Anencephaly

Definition

Definition of Anencephaly
Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp. Strictly speaking, the translation of the Greek term to English is "no brain" (that is, totally lacking), but it is accepted that children with this disorder are born without a forebrain, the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for higher-level cognition, i.e. thinking. The remaining brain tissue is often exposed - not covered by bone or skin. Most babies with this genetic disorder do not survive birth, however there have been notable exceptions.

Symptoms

Symptoms of Anencephaly
The National Institute of Neurological Disorders and Stroke (NINDS) describes the presentation of this condition as follows: "A baby born with anencephaly is usually blind, deaf, unconscious, and unable to feel pain. Although some individuals with anencephaly may be born with a main brain stem, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining consciousness. Reflex actions such as breathing and responses to sound or touch occur."

Causes

Causes of Anencephaly
The cause of anencephaly is disputed. Generally, neural tube defects do not follow direct patterns of heredity, though there is some indirect evidence of inheritance, and recent animal models indicate a possible association with deficiencies of the transcription factor TEAD2. Studies show that a woman who has had one child with a neural tube defect such as anencephaly has about a 3% risk of having another child with a neural tube defect.

It is known that women taking certain medications for epilepsy and women with insulin-dependent diabetes have a higher risk of having a child with a neural tube defect. Genetic counseling is usually offered to women at a higher risk of having a child with a neural tube defect to discuss available testing.

Diagnosis

Diagnosis of Anencephaly
Anencephaly can often be diagnosed before birth through an ultrasound examination. The maternal serum alpha-fetoprotein (AFP screening) and detailed fetal ultrasound can be useful for screening for neural tube defects such as spina bifida or anencephaly.

Treatment

Treatment of Anencephaly
There is no current therapy. Talk to your doctor about care decisions.

Prognosis

Prognosis of Anencephaly
There is no cure or standard treatment for anencephaly and the prognosis for patients is death. Most anencephalic fetuses do not survive birth, accounting for 55% of non-aborted cases. If the infant is not stillborn, then he or she will usually die within a few hours or days after birth from cardiorespiratory arrest. There are longer-surviving examples, namely Stephanie Keene, who lived for 2 years 174 days and Nicholas Coke, who as of 2010, survived to 2 years old.

Prevention

Prevention of Anencephaly
It is important for women who may become pregnant to get enough folic acid.

There is good evidence that folic acid can help reduce the risk of certain birth defects, including anencephaly. Women who are pregnant or planning to become pregnant should take a multivitamin with folic acid every day. Many foods are now fortified with folic acid to help prevent these kinds of birth defects.