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PubMed1989

Biomechanical basis of diazepam-induced neural tube defects in early chick embryos: a morphometric study.

The biomechanical basis of diazepam (Valium/Roche)-induced neural tube defects in the chick was investigated using a combination of electron microscopy and morphometry. Embryos at stage 8 (four-somite stage) of development were explanted and grown for 6 hr in nutrient medium containing 400 micrograms/ml diazepam. Nearly 80% of these embryos exhibited neural tube defects that were most pronounced in the forming midbrain region and typified by a "relaxation" or "collapse" of neural folds. The hindbrain and spinal cord regions were less affected. Electron microscopy revealed that neuroepithelial cells in diazepam-treated embryos had smoother apical surfaces and broader apical widths than did controls. Morphometric measurements supported this observation and further showed that these effects were focused at sites within the wall of the forming neural tube that typically exhibit the greatest degree of bending and apical constriction (i.e., the floor and midlateral walls). Overall results indicate that neural tube defects associated with exposure to diazepam are due largely to a general inhibition of the contractile activity of apical microfilament bundles in neuroepithelial cells. These findings 1) emphasize the important contribution of microfilament-mediated apical constriction of neuroepithelial cells in providing the driving forces for bending of the neuroepithelium during neural tube formation and 2) suggest that agents or conditions that impair their contractile activity could play a role in the pathogenesis of certain types of neural tube defects.

Animals↗
PubMed1982

Prenatal diagnosis of open neural tube defects using the amniotic fluid acetylcholinesterase assay.

The most reliable tool at present for the prenatal detection of open neural tube defects is the amniotic fluid alpha-fetoprotein assay. Nevertheless its nonspecificity and false-positive results produced by fetal blood admixture and other less well-defined causes have spurred the search for a more specific test. Increased amniotic fluid acetylcholinesterase activity has been reported in association with open neural tube defects. The authors have assayed acetylcholinesterase in second-trimester amniotic fluid samples with previously determined alpha-fetoprotein values from 200 pregnancies with 96.5% of the outcomes known. These pregnancies were selected because of known fetal abnormalities or difficulties in prenatal diagnosis. High alpha-fetoprotein and acetylcholinesterase activity was detected in all 66 cases of open neural tube defects. The authors were able to reclassify correctly 89% of normal pregnancies with spuriously high alpha-fetoprotein by demonstrating no acetylcholinesterase band after slab gel in electrophoresis. Nine cases with a normal outcome but high alpha-fetoprotein values and acetylcholinesterase activity constitute the remaining false-positive results. Notwithstanding the false-positive results, which may have been due to undetected fetal blood admixture, the acetylcholinesterase gel electrophoresis assay is clearly a valuable adjunctive test to the alpha-fetoprotein assay for the prenatal detection of neural tube defects. Although no specific for open neural tube defects, acetylcholinesterase analysis by gel electrophoresis of amniotic fluid is significantly less influenced by fetal blood than is alpha-fetoprotein and, furthermore, may prove as reliable a diagnostic test for open neural tube defect.

Acetylcholinesterase↗
PubMed1989

Multivitamin/folic acid supplementation in early pregnancy reduces the prevalence of neural tube defects.

We examined the relation of multivitamin intake in general, and folic acid in particular, to the risk of neural tube defects in a cohort of 23,491 women undergoing maternal serum alpha-fetoprotein screening or amniocentesis around 16 weeks of gestation. Complete questionnaires and subsequent pregnancy outcome information was obtained in 22,776 pregnancies, 49 of which ended in a neural tube defect. The prevalence of neural tube defect was 3.5 per 1000 among women who never used multivitamins before or after conception or who used multivitamins before conception only. The prevalence of neural tube defects for women who used folic acid-containing multivitamins during the first 6 weeks of pregnancy was substantially lower--0.9 per 1000 (prevalence ratio, 0.27; 95% confidence interval, 0.12 to 0.59 compared with never users). For women who used multivitamins without folic acid during the first 6 weeks of pregnancy and women who used multivitamins containing folic acid beginning after 7 or more weeks of pregnancy, the prevalences were similar to that of the nonusers and the prevalence ratios were close to 1.0.

Adult↗
PubMed1978

Amniography in the prenatal diagnosis of neural tube defects.

Amniography for the visualization and confirmation of suspected neural tube defect was performed in 9 midtrimester gravidas. In all cases, amniotic fluid alpha-feto protein (AFP) was abnormally elevated. Four cases of anencephaly and one of spina bifida were demonstrated by amniography. These pregnancies were terminated and the defects were confirmed by gross pathologic examination. In 4 remaining cases, amniography was normal. Three of these pregnancies proceeded to term, culminating in the birth of a normal child. The fourth patient had spontaneous abortion of a normal fetus at 23 weeks of gestation. The experience reported here suggests that amniography is an important adjunctive diagnostic technique in the prenatal diagnosis of neural tube defect, and if used correctly, may significantly reduce the chance of false-positive diagnosis.

Adult↗
PubMed1991

Ultrasound detection of neural tube defects in patients with elevated maternal serum alpha-fetoprotein.

We conducted this study to determine the accuracy of ultrasound in the prenatal diagnosis of neural tube defects in women with elevated maternal serum alpha-fetoprotein (MSAFP). Among 905 pregnancies, 49 neural tube defects were correctly diagnosed by ultrasound alone; one was not. Ultrasound scanning had 98% sensitivity and 100% specificity for the detection of neural tube defects. The predictive value of a positive ultrasound diagnosis was 100% and of a negative ultrasound 99.9% for neural tube defects. Forty-three other structural abnormalities were also detected in patients with elevated MSAFP, including 19 abdominal wall defects, seven chromosomal abnormalities, five urinary tract abnormalities, one cardiac abnormality, and 11 others. Two chromosomal abnormalities were not detected. We suggest that ultrasound can be used reliably to detect neural tube defects, thereby avoiding the risks of amniocentesis.

Female↗
PubMed1988

Birth prevalence and recurrence rates of neural tube defects in southern Alberta in 1970-81.

Given the observed variation in birth prevalence and recurrence rates of neural tube defects, it is important to obtain such data specific to a given locality for research and genetic counseling purposes. A review of hospital medical charts, the patient lists of the Medical Genetics and Myelomeningocele clinics at Alberta Children's Hospital and data from the Canadian Congenital Anomalies Surveillance System revealed the annual birth prevalence rate of neural tube defects in southern Alberta in 1970-81 to be 1.62/1000 total births. This figure suggests southern Alberta to be a low-frequency area. There was no significant variation in the annual rates of spina bifida, encephalocele or all neural tube defects combined over the study period. A significant linear decline in the frequency of births of anencephalic infants, however, was noted (p = 0.025). Information on the total reproductive history of the mothers revealed that the empiric risk of recurrence of a neural tube defect was 2.2%, and the risk to all siblings was estimated to be 2.3%. In future prevalence studies multiple sources of case ascertainment should be used, including data on pregnancies terminated because of a fetal neural tube defect.

Alberta↗
PubMed1990

Neural tube defects: are neurulation and canalization forms causally distinct?

Neural tube defects (NTD) may be separated according to the overall location and probable embryological origin into 2 groups: upper or neurulation defects, and lower or canalization defects. Evidence as to whether these 2 forms are causally related or distinct was sought from 2 sources. Families with more than one NTD individual were studied to examine whether there was concordance within sibships for these 2 types of lesion. Seven of the 38 sibships were discordant (18%). Eight of the 10 cases of NTD that had arisen despite maternal periconceptional vitamin supplementation were neurulation defects and 2 were canalization defects. Both observations suggest that upper and lower types of NTD are causally related, and offer no support for the suggestion that they are distinct.

Humans↗
PubMed1982

Sonography as a procedure complementary to alpha-fetoprotein testing for neural tube defects.

Forty-four fetuses were studied sonographically because of an elevated amniotic fluid alpha-fetoprotein level noted during routine amniocentesis, questionable findings during an ultrasound examination at another institution, or a history of a neural tube defect in prior pregnancy. Eleven neural tube defects, 16 non-neural tube defect anomalies, and 17 normal fetuses were all correctly identified by sonography. Ultrasound answers the need for a second diagnostic tool to complement the alpha-fetoprotein measurement.

Amniotic Fluid↗
PubMed1984

The improvement of the antenatal detection of fetal neural tube defects using discriminant analysis.

Discriminant analysis was applied to the antenatal diagnosis of fetal neural tube defects. Alpha-fetoprotein, gestational age, and seven easily assayed biochemical variables were used to generate the discriminant function, which was derived from a retrospective study on data from 130 pregnancies, including 25 which were associated with fetal anencephaly and 13 with fetal spina bifida. This function was used to generate a diagnosis in a blind study of 40 previously unassayed samples: 20 problem samples from another centre interspersed with 20 normal samples. The same function was used over a period of 2 years to predict prospectively the outcome of 669 pregnancies with respect to neural tube defects. Of these 55 were found to be associated with fetal neural tube defects. Classification is shown to be more reliable than using alpha-fetoprotein and gestational age alone. The results demonstrate a successful application of discriminant analysis to medical diagnosis.

Amniotic Fluid↗
PubMed1982

Neural tube defects in Havana City--incidence and prenatal diagnosis.

An evaluation was made of all cases of neural tube defects born in seven gynaecological hospitals and obstetric centres of Havana, between 1970 and 1980. Neural tube defects were recordable from 492 infants out of 319,228 births. The families concerned were briefed in human genetics and informed about the possibility of prenatal diagnosis of anencephaly and bifid spine (spina bifida aperta). Some of them had a record of this defect. Amniocentesis was applied to 30 women with an empirical risk of 1:20, and alphafoetoprotein was analysed in their amniotic fluid. Anencephaly was diagnosed in one case and confirmed by termination of pregnancy. The occurrence of neural tube defects usually is of spontaneous nature, and incidence is relatively high. Therefore efforts are now being made to introduce a scheme of prenatal screening based on alphafoetoprotein assessment in the serum of pregnant women.

Amniocentesis↗
PubMed1989

[Quantitative acetylcholinesterase (AChE)--determination in amniotic fluid--potential for differential diagnosis in consistently high AFP levels during general AFP screening for prenatal diagnosis of open neural tube defects].

Measurement of maternal serum alpha-fetoprotein concentration for prenatal detection of open neural tube defects had been introduced into the obstetrical care of pregnant women in the district of Schwerin since 1983. In cases of high risk for presence of an open neural tube defect, noticed by elevated levels of maternal serum alpha-fetoprotein concentration step by step further diagnostic steps are necessary. In addition to special examination by ultrasound and measurement of alpha-fetoprotein concentration in amniotic fluid quantitative analysis of acetylcholinesterase activity in amniotic fluid seems to be valuable. Reliability of detecting open neural tube defects in prenatal care had been proved by quantitative analysis of acetylcholinesterase activity in amniotic fluid. The existing results up to now were very reliable, especially biological transit stages from normal to pathological findings were taken into consideration, too. In these cases further controls are necessary. Levels of acethylcholinesterase activity below the 90th percentile can be considered as normal findings, levels above the 99th percentile must be interpreted as pathological findings. These are our experiences up to date.

Acetylcholinesterase↗
PubMed1979

Amniotic-fluid acetylcholinesterase as a possible diagnostic test for neural-tube defects in early pregnancy.

Raised levels (greater than or equal to 4.5 munits/ml) of acetylcholinesterase (AChE) activity in amniotic fluid at 14--23 weeks of pregnancy were significantly associated with open fetal neural-tube defects. Out of 72 pregnancies correctly classified by the amniotic-fluid alpha-fetoprotein (A.F.P.) test, 2 of 56 without neural-tube defects and all 16 with open neural-tube defects (8 with anencephaly and 8awith open spina bifida) had raised levels of AChE. Out of 5 pregnancies misclassified by the A.F.P. test (4 without neural-tube defects and 1 with open spina bifida), only 1 was misclassified by the AChE test--namely, one of those without a neural-tube defect. Thus, only 3 of the 77 pregnancies tested were misclassified by the quantitative AChE test. A qualitative test for an isoenzyme of AChE found in cerebrospinal fluid correctly classified these 3 pregnancies. These findings suggest that the analysis of AChE in amniotic fluid may be a useful test in the diagnosis of open neural-tube defects.

Acetylcholinesterase↗
PubMedDate not supplied

Early pregnancy screening for neural tube defects in Israel.

A pilot project to detect neural tube defects (NTD) of the fetus by maternal serum alpha-fetoprotein (MSAFP) screening of women in early pregnancy was initiated in Tel Aviv in 1982 at the instigation of the Israel Ministry of Health. The program was designed to be an extension of routine pregnancy care, which in this city is provided in municipal family clinics that are attended by about 50% of pregnant women before the 20th week of pregnancy. Of these women, 89% complied with the program. Women with a MSAFP level above a cutoff point of 2.4 multiples of the median (MOM) were invited for an ultrasound examination of the fetus, without having to repeat the MSAFP test, thereby reducing maternal anxiety. This deviation from the usual test system protocol did not impair sensitivity (87%), or specificity of the test on its own (95.6%), or in combination with ultrasound examination of the fetus and alpha-fetoprotein and acetylcholinesterase testing of the amniotic fluid (99.9%). The program detected 13 fetuses with an NTD; there were two false-negative results and one false-positive. The predictive value of a positive test was 93%. Its effectiveness as a preventive measure was impaired by the fact that 50% of pregnant women did not attend the family clinic before the 20th gestational week. An educational program for professionals and for the public is contemplated in order to reduce this proportion. Only 50% of normal twin pregnancies had an elevated MSAFP. A check on compliance with other screening systems during the interview for MSAFP screening led to the detection and elective abortion of two fetuses with Tay-Sachs disease. MSAFP screening in Israel is cost-effective rather than cost-beneficial.

Amniocentesis↗
PubMed1977

Amniography for the early detection of neural tube defects.

Among the methods available for the midtrimester diagnosis of neural tube defects, it has been suggested that amniography be used to determine the presence of meningomyelocele. Twelve studies are reported in which the procedure was utilized. In 3 cases, a neural tube defect was present but was not detected by this method. The experience reported here challenges the value of this procedure and suggests that it should be evaluated further by utilizing it in cases where a positive diagnosis has been made by other methods and pregnancy termination is to be performed.

Adolescent↗
PubMed1983

Prevention of neural tube defects in an urban health district.

An evaluation of voluntary prenatal screening for neural tube defects with serum alphafetoprotein (s-AFP) is presented. During a three year period, there were 52 fetuses with neural lesions. Of 46 mothers who bore a fetus with an open neural lesion, 25 were detected, of whom 23 agreed to the termination of their pregnancies. An unscreened group of 2331 mothers (17% of all deliveries) produced 14 fetuses with neural tube defects, an incidence of 6.0 per 1000, 1.8 times the incidence (3.3 per 1000) in the screened group. Pitfalls occurring in the assessment of hyper-alphafetoproteinemia included inaccurate gestational dating and allowance for excessive body weight. The results of a robust AFP-NTD screening programme supported in selected cases by ultrasonar visualisation of the spine argue for its continuance in this district.

Child, Preschool↗
PubMed1992

Sex ratios of affected and transmitting members of multiple case families with neural tube defects.

In order to study the genetic aspects of the relation between neural tube defects and sex, we selected families with at least two closely related affected members. The sex ratios of both affected and normal transmitting persons were determined in these multiple case families. Our results indicate that there is a relation between the position of the lesion in the spine and sex. Furthermore, the affected persons in one family show significant concordance for sex as shown by the analysis of families with just two affected members. To our surprise, the group of normal transmitters appears to consist of significantly more females than males. This is in contrast to similar families with non-syndromic cleft lip +/- palate, where males predominate both among affected persons and normal transmitters. Finally, affected females most often inherited the predisposition to a neural tube defect from their mother. The possible role of inherited factors is discussed.

Female↗