The presumed pathogenesis of acalvaria is the faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in the absence of the calvaria, but with an intact layer of skin over the brain parenchyma.

Physicians often use magnetic resonance imaging to confirm the diagnosis because in utero, acalvaria is sometimes confused with anencephaly or encephalocele.

[1] The primary presumed pathogenesis is problematic migration of the membranous neurocranium with respect to the normal positioning of the immature ectoderm.

[2] When an embryo develops normally, the anterior neural pore closes about the fourth week.

[5] ACE inhibitors and angiotensin II receptor antagonists are reported to cause prenatal hypocalvaria.

In addition to the lack of the skull cap, there were brain malformations in each case and all the pregnancies were terminated either electively or the fetuses were spontaneously aborted.