A congenital disorder characterized by abnormally large-sized head and brain in relation to the rest of the body.

Also called macrocephalia and megalocephaly, macrocephaly is diagnosed when the circumference of the head is more than two standard deviations above average for the child's age, sex, race, and period of gestation. The fontanelle (soft spot) of the newborn is wide, but facial features are usually normal. Macrocephaly is distinguished from hydrocephalus in that there is no intracranial pressure. The disorder can result from a defect in formation during the embryonic stage, or as a result of certain degenerative diseases such as Schilder's disease, Greenfield's disease, or congenital lipoidosis. Mental deficiency, seizures, and movement disorders are common in macrocephalic children.

When mental deficiency and the attendant diseases or disorders are severe, the child may be placed on a life-support system. When the mental deficiency is less severe, the child may...