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What is Anencephaly?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Anencephaly is the absence of a large part of the brain and the skull. It results from a defect in the closure of the neural tube in the early part of pregnancy. Between the 3rd and 4th week of pregnancy the neural tube folds and closes to form the brain and spinal cord. Anencephaly occurs when the "cephalic" or head end of the neural tube fails to close, resulting in the absence of a major portion of the brain, skull, and scalp.

Dr. Deborah Mulligan, MD
Pediatrician

The neural tube is the part of an embryo that develops into the brain and spinal cord, and the back of the skull and vertebrae.  If it fails to develop properly, a baby may be born with defects in any of these parts.  The most common type of defect is spina bifida.  Neural tube defects (NTDs) are congenital malformations of the brain and spinal cord caused by failure of the neural tube to close between 21 and 28 days following conception. Defects range from anencephaly, through encephalocoeles to spina bifida, which is more variable in severity and effect. Anencephaly is invariably associated with death as a stillbirth, a neonatal death or occasionally a post-neonatal death. Encephalocoele and spina bifida may be associated with neonatal death, infant death or with impairment which is frequently severe in the absence of surgery—for example, weakness or paralysis of the legs, urinary or bowel incontinence, convulsions and frequent central nervous system infections.

In an effort to reduce the occurrence of neural tube defects (NTDs), folic acid fortification of United States enriched grain products was authorized by the Food and Drug Administration in March 1996 and required by January 1998. Fortification has been shown to result in an important decline in the prevalence of spina bifida and anencephaly in the general US population.  The American Academy of Pediatrics and other medical organizations recommend that all women of childbearing age consume 400 micrograms of folic acid daily.

RHS Admin
Administration Specialist

Anencephaly is a defect in the closure of the neural tube during fetal development. The neural tube is a narrow channel that folds and closes between the third and fourth week of pregnancy to form the brain and spinal cord of the embryo. Anencephaly occurs when the "cephalic" or head end of the neural tube fails to close, resulting in the absence of a major portion of the brain, skull, and scalp. Infants with this disorder are born without a forebrain (the front part of the brain) and a cerebrum (the thinking and coordinating part of the brain). The remaining brain tissue is often exposed--not covered by bone or skin. 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 rudimentary 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 may occur.

The cause of anencephaly is unknown. Although a mother's diet and vitamin intake may play a role, some scientists believe that various other factors may also be involved.

Recent studies have shown that the addition of folic acid (vitamin B9) to the diet of women of childbearing age significantly reduces the incidence of neural tube defects. Therefore, it is recommended that all women of childbearing age consume 0.4 mg of folic acid daily.

This answer is based on source information from National Institute of Neurological Disorders and Stroke.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.