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PubMed1975

Prenatal diagnosis of a neural tube defect: Meckel syndrome.

A severe neural tube defect diagnosed in a 191/2-week-old "at risk" fetus on the evidence of a markedly elevated alpha-fetoprotein level in the amniotic fluid, turned out to be an occipital myelocoele. However, the fetus also had polycystic kidneys and postaxial hexadactyly on all extremities. The karyotype was normal. These are the features of the rare Meckel syndrome, caused by a pleiotropic, autosomal, recessive gene, and one and possibly two other sibs were also affected.

Abnormalities, Multiple↗

PubMed1987

Incidence and distribution of renal anomalies in patients with neural tube defects.

In 190 patients with neural tube defects the sensory levels to pin prick were compared with the incidence and distribution of congenital renal anomalies. 17 such anomalies comprised 3 examples of renal agenesis, 5 horseshoe kidneys, 8 ureteral duplications and one simple ureterocele. The pattern of anomalies showed that renal agenesis was associated with a sensory level in the dermatomes T5-8, horseshoe kidneys with T9-L1 and duplications predominantly with the sacral dermatomes.

Abnormalities, Multiple↗

PubMed1989

Changing incidence of neural tube defects in Aegean Turkey.

The incidence of neural tube defects was monitored among all live- and still-births delivered between June 1986 and July 1988. In all there were 19,115 total births. The incidence of neural tube defects (NTD) was 1.9 per 1000 among those whose conception time was prior to May 1986. However, in conceptions occurring in May, June and July 1986, the NTD rate increased to a level of 8.9 per 1000, subsequently gradually declining to previous levels within 9 months. This dramatic change in incidence, which parallels a previous finding from Turkey, suggests that this finding may be associated with the Chernobyl disaster of May 1986.

Accidents↗

PubMed1985

Analysis of the changing birth prevalence of neural tube defects in Hungary.

The birth prevalence of neural tube defects had a significant decrease in Hungary from the sixties till 1978. After this a slight but not significant increase was registered. The changing pattern had no correlation with the developmental (different groups of neural tube defects, still- and livebirth rate, sex ratio, birth weight distribution and twin rate), demographic (monthly and territorial distribution, maternal age, birth order) and medical (prevention program, genetic counselling) factors. There was only one obvious finding, a negative correlation with the standard of living of the population.

Anencephaly↗

PubMed1991

Importance of accurate diagnosis in counseling for neural tube defects diagnosed prenatally.

In cases of fetal neural tube defects (NTD), termination of pregnancy without ascertainment of specific etiology may lead to provision of incorrect recurrence risks and erroneous diagnosis in future pregnancies. Four patients are presented who illustrate the etiologic diversity of neural tube defects. The patients were referred for prenatal diagnosis because of elevated maternal serum alphafetoprotein (AFP). All four chose pregnancy termination. Diagnostic methods included fetal ultrasound, amniocentesis for fetal karyotyping and amniotic fluid AFP/acetylcholinesterase (AChE) and/or fetal karyotyping after delivery, and dysmorphology evaluation of the fetus after intact delivery. These cases highlight the benefits of fetal karyotype analysis and of an intact delivery and thorough clinical examination of the fetus when patients choose to terminate pregnancies with fetal anomalies.

Abnormalities, Multiple↗

PubMed1978

Neural tube defects: maternal serum screening and prenatal diagnosis.

Neural tube defects represent some of the most common and serious of the congenital malformations. Although elevation of alpha-fetoprotein in amniotic fluid is not diagnostic, it does indicate an abnormality of the fetus in a very high proportion of cases. A normal level, however, does not exclude the possibility of a closed neural tube defect. It is therefore recommended that all amniocenteses performed between 15 and 20 weeks of gestation include measurement of alpha-fetoprotein. Maternal serum alpha-fetoprotein assay is a screening test and pilot studies will be necessary to determine its value as a routine prenatal blood test.

Amniocentesis↗

PubMed1986

Neural tube defects in spontaneous abortions.

Nine specimens with neural tube defects (NTDs) were ascertained in a consecutive series of spontaneous abortions in New York City, giving a rate of 10.2 per 1,000 testable embryos and fetuses. All seven successfully karyotyped abortions had a chromosome anomaly. The rate of NTDs in miscarriages in New York is only one-third the rate in miscarriages in London, and the difference is due entirely to a deficit of fetuses with normal chromosomes. Our data, together with data from three other centers, indicate that there is a strongly positive association (r = 0.96) between rates of neural tube defects in early pregnancy and at term. The implications of these findings for genetic counseling and for etiologic studies are discussed.

Abortion, Spontaneous↗

PubMed1995

Parent preferences and prenatal testing for neural tube defects.

Previous analyses of prenatal screening for neural tube defects have generally found benefits to exceed costs. The usual screening battery follows an elevated maternal serum alpha-fetoprotein level with high-resolution ultrasound and/or amniocentesis. Current thinking focuses on weighing the risk of a false-negative (an abnormality missed) against the risk of an amniocentesis-induced fetal loss. This thinking neglects the risk of a false-positive (an unaffected fetus labeled abnormal) and individual parents' preferences concerning a false-negative vs a fetal loss. With these risks included, we find that high-resolution ultrasound is appropriate for all women with elevated serum alpha-fetoprotein. Women with moderately elevated serum alpha-fetoprotein who have negative ultrasound scans need no further testing, nor do women with highly elevated serum alpha-fetoprotein and positive ultrasound scans. Further testing using amniocentesis to confirm the ultrasound result is appropriate for women with moderately elevated serum alpha-fetoprotein and positive ultrasound scans, and for women with highly elevated serum alpha-fetoprotein and negative ultrasound scans. The actual cutoffs defining normal, moderately elevated, and highly elevated serum alpha-fetoprotein depend on several parameters, particularly the underlying prevalence of neural tube defects and the parents' preferences.

Cost-Benefit Analysis↗

PubMedDate not supplied

Folic acid for prevention of neural tube defects: pediatric anticipatory guidance.

The incidence of neural tube defects including myelomeningocele, which is one of the most common causes of infant and childhood disability, can be substantially reduced by folic acid supplementation to the diet of women before and during the early stages of pregnancy. All females of childbearing age should be taking folic acid supplements of 0.4 mg/day (400 micrograms/day) and consuming a diet rich in folate. Because many pregnancies are unplanned, supplementation should not await plans for pregnancy. Because pediatric nurse practitioners are in frequent contact with both adolescent patients and patients whose mothers are of childbearing age, and because pediatric nurse practitioners have an interest in preventing neural tube defects in future pediatric patients, they are in a good position to provide the necessary anticipatory guidance regarding the critical need for adequate folic acid intake by females of childbearing age. This article discusses and includes guidelines for providing this anticipatory guidance.

Adult↗

PubMed1984

Recurrence risk after neural tube defects in a genetic counselling clinic.

The recurrence of isolated neural tube defects in a population of women from a genetic counselling clinic was found to be 3.4%. After one baby with a neural tube defect the recurrence was 2.3%. Of the 15 pregnancies of women who had two previous babies with neural tube defects, there were three further recurrences. These findings show that the Hungarian recurrence risk of isolated neural tube defects has not changed with a declining birth prevalence, and that the rate in genetic counselling clinic patients is the same as in a previous population based epidemiological study.

Abnormalities, Multiple↗

PubMed1994

Genetic models of mammalian neural tube defects.

Several mouse mutations disturb the embryonic process of neurulation, yielding neural tube defects. Analysis of the mutations offers the most feasible approach to understanding the aetiology and pathogenesis of human neural tube defects. Interactions between the non-allelic mutant genes and between several of the mutant genes and modifying genes in the genetic background modulate the frequency and severity of the defects that develop. Environmental factors interact with the genetic predisposition either to increase or to decrease the incidence of defects. The gene loci corresponding to two of the mutations, splotch (Sp) and extra toes (Xt), have been identified as those encoding the transcription factors Pax-3 and Gli3, respectively; their human homologues are associated with Waardenburg type I syndrome and Greig's cephalopolysyndactyly. Embryological analysis reveals that several of the mutations disturb the process of neural tube closure at the posterior neuropore (in the lumbosacral region), yielding spina bifida and/or tail defects. The different mutations appear to achieve this developmental end-point by different underlying mechanisms. In curly tail (ct), non-neural tissues proliferate abnormally slowly causing ventral curvature of the neuropore region and inhibiting neural tube closure. Neural tube defects can be prevented in cultured ct/ct embryos by experimentally correcting either the proliferative imbalance or the ventral curvature. In Sp the primary defect appears to reside in the neuroepithelium. A combination of genetic analysis, gene cloning and experimental embryology is revealing that neural tube defects in mice and, by implication, in humans are a developmentally heterogeneous group of malformations.

Animals↗

PubMed1995

Neural tube defects, chromosome abnormalities and multiple closure sites for the human neural tube.

The hypothesis that during human embryogenesis there is multi-site closure of the neural tube, with possibly regionally distinct genetic control, is examined in the light of the neural tube defects (NTD) observed in trisomy 13, trisomy 18 and triploidy which survive at least to the mid-trimester. In a series of mid-trimester fetuses examined post-mortem, there were two spina bifidas in 25 cases of trisomy 13; eight spina bifidas and one anencephalic among 38 trisomy 18 individuals; and three spina bifidas in 13 triploids. Not only was there a predominance of spina bifida, but all the spina bifidas were similar in location along the neuraxis: regardless of chromosome constitution, they were all sacral or lumbosacral. A survey of the literature confirms this finding. While this regionally distinct type of NTD is not specific to a particular chromosome abnormality and thus by implication to any particular gene, it does seem to be specific to an imbalance caused by an excess of genetic material of a type which permits survival past the first few post-conception weeks, and thus lends some support to the hypothesis.

Chromosome Aberrations↗

PubMed1992

Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation.

BACKGROUND: The risk of recurrent neural-tube defects is decreased in women who take folic acid or multivitamins containing such during the periconceptional period. The extent to which folic acid supplementation can reduce the first occurrence of defects is not known. METHODS: We conducted a randomized, controlled trial of periconceptional multivitamin supplementation to test the efficacy of this treatment in reducing the incidence of a first occurrence of neural-tube defects. Women planning a pregnancy (in most cases their first) were randomly assigned to receive a single tablet of a vitamin supplement (containing 12 vitamins, including 0.8 mg of folic acid; 4 minerals; and 3 trace elements) or a trace-element supplement (containing copper, manganese, zinc, and a very low dose of vitamin C) daily for at least one month before conception and until the date of the second missed menstrual period or later. RESULTS: Pregnancy was confirmed in 4753 women. The outcome of the pregnancy (whether the fetus or infant had a neural-tube defect or congenital malformation) was known in 2104 women who received the vitamin supplement and in 2052 who received the trace-element supplement. Congenital malformations were significantly more prevalent in the group receiving the trace-element supplement than in the vitamin-supplement group (22.9 per 1000 vs. 13.3 per 1000, P = 0.02). There were six cases of neural-tube defects in the group receiving the trace-element supplement, as compared with none in the vitamin-supplement group (P = 0.029). The prevalence of cleft lip with or without cleft palate was not reduced by periconceptional vitamin supplementation. CONCLUSIONS: Periconceptional vitamin use decreases the incidence of a first occurrence of neural-tube defects.

Cleft Lip↗

PubMed1996

[Peri-conception use of folic acid in the prevention of neural tube defect: current concepts].

The incidence of neural tube defects (NTDs) is about 1.3 cases per 1000 live births. The higher incidence of NTDs occurs among certain ethnic groups, and geographic areas. The fetal morbimortality is high and the treatment for those babies who live is expensive with pour quality of live. It is unclear what biochemical mechanism involving folate explain the relationship of this vitamin to the pathogenesis of NTDs. However elevated concentrations of homocysteine or decreased methionine concentrations could be interfere with closure of the neural tube. The pharmacologic periconceptional intake of 0.4-4.0 mg/day of folic acid reduces the risk of occurrent NTDs by approximately 40-75%. A relatively high dietary intake of folate may also reduce the risk.

Dose-Response Relationship, Drug↗

PubMed1993

The early diagnosis of neural tube defects.

The sonographic diagnosis of fetal neural tube defects (NTDs) has been enhanced by the recognition of associated brain and skull anomalies. Previous reports have found these anomalies to be accurate in predicting spina bifida after 16 weeks' gestation, and an inverse correlation was suggested between the presence of these sonographic markers and gestational age. Therefore, we assumed that early second-trimester sonography would be at least as accurate as that performed after 16 weeks' gestation. To examine this hypothesis, we looked for the presence of these cranial sonographic markers suggestive of open NTDs in 8011 low-risk cases, using transvaginal sonography (TVS), between the 12th and 17th week of gestation (menstrual age). Fetal NTDs were identified in ten cases (1.25/1000). The NTDs were cervico-cranial in three, lumbo-sacral in six, and thoracal in one of the ten cases. None of the seven cases examined was dyskaryotic. Cerebellar dysmorphism, 'banana' sign, cerebellar absence, and hypoplasia were detected in all the low NTDs, usually before the detection of the spinal lesion. All the sonographically diagnosed malformations were confirmed by post-abortal examination except in one case, where the patient decided to continue the pregnancy and refused follow-up. We therefore conclude that transvaginal sonographic examination of the fetal skull before the 17th week of gestation is an accurate method for the detection of low NTDs.

Abortion, Therapeutic↗

PubMed2001

Interaction of folate and homocysteine pathway genotypes evaluated in susceptibility to neural tube defects (NTD) in a German population.

Neural tube defects (NTD) are likely to result from an interaction of several genes and environmental factors. Because periconceptional folate intake reduces the NTD risk in the fetus, and because mothers of children with NTD showed elevated plasma homocysteine levels, gene polymorphisms of the folate and homocysteine pathway, such as 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T, MTHFR 1298A-->C and cystathionine beta-synthase (CBS) 844ins68, have been implicated in the etiology of NTD. Several studies have demonstrated that these polymorphisms may indeed be associated with NTD in some populations. In order to evaluate the role of these polymorphisms and their interaction in NTD, we genotyped 417 individuals for case-control studies and 129 families for transmission disequilibrium tests. We are the first to present detailed data on MTHFR haploid genotypes in combination with CBS 844ins68. The MTHFR risk genotype 677CT/1298AC, known to be associated with decreased enzyme activity and increased homocysteine, was found significantly more often in patients than in controls (P = 0.02). A CBS insertion allele in addition to MTHFR 677CT/ 1298AC heterozygosity or MTHFR 677TT/1298AA homozygosity did not result in an increased risk for NTD. This is in agreement with the recently reported homocysteine-lowering effect of the CBS 844ins68 allele in carriers of MTHFR variants.

Alleles↗

PubMed1981

Prenatal screening for neural tube defects in South Africa. An assessment.

Neural tube defects (NTDs) occur in at least 1 in every 1000 babies born in South Africa. The incidence is uncertain but appears to be highest in Whites and Coloureds and lowest in Blacks. Spina bifida is a particularly serious problem because many affected babies survive and require extensive, costly treatment and care. A high maternal serum alpha-fetoprotein (AFP) level may indicate that the fetus has an NTD. Enzyme-linked immunosorbent assay is well suited to mass screening of maternal sera. The Natal population is used as a model here, and it is calculated that of some 122000 pregnancies annually 38725 might be screened. Of 98 expected fetuses with an NTD, 32 (16 with anencephaly and 16 with spina bifida) should be detected. If the 16 fetuses with spina bifida were not detected and those pregnancies terminated, the cost of caring for the affected children through their first decade is conservatively estimated at R145660, an average of R9 100 per patient; 92% of this would be incurred in the first 3 years. The cost of screening, at R2,27 per subject, is calculated to be R87 825, equivalent to R2 744 per fetus with an NTD detected or R5 489 per fetus with spina bifida detected. Financially the introduction of mass screening of maternal serum AFP is justified, but before this can be done adequate ultrasound facilities must be provided and a permanent health visitor must be available to trace women at risk and arrange their further investigations. A public education campaign should also be introduced. Some ethical and legal implications of mass screening for NTDs are discussed briefly.

Child↗

PubMed2000

Investigation of folate pathway gene polymorphisms and the incidence of neural tube defects in a Texas hispanic population.

Neural tube defects (NTDs) are multifactorial in their etiology, having both genetic and environmental factors contributing to their development. Recent evidence demonstrates that periconceptional supplementation of the maternal diet with a multivitamin containing folic acid significantly reduces the occurrence and recurrence risk for having a pregnancy complicated by NTDs. Unfortunately, the mechanism underlying the beneficial effects of folic acid remains unknown. NTD surveillance data from the Texas-Mexico border show that the high NTD rate (28/10,000 live births) noted during the 1990-1991 Cameron county NTD cluster was superimposed on a background Cameron county NTD rate (16/10,000 live births) which is considerably higher than that generally noted in the United States (8-10/10,000 live births). These data suggest that genetic factors as well as transient environmental factors may contribute to the etiology of the NTDs. Furthermore, clinical and experimental evidence imply that allelic forms of genes involved with folate metabolism and/or transport may explain some of the observed variation in the NTD rates found across different populations. Two folate pathway genes were selected for evaluation in this study. The loci investigated included two known alleles of the 5, 10-methylenetetrahydrofolate reductase (MTHFR) gene, as well as the promoter region of the folate receptor-alpha (FR-alpha) gene. Odds ratios (ORs) for the C677T polymorphism in the MTHFR gene were 1.8 (CI 0.47-6.8) for heterozygosity and 1.8 (CI 0.35-9.4) for homozygosity for the mutant 677T allele, relative to wildtype homozygotes. The odds ratio for the heterozygosity for the A1298C polymorphism in the same gene was 1.1 (CI 0.09-14). No individuals homozygous for the 1298C allele were observed. The OR for heterozygosity of FR-alpha gene polymorphisms detected at nucleotide 762 and at nucleotides 610/631 was 1.4 and 0.7, respectively. Neither of the FR-alpha polymorphisms was observed in the homozygous condition. No statistically significant associations were observed for any of the polymorphisms examined, as the 95% confidence intervals for all of the ORs included one. However, the frequency of the MTHFR 677T allele in the largely Hispanic control group from Texas was significantly different from other populations (P < 0.005), and among the highest reported for any control populations examined.

Adult↗