<unk>  is a type of cephalic disorder. This is a rare condition in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid.
In "hemihydranencephaly", only half of the brain is filled with fluid.
Hydranencephaly
Schizencephaly
Megalencephaly
Holoprosencephaly
Lissencephaly
Anencephaly
Spina bifida
Deformational plagiocephaly