What is anencephaly?

Anencephaly: Anencephaly is one of a group of malformations of the central nervous system collectively called neural tube defects. Anencephaly is readily apparent at birth because of the absence of the skull and scalp and with exposure of the underlying brain.

Failure to form: The nervous system forms in a specific sequence. A neural groove (nerve cells)forms in a line somewhat like a ditch, gets deeper and begins to close over on itself. It closes from the center outward in both directions.If the top doesn't close, the skull doesn't finish to cover the brain,which is exposed.If the bottom doesn't close, you have spina bifida. Both are sporadic malformations.