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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. Neural tube defects, spina bifida (open spine) and anencephaly (open skull) are seen in one to two per 1,000 live births.
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 (80 percent of the time), or covered with bone or skin (20 percent of the time).
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 over 90 percent of the 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.
Some of the environmental factors include uncontrolled diabetes in the mother, and certain medications that are available by prescription only. According to the Centers for Disease Control and Prevention (CDC), the occurrence rate of ONTDs can vary from state to state and from country to country. The rate of ONTD occurrence in Arkansas is 7.8 out of 10,000 births and 30 out of 10,000 births in Washington. The country with the highest number of documented cases is Ireland, where spina bifida occurs in approximately 4.2 out of 1,000 live births. The environmental factors causing these differences are not well understood.
ONTDs are seen five times more often in females than males. Once a child has been born with an ONTD in the family, the chance for an ONTD to happen again is increased to 3 to 5 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 ear
- 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 physician 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 medical treatment for anencephaly. Due to the lack of development of the brain, approximately 75 percent of infants are stillborn and the remaining 25 percent of babies die within a few hours, days, or weeks after delivery. Care will be aimed at providing emotional support to the family.
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.
Genetic counseling may be recommended by the physician 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. You cannot obtain the proper amount of folic acid in a multivitamin. A prescription from an obstetrician or other healthcare provider (prior to pregnancy) is needed in order to have the proper dosage.
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