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Health Library : Neurological Disorders

 

Anencephaly

What is anencephaly?

Anencephaly is a condition present at birth that affects the formation of the brain and the skull bones that surround the head. Anencephaly results in only minimal development of the brain. Often, the brain lacks part or all of the cerebrum (the area of the brain that is responsible for thinking, vision, hearing, touch, and movement). There is no bony covering over the back of the head and there may also be missing bones around the front and sides of the head.

What causes anencephaly?

Anencephaly is a type of neural tube defect that occurs in about one of 10,000 pregnancies in the U.S. each year. The actual number is unknown because many of these births result in miscarriages. According to the CDC, one in every 4,859 newborns in the United States has this condition.

During pregnancy, the human brain and spine begin as a flat plate of cells, which rolls into a tube, called the neural tube. If all or part of the neural tube fails to close, leaving an opening, this is known as an open neural tube defect, or ONTD. This opening may be left exposed or covered with bone or skin.

Anencephaly and spina bifida are the most common ONTDs, while encephaloceles (where there is a protrusion of the brain or its coverings through the skull) are much rarer. Anencephaly occurs when the neural tube fails to close at the base of the skull, while spina bifida occurs when the neural tube fails to close somewhere along the spine.

ONTDs happen to couples without a prior family history of these defects in the vast majority of cases. ONTDs result from a combination of genes inherited from both parents, coupled with environmental factors. For this reason, ONTDs are considered multifactorial traits, meaning many factors, both genetic and environmental, contribute to their occurrence.

Once a child has been born with an ONTD in the family, the chance for an ONTD to happen again is increased by 4 to 10 percent. It is important to understand that the type of neural tube defect can differ the second time. For example, one child could be born with anencephaly, while the second child could have spina bifida.

What are the symptoms of anencephaly?

The following are the most common symptoms of anencephaly. However, each child may experience symptoms differently. Symptoms may include:

  • Absence of bony covering over the back of the head
  • Missing bones around the front and sides of the head
  • Folding of the ears
  • Cleft palate. A condition in which the roof of the child's mouth does not completely close, leaving an opening that can extend into the nasal cavity.
  • Congenital heart defects
  • Some basic reflexes, but without the cerebrum, there can be no consciousness and the baby cannot survive

The symptoms of anencephaly may resemble other problems or medical conditions. Always consult your child's doctor for a diagnosis.

How is anencephaly diagnosed?

The diagnosis of anencephaly may be made during pregnancy, or at birth by physical examination. The baby's head often appears flattened due to the abnormal brain development and missing bones of the skull.

Diagnostic tests performed during pregnancy to evaluate the baby for anencephaly include the following:

  • Alpha-fetoprotein. A protein produced by the fetus that is excreted into the amniotic fluid. Abnormal levels of alpha-fetoprotein may indicate brain or spinal cord defects, multiple fetuses, a miscalculated due date, or chromosomal disorders.
  • Amniocentesis. A test performed to determine chromosomal and genetic disorders and certain birth defects. The test involves inserting a needle through the abdominal and uterine wall into the amniotic sac to retrieve a sample of amniotic fluid.
  • Ultrasound (also called sonography).A diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.
  • Blood tests

Treatment of the newborn with anencephaly

There is no cure or standard medical treatment for anencephaly. Treatment is supportive.

Experiencing the loss of a child can be very traumatic. Grief counseling services are available to help you cope with the loss of your child.

Future pregnancies

Genetic counseling may be recommended by the doctor to discuss the risk of recurrence in a future pregnancy as well as vitamin therapy (a prescription for folic acid) that can decrease the recurrence for ONTDs. Extra folic acid, a B vitamin, if taken one to two months prior to conception and throughout the first trimester of pregnancy, has been found to decrease the reoccurrence of ONTDs for couples who have had a previous child with an ONTD. The CDC also recommends to avoid smoking and drinking alcohol during pregnancy.

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Online Resources of Neurological Disorders


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