Microcephaly Diagnosis: Is it Genetic?

A microcephaly diagnosis is usually based on its primary sign: a significantly smaller than average head size in a child. This is based on the circumference of the child’s head, that is, the distance around the top of the head.

While some children may simply have smaller heads, with a measurement as low as the first percentile, a child with microcephaly will have a head size that is drastically below expected measurements, sometimes even below the first percentile on standardized growth charts for age and sex. With more acute microcephaly, the child’s forehead may also slope backwards.

Pronounced my-kroh-SEF-uh-lee, microcephaly is a rare condition. This neurological disorder may be detected at birth, or even during prenatal fetal scans. It is most often congenital: an infant may be born with microcephaly. Microcephaly may also be developed after birth. Microcephaly is in many cases the result of abnormal development of the brain in the womb, or it may emerge as a result of slowed or halted growth of the brain after birth.

What causes microcephaly?

Microcephaly may be genetic, or it may be caused by environmental catalysts, but either way, it is most often congenital, meaning born with the condition. A diagnosis of microcephaly will be based more on the actual measurements of the child’s head rather than on a genetic test since that is its primary marker.

Congenital causes of microcephaly (before birth)

Genetic mutation: There are as many as several hundred genes linked with microcephaly, with more being discovered. Flaws or abnormalities in these genes can interfere with brain growth. Microcephaly may in some cases be related to Down syndrome or other neurometabolic syndromes and disorders.

Prenatal infection: The best-known prenatal infectious cause of microcephaly is the Zika virus. Exposure during pregnancy, especially in the first trimester, may damage brain cells, specifically nerve cells. Other infections that may cause microcephaly include chicken pox, rubella (also known as German measles), toxoplasma, and cytomegalovirus (CMV), a common virus that may show no symptoms but remains for life. For women who are or think they may be pregnant, testing for active CMV in the mother and, generally speaking, careful hygiene, as well as avoiding known infectious persons, may be crucial.

Other prenatal causes: Alcohol or substance abuse, starvation or inadequate nutrition, untreated phenylketonuria (PKU) in mother (or, after birth, in the baby), some prescription drugs, or exposure to heavy pollution and toxic chemicals can cause microcephaly in infants.

Microcephaly causes in infancy

Traumatic brain injury, lack of oxygen to the brain, a brain infection, or genetic mutations may all cause microcephaly in an infant after it is born. In the case of genetic mutations, the microcephaly diagnosis is based on genetic causes, that is to say, on abnormalities in genes, but may not be present before birth, rather it is developed as genes mutate in the infant.

A microcephaly diagnosis: what does it mean?

The cause of microcephaly is important to know as it can help predict what symptoms will appear in the child. There may be severe developmental delay or a high risk of seizure, impaired motor function, or other affected organs, or, in the case of a link with Zika or other prenatal infectious diseases, there may be vision and hearing complications for the child.

Some children with microcephaly may have average intelligence and normal development, but heads that remain smaller than average for their age and sex. Even if all seems well and a child has been told that they are likely to have normal development, regular medical follow-ups are a must.

Depending on the cause and severity, some children with microcephaly may have other difficulties and complications. This may include low intelligence, developmental delays, poor speech and language, lack of coordination and balance, convulsions, and in some cases, a shorter than normal life expectancy.

There is no treatment for microcephaly. No medical or surgical treatment can change the size of the child’s head or increase brain growth. However, early intervention and supportive therapies may help improve and enhance the child’s development and quality of life. If your child has received a diagnosis of microcephaly, whether congenital, genetic, or developed after birth, you should speak with a genetic counselor and see what options are available to you for speech and occupational therapy as well as medical check-ups.

Other signs and symptoms of a microcephaly disorder (genetic or not)

Symptoms vary tremendously and must be judged and followed up with an individualized diagnosis and medical or health plan.

Some signs and symptoms can include:

Very short stature, dwarfism

Facial deformities

Joint deformities (sometimes related to a prenatal Zika infection)

Problems with vision and hearing 

Seizures or convulsions

Poor weight gain and growth

Poor appetite or feeding

Difficulty with movement and balance

Abnormal muscle tone: muscles may be either too tight or too loose

Speech delays

Mild to severe learning disabilities

Genetic counseling and diagnosis for a microcephaly diagnosis

While an original diagnosis of microcephaly is, as we stated earlier, made by measurement and observation of an infant or child’s head circumference, further genetic testing may be indicated to find out the root cause of the problem. This can help indicate how the child may develop, in some cases, or may alert the child’s parents or carers as well as medical professionals to the possibility of severe impairment. It is also advisable to speak with a genetic counselor with regard to possible future pregnancies or with an eye to the child’s future, healthwise and in relation to developmental difficulties that may require therapy or therapies that should be started as early as possible.

If your healthcare provider has referred you for genetic testing or genetic counseling, it may likely be covered by your healthcare system. If not, or if it is your choice to look into further genetic testing, for a possible rare disease diagnosis, aside from any that has been recommended for you, there are private genetic testing options available.


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