Anencephaly - causes, symptoms and prevention

This developmental disorder causes malformations of the baby's head during gestation.

Neural tube defects are disorders that occur during the first weeks of fetal development and cause malformations of varying severity. While some of them are incompatible with life, others may cause only mild paralysis.

The case of anencephaly is particularly severe; the brain is not fully formed, so babies with this disorder do not live for long. Let's look at the symptoms and causes of anencephaly. symptoms and causes of anencephaly and how it can be prevented. and how this defect can be prevented.

What is anencephaly?

Anencephaly is also known as "aprosencephaly with open skull". Anencephaly is a developmental disorder of the neural tube that causes severe alterations in the growth of the fetus.

In anencephaly the brain and skull do not develop as expected, but incompletely.but do so incompletely. This causes babies with anencephaly to be born without extensive regions of the brain, without some bones of the head and without portions of the scalp, so that the brain is partially exposed.

This alteration occurs in approximately 1 in every 1,000 pregnancies; however, since most of the time the fetus' life ends in a spontaneous abortion, the number of babies with anencephaly that are born is 1 in every 10,000 newborns. It is more common in girls than in boys.

The defects caused by anencephaly are extremely severe and prevent the baby from being able to live. prevent the baby from being able to live. Most affected infants die within hours or days after birth, although there have been cases of children with anencephaly who have lived for almost 4 years.

Anencephaly can be total or partial.. It is considered partial when the roof of the skull, the optic vesicles and the back of the brain are developed to some degree, while if these regions are absent we speak of total anencephaly.

Symptoms and signs

In infants affected with anencephaly, the telencephalon, which contains the cortex and thus the cerebral hemispheres, is usually absent, as are the skull, meninges and skin. In their place is usually a thin layer of membrane.

As a result, anencephaly means that the baby is unable to carry out basic or higher functions, such as feeling pain, hearing, seeing, moving, feeling emotions or thinking.even though in some cases they can emit reflex responses. This means that children with this disorder never become aware of their environment.

In addition to these signs and symptoms, anomalies in the face and cardiac defects are frequent. The greater the missing part of the brain and skull, the more marked the abnormalities are.

The diagnosis of anencephaly may be made during pregnancy by different procedures. Ultrasonography can reveal the presence of polyhydramnios (excess amniotic fluid), while amniocentesis can detect elevated levels of alpha-fetoprotein.

Causes of this disorder

Anencephaly occurs as a result of a defect in the development of the neural tube. defect in the development of the neural tube which normally occurs in the fourth week of embryonic development. The neural tube is the structure that gives rise to the central nervous system, i.e. the brain and spinal cord. In this particular case, the tube fails to close at its rostral or upper end.

There are other disorders that are due to abnormal development of the neural tube; collectively they are known as "neural tube defects", and in addition to anencephaly include spina bifidain which the spinal column closes incompletely, and Chiari malformations, which cause brain tissue to spread into the spinal canal.

Failure of the neural tube to close properly causes the amniotic fluid that protects the fetus to come into contact with the nervous system, damaging the neural tissue and preventing normal development of the brain and cerebellum, thus causing deficits or even the absence of the functions associated with these.

Genetic and environmental risk factors

Normally the appearance of this defect does not depend on heredity but on a combination of genetic and environmental factors. combination of genetic and environmental factors. However, some cases have been detected in which anencephaly has occurred repeatedly in the same family, and having a baby with anencephaly increases the risk of it also occurring in successive pregnancies.

The specific hereditary mechanism by which this happens is not known, although it is believed that there is a link between anencephaly and the MTHFR gene, involved in the processing of the vitamin B9, also known as folic acid or folate.. Alterations in this gene appear to increase the risk of anencephaly, although not very significantly.

The homeoprotein CART1, which enables the development of cartilage cells, has also been associated with the development of anencephaly.

Environmental risk factors affecting the mother are probably more relevant than genetic ones. Among these factors, scientific research highlights the following:

• Vitamin B9 deficiency.
• Obesity.
• Diabetes mellitus, especially if it is type I and uncontrolled.
• Exposure to high temperatures (e.g. fever, saunas).
• Consumption of anticonvulsant drugs such as lamotrigine..

It also appears that anencephaly is more common in babies born to Asian, African and Hispanic mothers, although the reason for this increased risk is not known.

Treatment and prevention

Anencephaly cannot be cured. Babies born with the condition are usually given food and water and made comfortable, but the use of medication, surgery or life support is considered irrelevant; since the infant will never become conscious, they are usually left to die naturally, without artificial resuscitation.

Research has shown that the consumption of folic acid (vitamin B9) greatly reduces the risk of neural tube defects, including anencephaly and spina bifida. This vitamin is found both in foods, e.g. green leafy vegetables, and in dietary supplements; in the latter case, 0.4 mg daily seems to be sufficient.

However, vitamin B9 must be taken before pregnancy, since these alterations normally occur during the first phase of fetal development, before the woman detects that she is pregnant. Thus, specialists recommend increasing the intake of this vitamin when starting to try to have a baby.