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At least 19 recordsLinked to original sources
PubMed1992

The thymic findings in stillborns with neural tube defects.

Neural tube defects are among the most common congenital anomalies causing perinatal deaths. Other organ system anomalies may be associated with neural tube defects: for instance, various types of thymus pathology have been reported in these patients. In this study thymic changes were investigated in 30 stillborns with neural tube defects seen between January 1988 and June 1989. Thymic weights were significantly reduced in 14 cases and increased in 7. One patient had a double thymus, and in two cases no thymus tissue could be found. These findings suggest a primary developmental defect of the neural crest, affecting the orderly development of the thymus gland.

Female↗
PubMed1992

Is there etiologic heterogeneity between upper and lower neural tube defects?

Neural tube defects are thought to arise from two different embryologic mechanisms depending on the level of the defect: neurulation defects associated with anencephaly and upper spina bifida and canalization defects associated with lower spina bifida. To investigate whether the risk profiles of neural tube defect cases differ according to the level of the defect, the authors examined data from the Atlanta Birth Defects Case-Control Study. Cases were infants live- or stillborn from 1968 to 1980 with these defects, and controls were infants without defects randomly selected and frequency matched to cases by race, birth year, and hospital of birth. By multivariate polychotomous logistic regression, 1,186 controls were compared with cases: 145 with anencephaly, 59 with upper spina bifida (cervical/thoracic lesions), and 100 with lower spina bifida (lumbar/sacral lesions). Infant's sex and sibling recurrence of neural tube defects were the only factors for which the case subgroups significantly differed in risk. The risks associated with selected maternal exposures during the first trimester of pregnancy did not differ among the case subgroups. Although these results do not support the concept that upper and lower neural tube defects differ in risks from exogenous factors, differences in sibling recurrence and in risks by sex between the two groups suggest an underlying heterogeneity in genetic susceptibility factors.

Anencephaly↗
PubMed1986

Ultrastructural analysis of chromosome translocation-induced neural tube defects.

Neural tube closure defects occurred in 33% of the embryos obtained from matings of male mice heterozygous for a reciprocal chromosome translocation (T(2;4)1Sn) with normal female CFLP mice. Light and electron microscopic observations of neuroepithelium and mesenchyme in affected embryos indicated two distinct types of anomalies occurred. The first consisted of neuroepithelial hypertrophy and neural tube closure defects. These defects most frequently affected the midbrain and hindbrain, but occasional defects of the lumbosacral neural tube were also observed. Unlike the highly organized, pseudostratified neuroepithelium in control embryos, neuroepithelial cells became stratified and formed cell islands with secondary lumina within the wall of the neural tube. The second condition was associated with a reduction in neuroepithelial thickness, considerable neuroepithelial and neural crest cell death, basal lamina alterations and premature invasion of the neuroepithelium by subjacent endothelial cells. In both cases, the cephalic mesenchyme cells, rather than their normal stellate appearance, were markedly elongated in shape and reduced in area. The number of cell-cell contacts between mesenchymal cells was also reduced significantly. These results are discussed in light of recent theories regarding the role of mesenchyme and extracellular matrix in neurulation.

Animals↗
PubMedDate not supplied

Neural tube defects.

Neural tube defects (NTDs) are a group of malformations of the brain and spinal cord that originate at various times during gestation. The most common NTDs are anencephaly and meningomyelocele, which arise during the process of neurulation, a well-defined period between the 17th and 30th day after ovulation. These NTDs are clinically apparent by being open, ie, leaving nervous tissue exposed, in contrast to postneurulation NTDs that are skin covered. The incidence of NTDs is declining in several areas of the world, including the United States. While the reasons for this are unclear, there seems to be some effect from prenatal diagnosis, genetic counseling, and possibly nutritional supplementation.

Gestational Age↗
PubMed1985

Sonography, a complementary examination to alpha-fetoprotein testing for fetal neural tube defects.

Neural tube defects (NTDs) are among the most common congenital anomalies in the United States, with an estimated prevalence of 16 per 10,000 births. The measurement of amniotic fluid alpha-fetoprotein (AF-AFP) concentration has been used to detect NTDs since the early 1970s. When the AF-AFP concentration is elevated, ultrasonography is commonly used to confirm the presence of a NTD. In this study, patient charts, amniocentesis records, and ultrasound reports from a three-year period were reviewed. The 97 fetuses identified as being at high risk for NTDs were divided into four groups: those with high AF-AFP concentrations (Groups 1 and 2, with from 3 to 5 standard deviations (SD) above the mean and with more than 5 SD above the mean, respectively): those referred from other institutions because of suspicious sonographic results (Group 3); and those at risk because of a previous sibling with a NTD (Group 4). Ultrasonography was 100 per cent sensitive and 100 per cent specific in diagnosing NTDs. Thus, in pregnancies with an elevated AF-AFP concentration, ultrasonography can reliably identify normal fetuses as well as differentiate between those with NTDs and those with other congenital anomalies. Also, since AF-AFP concentrations decline after 20 weeks' gestation, ultrasonography may be a better test than a repeat amniocentesis in equivocal cases of AF-AFP elevation.

Adult↗
PubMed1992

Neural tube defects without neural crest defects in splotch mice.

Homozygous Splotch mutant mice (Sp/Sp) die on day 14 of gestation with neural tube defects, curly tail, and malformations of neural crest derivatives. Sp1H mice, which have a radiation-induced allele of Splotch with a similar phenotype, were used for this study. The neural tube defects are always located in the lumbosacral region and in 50% of the cases also in the region of the hindbrain. In this report, rare cases of neural tube defects and tail defects among the offspring of crosses between Splotch (Sp1H) heterozygotes are presented, which are not associated with a neural crest defect. This suggests that the development of the neural tube and neural crest defects in this mutant is caused by independent mechanisms or is dependent on the dosage of the mutant gene, with different thresholds being pathogenetic in the neural tube and neural crest, respectively.

Abnormalities, Multiple↗
PubMed1986

Neural tube defects: a review of human and animal studies on the etiology of neural tube defects.

Although neural tube defects are a common congenital anomaly, their etiology is not known. Human studies have emphasized the pathology and epidemiology of the defects and suggest that in the majority of cases the etiology is multifactorial. Factors which appear possibly to be important are genetic predisposition, maternal illness, and fetal drug exposure. Animal studies have utilized naturally occurring neural tube defects and teratologically induced lesions. No animal model has been convincingly established as the equivalent of human neural tube defects. However, animal models have allowed investigation of the mechanisms of suggested human teratogens and determination of the pathogenesis of naturally occurring animal defects. Their most important contribution has been in furthering the understanding of the normal mechanisms of neural tube closure. It may be through this understanding that the etiology of human neural tube defects will be determined.

Animals↗
PubMed1991

Use of folic acid for prevention of spina bifida and other neural tube defects--1983-1991.

Neural tube defects--including spina bifida, anencephaly, and encephalocele--are common, serious birth defects that are important causes of infant mortality and disability. Women in the United States who have had a pregnancy resulting in an infant or fetus with a neural tube defect have a 2%-3% risk for having another pregnancy resulting in an infant or fetus with a neural tube defect (i.e., a recurrence) The British Medical Research Council (MRC) Vitamin Study Group recently reported the results of a randomized prevention trial that indicated that daily oral supplementation with folic acid before conception and during early pregnancy substantially reduces the recurrence of neural tube defects. This report summarizes the findings of that study and provides recommendations for supplementation with folic acid to prevent the recurrence of neural tube defects.

Anencephaly↗
PubMed1989

The absence of a relation between the periconceptional use of vitamins and neural-tube defects. National Institute of Child Health and Human Development Neural Tube Defects Study Group.

Whether taking multivitamins or folate around the time of conception can reduce a woman's risk of having a child with a neural-tube defect is controversial. To investigate this question, we examined the periconceptional use of vitamin supplements by women who had a conceptus with a neural-tube defect (n = 571), women who had had a stillbirth or a conceptus with another malformation (n = 546), and women who had had a normal conceptus (n = 573). Women with conceptuses with neural-tube defects were identified either prenatally or postnatally and were matched to control mothers for gestational age. To minimize recall bias, we interviewed nearly all the women within five months of the diagnosis of a birth defect or the birth of the infant (mean, 84 days); information on vitamin use was obtained by an interviewer who was unaware of the outcome of pregnancy. The rate of periconceptional multivitamin use among the mothers of infants with neural-tube defects (15.8 percent) was not significantly different from the rate among mothers in either the abnormal or the normal control group (14.1 percent and 15.9 percent, respectively). After adjustment for potential confounding factors, the odds ratio for having an infant with a neural-tube defect among women classified as having had full supplementation with multivitamins was 0.95 as compared with the mothers of the abnormal infants (95 percent confidence interval, 0.78 to 1.14) and 1.00 as compared with the mothers of normal infants (95 percent confidence interval, 0.83 to 1.20). There were no differences among the groups in the use of folate supplements. The adjusted odds ratio for having an infant with a neural-tube defect among those receiving the recommended daily allowance of folate was 0.97 as compared with the mothers of abnormal infants (95 percent confidence interval, 0.79 to 1.18) and 0.98 as compared with the mothers of normal infants (95 percent confidence interval, 0.80 to 1.20). We conclude that the periconceptional use of multivitamins or folate-containing supplements by American women does not decrease the risk of having an infant with a neural-tube defect.

Adult↗
PubMed1986

Strain differences in heat-induced neural tube defects in mice.

Neural tube defects are common congenital anomalies affecting approximately 0.1% of liveborn infants. It is widely accepted that these disorders are of a multifactorial origin, having both a genetic and an environmental component to their development. In a study designed to elucidate the genetic factors involved in a mouse model of hyperthermia-induced neural tube defects, it is apparent that a hierarchy of susceptibility exists among various inbred mouse strains. Female SWV mice were extremely sensitive to a 10-minute hyperthermic treatment on day 8.5 of gestation, with 44.3% of their offspring having exencephaly. The other strains used in these studies (LM/Bc, SWR/J, C57BL/6J, and DBA/2J) all had less than 14% affected offspring. In experimental situations where the environment is held constant and the only difference between the strains is their genotype, it is assumed that the difference in response to a teratogen is genetically mediated. To test the hypothesis that several genes are involved, reciprocal crosses were made between strains of high, moderate, and low sensitivity. When this was done, the high sensitivity of the SWV strain was lost in the F1 hybrid, implying not only that multiple genes are involved, but that it is the embryo's genotype and not the maternal genotype that is the major factor in determining susceptibility to heat-induced neural tube defects.

Animals↗
PubMed1990

The pattern of neural tube defects created by secondary reopening of the neural tube.

The usual location of human neural tube defects at the rostral or caudal end of the primary neural tube suggests they are caused by failure of closure of the neural tube. In this study, neural tube defects were created by surgical reopening of the neural tube of 3-day-old duck embryos in one of three sites: the forebrain, cervicothoracic region, or thoracolumbar region. It was determined that of the 31 survivors with forebrain incisions, 39% had exencephaly; of the 42 survivors with thoracolumbar incisions, 31% had myeloschisis; but of the 37 with a cervicothoracic incision, only 14% had exposed spinal cord. This indicates that a rostral-caudal distribution of neural tube defects can be seen in a model created by secondary reopening of the neural tube.

Anencephaly↗
PubMed1992

Neural tube defects--prenatal diagnosis and management.

Neural tube defects rank second to congenital heart disease as a major cause of congenital malformation. Recent developments in ultrasound have improved prenatal diagnosis. Due to anomaly scans at 18 weeks gestation and the availability of a genetic clinic, prenatal diagnosis of neural tube defects at the Royal Maternity Hospital was 91.2% during 1987-1989. However, only 50% of parents accept termination of pregnancy and it is questionable if prenatal diagnosis is of benefit to those who wish to continue with the pregnancy. Parents may accept the situation better at birth, having had time to come to terms with it, helped with support from the obstetrician, clinical geneticist, paediatrician, genetic nurse and social worker. For some affected fetuses who have better muscle function and leg movement at term it appears from the literature that the outcome may be improved by caesarean section delivery. In Ireland fetuses with neural tube defects will continue to be delivered, as termination is unacceptable to many, but despite this there may be a positive benefit from prenatal diagnosis of neural tube defects. Prospective randomised controlled trials are needed to confirm benefit from delivery by caesarean section for fetuses with a good prognosis. As a result of prenatal diagnosis of a neural tube lesion the fetus should enjoy benefit in terms of physical morbidity, and the parents should benefit in terms of psychological morbidity.

Abortion, Induced↗
PubMed1987

Prenatal diagnosis policy without routine amniocentesis in pregnancies with a positive family history for neural tube defects.

The recurrence risk for neural tube defects in pregnancies of women with a family history of neural tube defects greatly exceeds the general population risk. In these high risk pregnancies, we used a prenatal diagnostic method differing from that usually employed, relying mainly on the results of maternal serum alpha-fetoprotein (MSAFP) and ultrasound examination, without routine amniocentesis. During the 6 years reviewed in this study, this method was applied in 539 pregnancies. Of a total of 20 neural tube defects, 19 were detected using this combination of MSAFP, ultrasound, and selective amniocentesis, and the authors estimate that about 8-10 spontaneous abortions were avoided because only 28 amniocenteses were carried out instead of 539. The risk of recurrence was found to be lower than that experienced earlier.

Amniocentesis↗
PubMed1985

Maternal serum alpha-fetoprotein screening for neural tube defects. Report of a combined study in Germany and short overview on screening in populations with low birth prevalence of neural tube defects.

The basis of maternal serum alpha-fetoprotein (AFP)-screening for neural tube defects is discussed. A report is given of a large scale screening study in the Federal Republic of Germany combining the experiences in Giessen and Hannover on over 50,000 pregnant women, about evenly distributed among both centers. Published and known forthcoming data from other low incidence populations, particularly of European countries, are reviewed briefly. The conclusion is reached that general screening could effectively be instituted and in the final result should also be cost-beneficial.

Amniotic Fluid↗
PubMed1991

The changing incidence of neural tube defects in Scotland.

The impact of neural tube defects on neonatal surgery has been declining in Scotland over the past two decades. The Scottish statistics for neural tube defects were studied from 1971 to 1988. The incidence of neural tube defects in Scotland has declined from 5.50 to 1.10 per 1,000 births over this period (3.00 to 0.58 per 1,000 births for spina bifida and 2.50 to 0.52 per 1,000 births for anencephaly). Antenatal maternal alpha-fetoprotein (AFP) screening was introduced to Scotland on a wide scale in 1976. The number of terminations for anencephaly peaked in 1980 (85), and for spina bifida in 1981 (70), and both have since declined. The Scottish birth rate has been about 67,000 per year over this period. The declining incidence of neural tube defects is not explained by the effect of antenatal screening and terminations alone. A downward trend was apparent before 1976, and although antenatal screening has had a considerable impact on anencephaly births (peak terminations 89% in 1983), it has had only a modest impact on spina bifida births (peak terminations 53% in 1984). We conclude that the natural decline in incidence of neural tube defects is the major factor in the observed decline in neonatal surgical admissions for these defects.

Abortion, Eugenic↗
PubMedDate not supplied

Neural tube defects: epidemiology, detection, and prevention.

Neural tube defects are common congenital malformations of the central nervous system and include anencephaly, spina bifida, and encephalocele. Prenatal detection by amniotic fluid analysis of alpha-fetoprotein is possible in those women known to be at high risk for neural tube defects. Maternal serum screening for increased alpha-fetoprotein levels is now available nationally and has the potential to identify women who otherwise would not be known to be at risk. The epidemiology, detection, screening, and prevention of neural tube defects are discussed, and an explanation of alpha-fetoprotein and its use in screening is offered.

Acetylcholinesterase↗
PubMed1987

Vascular basis for neural tube defects: a hypothesis.

A hypothesis is set forth that neural tube defects are produced by inadequate nutrient supply to the rapidly growing neural folds. According to this hypothesis, a delay in establishing blood flow or an aberration of blood supply to neural tissue may interfere with nutrition and prevent neural tube closure. The hypothesis was tested by examining the vasculature of fetuses with spinal neural tube defects. In each case, the arterial supply to the region of the neural tube defect was disturbed. Because development of arterial supply to the neural folds predates neural tube closure, these vascular abnormalities are considered to be primary malformations that lead to neural tube defects rather than secondary morphologic disturbances resulting from neural tube defects.

Blood Vessels↗