[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) › Microcephaly [Embryology](https://durgical.com/en/embryology/) · [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) # Microcephaly - Malformation The baby's head is much smaller than expected because the brain did not grow well; Zika put it in the news in Colombia in 2016. Updated 2026-11-01 **See it in 3D:** [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/) · [Parietal lobe](https://durgical.com/en/anatomy/superior-parietal-lobule/) · [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) ## Key points - Small head = small brain. - Zika, CMV, toxoplasmosis and rubella are key infectious causes. - Congenital Zika: severe microcephaly with calcifications and retinal lesions. - Measure head circumference at birth and follow it over time. - Colombia confirmed its first Zika-associated cases in April 2016. ## What it is Microcephaly is a head circumference far below what is expected for age and sex. Because the skull grows as the brain pushes it, it reflects a small brain. It can be genetic or acquired through prenatal infections, alcohol, malnutrition or poor blood supply; the 2015–2016 Zika epidemic put it at the center of birth defect surveillance in Colombia. ## Key facts - Skull size depends on brain growth: the underlying defect is in the brain. - Genetic causes: autosomal recessive forms that reduce neural progenitor proliferation. - Acquired causes: Zika, toxoplasmosis, CMV, rubella, alcohol, maternal or infant malnutrition, blood supply problems. - It can be present at birth or appear later (postnatal microcephaly). - Colombia: on 14 April 2016 the INS confirmed the first two cases of Zika-associated microcephaly (Norte de Santander and Cundinamarca). ## Embryological cause - The ventricular zone of the neural tube makes too few neurons: neural progenitor proliferation or survival fails. - In genetic forms, spindle and centrosome genes shorten the period in which progenitors divide. - Zika virus infects neural progenitors and kills them, leaving a thin cortex and calcifications. - Without the push of the brain the skull grows little; in severe Zika the skull may look collapsed with redundant scalp. ## Markers - ASPM - MCPH1 - CDK5RAP2 ## How it presents - Low head circumference, ideally measured within the first 24 hours and compared with charts (CDC or INTERGROWTH-21st). - Seizures, developmental delay, intellectual disability, movement and balance problems. - Feeding difficulty, hearing loss and vision problems. - In congenital Zika, retinal lesions, joint contractures and hypertonia may accompany it. ## Diagnosis - Prenatal ultrasound: usually detected late in the second or early in the third trimester. - Head circumference at birth against reference charts. - MRI or CT: calcifications, cortical abnormalities, ventriculomegaly. - In Colombia the INS Zika protocol included molecular tests, genetics, brain imaging and eye and hearing evaluation. ## Memory aid 'The skull is a tent and the brain is the pole': if the pole does not grow, the tent stays low. ## Test yourself Think of the answer, then tap the question to see it. ## Why does microcephaly reflect a brain problem rather than a skull problem? Because the skull grows as the brain grows; if the brain grows little, so does the skull. ## Which cells does Zika virus infect to cause microcephaly? The neural progenitors of the developing brain, whose death reduces neuron production. ## When did Colombia confirm its first cases of Zika-associated microcephaly? On 14 April 2016 the INS announced two confirmed cases, in Norte de Santander and Cundinamarca. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/embryology/microcephaly/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/) - [Parietal lobe](https://durgical.com/en/anatomy/superior-parietal-lobule/) - [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) ## Related - [Congenital Zika syndrome](https://durgical.com/en/embryology/congenital-zika-syndrome/) - [TORCH infections: what each agent does to the embryo and fetus](https://durgical.com/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/) - [Congenital rubella syndrome](https://durgical.com/en/embryology/congenital-rubella-syndrome/) - [Alcohol: fetal alcohol spectrum disorder](https://durgical.com/en/embryology/alcohol-fetal-alcohol-spectrum-disorder/) - [Brain vesicles: from three to five and what each becomes](https://durgical.com/en/embryology/brain-vesicles-from-three-to-five-and-what-each-becomes/) - [Holoprosencephaly](https://durgical.com/en/embryology/holoprosencephaly/) ## Related conditions - [Zika virus infection](https://durgical.com/en/conditions/zika-virus-infection/) - [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) - [Cerebral palsy](https://durgical.com/en/conditions/cerebral-palsy/) - [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/) ## Microorganisms - [Zika virus](https://durgical.com/en/microbiology/zika-virus/) - [Cytomegalovirus](https://durgical.com/en/microbiology/cytomegalovirus/) - [Toxoplasma gondii](https://durgical.com/en/microbiology/toxoplasma-gondii/) - [Rubella virus](https://durgical.com/en/microbiology/rubella-virus/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Microcephaly](https://www.cdc.gov/birth-defects/about/microcephaly.html) (Centers for Disease Control and Prevention, 2024); [Colombia confirmó dos primeros casos de microcefalia asociados a zika](https://www.ins.gov.co/Noticias/Paginas/Colombia-confirmó-dos-primeros-casos-de-microcefalia-asociados-a-zika.aspx) (Instituto Nacional de Salud (Colombia), 2016); [CMV in Newborns](https://www.cdc.gov/cytomegalovirus/congenital-infection/index.html) (Centers for Disease Control and Prevention, 2024); Langman's Medical Embryology, 13th ed., ch. 18: Central Nervous System (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/microcephaly/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/microcephaly/