Microcephaly

"Microcephalus" redirects here. For the genus of beetle, see Microcephalus (beetle). For the genus of spider, see Argyrodes.
Microcephaly
A baby with microcephaly (left) compared to a baby with a typical head size
Pronunciation
SpecialtyMedical genetics, Psychiatry, Neurology
SymptomsAbnormally small head and brain, neurological impairments
ComplicationsNeurological impairments
Usual onsetCongenital
DurationLifelong
CausesUsually genetic or toxin exposure during pregnancy
PreventionAvoiding alcohol consumption while pregnant
Frequency2–12 per 10,000 births[1]
A mother holding her son who was born with microcephaly due to vertically transmitted infection with Zika virus

Microcephaly (from Neo-Latin microcephalia, from Ancient Greek μικρός mikrós "small" and κεφαλή kephalé "head"[2]) is a medical condition involving a smaller-than-normal head.[3] Microcephaly may be present at birth or it may develop in the first few years of life.[3] Brain development is often affected; people with this disorder often have an intellectual disability, poor motor function, poor speech, abnormal facial features, seizures and dwarfism.[3]

The disorder is caused by a disruption to the genetic processes that form the brain early in pregnancy,[3] though the cause is not identified in most cases.[4] Many genetic syndromes can result in microcephaly, including chromosomal and single-gene conditions, though almost always in combination with other symptoms. Mutations that result solely in microcephaly (primary microcephaly) exist but are less common.[5] External toxins to the embryo, such as alcohol during pregnancy or vertically transmitted infections, can also result in microcephaly.[3] Microcephaly serves as an important neurological indication or warning sign, but no uniformity exists in its definition. It is usually defined as a head circumference (HC) more than two standard deviations below the mean for age and sex.[6][7] Some academics advocate defining it as head circumference more than three standard deviations below the mean for the age and sex.[8]

There is no specific treatment that returns the head size to normal.[3] In general, life expectancy for individuals with microcephaly is reduced, and the prognosis for normal brain function is poor. Occasional cases develop normal intelligence and grow normally (apart from persistently small head circumference).[3][9] It is reported that in the United States, microcephaly occurs in 1 in 800-5,000 births.[4]

  1. ^ "Microcephaly". Health Library: Diseases & Conditions. Cleveland Clinic. April 2023.
  2. ^ "Microcephaly - Definition of Microcephaly by Merriam-Webster". Archived from the original on 2014-09-14.
  3. ^ a b c d e f g "NINDS Microcephaly Information Page". NINDS. June 30, 2015. Archived from the original on 2016-03-11. Retrieved 11 March 2016.
  4. ^ a b "Facts about Microcephaly | Birth Defects | National Center on Birth Defects and Developmental Disabilities". Centers for Disease Control and Prevention. 2016-12-07. Retrieved 2019-07-30.
  5. ^ Faheem, Muhammad; Naseer, Muhammad Imran; Rasool, Mahmood; Chaudhary, Adeel G; Kumosani, Taha A; Ilyas, Asad Muhammad; Pushparaj, Peter Natesan; Ahmed, Farid; Algahtani, Hussain A; Al-Qahtani, Mohammad H; Saleh Jamal, Hasan (2015). "Molecular genetics of human primary microcephaly: an overview". BMC Medical Genomics. 8 (Suppl 1): S4. doi:10.1186/1755-8794-8-S1-S4. PMC 4315316. PMID 25951892.
  6. ^ Leviton, A.; Holmes, L.B.; Allred, E.N.; Vargas, J. (2002). "Methodologic issues in epidemiologic studies of congenital microcephaly". Early Hum Dev. 69 (1): 91–105. doi:10.1016/S0378-3782(02)00065-8. PMID 12324187.
  7. ^ Opitz, J. M.; Holt, M. C. (1990). "Microcephaly: general considerations and aids to nosology". Journal of Craniofacial Genetics and Developmental Biology. 10 (2): 75–204. PMID 2211965.
  8. ^ Behrman, R.E.; Kligman, R. M.; Jensen, H.B. (2000). Nelson's Textbook of Pediatrics (16th ed.). Philadelphia: WB Saunders. ISBN 978-0-7216-7767-5. OCLC 44552900.
  9. ^ Stoler-Poria, S.; Lev, D.; Schweiger, A.; Lerman-Sagie, T.; Malinger, G. (2010-01-12). "Developmental outcome of isolated fetal microcephaly". Ultrasound in Obstetrics and Gynecology. 36 (2). Wiley: 154–8. doi:10.1002/uog.7556. ISSN 0960-7692. PMID 20069548. S2CID 30379486.