Congenital Abnormality
macrocephaly
mac·ro·ceph·a·ly
Subclass of:
Malformations of Cortical Development, Group I; Craniofacial Abnormalities
Definitions related to macrocephaly:
  • An abnormal increase in head circumference, which can have a variety of causes, including hydrocephalus, enlarged brain, and cranial hyperostosis.
    NCI
    U.S. National Cancer Institute, 2021
  • (megalencephaly) 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).
    NLM Medical Subject Headings
    U.S. National Library of Medicine, 2025
  • (megalencephaly) Diffuse enlargement of the entire cerebral hemispheres leading to macrocephaly (with or without overlying cortical dysplasia).
    Human Phenotype Ontology (HPO)
    The Human Phenotype Ontology Project, 2025
  • Macrocephaly (megacephaly) is a head circumference > 2 standard deviations above the mean for age (1, 2).
    Merck Manuals
    Merck & Co., Inc., 2025
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This content should not be used in place of medically-reviewed decision support reference material or professional medical advice. Some terms may have alternate or updated definitions not reflected in this set. The definitions on this page should not be considered complete or up to date.