<unk>  is a condition in which the brain's cerebral hemispheres are absent to a great degree and the remaining cranial cavity is filled with cerebrospinal fluid. "Cephalic" is the scientific term for "head" or "head end of body".<unk>  is a type of cephalic disorder. These disorders are congenital conditions that derive from damage to, or abnormal development of, the fetal nervous system in the earliest stages of development in utero. These conditions do not have any definitive identifiable cause factor. Instead, they are generally attributed to a variety of hereditary or genetic conditions, but also by environmental factors such as maternal infection, pharmaceutical intake, or even exposure to high levels of radiation.<unk>  should not be confused with hydrocephalus, which is an accumulation of excess cerebrospinal fluid in the ventricles of the brain. In hemihydranencephaly, only half of the cranial cavity is affected.
Hydranencephaly
Hemihydranencephaly
Microhydranencephaly
Schizencephaly
Megalencephaly
Holoprosencephaly
Lissencephaly
Microlissencephaly