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Microcephaly is a term used when there is sub-optimal growth of the brain, which causes it to be smaller than usual. Microcephaly is discovered after measuring the child's head circumference and comparing this measurement with close relatives (eg parents) and the range of measurements identified in the whole population.


Medical text written May 2002 by Dr J Tolmie. Last updated September 2012 by Dr J Tolmie, Consultant Clinical Geneticist, Ferguson-Smith Centre for Clinical Genetics, Glasgow, UK.

What are the symptoms?

Children and adults who are affected by microcephaly have variable neurological impairments, from very mild learning disability to much more severe problems including feeding difficulties, profound learning disability, epilepsy and other neurological problems such as spasticity (tightness of the muscles) or hypotonia (reduced muscle tone).

What are the causes?

Microcephaly is caused by many different conditions that may be genetic or non-genetic in origin. A number of mutations in microcephaly genes have been discovered, but it is still quite rare for any of these to be detected in a single child. At present, the most commonly discovered gene mutations are found in the ASPM and WDR62 genes.

Non-genetic causes include infections contracted by the baby in the womb (intrauterine infections), reduction in blood supply to the developing fetal brain during pregnancy and some post-natal infections or traumas.

Intrauterine infections which can cause microcephaly include cytomegalovirus (CMV), toxoplasmosis  and rubella  (German measles).

Rare syndromes which cause disturbed brain development and microcephaly, usually with other physical disabilities, include Cornelia De Lange syndrome, Rubinstein Taybi syndrome and Seckel syndrome.

How is it diagnosed?

At or after birth, microcephaly is detected by measuring the head circumference of a baby. Detailed brain imaging, such as a magnetic resonance imaging (MRI) scan, may demonstrate an alteration in brain structure, for example, a decrease in the number and complexity of the folds on the surface of the brain (see entry Cortical Malformations). However, quite frequently, the brain scan appearance simply confirms reduction in overall size of the brain.

It is very likely that the advent of new genetic technologies will permit testing for many different types of genetic microcephaly in the next few years. In the meantime, children who do not have a specific diagnosis or reason for microcephaly, could be eligible for detailed genetic testing that is available via the Deciphering Developmental Disorders research project.

How is it treated?

There is at present no treatment that will reverse microcephaly but, as with other central nervous system disorders, treatments may be given to reduce complications such as feeding difficulties, epilepsy or increased muscle tone.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Complexity arises because several different inheritance patterns (autosomal dominant, autosomal recessive, X-chromosome linked, mitochondrial) of genetic microcephaly are possible.

Prenatal diagnosis
It is unusual for genetic microcephaly to be diagnosed by ultrasound scan in early pregnancy, but a reduction in fetal brain growth may be discovered by scans undertaken during the last few months of pregnancy. In the future in many families. DNA-based tests will be available to diagnose genetic microcephaly in early pregnancy.

Is there support?

There is no support for microcephaly in the UK. Cross referrals to other medical information entries on our website are intended to provide relevant support for those particular features of the condition. Organisations identified in those entries do not provide support specifically for microcephaly.

Families can use Contact a Family's freephone helpline for advice, information and, where possible, links to other families. Contact a Family's web-based linking sevice can be found at MakingContact.org.

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