Heron Werner, MD & Pedro Daltro, MD
Clínica de Diagnóstico por Imagem (CDPI) & Instituto Fernandes Figueira (IFF) – FIOCRUZRio de Janeiro – Brazil

Dorothy I. Bulas M.D.
Professor of Radiology and Pediatrics
Children"s National Medical Center
George Washington University Medical Center
111 Michigan Ave, NW,   Washington D.C. 20010

Exencephaly is a rare and fatal anomaly in which the bones of the cranial vault are absent with protrusion of brain tissue into the amniotic cavity. The origin is due to the failure of the closing of the neural tube during the fourth week of embryonic development. It can be detected early in gestation, when the normal calcification of the cranial bones is not present. Later in gestation, the most common finding is the presence of a large quantity of disorganized brain tissue. It can be associated with other anomalies such as amniotic bands, omphalocele and pentalogy of Cantrell.