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At least 19 recordsLinked to original sources
PubMed1984

Generation of anencephaly: 1. Aberrant neurulation and 2. Conversion of exencephaly to anencephaly.

An experimental model for anencephaly was used to focus on two important aspects of the development of anencephaly: neurulation and conversion of exencephaly to anencephaly. Vitamin A was administered to pregnant rats on gestational days nine and ten. The animals were killed on successive gestational days to allow study of the development of anencephaly. The scanning electron microscope revealed filopodia and lamellopodia as the predominant mode of initial neural fold contact in the controls. Intertwining and overlapping of filopodia and lamellopodia with fusion of the adjacent cutaneous ectoderm completed neurulation. In embryos developing anencephaly, filopodia and lamellopodia never made contact above the cervical region and exencephaly resulted. The first evidence of the conversion of exencephaly to anencephaly was profound, labyrinthine expansion of the extracellular space of the telencephalic mantle. In spite of normal vascular patency and intact vessel walls, the exencephalic malformation spontaneously disintegrated, converting the lesion to anencephaly. The causes for tissue disintegration other than infarction must be considered in reconstructing the pathogenesis of anencephaly.

Anencephaly↗
PubMed1971

Is anencephaly a single entity? A brief note on the morphologic heterogeneity of anencephaly.

Considerations of the genetics of anencephaly have been based on the premise that this dysraphism is a single entity. However, morphologically anencephaly is a heterogeneous group made up of at least four major morphologic types-anencephalus craniorachischisis, anencephalus acrania, microcephalus acrania and microcephalus craniorachischisis. While I believe that the various types of anencephaly represent only degrees of severity of the same basic underlying defect(s), the possiblity of genetic as well as morphologic heterogeneity should be considered.

Anencephaly↗
PubMed1995

Surveillance for anencephaly and spina bifida and the impact of prenatal diagnosis--United States, 1985-1994.

PROBLEM/CONDITION: The reported prevalence of anencephaly and spina bifida in the United States has steadily declined since the late 1960s. During this time, the ability to diagnose these defects prenatally has progressed rapidly. Many U.S. birth defects surveillance systems ascertain defects only among live-born infants or among infants and fetuses beyond a certain gestational age, thus excluding defects among pregnancies prenatally diagnosed as being affected by a neural tube defect (NTD) and electively terminated before the gestational age limit. The impact of prenatal diagnosis and subsequent pregnancy termination on the reported prevalence of anencephaly and spina bifida in the United States has not been well established. However, assessment of this impact is crucial to the use of surveillance data to monitor trends in the occurrence of NTDs and the effectiveness of interventions for these defects (e.g., increased consumption of folic acid). REPORTING PERIOD: This report presents data from birth defects surveillance systems in six states over different time periods: Arkansas, 1985-1989; California, 1989-1991; Georgia, 1990-1991; Hawaii, 1988-1994; Iowa, 1985-1990; and South Carolina, 1992-1993. DESCRIPTION OF SYSTEMS: Population-based data about a) live-born and stillborn infants with anencephaly and spina bifida and b) pregnancies electively terminated after prenatal diagnosis of these defects were analyzed from the Arkansas Reproductive Health Monitoring System; the California Birth Defects Monitoring Program; CDC's Metropolitan Atlanta Congenital Defects Program; the Iowa Birth Defects Registry, the University of Iowa, and the Iowa Department of Public Health; and the Greenwood Genetic Center in South Carolina. Data also were analyzed from the Hawaii Birth Defects Monitoring Program, which includes data for some women who were not residents of the state. The systems differed in the size and racial/ethnic composition of the populations studied, the surveillance methods used, the completeness of ascertainment, and the availability and utilization of prenatal testing and pregnancy termination. RESULTS AND INTERPRETATION: Among all pregnancies ascertained in which the infant or fetus had anencephaly or spina bifida, the percentages that were electively terminated ranged from 9% in Arkansas to 42% in Atlanta and Hawaii, with a corresponding increase in the adjusted prevalence of these defects compared with the prevalence at birth. In each system, pregnancies associated with anencephaly were terminated more frequently than were those associated with spina bifida. These data indicate that the impact of prenatal diagnosis and subsequent pregnancy termination on the prevalence at birth of anencephaly and spina bifida differs among geographic areas and populations. Comprehensive surveillance for these defects requires inclusion of pregnancies that are prenatally diagnosed and then terminated. ACTIONS TAKEN: CDC will use these data to promote the inclusion of prenatally diagnosed and terminated pregnancies in estimates of the prevalence of anencephaly and spina bifida generated by birth defects surveillance programs in the United States. Including such pregnancies is crucial to the ability of these programs to monitor trends accurately and to establish the effectiveness of interventions, including the use of folic acid, for these defects.

Abortion, Induced↗
PubMed2002

Reviewing old concepts at the start of a new millenium: growth restriction, adrenal hypoplasia, and thymomegaly in human anencephaly.

BACKGROUND: Anencephaly has been associated frequently with intrauterine growth retardation (IUGR), consistently with adrenal hypoplasia, and occasionally with an enlarged thymus. Few studies have analyzed the relationship between gestational age (GA), IUGR, associated anomalies and thymomegaly in anencephaly. The aims of our study were to evaluate this relationship and to highlight the usefulness of anencephaly as a model when investigating immune-endocrine interactions. METHODS: Fifty-two anencephalics' autopsies were reviewed retrospectively. Body weight, adrenal, and thymus weights were compared to prenatal, postnatal, and stillborn control values, and between associated and isolated anencephalic cases (presenting with and without other unrelated anomalies). Comparisons of adrenal and thymus weights were done by GA and by body weight. Thymus weight:body weight (TW:BW) ratios were compared to expected values. RESULTS: Anencephalics' body and adrenal weights were lower than their control values, whereas thymus weights did not differ. Body and thymus weights were twice as high in isolated than in associated anencephaly, whereas adrenal weights did not differ. Anencephalics TW:BW ratios were higher than their control values, higher in cases with IUGR, and higher in isolated rather than associated cases. When distributed by GA, thymus weights in anencephaly increased at a higher-than-expected rate. CONCLUSIONS: Our results suggest that adrenal hypoplasia is invariably present in anencephaly, and depending on an underdeveloped pituitary gland, seems to be independent of its etiology. On the contrary, IUGR mainly exists in associated cases and thymus enlargement mainly exists in isolated cases, suggesting a relationship with the underlying cause.

Abnormalities, Multiple↗
PubMed1995

[The exencephaly-anencephaly sequence. Ultrasound diagnosis in early pregnancy].

AIM: In animal studies exencephaly is well described as a precursor of anencephaly. We have evidence that also in the human fetus the transition from exencephaly to anencephaly is possible. METHOD: We diagnosed either exencephaly or anencephaly by high-frequency vaginal ultrasound in 14 human fetuses at gestational ages varying between 9 + 4 and 22 + 3 weeks. RESULTS: In the first trimester exencephaly was the predominant finding, while in the second trimester the classic appearance of anencephaly was seen more often. In one fetus with exencephaly diagnosed at a gestational age of 12 + 2 weeks, where the parents decided not to intervene, the transition to anencephaly was documented by serial ultrasound examinations. CONCLUSIONS: Our findings support an exencephaly-anencephaly sequence also in humans. The cephalic changes resulting in the classic anencephalic appearance are of importance for the first trimester diagnosis with high resolution vaginal probe ultrasound.

Anencephaly↗
PubMed2002

Spina bifida and anencephaly prevalence--United States, 1991-2001.

Spina bifida and anencephaly are serious birth defects. To reduce the occurrence of these birth defects, the Food and Drug Administration authorized the fortification of all enriched cereal grain products with folic acid in March 1996, with compliance mandatory by January 1998. This report reviews data reported to CDC's National Center for Health Statistics (NCHS) regarding spina bifida and anencephaly prevalence for live births in the United States during 1991-2001. Since 1989, NCHS has compiled birth defect data from checkboxes that appear on birth certificates. For consistency in trends, this report uses data for 1991-2001 from all U.S. reporting areas except Maryland, New Mexico, and New York. Data for 2001 are preliminary. During 1996-2001, a 23% decline occurred in neural tube defects (spina bifida and anencephaly combined). Spina bifida declined 24% during this period, and anencephaly declined 21%. The United States has experienced declines in spina bifida and anencephaly cases since folic acid fortification of all enriched cereal grain products. The observed declines have translated into approximately 920 infants being born without these serious defects each year. Continued monitoring of the occurrence of spina bifida and anencephaly will be necessary to evaluate the effectiveness of folic acid fortification.

Anencephaly↗
PubMed2002

Prevalence of spina bifida and anencephaly during the transition to mandatory folic acid fortification in the United States.

BACKGROUND: In 1992, the United States Public Health Service recommended that all women of childbearing age consume 400 microg of folic acid daily. The Food and Drug Administration authorized the addition of synthetic folic acid to grain products in March 1996 with mandatory compliance by January 1998. The impact of these public health policies on the prevalence of neural tube defects needs to be evaluated. We sought to determine the prevalences of spina bifida and anencephaly during the transition to mandatory folic acid fortification. METHODS: Twenty-four population-based surveillance systems were used to identify 5,630 cases of spina bifida and anencephaly from 1995-99. Cases were divided into three temporal categories depending on whether neural tube development occurred before folic acid fortification (January 1995 to December 1996), during optional fortification (January 1997 to September 1998), or during mandatory fortification (October 1998 to December 1999). Prevalences for each defect were calculated for each time period. Data were also stratified by programs that did and did not ascertain prenatally diagnosed cases. RESULTS: The prevalence of spina bifida decreased 31% (prevalence ratio [PR] = 0.69, 95% confidence interval [CI] = 0.63-0.74) from the pre- to the mandatory fortification period and the prevalence of anencephaly decreased 16% (PR = 0.84, 95% CI = 0.75-0.95). Stratification by prenatal ascertainment did not alter results for spina bifida but did impact anencephaly trends. CONCLUSIONS: The decline in the prevalence of spina bifida was temporally associated with folic acid fortification of US grain supplies. The temporal association between fortification and the prevalence of anencephaly is unclear.

Anencephaly↗
PubMed1987

The binding and metabolism of low-density lipoprotein by skin fibroblasts of fetuses and newborns with anencephaly.

We have previously demonstrated that the fetus with anencephaly is hypercholesterolemic. The plasma levels of total cholesterol and low-density lipoprotein cholesterol are threefold greater than those of normal fetuses. We have provided evidence that elevated low-density lipoprotein cholesterol levels were caused by reduced uptake and metabolism of low-density lipoprotein by atrophic adrenal glands deficient in low-density lipoprotein receptors. The purpose of the present investigation was to determine if other tissues, namely, skin fibroblasts, of the fetus with anencephaly were also deficient in low-density lipoprotein receptors. We compared the binding and metabolism of low-density lipoprotein by skin fibroblasts of fetuses with anencephaly and normal subjects. Cultures of skin fibroblasts were grown to confluency. Thereafter, the medium was changed to lipoprotein-deficient serum for 24 hours. The rate of uptake and degradation of iodine 125-iodo-LDL was determined as a function of time and concentration of low-density lipoprotein. The maximal specific binding of low-density lipoprotein was also determined. The rate of uptake, degradation, and the maximal binding of low-density lipoprotein was similar in skin fibroblasts of infants with anencephaly and normal subjects. We conclude that the elevated level of low-density lipoprotein cholesterol in cord blood of fetuses with anencephaly is not caused by deficiency of low-density lipoprotein receptors and metabolism in skin fibroblasts but instead by deficiency of low-density lipoprotein receptors and metabolism by atrophic adrenal glands.

Adrenal Glands↗
PubMedDate not supplied

[Anencephaly at 20 weeks gestation. What is the optimal gestational age for early diagnosis?].

Anencephaly is a lethal defect resulting from a disturbed closure of the neural tube. Prenatal diagnosis during first-trimester-scan is essential but implies pitfalls. Three findings of anencephaly at 20 weeks gestation are reported. Fetuses with anencephaly are correctly identified at 12 to 13 weeks gestation. Anencephaly occurs in absence of the cranial vault. Ultrasound findings can be normal until onset of ossification has definitely failed. A first trimester scan at 12 to 13 weeks allows reliable diagnosis and active management of anencephaly. At this gestational age fetal anatomy can be screened in detail by transvaginal ultrasound and nuchal translucency can be measured.

Abnormalities, Multiple↗
PubMed1976

Twinning and anencephaly.

The literature on anencephaly in twins ascertained in series has been reviewed and some hitherto unpublished data presented. 1. Anencephaly rates in opposite-sexed twin pairs seem not to differ appreciably from those in related singleton births. 2. There is good evidence that the incidence of anencephaly is higher in same-sexed twin pairs than in opposite-sexed pairs. One would infer that anencephaly is commoner in MZ than DZ pairs: this inference is supported by some data on anencephaly in twins of which the zygosity has been diagnosed. It is estimated that members of MZ twin pairs are about 1 2/3 times as likely to be anencephalic as are other individuals. 3. Concordance rates are not low, as is sometimes suggested, but are of the same order as recurrence rates. 4. It seems likely that concordance rates are higher in same-sexed than in opposite-sexed pairs. This would be expected because of the sex-preferential nature of the condition, and the hypothesized higher incidence rates in MZ pairs.

Anencephaly↗
PubMed1981

Differences between the events preceding spina bifida and anencephaly.

It is usually held that there is a time continuum in the formation of monoxygotic (MZ) twins which is indexed by their placentation, running from dichorionic to monochorionic diamniotic to monochorionic monoamniotic and conjoined pairs. There is good evidence that this continuum is characterised by a continuum of predisposition to anencephaly, slightly raised in dichorionic pairs but very high in some sorts of conjoined pairs. Although MZ twins, especially monoamniotic and conjoined pairs, are peculiarly liable to anencephaly, they are not particularly susceptible to spina bifida. Among twin pairs concordant for anencephaly or spina bifida, there are strikingly few concordant in the sense of one twin having anencephaly and the other spina bifida, in contrast with the numbers of pairs concordant for the same malformation. The prevalence of anencephaly in double monsters varies with the type of monster, being high in diprosopus. These findings may be explained by the timing of embryonic events.

Anencephaly↗
PubMed1991

Anencephaly in the United States, 1968-1987: the declining incidence among white infants.

The ethical issues concerning the use of fetal tissue as a source for organ transplantation has focused interest on anencephaly. For reasons that are not entirely clear, the incidence of anencephaly has been declining. As anencephaly is easily recognized and invariably fatal, mortality figures provide an excellent reflection of incidence. In the United States, between 1968 and 1987, infant mortality rates per 100,000 live births due to anencephaly declined from 22.4 to 12.1 (46.0%) for male infants and from 32.7 to 16.6 (49.2%) for female infants. However, when separated by race, the mortality rate declined for white male infants from 25.0 to 13.3 (46.8%) but only decreased from 9.0 to 7.7 (14.4%) for nonwhite male infants. The mortality rate declined for white female infants from 36.7 to 17.6 (52.0%) and actually increased slightly from 12.8 to 13.2 (3.1%) for nonwhite female infants. Thus, the declining incidence of anencephaly reflects a declining incidence of affected white infants but not of affected nonwhite infants.

Anencephaly↗
PubMed2000

[Maternal risk factors associated with anencephaly].

INTRODUCTION: Anencephaly has factors of risk genetics, environmental and maternal. OBJECTIVE: Identify maternal factors of risk for anencephaly. DESIGN: Case-control study. SETTING: Department of Gyneco-Obstetrics and Pediatrics; second level Social Security Hospital. PARTICIPANTS: 69 pregnant patients attended in their delivery, 23 cases and 46 controls. INTERVENTIONS: We applied a questionnary with questions about factors of risk to each patient with anencephaly children (cases), and to two mothers with healthy children (controls). MEASUREMENTS: The data were analyzed and in boards 2 x 2 resisting differentiates them with x2 test, and the association was measured with odds ratio (OR). Results greater than 1.5 with IC95% by above 1 were significant. RESULTS: Incidence of anencephaly is 2.82/1,000 live births. Association with maternal age, pregnancy, gestational pathology, exposition to high temperatures, mother occupation, exposition to chemical or physical agents, was not found. Protective effects associated, with drug administration during gestation, mainly multivitamin preparations, was found. CONCLUSIONS: The incidence is high, it is a public health problem. During pregnancy probability of anencephaly was less frequent in mothers receiving multivitamin preparations.

Adolescent↗
PubMed2000

Prenatal tea consumption and risks of anencephaly and spina bifida.

PURPOSE: To evaluate the relationship between prenatal tea consumption and risk of anencephaly and spina bifida.METHODS: Data from the population-based Atlanta Birth Defects Case-Control Study were examined. Cases were infants with anencephaly (n = 122) or spina bifida (r = 154) and no other associated anomalies, and identified between 1968 and 1980. Controls were infants without birth defects (n = 3029) identified from birth certificates of the same birth cohort and frequency matched to cases by race, period of birth, and hospital of birth.RESULTS: Maternal tea consumption during the periconceptional period (3 months before through the first trimester of pregnancy) was reported at 82, 83.6, and 92.9% among controls, anencephaly, and spina bifida cases, respectively. With subjects whose mothers consumed no tea as a reference, odds ratios (OR) for tea consumption during the periconceptional period (adjusted for gender, race, period of birth, maternal age, education, alcohol consumption, smoking, and periconceptional multivitamins) were: anencephaly 0.9 (95% confidence limits (CI) 0.5-1.5); spina bifida 2.3 (CI 1.2-4.4). Odds ratios for spina bifida and number of cups of tea consumed/day were: 1-2 cups 2.1 (CI 1.1-4.0); 3+ cups 2.8 (CI 1.4-5.6). Consumption of other caffeinated beverages was not associated with risk for anencephaly or spina bifida.CONCLUSIONS: Further studies are warranted to corroborate and elucidate the observed association between tea consumption and spina bifida.

Journal Article↗
PubMed1994

Prevention of folic acid-preventable spina bifida and anencephaly.

The results of the British Medical Research Council's randomized controlled trial proved that folic acid can prevent spina bifida and anencephaly. The trial provided critical scientific data upon which to base public health policy for preventing folic acid-preventable spina bifida and anencephaly. Within weeks of publication of the results, the Centers for Disease Control and Prevention in the US developed and issued guidelines for women who had had a pregnancy affected by spina bifida or anencephaly. A year later, the US Public Health Service issued the recommendation that all women of child-bearing age who are capable of becoming pregnant should consume 0.4 mg of folic acid per day. The Public Health Service needed a year to make inferential judgements about dose, target groups, safety, timing of ingestion, and existing and proposed vitamin and drug policies and regulations. Current policy discussions concern whether to permit manufacturers of vitamins or food products to claim that folic acid will prevent folic acid-preventable spina bifida and anencephaly and whether to allow a food staple to be fortified with folic acid.

Anencephaly↗
PubMed1995

Major gene is responsible for anencephaly among Iranian Jews.

Anencephaly is relatively frequent in Jews originating from Iran, in particular when its incidence is compared to that of open spina bifida in the same population (12 cases of anencephaly out of 14 cases of neural tube defects). The high incidence of this disorder in Iranian Jews, a relatively isolated community with a very high rate of consanguinity, suggests that anencephaly is caused by a major recessive gene. This possibility is supported by the sex ratio among these patients, which was significantly different from that observed for patients with anencephaly in other populations.

Anencephaly↗
PubMed2002

Sequential observations of exencephaly and subsequent morphological changes by mouse exo utero development system: analysis of the mechanism of transformation from exencephaly to anencephaly.

Anencephaly has been suggested to develop from exencephaly; however, there is little direct experimental evidence to support this, and the mechanism of transformation remains unclear. We examined this theory using the exo utero development system that allows direct and sequential observations of mid- to late-gestation mouse embryos. We observed the exencephaly induced by 5-azacytidine at embryonic day 13.5 (E13.5), let the embryos develop exo utero until E18.5, and re-observed the same embryos at E18.5. We confirmed several cases of transformation from exencephaly to anencephaly. However, in many cases, the exencephalic brain tissue was preserved with more or less reduction during this period. To analyze the transformation patterns, we classified the exencephaly by size and shape of the exencephalic tissue into several types at E13.5 and E18.5. It was found that the transformation of exencephalic tissue was not simply size-dependent, and all cases of anencephaly at E18.5 resulted from embryos with a large amount of exencephalic tissue at E13.5. Microscopic observation showed the configuration of exencephaly at E13.5, frequent hemorrhaging and detachment of the neural plate from surface ectoderm in the exencephalic head at E15.5, and multiple modes of reduction in the exencephalic tissue at E18.5. From observations of the vasculature, altered distribution patterns of vessels were identified in the exencephalic head. These findings suggest that overgrowth of the exencephalic neural tissue causes the altered distribution patterns of vessels, subsequent peripheral circulatory failure and/or hemorrhaging in various parts of the exencephalic head, leading to the multiple modes of tissue reduction during transformation from exencephaly to anencephaly.

Abnormalities, Drug-Induced↗