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PubMed1983

Neural tube defects in the Sikhs.

Background information on the incidence of neural tube defects (NTD) in Sikhs in India and elsewhere is given. The incidence of NTD in the Sikh population of British Columbia is estimated for 4 years and found to be 2.86 per 1,000 births. The overall rate for NTD in all B.C. births for these same years is 1.26 per 1,000 births. This difference is statistically significant. Analysis of cases showed that a greater proportion of Sikh cases are stillborn, and these account for much of the excess over expected. It appears that the incidence of NTD in Sikhs is increased compared to the general population incidence of these birth defects in B.C.

British Columbia↗
PubMed2006

Etiology, pathogenesis and prevention of neural tube defects.

Spina bifida, anencephaly, and encephalocele are commonly grouped together and termed neural tube defects (NTD). Failure of closure of the neural tube during development results in anencephaly or spina bifida aperta but encephaloceles are possibly post-closure defects. NTD are associated with a number of other central nervous system (CNS) and non-neural malformations. Racial, geographic and seasonal variations seem to affect their incidence. Etiology of NTD is unknown. Most of the non-syndromic NTD are of multifactorial origin. Recent in vitro and in vivo studies have highlighted the molecular mechanisms of neurulation in vertebrates but the morphologic development of human neural tube is poorly understood. A multisite closure theory, extrapolated directly from mouse experiments highlighted the clinical relevance of closure mechanisms to human NTD. Animal models, such as circle tail, curly tail, loop tail, shrm and numerous knockouts provide some insight into the mechanisms of NTD. Also available in the literature are a plethora of chemically induced preclosure and a few post-closure models of NTD, which highlight the fact that CNS malformations are of hetergeneitic nature. No Mendelian pattern of inheritance has been reported. Association with single gene defects, enhanced recurrence risk among siblings, and a higher frequency in twins than in singletons indicate the presence of a strong genetic contribution to the etiology of NTD. Non-availability of families with a significant number of NTD cases makes research into genetic causation of NTD difficult. Case reports and epidemiologic studies have implicated a number of chemicals, widely differing therapeutic drugs, environmental contaminants, pollutants, infectious agents, and solvents. Maternal hyperthermia, use of valproate by epileptic women during pregnancy, deficiency and excess of certain nutrients and chronic maternal diseases (e.g. diabetes mellitus) are reported to cause a manifold increase in the incidence of NTD. A host of suspected teratogens are also available in the literature. The UK and Hungarian studies showed that periconceptional supplementation of women with folate (FA) reduces significantly both the first occurrence and recurrence of NTD in the offspring. This led to mandatory periconceptional FA supplementation in a number of countries. Encouraged by the results of clinical studies, numerous laboratory investigations focused on the genes involved in the FA, vitamin B12 and homocysteine metabolism during neural tube development. As of today no clinical or experimental study has provided unequivocal evidence for a definitive role for any of these genes in the causation of NTD suggesting that a multitude of genes, growth factors and receptors interact in controlling neural tube development by yet unknown mechanisms. Future studies must address issues of gene-gene, gene-nutrient and gene-environment interactions in the pathogenesis of NTD.

Anencephaly↗
PubMed2004

Neural tube defects.

Defects of development of the neural tube can result in a number of seemingly different malformations. Understanding the abnormal embryology helps one understand the malformations and their surgical treatments. The clinical presentations and the follow-up of these patients require attention to various end organs besides the nervous system. For most of these conditions, long-term follow-up is necessary regardless of initial treatment. A decline in function is not a part of the natural history of these malformations and requires prompt evaluation and treatment.

Humans↗
PubMed1990

Risk of neural tube defects in relation to maternal fertility and fertility drug use.

In a case-control study to investigate whether women who use drugs to induce ovulation are at increased risk of conception of a child with a neural tube defect, 571 women who had a fetus or child with a neural tube defect, 546 women who had a fetus or child with other abnormalities, and 573 women who had an apparently normal fetus or child were questioned about infertility, fertility drug use, and related obstetric problems. The rate of maternal fertility drug use around the time of conception was not significantly higher for neural tube defects than for other abnormalities (odds ratio 1.28; 95% confidence interval 0.39, 4.51) or no abnormalities (odds ratio 0.80; 95% Cl 0.27, 2.27). Fertility drug use at any time was not significantly more frequent for neural tube defects than for other abnormalities (odds ratio 1.37; 95% Cl 0.70, 2.74) or no abnormalities (odds ratio 1.05; 95% Cl 0.56, 1.98).

Abnormalities, Drug-Induced↗
PubMed2005

Crooked tail (Cd) model of human folate-responsive neural tube defects is mutated in Wnt coreceptor lipoprotein receptor-related protein 6.

A cranial neural tube defect in Crooked tail (Cd) mice is prevented with prenatal dietary folic acid Cd positional cloning reveals a missense mutation of a highly conserved amino acid in the low density lipoprotein receptor-related protein 6 (Lrp6), a coreceptor required for Wnt canonical signaling. Molecular modeling predicts that Lrp6(Cd) alters a hinge region of the second YWTD beta-propeller domain. Mutant LRP6 binds to Wnt and Dickkopf1 (Dkk1) but not Mesd1, and Dkk1 cannot antagonize Wnt in Cd/Cd cells, resulting in hyperactivity. NIH 3T3 cells transfected with a mutant Lrp6 plasmid resist Dkk1 antagonism much like Cd/+ cells, confirming the significance of the mutation. The Lrp6 mutation in Cd mice provides evidence for a functional connection between Wnt signaling and folate rescue of neural tube defects.

Amino Acid Sequence↗
PubMed1991

Computer modelling of neural tube defects.

Neurulation, the curling of the neuroepithelium to form the neural tube, is an essential component of the development of animal embryos. Defects of neural tube formation, which occur with an overall frequency of one in 500 human births, are the cause of severe and distressing congenital abnormalities. However, despite the fact that there is increasing information from animal experiments about the mechanisms which effect neural tube formation, much less is known about the fundamental causes of neural tube defects (NTD). The use of computer models provides one way of gaining clues about the ways in which neurulation may be compromised. Here we employ one computer model to examine the robustness of different cellular mechanisms which are thought to contribute to neurulation. The model, modified from that of Odell et al (Odell, G.M., Oster, G., Alberch, P. and Burnside, B., (1981)) mimics neurulation by laterally propagating a wave of apical contraction along an active zone within a ring of cells. We link the results to experimental evidence gained from studies of embryos in which neurulation has been perturbed. The results indicate that alteration of one of the properties of non-neural tissue can delay or inhibit neurulation, supporting the idea, gained from observation of embryos bearing genes which predispose to NTD, that the tissue underlying the neuroepithelium may contribute to the elevation of the neural folds. The results also show that reduction of the contractile properties of a small proportion of the neuroepithelial cell population may have a profound effect on overall tissue profiling. The results suggest that the elevation of the neural folds, and hence successful neurulation, may be vulnerable to relatively minor deficiencies in cell properties.

Animals↗
PubMed1990

Neural tube defects: a study in Puerto Rico.

Recent literature reports an apparent decline in the incidence of neural tube defects throughout the world. A revision of stillbirth certificates and surgical reports of closure procedures for open neural tube defects was done in order to establish the incidence and its trend during a nine year period in Puerto Rico. The current prevalence of the syndrome was estimated using the death certificates in addition to the fore-mentioned surgical reports. Our results indicate that Puerto Rico carries probably the highest incidence of the US territories and that the trend is not declining one.

Cohort Studies↗
PubMed1984

Management of the unanticipated neural tube defect in late pregnancy.

The physician who encounters a patient in late pregnancy with a neural tube defect is presented with a difficult task of management and treatment. A thorough examination of the defect(s) is mandatory. This can be accomplished best with ultrasound examination. It is then imperative to assess the severity and survivability of the fetus, and to counsel properly the patient as to diagnosis, severity, and options available. After discussion with the proper consultants, patients should have considerable input into the management, and should be informed adequately to make an intelligent and proper decision. After careful assessment and thorough consultation and counseling with the patient and her support person, therapy can be initiated, followed by some type of grief counseling with appropriate follow-up. Patients also should be informed as to subsequent risks and what, if anything, could possibly be done to prevent recurrences. By this careful and thorough approach it is hoped that physicians who encounter neural tube defects late in pregnancy will make a considerable difference in the physical as well as the emotional health of the patient.

Counseling↗
PubMed1988

Neural tube defects and omphalocele in trisomy 18.

A trisomy 18 fetus with severe congenital anomalies including craniorachischisis, large omphalocele, and bilateral cleft lip and palate is reported. The occurrence of neural tube defects and/or omphalocele in reported cases of trisomy 18 is discussed and the frequency of these anomalies in 85 trisomy 18 patients evaluated at Indiana University School of Medicine from 1963 to 1986 is reviewed. In this series of patients the frequency of neural tube defects was 7.0% and the frequency of omphaloceles was 5.9%. The percentage of these findings in our cases supports the premise that neural tube defects and omphaloceles are part of the trisomy 18 phenotype. Since fetuses with trisomy 18 are subject to early fetal loss or premature birth, the more subtle physical features of this condition may not be apparent. Thus, karyotyping of fetuses and premature infants with either neural tube defect or omphalocele should be considered.

Abnormalities, Multiple↗
PubMed2007

Folate and neural tube defects.

A protective effect of folate against the development of neural tube defects (NTDs), specifically, anencephaly and spina bifida, is now well recognized, having been established by a chain of clinical research studies over the past half century. This article summarizes the more important of these studies, which have led to the current situation in which all women capable of becoming pregnant are urged to ingest folic acid regularly. The recommended intakes are 4 mg/d for those at high risk (by virtue of a previous NTD pregnancy outcome) and 0.4 mg/d for all others. However, a reduction in NTD births did not follow promulgation of these recommendations, and so folic acid fortification was mandated in the United States and some other countries. Although some controversy remains about the adequacy of fortification levels, the process was followed by significant improvement in folate indexes and a reduction of 25-30% in NTD frequency (about one-half of the proportion of cases assumed to be responsive to folate). The folate-NTD relation represents the only instance in which a congenital malformation can be prevented simply and consistently. Nevertheless, several research gaps remain: identification of the mechanism by which the defect occurs and how folate ameliorates it; characterization of the relative efficacy of food folate, folic acid added to foods, and folic acid by itself; delineation of the dose-response relations of folate and NTD prevention; and more precise quantification of the dose needed to prevent recurrences.

Adult↗
PubMed2005

A decreasing rate of neural tube defects following the recommendations for periconceptional folic acid supplementation.

BACKGROUND/AIM: Neural tube defects (NTDs) are the most common birth defects, resulting in severe mortality and morbidity. In 1995, the supplementation of folic acid periconceptionally was officially recommended in Germany. The impact of the recommendations on the rate of NTDs was assessed. METHODS: An active surveillance system was established in the northern Rhine area. From 1996, all departments of obstetrics were asked to report cases of NTDs in all abortions, live births and stillbirths. Compliance with the recommendations was evaluated in a sample of mothers who delivered at the Department of Obstetrics of Düsseldorf University in 2001. RESULTS: From 1996-2003, 520 NTDs were reported. Compared to the rate of NTDs in 1996 (10.5/10,000), the average incidence in the years 1997 to 2003 dropped (6.8/10,000). The intake of folic acid, as recommended, was low among the general population (21.1%). CONCLUSION: Active surveillance data on the rate of NTDs are compatible with the maximum decrease of about 20% to be expected from data on the implementation of the recommendations. A much greater decrease in NTDs should be the challenge for the future.

Anencephaly↗
PubMed1986

Fetal mortality in sibships of cases with neural tube defects.

Rates of fetal mortality in sibships of probands with neural tube defects (NTDs) may reflect liability to NTDs. Expectations from the multifactorial model predict that fetal loss should be higher in sibships of male probands; in multiplex sibships; and sibships where the proband had no additional malformations. This was analysed for 715 pregnancies from 398 sibships. In general, the results did not support the expectations of the multifactorial model.

Abortion, Spontaneous↗
PubMed1990

Neural tube defects and first trimester operations.

Swedish health care registries were used to identify women who had surgery during pregnancy and their offspring. Among the 2,252 infants born to women who had first trimester operations during 1973-1981, six had definite diagnoses of neural tube defects (expected number, 2.5). Scrutiny of the records showed that 572 operations occurred during gestational weeks 4-5, the period of neural tube formation, and that the mothers of five of the six infants with neural tube defects had an operation during that period (expected number of neural tube defects, 0.6) although one of the offspring probably had Meckel's syndrome. The relationship between neural tube defects and operation during pregnancy is discussed including the possibility that the association may be random.

Abnormalities, Drug-Induced↗
PubMed1994

Methanol-induced neural tube defects in mice: pathogenesis during neurulation.

A spectrum of cephalic neural tube defects was observed in near-term (gestation day [GD] 17) mouse fetuses following maternal inhalation of methanol at a high concentration (15,000 ppm) for 6 hr/day during neurulation (GD 7-9). Dysraphism, chiefly exencephaly, occurred in 15% of fetuses, usually in association with reduction or absence of multiple bones in the craniofacial skeleton and ocular anomalies (prematurely open eyelids, cataracts, retinal folds). Measurements of cerebrocortical width in grossly normal, methanol-exposed fetuses revealed significant semiquantitative differences in the thicknesses of the frontal cortex and its constituent layers (neuroepithelium, intermediate cortex/subventricular plate, and cortical layer 1) as well as apparent increases in subventricular plate cellularity relative to controls. Subsequently, the early morphogenesis of these neural changes was investigated in neurulating mouse embryos to define tissue-specific patterns of methanol-induced damage that lead to cephalic axial dysraphism. Following daily 6-hr maternal inhalations of 15,000 ppm methanol during GD 7-8, the cephalic neural fold margins were swollen, blunted, and poorly elevated on GD 8.5 and 9 relative to controls. Histopathology of exposed GD 8.5 embryos revealed microcephaly in association with reductions in the cell density and mitotic index of at least 47% in the cranial mesoderm. The mitotic index in the embryonic neuroepithelium was also reduced by 55%, and groups of neural crest cells were displaced to the neural folds dorsal to the foregut (relative to the more ventral location in the facial regions of control embryos). When examined on GD 9.5 and 10.5, maternal methanol exposure (15,000 ppm for 6 hr/day) during GD 7-9 resulted in stunting, delayed rotation, and microcephaly in over 90% of the affected embryos. Persistent patency of the anterior neuropore and prosencephalic hypoplasia were seen in > 40% and up to 90% of embryos, respectively. Shallow optic vesicles, stunted branchial arches, scoliosis, and hydropericardium were also observed. Many 10.5-day-old embryos were edematous. Occult dysraphism, recognized grossly by abnormally narrow cephalic conformation and histopathologically by the absence of mesoderm in the mesencephalon, was present in at least 21% of methanol-exposed embryos on GD 9.5 and 10.5. Nile blue vital dye staining of methanol-exposed embryos revealed no difference in dye accumulation between control and treated embryos on GD 8.5, 9.0, or 9.5. There were no apparent dysmorphogenic effects in control embryos at any stage of development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

Whole genomewide linkage screen for neural tube defects reveals regions of interest on chromosomes 7 and 10.

Neural tube defects (NTDs) are the second most common birth defects (1 in 1000 live births) in the world. Periconceptional maternal folate supplementation reduces NTD risk by 50-70%; however, studies of folate related and other developmental genes in humans have failed to definitively identify a major causal gene for NTD. The aetiology of NTDs remains unknown and both genetic and environmental factors are implicated. We present findings from a microsatellite based screen of 44 multiplex pedigrees ascertained through the NTD Collaborative Group. For the linkage analysis, we defined our phenotype narrowly by considering individuals with a lumbosacral level myelomeningocele as affected, then we expanded the phenotype to include all types of NTDs. Two point parametric analyses were performed using VITESSE and HOMOG. Multipoint parametric and nonparametric analyses were performed using ALLEGRO. Initial results identified chromosomes 7 and 10, both with maximum parametric multipoint lod scores (Mlod) >2.0. Chromosome 7 produced the highest score in the 24 cM interval between D7S3056 and D7S3051 (parametric Mlod 2.45; nonparametric Mlod 1.89). Further investigation demonstrated that results on chromosome 7 were being primarily driven by a single large pedigree (parametric Mlod 2.40). When this family was removed from analysis, chromosome 10 was the most interesting region, with a peak Mlod of 2.25 at D10S1731. Based on mouse human synteny, two candidate genes (Meox2, Twist1) were identified on chromosome 7. A review of public databases revealed three biologically plausible candidates (FGFR2, GFRA1, Pax2) on chromosome 10. The results from this screen provide valuable positional data for prioritisation of candidate gene assessment in future studies of NTDs.

Chromosomes, Human, Pair 10↗
PubMed1998

Socioeconomic status, neighborhood social conditions, and neural tube defects.

OBJECTIVES: This study evaluated the contributions of lower socioeconomic status (SES) and neighborhood socioeconomic characteristics to neural tube defect etiology. The influence of additional factors, including periconceptional multivitamin use and race/ethnicity, was also explored. METHODS: Data derived from a case-control study of California pregnancies from 1989 to 1991. Mothers of 538 (87.8% of eligible) case infants/fetuses with neural tube defects and mothers of 539 (88.2%) nonmalformed infants were interviewed about their SES. Reported addresses were linked to 1990 US census information to characterize neighborhoods. RESULTS: Twofold elevated risks were observed for several SES indicators. Risks were somewhat confounded by vitamin use, race/ethnicity, age, body mass index, and fever but remained elevated after adjustment. A risk gradient was seen with increasing number of lower SES indicators. Women with 1 to 3 and 4 to 6 lower SES indicators had adjusted odds ratios of 1.6 (1.1-2.2) and 3.2 (1.9-5.4), respectively, compared with women with no lower SES indicators. CONCLUSIONS: Both lower SES and residence in a SES-lower neighborhood increased the risk of an neural tube defect-affected pregnancy, with risks increasing across a gradient of SES indicators.

Adult↗
PubMed1987

Use of genetic counselling services for neural tube defects.

Genetic counselling is recommended for parents of children with neural tube defects (NTDs) to inform them of the recurrence risks and the option of prenatal diagnosis. British Columbia provides an excellent site to examine the use by parents of genetic counselling services for NTDs. Genetic services for the entire province are centralized, and there is virtually complete ascertainment of all NTD births. The results from this study indicate that use of genetic counselling services is influenced by the type of NTD present and whether the index case was live or stillborn. Genetic counselling is most often sought after the birth of a liveborn infant with spina bifida.

Anencephaly↗
PubMedDate not supplied

Maternal hair zinc and neural tube defects: no evidence of an association from a case-control study in Western Australia.

In a case-control study of isolated neural tube defects in Western Australia, zinc was estimated by flame spectrophotometry in post-partum hair specimens from 54 mothers of infants with neural tube defects, and from 128 mothers of normal infants. The distribution of the estimates of zinc was divided into quartiles. Using the lowest quartile as the reference group, the crude odds ratios (and their 95% confidence intervals) for quartiles two through four were 1.07 (0.44, 2.59), 1.02 (0.41, 2.56), and 0.70 (0.28, 1.73). Adjustment for several potential confounding variables (parental country of birth, social class, previous pregnancy outcome, interval between previous and index pregnancy, pregnancy order, and interval from birth to interview) made little difference to the odds ratios. This study provides no evidence of an association between post-partum, maternal hair zinc and offspring with neural tube defects.

Case-Control Studies↗