Microcephaly

Definition

Microcephaly is a rare neurological condition in which a person's head is significantly smaller than expected based on standardized charts.

Severe microcephaly

• Severe microcephaly is a more serious, extreme form of this condition where a baby’s head is much smaller than expected.
• Severe microcephaly can result because a baby’s brain has not developed properly during pregnancy, or the brain started to develop correctly and then was damaged at some point during pregnancy.

Epidemiology

Microcephaly is not a common condition. Researchers estimate that about 1 in every 800-5,000 babies is born with microcephaly in the United States.

Causes and riskfactors

• The causes of microcephaly in most babies are unknown.
• Some babies have microcephaly because of changes in their genes.

Other causes of microcephaly, including severe microcephaly, can include the following exposures during pregnancy:

• Certain infections during pregnancy, such as rubella, toxoplasmosis, or cytomegalovirus
• Severe malnutrition, meaning a lack of nutrients or not getting enough food
• Exposure to harmful substances, such as alcohol, certain drugs, or toxic chemicals
• Interruption of the blood supply to the baby’s brain during development
• Some babies with microcephaly have been reported among mothers who were infected with Zika virus while pregnant.

Signs and symptoms

Babies with microcephaly can have a range of other problems, depending on how severe their microcephaly is. Microcephaly has been linked with the following problems:

• Seizures
• Developmental delay, such as problems with speech or other developmental milestones (like sitting, standing, and walking)
• Intellectual disability (decreased ability to learn and function in daily life)
• Problems with movement and balance
• Feeding problems, such as difficulty swallowing
• Hearing loss
• Vision problems

These problems can range from mild to severe and are often lifelong. Because the baby’s brain is small and underdeveloped, babies with severe microcephaly can have more of these problems, or have more difficulty with them, than babies with milder microcephaly. Severe microcephaly also can be life-threatening. Because it is difficult to predict at birth what problems a baby will have from microcephaly, babies with microcephaly often need close follow-up through regular check-ups with a healthcare provider to monitor their growth and development.

Diagnosis

Microcephaly can be diagnosed during pregnancy or after the baby is born.

During Pregnancy During pregnancy, microcephaly can sometimes be diagnosed with an ultrasound test (which creates pictures of the body). To see microcephaly during pregnancy, the ultrasound test should be done late in the 2nd trimester or early in the third trimester.

After the Baby is Born

• To diagnose microcephaly after birth, a healthcare provider will measure the distance around a newborn baby’s head, also called the head circumference, during a physical exam.
• The provider then compares this measurement to population standards by sex and age.
• Microcephaly is defined as a head circumference measurement that is smaller than a certain value for babies of the same age and sex.
• This measurement value for microcephaly is usually more than 2 standard deviations (SDs) below the average.
• The measurement value also may be designated as less than the 3rd percentile.
• This means the baby’s head is extremely small compared to babies of the same age and sex.

Treatment

Microcephaly is a lifelong condition. There is no known cure or standard treatment for microcephaly. Because microcephaly can range from mild to severe, treatment options can range as well. Babies with mild microcephaly often don’t experience any other problems besides small head size. These babies will need routine check-ups to monitor their growth and development. Developmental services early in life will often help babies with microcephaly to improve and maximize their physical and intellectual abilities. Sometimes medications also are needed to treat seizures or other symptoms.

NIH genetic and rare disease info

• NIH info on Microcephaly

Microcephaly is a rare disease.

Microcephaly Resources
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