Exencephaly

 is a type of cephalic disorder wherein the brain is located outside of the skull. This condition is usually found in embryos as an early stage of anencephaly. As an exencephalic pregnancy progresses, the neural tissue gradually degenerates.

The prognosis for infants born with exencephaly is extremely poor. It is rare to find an infant born with exencephaly, as most cases that are not early stages of anencephaly are usually stillborn. Those infants who are born with the condition usually die within hours.

-- Two mouse models that represent exencephaly are:

Cited2: Cited2 mice that are homozygous (null) show heart defects and exenchephaly. Feeding these mice folic acid reduces their chance of neural tube defect (which in this case is exencephaly) but apoptosis of the brain still occurs, possible due to exposure of the brain to amniotic fluid.

Splotch2H: Homozygous splotch 2H mice have exencephaly, heart defects and/or spina bifida. Folic acid reduces the chance of getting any of these neural tube defects and prevents symptoms of abnormal metabolism.