Anencephaly

Anencephaly is a severe birth defect that can occur as a result of a lack of brain development along with the loss of a portion of the foetal skull. It occurs in about one in 10,000 births. It is believed to occur in as many as 1 in 1000 pregnancies but only a tenth of these survive until term. The rest are miscarried or end in foetal death or termination of the pregnancy. There are sometimes clusters of anencephalic babies born but this is rare and is usually managed by aggressive campaigning for folic acid use in and prior to getting pregnant. Anencephaly has somewhat of a hereditary basis, with anencephaly clustering in families. Interestingly, high dose folic acid seems to manage these hereditary causes of anencephaly as well. There are areas of the world, such as Guatemala, Mexico, parts of the UK and northern China, where anencephaly has a higher than average rate for unknown reasons.

Anencephaly is practically 100 percent lethal in the first few hours or days of life and heroic treatment to save the baby's life is not recommended. Many anencephalic infants are born stillborn or are aborted as a miscarriage without being recognized as being anencephalic. Hispanic and whites have a higher rate of anencephaly than blacks and there are more anencephalic females than males. It is a condition that can be determined by the 28th day after conception so that it is always noted at the time of birth or via an early ultrasound.

Anencephaly is a defect in the closure of the upper end of the neural tube. This results in a lack of development of all but the most rudimentary aspects of the brain and the skull. The cerebrum and cerebellum are absent or, at best, reduced in size and development. The defect occurs around the third to fourth weeks of development, so that foetal or neonatal loss is guaranteed.

It is believed that genetic and environmental factors play a role in getting anencephaly. The mother must take in at least 400 mcg of folic acid every day in the first trimester in order to have enough for neural tube development. A larger chromosome abnormality may play a role in developing the condition or a specific gene may play a role. Most cases of anencephaly are believed to have multifactorial origin.

Anencephaly is readily seen at birth with an absence of the skull visible neural structures seen at the back and top of the head. The facial features are seen but can be deformed to a degree because of the skull absence. The cranial lesion can be covered by skin but this is not usually the case. When it is covered by skin, the maternal alpha fetoprotein level is usually normal. The disease is usually seen as an isolated lesion not associated with other infant abnormalities.

Valproic acid, taken for seizures, can interfere with folic acid metabolism so that it can cause anencephaly in women who take it during pregnancy. Diabetes mellitus type I also increases the risk of neural tube defects such as anencephaly. In addition, NIDDM type I makes the serum alpha fetoprotein level lower so that the diagnosis of anencephaly is harder to make. Maternal hyperthermia such as with hot tubs and saunas can contribute to anencephaly so pregnant women should avoid these activities. Rare cases of autosomal dominant or autosomal recessive anencephaly have been reported.

Testing for anencephaly includes getting a serum alpha fetoprotein level in the pregnant mother. It is done in the second trimester and is followed up with amniotic alpha fetoprotein levels, if the serum level is elevated. An ultrasound in the first or second trimester can also show the presence of anencephaly.

The treatment of anencephaly is completely supportive. There are no heroic measures available to treat anencephaly so infants and parents are kept comfortable until the child dies. The focus should be on the parents and on their understanding of the condition and its lethal implications. Families will often want to take pictures of their infant and hold their infant, which should take precedence over the unnecessary use of medical care. Grief resolution should also be the focus of care of these families, especially if they did not know the child was anencephalic before the time of birth.