ANENCEPHALY: SYMPTOMS, CAUSES, TREATMENTS - NEUROPSYCHOLOGY - 2024

The Anencephaly is a type of medical condition that prevents the brain and bones of the skull to develop normally. When one of the essential embryonic structures, the neural tube, does not close properly during the first weeks of pregnancy, it will produce a wide variety of congenital alterations: spina bifida, encephalocele, myelomeningocele, among others.

Specifically, anencephaly occurs when the most anterior "cephalic" end or head of the neural tube does not close normally, resulting in the absence of all or a significant part of the brain, skull and / or scalp.

A baby born with anencephaly has a significant absence of much of the brain, usually anterior areas. They generally present in an unconscious state, unable to process much of the external sensory stimulation.

These babies usually cannot see or hear. In addition, in most cases areas of brain tissue can be exposed due to the lack of parts of the skull.

In other cases, some babies are born with areas of the brainstem formed, so they appear to have some primitive responses to sound or somatic stimuli, however they are usually involuntary reactions generated by the brainstem.

These birth defects usually occur during the first month of pregnancy, in many cases before a woman knows she is pregnant. Unfortunately, many of the cases of anencephaly do not reach term of gestation, and many others who are born with this pathology do not usually exceed the hours or days of life, except for some very exceptional cases.

Although the cause of anencephaly is not exactly known, some vitamin components or components of the mother's diet may play an important role, along with other genetic and hereditary factors.

Physiology

Stillborn child with anencephaly.

Anencephaly is a pathology in which a serious defect occurs in the embryonic development of the nervous system, that is, in the formation of the brain, the spinal cord and also in the cranial vault.

The neural tube is an embryonic structure, which during fetal development will give rise to the brain and spinal cord. Because anencephaly is the product of an abnormal closure of this structure, it is classified within the pathologies called with the term "Neural tube defect".

The fusion of this structure usually takes place around days 18 and 26 of gestation and the caudal area of ​​the neural tube will give rise to the spine; the rostral part will form the brain and the cavity will constitute the ventricular system.

The alterations in the formation of the neural tube are produced as a consequence of a defect in its closure. When there is a general failure of the closure of the neural tube, anencephaly occurs.

On the other hand, when a defective closure of the posterior area occurs, it will lead to affectations such as encephalocele and spina bifida occulta. Spina bifida and anencephaly are the two most common neural tube malformations, affecting 1-2 out of every 1,000 live births.

If the neural tube does not close normally, both the brain and the spinal cord will be exposed during their development and formation to the amniotic fluid that contains the fetus in the uterus.

Direct exposure to this liquid will have a strong impact on the formation of the nervous system, as it will progressively degenerate or decompose it.

As a result, anencephaly produces the lack of all or large areas of the brain, regions as important as those responsible for controlling vision, hearing, emotion, movement, coordination, thought, etc. Furthermore, the bones that make up the skull may also be absent or incompletely formed.

All these abnormalities of the nervous system will produce an extremely serious medical condition, due to this in most cases of babies with anencephaly they die before birth or a few hours and days after it.

Types of anencephaly

We can distinguish two types of anencephaly based on their severity:

• Total anencephaly: it occurs as a consequence of damage to the neural plate or lack of induction of the neural tube between the second and third week of gestation. It presents with the absence of the three cerebral vesicles, absence of the hindbrain and without the development of both the roof of the skull and the

  optic vesicles.

• Partial anencephaly: there is a partial development of the optic vesicles and the hindbrain.

Statistics

Anencephaly is one of the most common types of neural tube defects. Overall, it is estimated to affect approximately 1 in 1,000 pregnancies.

Because the majority of these pregnancies result in miscarriage, the prevalence of the disease in newborn babies is lower, about 1 in 10,000.

As we have pointed out, although in most cases of anencephaly pregnancies do not reach term, in the case of the United States, it is estimated that each year approximately 1 in 4,859 babies are born with anencephaly.

On the other hand, in the case of Central Europe, cases of anencephaly usually occur in a proportion of 1 per 1,000 births, despite this, this rate varies considerably depending on the population.

Although the exact figures are not known, different statistical reports indicate that each year there are approximately 5,000 births of babies with anencephaly.

Furthermore, it is observed that more cases occur in girls than in boys, probably due to a higher rate of spontaneous abortion in male fetuses.

Signs and symptoms

With regard to the signs and symptoms that may be indicating the presence of anencephaly, we can refer to both those that are present in the mother during the gestation stage, and those that are present in the fetus.

In the case of the mother, in pregnancies affected by anencephaly, it is possible to observe high levels of a specific protein, alpha-fetoprotein. In addition, it is also possible to identify excess fluid in the amniotic sac (polyhydramnios).

In the case of the affected person, the characteristic features of this pathology can be identified before birth. Specifically, anencephaly is characterized by:

- Absence or malformation of the cranial vault.

- Absence of large areas of the brain, generally the above.

- Possible presence of stem or brainstem.

- Absence or malformations in the scalp.

- Abnormalities in facial features.

On a clinical level, in babies born suffering from this condition, it is expected that they cannot process any type of stimulation or perform coordinated and voluntary movements or actions. Normally, they are born blind and deaf. In general, they are totally isolated.

Despite this, there are cases in which babies show behaviors and behaviors classified as "reflexes", such as making sounds or crying, urinating and defecating, maintaining sleep-wake rhythms, sucking, among others.

Causes

The etiological causes that give rise to the development of this pathology are currently unknown.

However, it has been identified that a deficiency of folic acid (Vitamin B9) both before and during pregnancy can considerably increase the risk of developing neural tube defects during pregnancy, such as anencephaly and spina bifida. On the other hand, the intake of some drugs during pregnancy can also increase the risk.

In most cases, specifically in 90%, parents who have a child with anencephaly do not usually have a family history of this pathology. Despite this, those who have already had a child with anencephaly, have a higher risk of having a child with this pathology again.

The recurrence rate of anencephaly is 4-5% and can increase up to 10-13% if the parents have already had two children with anencephaly.

Most cases of anencephaly are sporadic, occurring in people who do not have a family history of the disease. Although a small percentage of cases run in families, the pathology does not have a clear pattern of heritability.

Anecephaly is a very complex medical condition that is probably the consequence of the interaction between multiple genetic and environmental factors.

Diagnosis

Normally the presence of anencephaly is identified before birth, through the use of various diagnostic tests:

- Blood test: used to identify the presence / absence of high levels of alpha-fetoprotein.

- Amniocentesis: a small amount of amniotic fluid is withdrawn through the abdomen to measure both alpha-fetoprotein and acetylcholinerase levels, since elevated levels may be associated with the presence of neural tube defects.

- Ultrasound: this type of test is delayed ultrasound and is capable of visually identifying anatomical abnormalities.

- Fetal magnetic resonance: it is a brain imaging procedure, used to identify the presence of structural malformations. Because it uses magnetic fields, their use is considerably restricted and they are used between 14 and 18 weeks to confirm the diagnosis.

- Physical examination: after birth the characteristic features of anencephaly are more than evident, so the physical examination is sufficient to confirm the diagnosis.

Is there treatment?

There is currently no specialized cure or treatment for anencephaly. The therapeutic averages used are restricted to life support and the improvement of quality of life.

Prevention

Methods that medical specialists point to as important factors in preventing anencephaly include:

Adequate food and nutrition

It is essential to eat foods with high nutritional content, in addition to using vitamin supplements before and during pregnancy.

Specifically, the consumption of vitamin B9 or folic acid, present in some vegetables or fruits, such as green leafy vegetables or orange, is usually recommended. Also products such as rice, bread, pasta or cereals are fortified with folic acid.

Folic acid pharmacological supplements

In some cases, pregnant women may have deficient levels of folic acid, so it is not unusual for a medical specialist to prescribe a pharmacological treatment based on a vitamin supplement with folic acid.

Forecast

Most fetuses with anencephaly do not survive. However, in many cases, when they arrive at the time of birth, they usually die approximately a few hours or days later.

Despite this, there have been several cases of children who have survived longer:

- Stephanie Keene from Falls Church, Virginia, who lived for 2 years-

- Vitoria de Cristo, born in Brazil, 2 years old.

- Nickolas Coke from Pueblo, Colorado, who lived 3 years and 11 months ago.

- Jaxon Buell, Boston, 13 months old.

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