Anencephaly | |
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Illustration of an anencephalic fetus | |
Specialty | Medical genetics; pediatrics |
Symptoms | Absence of the cerebrum and cerebellum |
Risk factors | Folic acid deficiency |
Prevention | Mother taking enough folic acid |
Prognosis | Death typically occurs within hours to days after birth. |
Frequency | 1 in 4600 in the U.S. |
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development.[1] It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception.[2] Strictly speaking, the Greek term translates as "without a brain" (or totally lacking the inside part of the head), but it is accepted that children born with this disorder usually only lack a telencephalon,[3] the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually covered only by a thin layer of membrane—skin, bone, meninges, etc., are all lacking.[4] With very few exceptions,[5] infants with this disorder do not survive longer than a few hours or days after birth.