A congenital abnormality in which the occipitofrontal circumference is greater than two standard deviations above the mean for a given age. It is associated with HYDROCEPHALUS; SUBDURAL EFFUSION; ARACHNOID CYSTS; or is part of a genetic condition (e.g., ALEXANDER DISEASE; SOTOS SYNDROME).

Synonyms: Macrocephalies, Megacephalies, Megalencephaly, Megalencephalies, Megacephaly, Megalocephaly, Macrocephaly, Megalocephalies