Anencephaly

Anencephaly
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.