

Congenital anomalies in the teratological collection of Museum Vrolik in Amsterdam, The Netherlands. IV: closure defects of the neural tube

The Museum Vrolik collection of the Department of Anatomy and Embryology of the University of Amsterdam, founded by Gerardus Vrolik (1775-1859) and his son Willem Vrolik (1801-1863), consists of more than 5,000 specimens of human and animal anatomy, embryology, pathology, and congenital anomalies. Recently, the collection of congenital anomalies, comprising 360 specimens, was recatalogued and redescribed according to contemporary morphogenetic opinions. The original descriptions, as far as preserved, were compared with the clinical and additional findings. Based on the classification by closure site, proposed by Van Allen et al. [1993], the following closure defects of the neural tube were diagnosed in 107 specimens: craniorachischisis, holoacranium with partial rachischisis, faciocranioschisis, holoacranium, meroacranium, occipital cranioschisis, frontal encephalocele, parietal encephalocele, occipital encephalocele, occipital encephalocele with rachischisis, occipito-cervical encephalocele, thoracolumbar spina bifida, lumbosacral spina bifida, occult sacral dysraphism, and sacrococcygeal dysgenesis. Furthermore, we diagnosed three conditions that did not appear in the aforementioned classification; we named these conditions craniorachischisis totalis, occipital craniorachischisis, and thoracolumbosacral spina bifida. The results of our study are in line with the assumption that particularly occipito-cervical neural tube defects are associated with concomitant anomalies and are more common in females. The results support the idea of multisite closure of the human neural tube.

Central nervous system anomalies

The authors review the most common congenital anomalies of the central nervous system (CNS): neural tube defects (NTDs), ventriculomegaly/holoprosencephaly, hydranencephaly, holoprosencephaly sequence, iniencephaly, and microcephaly. They emphasize the importance of the diagnostic tools (biochemical markers of the maternal serum, ultrasound screening, invasive techniques), methods which are complementary to each other.

Prenatal Diagnosis of Exenceplhaly

Exencephaly is a rare congenital anomaly, thought to be a precursor of anencephaly. Like anencephaly, this abnormality is characterized by absence of the cranial vault above the orbits. However, unlike anencephaly, discrete, sometimes disorganized, brain tissue can be identified above the cranial defect. In this article, the authors report a case of exencephaly diagnosed prenatally during transvaginal ultrasound examination, with anatomic and pathologic correlation.

Fetal acrania: five new cases and review of the literature

Acrania is a lethal malformation in which there is an absence of the flat skull bones covering the brain. Five new cases are described, and a review of the English-language medical literature is presented. The sonographic differential diagnosis of acrania includes anencephaly, large cephalocele, osteogenesis imperfecta, and hypophosphatasia. The diagnosis of acrania can be established sonographically even in the first trimester if a large mass of disorganized brain tissue covered only by a thin membrane is detected.

Crown-chin length in normal and anencephalic fetuses at 10 to 14 weeks' gestation

OBJECTIVE

Our goal was to establish a reference range for the fetal crown-chin length at 10 to 14 weeks' gestation and to determine its usefulness in the prenatal detection of anencephaly in the first trimester.

STUDY DESIGN

Women attending our center for transabdominal ultrasonographic screening at 10 to 14 weeks' gestation were prospectively recruited for this study. The crown-chin length was measured in a sagittal view of the fetal head, which included the fetal profile, from the highest point of the head to the most anterior aspect of the jaw. Nomograms for the crown-chin length and the ratio of the crown-chin length to the crown-rump length according to gestational age were generated. Additionally, the crown-chin length and the ratio of the crown-chin length to crown-rump length were obtained from a subset of 13 anencephalic fetuses and plotted against the reference range.

RESULTS

In normal fetuses the crown-chin length increased (Crown-chin length = 65.2 x Gestational age in days - 28.4; r = 0.74%, p <0.0001) and the ratio of the crown-chin length to the crown-rump length decreased (Ratio of crown-chin length to crown-rump length -17.2 x Gestational age in days + 60.5; r = 0.23, p <0.0001) with advancing gestation. In anencephalic fetuses crown-chin length measurements and the ratio of the crown-chin length to the crown-rump length were below the 5th percentile in 77% and 62% of the cases, respectively. The slope of change in the ratio of the crown-chin length to the crown-rump length with gestational age was significantly different in anencephalic fetuses compared with normal fetuses (t = 2.7, p <0.003).

CONCLUSION

Measurement of the crown-chin length at 10 to 14 weeks' gestation provides a technique that can assist in the early recognition of anencephaly.

Exencephaly in autosomal dominant brachydactyly syndrome

Exencephaly was diagnosed at 17 weeks in a 27-year-old primigravida with abnormalities of the hands and a family history suggestive of autosomal dominant brachydactyly and clinodactyly. In this family there was also a history of 'anencephaly'. To our knowledge, this is the first report on the association of exencephaly and autosomal dominant brachydactyly. As the relationship between hand and cranial anomalies is well established, we suggest that this association in our case could be due to a defect in the same gene.

Prenatal diagnosis of central nervous system abnormalities

Fetal anomalies have been the subject of innumerable publications both in the prenatal and neonatal literature. This has significantly increased in the last 10 years, mainly because of the advent of high-resolution ultrasound equipment and improvement of scanning techniques. In addition, guidelines issued by professional organizations involved in prenatal diagnosis have encouraged a more universal approach to the imaging and documentation of prenatal findings. The fetal central nervous system is the most frequently investigated organ system, mainly because of its easy accessibility and prominence even in the early stages of embryologic development. The biparietal diameter was the first fetal measurement to be widely used in determining gestational age. As investigators gained more experience, the appearance of ultrasound images achieved the resolution that allows direct comparisons with gross specimens and more recent sophisticated techniques of computed tomography and magnetic resonance imaging. Now endovaginal ultrasound can document early first trimester development and compare it to known embryologic landmarks. Interest in demonstrating the ultrasound counterpart of central nervous system structures in the early stages of development has resulted in a plethora of articles proving the unique ability of ultrasound in imaging the developing fetus. In view of all these developments, the beginning ultrasound specialist is faced with the challenge and responsibility not only of being familiar with the literature but also of the mastery of scanning techniques that allow accurate prenatal diagnosis. It is therefore helpful to review key developmental milestones in embryologic life and correlate them with the corresponding prenatal ultrasound appearance. In addition, the changing appearance of the developing fetus has created a need for a systematic approach in the evaluation of structures so routine protocols can be established. This has been the subject of other publications that allow the novice to draw from the cumulative experience of different centers around the world. It is important to pay attention to the specifics described in the literature when duplicating results in one's laboratory. The frustration of not being able to reproduce results is common, especially when technical limitations prevent imaging under ideal conditions. This is especially true in patients who are first seen in the later third trimester with no prior prenatal care.(ABSTRACT TRUNCATED AT 400 WORDS)

Prenatal diagnosis of exencephaly

This paper presents a sonographic diagnosis of exencephaly made during the last trimester of gestation. The sonogram showed the absence of bones in the cranial vault together with the presence of a disorganized cerebral mass, with loss of its normal anatomy. Post-partum examination of the newborn confirmed the findings of the sonogram. We briefly review the characteristics of exencephaly, its aetiology, and its relationship to anencephaly.