• A congenital abnormality in which the CEREBRUM is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (Desk Reference for Neuroscience, 2nd ed.)
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• A congenital or acquired developmental disorder in which the circumference of the head is smaller than normal for the person's age and sex.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021
• Condition in which the head is unusually small as a result of defective brain development and premature ossification of the skull.
  Sadock's Comprehensive Glossary of Psychiatry and Psychology
  BJ Sadock Titles Press, 2012
• (micrencephaly) Abnormal smallness of the brain.
  CRISP Thesaurus
  National Institutes of Health, 2006
• (isolated congenital microcephaly) A rare neurological disorder characterized by a reduced head circumference at birth with no gross anomalies of brain structure. It can be an isolated finding or it can be associated with seizures, developmental delay, intellectual disability, balance disturbances, hearing loss or vision problems.
  OrphaNet
  INSERM, 2021
• Microcephaly (my-kroh-SEF-uh-lee) is a rare neurological condition in which an infant's head is significantly smaller than the heads of other children of the same age and sex. Sometimes detected at birth, microcephaly usually is the result of the brain developing abnormally in the womb or not growing as it should after birth.
  Mayo Clinic
  Mayo Foundation for Medical Education and Research
• Microcephaly is a rare neurological condition in which a person's head is significantly smaller than expected based on standardized charts. Some cases of microcephaly are detected at birth, while others develop in the first few years of life. Some children with microcephaly have normal intelligence and development. However, microcephaly...
  NIH Genetic and Rare Diseases
  National Center for Advancing Translational Sciences
• Microcephaly, congenital condition in which an infant's head is smaller than the typical size for its age and sex. A microcephalic individual usually also has a brain of diminished size, though often normal in structure. Microcephaly is rare, generally occurring in anywhere from 1 in 10,000 to 1 in...
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2020