Megalencephaly

**Definition:** 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).

**Tree numbers:** - C05.660.207.536 - C10.500.507.400.249 - C16.131.621.207.532 - C16.131.666.507.400.249

**Synonyms:** - Macrocephaly - Megacephaly - Megalocephaly