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NORD is very grateful to Cynthia A. Moore, MD, PhD, and Phoebe G. Thorpe, MD, MPH, Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, for assistance in the preparation of this report.
Synonyms of Anencephaly
- No synonyms found.
- No subdivisions found.
Anencephaly is a term that refers to the incomplete development of the brain, skull, and scalp and is part of a group of birth defects called neural tube defects (NTD). The structure which will become the neural tube is supposed to fold and to close together (to form a tube) during the third and fourth weeks of pregnancy. From this neural tube, the brain and spinal cord of the embryo develop. Neural tube defects happen when the neural tube does not close as expected. Anencephaly occurs when the end of the neural tube that would have developed into the brain does not close properly, resulting in the failure of the development of major portions of brain, skull and scalp. Other neural tube defects, such as spina bifida, form when the neural tube does not close properly in a different part of the neural tube.
Infants with anencephaly are born without the front part of the brain, (forebrain) and the thinking and coordinating part of the brain (cerebral hemispheres and cerebellum). Most of the time the remaining brain tissue may be exposed, without skull or scalp to cover and protect it. Although reflex actions such as breathing and responses to touch or sound may occur, gaining consciousness is not possible. Usually infants with anencephaly do not survive more than a few days or weeks.
Meroanencephaly and holoanencephaly are terms refer to the extent of the cranial defect, however, they typically are not used in clinical descriptions and are not predictive of severity of the condition. The term acrania has been used interchangeably with anencephaly in some parts of the world but that practice is discouraged as it confuses two very different conditions.
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