Fetal anomaly characterized by the absence of the cranium is

Anencephaly is characterized by the absence of the cranium and telencephalic structures, with the skull base and orbits covered only by angiomatous stroma. Acrania is the absence of the cranium, with protrusion of disorganized brain tissue. Both are generally grouped together, and anencephaly is considered to be the final stage of acrania.Ref: William&;s Obstetrics; 24th edition; Chapter: 10