Which condition is characterized by the absence of a cranial vault and little cerebral tissue?

The condition characterized by the absence of a cranial vault and little cerebral tissue is known as anencephaly. Anencephaly is a severe neural tube defect that occurs during early fetal development, typically resulting in the formation of a small or absent brain and skull. Infants born with this condition often lack major portions of the brain, especially the cerebrum, which is responsible for many higher brain functions.

The absence of the cranial vault means that there is insufficient space for normal brain development, leading to profound neurological deficits. This condition is associated with a high mortality rate shortly after birth, as there is little brain function present to sustain life.

Other conditions mentioned have distinct characteristics: hydrocephalus involves the accumulation of cerebrospinal fluid within the brain, microcephaly refers to an abnormally small head due to underdeveloped brain tissue, and macrocephaly refers to an enlarged head size usually related to various conditions that cause increased brain volume or fluid. Each of these conditions affects cranial structure and brain function differently than anencephaly.