1/5. 3D-reconstruction of craniofacial structures of a human anencephalic fetus. Case report.It was the purpose of this study to investigate the craniofacial bones, cartilages and major blood vessels of a human anencephalic fetus and to describe the malformations of these structures accompanying this developmental disruption. The head of a 16 week old human fetus with anencephaly was serially sectioned and the craniofacial bones, cartilages and major blood vessels were traced and reconstructed by 3D-computer technology. The sphenoidal, temporal and occipital bones showed severe malformations, whereas the bones of the facial cranium were normally developed. Both internal carotid arteries ended within the cerebro-vascular area with no further branches. The vertebral arteries also ended within the cerebro-vascular area. No arterial circle of willis was developed. The notochord terminated normally in the sphenoid body. The observations indicate that the possible reason for this malformation was non-closure of the anterior neuropore of the neural tube. The normal termination of the notochord suggests that it had no influence on the pathogenesis of this malformation. The malformations of the temporal and occipital bones are contradictory to the hypothesis of Marin-Padilla (1991) that anencephaly is caused by a maldevelopment of the sphenoidal bone.- - - - - - - - - - ranking = 1keywords = closure (Clic here for more details about this article) |
2/5. Heterotopic brain tissue in the submandibular region and lung. Report of two cases and comments about pathogenesis.Two cases of extracranial heterotopia of the brain are reported. Case 1, in an otherwise normal female baby, had a brain heterotopia in the submandibular region. Case 2, in a still-born female baby with anencephaly, had the heterotopia in the lung. The lesion in case 1 is believed to be an encephalocele that has been pinched off through a cleft in the bone or through a foramen of the skull; the pathogenesis is similar to that of the so-called "nasal glioma". Concerning the pathogenesis of case 2, contrary to the generally supported embolism theory, observation of serial sections of the tumor in the lung favors the aspiration theory according to which amniotic brain tissue fragments, which are dislocated into the amnion because of nonclosure of the ventricle or following destruction of the fetal brain, are aspirated by fetal respiratory movements in the 4th to 6th month of intra-uterine life.- - - - - - - - - - ranking = 1keywords = closure (Clic here for more details about this article) |
3/5. Clinical teratology counseling and consultation case report: two distinct anterior neural tube defects in a human fetus: evidence for an intermittent pattern of neural tube closure.Human neural tube closure is believed to be a continuous process that begins in the cervical region and progresses both rostrally and caudally. In contrast, an intermittent pattern of anterior neural tube closure has been demonstrated in rodents. Based on individual case photographs, a similar pattern of anterior neural tube closure, with multiple sites of closure, may also exist in humans. We report a human fetus with two distinct anterior neural tube defects separated by a cutaneous and mesenchymal bridge. The two defects occurred within distinct closure sites predicted by the murine model, one falling within closure II and the second within closure IV. Although one defect had adherent amniotic bands, evidence is presented to support a primary dysraphy rather than disruption from an amniotic band. This case provides further evidence supporting an intermittent pattern of anterior neural tube closure in human embryogenesis.- - - - - - - - - - ranking = 12keywords = closure (Clic here for more details about this article) |
4/5. Evidence for multi-site closure of the neural tube in humans.Four separate initiation sites for neural tube (NT) fusion have been demonstrated recently in mice and other experimental animals. We evaluated the question of whether the multisite model vs. the traditional single-site model of NT closure provided the best explanation for neural tube defects (NTDs) in humans. Evidence for segmental vs. continuous NT closure was obtained by review of our recent clinical cases of NTDs and previous medical literature. With the multi-site NT closure model, we find that the majority of NTDs can be explained by failure of fusion of one of the closures or their contiguous neuropores. We hypothesize that: anencephaly results from failure of closure 2 for meroacranium and closures 2 and 4 for holoacranium. Spina-bifida cystica results from failure of rostral and/or caudal closure 1 fusion. Craniorachischisis results from failure of closures 2, 4, and 1. Closure 3 non-fusion is rare, presenting as a midfacial cleft extending from the upper lip through the frontal area ("facioschisis"). Frontal and parietal cephaloceles occur at the sites of the junctions of the cranial closures 3-2 and 2-4 (the prosencephalic and mesencephalic neuropores). Occipital cephaloceles result from incomplete membrane fusion of closure 4. In humans, the most caudal NT may have a 5th closure site involving L2 to S2. Closure below S2 is by secondary neurulation. Evidence for multi-site NT closure is apparent in clinical cases of NTDs, as well as in previous epidemiological studies, empiric recurrence risk studies, and pathological studies. Genetic variations of NT closures sites occur in mice and are evident in humans, e.g., familial NTDs with Sikh heritage (closure 4 and rostral 1), Meckel-Gruber syndrome (closure 4), and walker-warburg syndrome (2-4 neuropore, closure 4). Environmental and teratogenic exposures frequently affect specific closure sites, e.g., folate deficiency (closures 2, 4, and caudal 1) and valproic acid (closure 5 and canalization). classification of NTDs by closure site is recommended for all studies of NTDs in humans.(ABSTRACT TRUNCATED AT 400 WORDS)- - - - - - - - - - ranking = 24keywords = closure (Clic here for more details about this article) |
5/5. anencephaly and faciocranioschisis: evidence of complete failure of closure 3 of the neural tube in humans.We report on a patient with median cleft of face and anencephaly as apparent consequence of delayed closure of the most rostral end of the neural tube. No other structural anomalies were found. To our knowledge, this child represents the first description of an isolated and complete failure of closure 3 of the neural tube and supports the hypothesis of a multi-site model of neural tube closure in humans.- - - - - - - - - - ranking = 7keywords = closure (Clic here for more details about this article) |