- What is anencephaly?
- What role does the brainstem play?
- What do we know about anencephaly?
- Children most affected?
- Can it be treated?
- What causes an anencephaly?
- Is it caused by anything the parents did?
- Life expectancy?
- At what point can an anencephaly be diagnosed?
- What is AFP?
- Is the diagnosis reliable?
- Might the mother’s health be jeopardised?
- What does an anencephalic child look like?
- Can an anencephalic child sense or do anything?
- What happens during the birth of an anencephalic child?
- Can anencephalic children be organ donors?
- What is the rate of recurrence?
- Can anencephaly be prevented?
- What research is being done?
Anencephaly is a congenital birth defect (from the Latin congenitus, “born with”). It begins to develop right at the start of life in the womb. The word anencephaly means “without an encephalon”, the encephalon being the set of nervous center contained in the brain. This is not an entirely accurate definition: whilst a child with anencephaly is indeed born without a scalp, without a vault of the cranium, without meninges, without either brain hemisphere and without a cerebellum, the child is nevertheless usually born with part of its cerebral trunk, brainstem. Many children with an anencephaly die during delivery. The life expectancy of those who survive is only a few hours or days.
Approximately 20 percent of affected infants have additional congenital anomalies (Botto 1999).
Together with the spinal chord, it controls many of the body’s unconscious functions, such as the heart beat, and it coordinates most voluntary movements.
Approximately one child for every 1000 births (Central Europe). This rate varies according to populations. (Sadler, T.W. 2005)
Anencephaly affects more girls than it does boys.
Unfortunately, there is no known treatment for a child with an anencephaly.
Anencephaly belongs to the family of neural tube defects. A neural tube defect (NTD) is a congenital malformation which occurs between the 20th and 28th day after conception (Sadler 1998). The cells of the neural plate make up the foetus’ nervous system. In normal development, they fold back onto themselves in order to create what is called the neural tube, which then becomes the back bone and the spinal cord. After a number of transformations, the superior pole eventually becomes the brain. One can liken this process to a coin whose edges merge at its centre. In the case of an NTD, the neural tube is unable to close completely. Anencephaly occurs when the head end of the neural tube fails to close. Infants with this disorder are born without a scalp or cerebellum. Their meninges, both hemispheres of the brain and the vault of the cranium/skull are also missing, though they usually do have part of the brain stem. The remaining brain tissue is protected only by a thin membrane. The infant can be blind and has no, or very few, reflexes. About ¼ of anencephalic babies die at birth; those who survive have a life expectancy of a few hours or days.
It is still not known what causes anencephaly. It is probably triggered by a combination of genetic and environmental factors (Sadler 2005). We nevertheless know that taking Folic Acid can prevent anencephaly. Some medicines (the pill, valproic acid, antimetabolic drugs and others) lower Folic Acid levels, hence taking them increases the risk of giving birth to a child with anencephaly (Sadler, 2005).
Chromosomal abnormalities, single-gene mutations, and teratogenic causes are indentified in fewer than 10 percent of affected infants (Holmes 1976)
No, no one is to blame for the baby having anencephaly
About 25% of anencephalic children who live to the end of the pregnancy die during delivery; 50% have a life expectancy of between a few minutes and 1 day, 25% live up to 10 days.
Get more information: Report about the birth and life of babies with anencephaly
An experienced specialist using a high-resolution ultrasound scan can detect an anencephaly as early as the 10th week. In less-than-ideal circumstances, however, an anencephaly cannot be picked up or ruled out by an ultrasound scan until the 16th week of the pregnancy.
AFP levels can be measured via a maternal serum screening test (blood test). If levels are high, there is a risk that the child may be suffering from an NTD. Further tests must then be carried out (ultrasound scan or amniocentesis) to determine whether there really is a problem. Screening must take place between the 15th and the 20th week, the best time being the 16th week.
The foetus, through its urine, releases into the amniotic liquid a protein called alpha-fetoprotein (AFP). The exposed tissue of a child suffering from an NTD release greater quantities of AFP into the amniotic liquid. The AFP then enters the mother’s blood stream through the placenta and can hence be measured.
Anencephaly is a malformation which is very easy to see on an ultrasound scan. If a qualified doctor has made an ultrasound scan diagnosis after the 16th week, the likelihood of a misdiagnosis is minimal. A positive maternal serum screening test, however, simply shows that there is a higher risk that the baby has Trisomy 21 or 18, or an neural tube defect. Most women who test positive give birth to healthy babies. Additional tests must be carried out to determine whether the baby is suffering from one of those ailments.
No. Pregnancy is unaffected. In around a quarter of cases, too much amniotic liquid is produced (polyhydramnios). This is due to the fact that the child does not have the reflexes to enable it to swallow the amniotic liquid. If the volume of liquid is excessive, it can cause discomfort for the mother. Labour may be triggered prematurely, or waters may break. An amniocentesis can then be carried out to reduce the amount of liquid; Amniotic liquid is removed with a syringe, thus providing the mother with temporary relief.
The body of an anencephalic child is entirely unaffected. However, the vault of the cranium is missing from the eye-brows up. Half-way up to the back of the head is usually covered by skin and hair. Vivid dark red neural tissue covered by nothing more than a thin membrane can be seen through an opening in the head. The size of this opening varies considerably from one child to another. The eyeballs can protrude because of a malformation of the eye-sockets, which is why anencephalic children are sometimes pejoratively described as looking like frogs. Pictures of anencephalic babies
fig. 1 diagram of an anencephalic baby's head, click on the thumbnail to enlarge
Doctors will tell you that an anencephalic child can neither see nor hear, nor feel pain, that he or she is a vegetable. However, that does not match up with the experience of many families who have had an anencephalic child. The brain is affected to varying degrees, according to the child; the brain tissue can reach different stages of development. Some children are able to swallow, eat, cry, hear, feel vibrations (loud sounds), react to touch and even to light. But most of all, they respond to our love: you don’t need a complete brain to give and receive love- all you need is a heart!
Normally, the baby helps to trigger labour with its pituitary gland and suprarenals (glands of the kidneys). However, these are either missing or their development has been stunted in anencephalic children, hence labour does not always begin spontaneously. As a result, many women ask that labour be induced at the end of their pregnancy. As the vault of the cranium is missing, it is important that the waters do not break for as long as possible during labour so that they can exert the necessary pressure on the cervix for it to dilate. If it is possible to keep the waters intact, the birth of an anencephalic child will happen in almost the same way as if the mother were giving birth to a healthy child, and will take as long. The experience of mothers of anencephalic children has shown that the artificial breaking of waters significantly reduces the chances of the baby being born alive. (see report about the birth and life of babies with anencephaly)
Theoretically they can. In practice, there are certain problems.
The science of organ grafting in newly-born babies is incipient; its medium-term results are not well known, whereas its long-term results are not known at
all. The organs of an anencephalic child can only be removed if the child has been certified dead. However, the criteria that define cerebral death cannot usually be applied to children under 7 days old. Before cerebral death is confirmed, the organs of such children may become so damaged that they are unfit for organ-donation. Anencephalic children do not have a rear brain but they do have a forebrain which usually functions normally at birth. The forebrain dies slowly and other organs may die in the intervening period of time. It has been observed that clinical cerebral death (complete absence of reactions and reflexes and absence of spontaneous breathing) almost always occurs after the heart has begun to fail. Therefore anencephalic children would only rarely be able to donate organs.
In some countries, the heart valves can be removed for use in a later transplant. The problems mentioned above are less relevant because the valves can be removed up to 8 hours after the death of the child and are frozen until a recipient is found.
Find Links about organ donation in anencephalic infants
In most cases it is an isolated anomaly and it is very unlikely that it should occur again in the same family. Statistically, the rate of recurrence for a woman who has already had an anencephalic child is 4%.
For some time now, the aetiology of Neural Tube Defects has cited diet and environmental factors. Clinical studies have confirmed that taking a vitamin called Folic Acid reduces the risk of developing a Neural Tube Defect. If all women of child-bearing age took 0.4 mgs of Folic Acid every day before conception and at least until the end of the first term of pregnancy, 50 to 70% of potential cases of anencephaly and Spina Bifida could be prevented (Ceizel and Dudas, 1992). Learn more about the prevention of neural tube defects
The National Institute of Neurological Disorders and Stroke conducts and supports a wide range of studies that explore the complex mechanisms of normal brain development. The knowledge gained from these fundamental studies provides the foundation for understanding how this process can go awry and, thus, offers hope for new means to treat and prevent congenital brain disorders including neural tube defects such as anencephaly.
The Duke Center for Human Genetics is currently conducting a genetic study called "The Hereditary Basis of Neural Tube Defects" to determine the causes of anencephaly and other NTDs. By studying families with anencephaly and other NTDs, they hope to identify the genes that contribute to the development of the neural tube. They hope this research will eventually lead to more accurate genetic counseling and risk assessment, improved treatments, better prevention methods, and possibly, a cure.
More information and how to participate: http://www.chg.duke.edu/diseases/anencephaly.html
* PONTI Study (Prevention Of Neural Tube defects by Inositol) www.pontistudy.ich.ucl.ac.uk
If you have had a pregnancy affected by a neural tube defect and planning another pregnancy, you might want to know about an important research project that aims to prevent neural tube defects with a vitamin treatment. UK only.
Botto LD et al, 1999. Neural-Tube Defects. N England J Med 341:1509-1519
Czeizel AE, Dudas I. 1992. Prevention of first occurence of neural tube defects by periconceptional vitamin supplementation. N Engl J Med 327:1832-1835
Holmes LB, Briscoll SG, Atkins L. 1976. Etiologie heterogeneity of neural-tube defects. N Engl J Med 1976;294:365-369
Sadler TW, 1998. Mechanisms of neural tube closure and defects. Ment Retard Dev Disabil Res Rev 1998;4:247-53
Sadler TW. 2005. Embryology of Neural Tube Development. American Journal of Medical Genetics Part C 135C:2-8
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