Definition: Exencephaly is a rare malformation in which the scalp and calvarium (acrania) are absent ant the cerebral mass is protected by a thick, dura mater-like membrane.
The brain consists of a disorganized, anarchic outgrowth of nervius tissue with polymicrogyria and nodules of heterotopias.
Etiology (examples)
amniotic band sequence (ABS)
References
Katsanis N. Ciliary proteins and exencephaly. Nat Genet. 2006 Feb;38(2):135-6. PMID: 16444248