Which skull abnormality involves exposure of brain tissue due to skull defects?

• A. Exencephaly
• B. Anencephaly
• C. Encephalocele
• D. Microcephaly

Answer: (A)

Exposure of brain tissue through an absent or severely underdeveloped skull is characteristic of exencephaly. In this neural tube defect, the cranial vault fails to form properly, so the brain remains present but is exposed outside the skull without a protective calvarium. This distinguishes it from encephalocele, where brain tissue protrudes through a skull defect into a sac and is covered by meninges and skin; from anencephaly, where most of the brain and skull are absent; and from microcephaly, where the head is simply unusually small but the skull and brain are otherwise formed. So, when brain tissue is exposed due to skull defects, exencephaly is the best fit.