[Embryo-pathogenic considerations and clinico-radiologic aspects of an enterogenous caudal cyst]

This is a description of a rare intestinal malformation. The authors consider the theories for development of gastrointestinal duplications and emphasize for the underscribed abnormality seen in a female infant the embryology of the tailgut and neuroenteric canal.

[A case of cervical intramedullary neurenteric cyst]

A case of cervical intramedullary neurenteric cyst was reported. A 12-year-old girl was admitted with severe pain over the nape and shoulders, and weakness of all extremities. At the age of 4 years, she had suffered from the nape pain and paraparesis which, however, cleared later spontaneously. Neurological examination revealed evidences of presumptive cervical intramedullary lesion, and myelography showed a complete block at the third cervical level accordingly. Surgical exploration through C3-C5 laminectomy disclosed an intramedullary cyst situated within the right half of the cord. The cyst was removed except for its upper and lower apices. Excellent clinical results followed the operation. The cyst was composed of collagen fibers with an inner epithelial lining, which consisted of single or pseudostratified layer of columnar, cuboidal or squamous cells. Cells were ciliated at some parts. The base of the epithelial cells rested upon the basement membrane. Nuclei were positioned near the base of the cells, to present a row. The cytoplasm in the majority of cells contained abundant mucin positive to PAS staining. Pathological diagnosis of neurenteric cyst was made on the basis of these histological findings. Usually intraspinal neurenteric cyst is located in the subarachnoid space and ventrally to the spinal cord. Neurenteric cyst appears histologically similar to ependymal cyst, though, in the latter the epithelial cells seldom contain mucin, and only in scanty amount, if any present. Embryogenesis during the third week of embryonic life was discussed in relation to the development of neurenteric cyst.

Comparative teratogenic effects of methyl salicylate applied orally or topically to hamsters

Methyl salicylate was administered topically to pregnant hamsters at 7d9h and the teratogenic results were compared with those obtained following oral treatment with the same compound. Both treatments produced the same defect in embryos recovered at day 9: failure of fusion of the neural tube, especially in the area of the developing brain. Analysis of serum salicylate levels following both treatments produced similar curves and indicated that teratogenic levels of salicylate can reach the maternal circulation after topical exposure.

Regrowth of diastematomyelic bone spur after extradural resection. Case report

Complete regrowth of a diastematomyelic bone septum producing progressive neurological deficits was found in a 15-year-old boy who had a previous extradural resection of a similar bone spur with the dural sleeve left untouched. This case and two similar cases in the literature documenting continued neurological deterioration after extradural removal of septum emphasize the need for resection of the dural sleeve along with the bone septum if adequate relief of tethering is expected. The capability of the septum to regenerate may be due to the persistence of residual mesenchymal cells associated with the embryogenesis of the midline septum.

[Dermoid and dermal sinus]

We report on a case of dermoid and asymptomatic dermal sinus both occurring in an 18-year-old man, a monozygotic twin.

Chromosome translocation (T(2;4)1 Sn)-induced neural tube defects in the mouse embryo

Neural tube closure was studied in embryos obtained from matings of male mice heterozygous for a reciprocal chromosome translocation (T(2;4)1 Sn) with normal female (CFLP) mice. When litters were examined on the 9th to 12th days of gestation, there was a high incidence of resorption, developmental delay and neural tube closure defects in these embryos. SEM observations indicated that the neural tube closure defects ranged in severity from a side-to-side flattening of the midbrain to extensive anomalies in which the entire cephalic neural tube had failed to close. In addition to cephalic defects, a number of embryos exhibited open defects or abnormal subectodermal blebbing in the future lumbosacral region. In spinal regions, even in areas in which the neural tube had previously closed, it often was irregular and folded. These observations are discussed in relation to studies of gene-related defects of neural tube closure.

Anomalies of neuroepithelial cell associations in the Splotch mutant embryo

Neuroepithelial development in Splotch mutant mouse embryos was examined using SEM and TEM. Unlike unaffected littermates, Sp/Sp embryos exhibited extensive neural tube closure defects, disorganization and misalignment of neuroepithelial cells in regions with open defects. Neuroepithelial cell processes often made lateral progress in these areas rather than maintaining their normal contact with the luminal surface. In addition, intercellular space was considerably increased and there were many ectopic cell processes in basal regions of affected areas. The role of altered cell-cell interactions in neurulation is considered.

Transfer of chromic chloride to embryonic mice and changes in the embryonic mouse neuroepithelium

Transfer of CrCl3 to embryonic mice and changes in the embryonic mouse neuroepithelium associated with Cr-induced neural tube defects were studied. A single intraperitoneal injection of 51CrCl3 was administered on the 8th day of gestation and animals were killed at various intervals for measurements of radioactivity in the maternal blood and embryos. Radioactivity per gram of fetal tissues increased during the observed period, while those of maternal blood decreased. Pregnant mice were injected intraperitoneally with a single dose of CrCl3 (non-radioactive) on the 8th day of gestation. Animals were killed at specified times after injection and embryos were removed and examined histologically. At 4, 8 and 12 h after injection many pyknotic cells were observed on the neural plate, especially at 8 h after injection. These data suggest that CrCl3 may affect embryos directly and cause neural tube defects and that pyknotic cells on the neural plate may be an early pathological finding in cases of developing exencephaly.

Analysis of the effects of Streptomyces hyaluronidase on formation of the neural tube

Chick embryos at stages 8 to 9 were treated in ovo with Streptomyces hyaluronidase (SH) to determine whether neurulation occurs normally in embryos depleted of hyaluronic acid, a major component of the extracellular matrix. Open neural tube defects occurred in 60-94% (depending on the particular enzyme batch) of the embryos treated with SH and examined after an additional 24 h of incubation. Defects were confined mainly to the spinal cord. The neural folds underwent elevation in defective regions but failed to converge and fuse across the dorsal midline. The extracellular matrix of embryos treated with SH was depleted consistently, as determined with sections stained with Alcian blue. Control experiments were done to ensure that neural tube defects were not caused by non-specific protease contamination of SH, or by digestion products of hyaluronic acid. We propose several plausible and testable mechanisms through which the extracellular matrix might influence the complex developmental process of neurulation.

Neural tube defects: clinical correlations

There are several approaches that can be applied to the analysis of malformations of the CNS. One practical way in making clinical correlations is to divide neural tube defects into those that arise during the period of neurulation and those that arise thereafter. This concept applies to cranial and spinal lesions and makes it possible to interpret clinical findings with embryological events. Malformations of the CNS that arise during the period of neurulation are not covered by skin and can be diagnosed prenatally by amniocentesis. Postneurulation CNS malformations are skin-covered and have differing patterns of associated malformation and etiologies. There is an overlap of the latter group with congenital tumors, and for the most part these malformations are not apt to be diagnosed prenatally.

Possible mesodermal origin for axial dysraphic disorders

We report four patients who provide clinical evidence supporting the hypothesis that axial dysraphic states may result from a primary disturbance in the chordoaxial mesoderm. One infant had complete craniorachischisis, an omphalocele, and ambiguous genitalia. A second infant had anencephaly and an omphalocele. The third had iniencephaly. The fourth had cervical vertebral fusion defects, an occipital menigocele, and a laterality malformation sequence. Alteration in the development of structures derived from the chordoaxial mesoderm could explain all of the structure defects observed in the four patients. This hypothesis accounts for the nature of the defects seen in association with dysraphic disorders and for the genetic relationship observed between neural tube defects and vertebral anomalies.

Scanning electronmicroscopy of experimental anencephaly development

The scanning electronmicroscope was used to study the development of anencephaly in an experimental model. Anencephaly was produced consistently, using vitamin A as the teratogen. Embryos destined to become anencephalic displayed failure of opposing sides of the rostral neural tube to fuse. Subsequently, the neural folds of the experimental embryos progressively curved laterally away from the midline, whereas the neutral folds of the control embryos fused in the midline by day 12. The anlage of the choroid plexus could be identified on the surface of the everting brain folds as early as gestational day 13. Thus, the abnormal eversion of the neural tube occurred before development of the choroid plexus. This study supports the view that anencephaly ultimately results from neural tube nonclosure.

Nasal dermal sinuses--new concepts and explanations

Utilizing a series of 13 consecutive patients with nasal dermal sinus-cyst (NDSC) as a basis for study, this area of embryopathology was re-examined in light of the known and also the speculative knowledge available. Four of these patients had NDSC that involved the intracranial cavity and these served as a basis for correlating preoperative radiologic findings with what was actually found at the time of surgery. In so doing, we have been able to show that the pathogenesis of these lesions is consistent and the predictability of their intracranial involvement is based on this consistency. The repeated penetration through the prenasal space and into the foramen cecum is accompanied by a characteristic deformity of the base of the skull that is entirely recognizable radiographically. A protocol of findings has been developed, therefore, that allows the surgeon to be forewarned regarding the depths to which NDSC extends, and as such to design the surgical procedure to fit the lesion. The more basic findings for this study relate to the demonstration in human embryos of an anatomic reason why intracranial dermal cysts grow in the manner in which they do, i.e., in the substance of the falx cerebri; and even more basically, with additional human embryo studies we have been able to demonstrate a neuroectodermal pathway through the prenasal space, thus definitively confirming previous speculated embryomorphologic information. By corroborating the placement of the dermal displacement in the prenasal space, we have speculated that the NDSC is often but one disorder in a spectrum of aberrations which involves not only dermal and neural displacement, but also cranial floor deformities.

Neural tube development in mutant (curly tail) and normal mouse embryos: the timing of posterior neuropore closure in vivo and in vitro

A dye-injection technique has been used to determine the developmental stage at which posterior neuropore (PNP) closure occurs in normal and mutant curly tail mouse embryos. In vivo, the majority of non-mutant embryos undergo PNP closure between 30 and 34 somites whereas approximately 50% of all mutant embryos show delayed closure, and around 20% maintain an open PNP even at advanced stages of development. A similar result has been found for embryos developing in vitro from the headfold stage. Later in development, 50--60% of mutant embryos in vivo develop tail flexion defects, and 15--20% lumbosacral myeloschisis. This supports the view that delayed PNP closure is the main developmental lesion leading to the appearance of caudal neural tube defects in curly tail mice. The neural tube is closed in the region of tail flexion defects, but it is locally over-expanded and abnormal in position. The significance of these observations is discussed in relation to possible mechanisms of development of lumbosacral and caudal neural tube defects. This paper constitutes the first demonstration of the development of a genetically induced malformation in vitro.

Amniotic and maternal serum alpha-fetoprotein levels of rats with induced neural tube defects

During the complete fetal period alpha-fetoprotein (AFP) was quantified in maternal sera and amniotic fluid from control, hypervitaminosis A and trypan blue treated normal rat fetuses, and from exencephalic and spina bifida aperta fetuses. The occurrence of histologic proven open neural tube defects was associated with amniotic fluid AFP levels that were much elevated over those of control and treated normal fetuses and those with closed neural tube defects at nearly the whole fetal period. In combining these results with the earlier reported morphologic data of the same rat fetuses as used in the present study, it is concluded that the elevation of amniotic AFP is caused by leakage of fetal serum through a disrupted and necrotic nervous tissue into the amniotic fluid. This experimental model of induced neural tube defects results in increase of amniotic fluid AFP levels similar to those found in human amniotic fluid in the presence of neural tube defects.

A review of congenital neurologic malformations

Congenital neurologic malformations present a difficult challenge to the clinician in regard to diagnosis, management, and prevention. The authors review normal ontogenesis and divide this complex process into three developmental phases: (1) induction, (2) cellular proliferation and migration, and (3) maturation of cellular organization, synaptic development, and myelin formation. A classification of malformations based on the timing of occurrence during the first and second stages of central nervous system development is presented. These disorders are described with particular attention to the clinical and diagnostic features. Various prenatal diagnostic screening tests are also reviewed in an attempt to identify the population at risk for congenital neurologic malformations.

Neurenteric cysts of the spinal cord mimicking multiple sclerosis

A 54-year-old man died following a 20-year course of intermittent neurologic symptoms. He carried a diagnosis of multiple sclerosis, with most severe involvement thought to be in the spinal cord. At autopsy, two neurenteric (enterogenous) cysts were found to indent the anterior spinal cord -- at the T4 and T11 cord levels. Partial diplomyelia was present in the lumbo-sacral cord. These findings represent a unique combination of congenital abnormalities. Their embryogenesis and pathogenesis are discussed.

Effect of acetaldehyde on the neuroepithelium of early mouse embryos

Female mice were injected intravenously with acetaldehyde on single (seventh, eighth or ninth), or on multiple (sixth to eighth, seventh to ninth) days, and examined on the tenth or twelfth day of gestation. Exposure to acetaldehyde on multiple days resulted in high incidence of embryonic resorptions. However, when females were injected on single days and examined on the tenth day, a high incidence of neural tube defects was encountered in surviving embryos. The neural tube anomalies were located at a number of sites along the neuraxis. When examined by scanning electron microscopy, the individual neuroepithelial cells in acetaldehyde-treated embryos exhibited a characteristic rounded-up appearance with small surface blebs and spiny processes. These characteristic cell surface features were seen in acetaldehyde-treated embryos at all stages of development examined. When additional females were examined on the twelfth day, a much lower incidence of open neural tube defects was observed. When embryos at this stage of development were examined in more detail by SEM, many had numerous subectodermal blebs along the dorsal mid-line, which were not initially apparent on gross inspection. The neuroepithelial morphology was also found to bae abnormal in embryos with no obvious external anomalies. The results confirm and elaborate on previous observations on the teratogenicity of acetaldehyde, stressing the ultrastructural changes that are induced in the cells of the neuroepithelium, and the possible relationship between the damage induced by this agent and certain features of the fetal alcohol syndrome.

Embryogenesis and prenatal development of congenital vertebral anomalies and their classification

Vertebral anomalies were studied in 144 patients. The specific anatomic defects were defined by serial roentgenograms: anterior approaches were used in 42 operations and posterior approaches in 74 operations. Growth features of the spine were examined histologically in 15 embryos and fetuses ranging in length from 6 to 120 mm. After an extensive review of the literature on normal human spine embryology and fetal development, and after defining the specific vertebral anatomic defects and their pathogenesis, some new concepts of congenital vertebral anomalies formation are proposed. Old concepts are found to be inadequate in light of our current knowledge of embryogenesis. The authors' new and all-inclusive classification of congenital vertebral anomalies is based on specific defects, pathogenesis, and time for origin in embryonic or fetal development.

The effects of cytochalasins on the ultrastructure of neurulating hamster embryos in vivo

Single intraperitoneal injections of cytochalasin B (CB) in dimethylsulfoxide were given to gravid Syrian hamsters on the eighth day of pregnancy at various dose levels. Exencephaly and encephalocele, the only defects which were seen in the term litters, occurred in dose-response patterns reaching peak frequencies of 14.9% and 53.2%, respectively, at the highest dose level, while accompanied by a mortality of 27.7% of implantations. Although these abnormalities were the same as those resulting from cytochalasin D (CD) treatment at this time, the frequencies were lower and the distribution of defects somewhat different. Morphological comparison of embryos fixed at various times after maternal treatment with 7.0 mg/kg CB or 1.5 mg/kg CD demonstrated qualitatively similar changes in response to either teratogen, leading to failure of the cranial neural folds to approximate and close. The principal ultrastructural changes involved alterations in the topography of the apical membranes of neuroectoderm cells. At doses which produced high frequencies of gross defects in the term litters, no changes were seen in the apical bundles of microfilaments in these cells, although much higher dose levels did disrupt these structures. The results support the hypothesis that the cell membrane is the primary target of these teratogens in vivo.

Anomalies of heart, spleen, kidneys, gut, and limbs may result from an overdistended neural tube: a hypothesis

A hypothesis is advanced that many congenital anomalies of non-neural organs may be produced by damage to their mesodermal or entodermal anlagen caused by overdistention of the embryonic neural tube. Evidence to support the hypothesis derives from: (1) seldom appreciated but unequivocal embryologic facts about prechoroid plexus neural tube morphogenesis; (2) an understanding of the role of neural tube overdistention in the production of various dysraphic conditions; (3) the frequency of association of non-neural anomalies with dysraphic conditions; and 4) an analysis of the anatomic features of the organ anomalies associated with dysraphism. The practical utility of the hypothesis is that (1) it helps explain a seemingly widely divergent subset of phenomenology and (2) it is testable. At present, treatment of children with congenital anomalies is largely palliative. Prevention of these distressing defects in the future will only be realizable if the mechanisms of their genesis are more clearly understood.

Neural tube defect discovered at routine ultrasound evaluation

A case is presented in which a major CM was discovered during routine ultrasound evaluation. Radiographic techniques offered ancillary assistance in establishing the diagnosis. With more frequent use of ultrasound in obstetrics, investigators must be constantly alert to the possibility of anatomic defects that may be identifiable, particularly in high-risk situations.

Development of the cerebrospinal fluid pathway in the normal and abnormal human embryos

The subarachnoid space, the chorioid plexus and the arachnoid villi are microscopically studied in 60 normal human embryos and in 3 abnormal human embryos with rhombencephaloschisis and cervical myeloschisis. The subarachnoid space has been generally considered to be developed by outflow of cerebrospinal fluid (CSF) of the choroid-plexus origin from the IVth ventricle. This generally accepted concept does not meet with our findings: (1) cavity formation in the meninx primitiva is seen before appearance of the choroid plexus; (2) the primitive subarachnoid space is developed earlier in the prepontine region than in the area dorsal to the rhombic roof, and (3) the primitive subarachnoid space is formed in the embryos with dysraphism where the perineural subarachnoid space is separated from the ventricles. Apparently the embryonic pattern of CSF circulation should be much different from the generally believed pattern of adult, since the arachnoid villi are absent in the embryos and the ability of production of CSF in the embryonic choroid plexus is questionable. It is suggested that such embryonic pattern of CSF production and absorption may partly persist in adult human being.

Neural tube defects in curly-tail mice. II. Effect of maternal administration of vitamin A

Vitamin A, a known teratogen of the central nervous system, was administered in various doses, at the time of active neural tube closure, to pregnant curly-tail mice which have a genetic predisposition to neural tube defects (n.t.d.), and to A Strong mice, which are not so predisposed. The curly-tail mice showed an enhanced susceptibility to the teratogenic effect of vitamin A given on day 8 of gestation, demonstrating a clear gene-environment interaction. There was a differential response by the two sexes. Females seemed to be more affected by the vitamin A than males. When vitamin A was administered on day 9, instead of day 8, of gestation, the incidence of n.t.d. decreased rather than increased. Furthermore, the number of mice affected by n.t.d. was markedly lower even than that found spontaneously in untreated curly-tail mice.

Gap junctional vesicles in the neural tube of the splotch (Sp) mutant mouse

The lumbosacral region of the neural tube was studied by means of transmission electron microscopy in retrospectively confirmed normal (+/+; Sp/+) and abnormal (Sp/Sp) embryos of the splotch mutant mouse early on the ninth day of gestation when the caudal neural groove is normally in the process of closing to form the neural tube. In abnormal embryos, a consistent feature is the presence of gap junctional vesicles, particularly in the region of the neural groove which subsequently fails to close, whereas these structures are rarely observed in similar areas of normal embryos. The possible significance of gap junctional vesicles is discussed in terms of cellular adhesion during early neurogenesis.

Light microscopic and ultrastructural observations in advanced stages of induced exencephaly and spinal bifida

This investigation was performed to demonstrate the morphologic basis of the elevation of fetal proteins in the amniotic fluid of fetuses with neural tube defects. Pregnant rats were treated with hypervitaminosis. A to induce exencephaly or with trypan blue to produce spina bifida aperta. The malformations were studied on days 15-20. On day 15 of gestation, edema developed in the primitive nervous tissue. This was followed by the appearance of quickly expanding hemorrhages throughout the ventricular and intermediate zones. Some capillaries did not rupture but collapsed and showed degenerative changes of the endothelium, probably due to lack of blood perfusion. The ventricular layer in exencephaly and spina bifida aperta was exposed to the amniotic cavity due to non closure of the neural tube. On day 17, this superficial lining of the primitive nervous tissue was disrupted by the expanding hemorrhages and subsequent necrosis. As a result vast amounts of fetal blood and cell debris were extruded into the amniotic fluid. During days 18 to 20, the degeneration of the nervous tissue proceeded rapidly. This process showed the same features in the ventricular cells, the primitive neurons and the neurons. Initially it was characterized by condensation of the nuclear chromatin and the cytoplasm, irregular outlines and breakdown of the plasma membrane. Only part of the cell debris was phagocytozed by macrophages. It is concluded that the leakage of fetal serum and cell debris causes the elevation of fetal protein levels in the amniotic fluid of fetuses with open neural tube defects.

Skin abnormalities of the back in diastematomyelia

The presence of congenital skin abnormalities on the back may be associated with a serious underlying spinal anomaly, diastematomyelia. The significance of the progressive development of neurological deficits, due to the presence of a bony or cartilaginous spur in the spinal cord, is stressed. An awareness of this condition should lead to an early diagnosis with a neurological evaluation and, if necessary, prophylactic surgery before irreversible nerve damage develops.

Myelomeningocele before birth

The authors report a study of 92 human embryos and four fetuses with myeloschisis. The characteristics of embryonic myeloschisis compared with spina bifida cystica in infants are: 1) the lesion is often more diffuse, involving the whole spinal cord (12 embryos); 2) the cervical cord is frequently affected (23 of the remaining 80 embryos); 3) holoprosencephaly is frequently associated (18 embryos); 4) meningocele is not found; and 5) hydrocephalus and Arnold-Chiari malformation are not yet developed. Hydrocephalus and Arnold-Chiari malformation are found in myeloschistic fetuses. Almost all embryos with diffuse and cervical myeloschisis or with holoprosencephaly are extruded before birth by spontaneous abortion. Absence of meningocele in the embryonic period implies that its appearance is deferred to the fetal period. The development of hydrocephalus and Arnold-Chiari malformation also seems to be delayed until the fetal period. Our observation implies that myelomeningocele is induced by non-closure of the neural tube, not by rupture once it was closed. "Neural overgrowth" and disturbed "recanalization process" are discussed in relation to the pathogenesis of myelomeningocele.