Microcephaly

Overview

Microcephaly means an unusually small head. Because the skull grows largely in response to the growth of the brain inside it, a head circumference well below the expected range for a child's age and sex usually indicates that the brain is smaller than normal or has not grown as it should. Microcephaly can be present at birth (congenital) or develop in the first months and years of life (acquired or progressive).

It is not a single disease but a sign that can result from many different causes, ranging from genetic conditions to infections during pregnancy to injuries that affect brain growth. The effect on a child's development varies widely. Some children with mild microcephaly develop typically, while others have significant developmental, movement, or seizure problems depending on the underlying cause and how the brain is affected.

Symptoms

The defining feature is a small head, but associated symptoms depend on the cause and severity.

• Small head circumference: Noticeably smaller than peers, sometimes with a sloping forehead.
• Developmental delays: Slower than expected progress in sitting, standing, walking, and speech.
• Intellectual differences: Ranging from mild learning difficulties to significant intellectual disability in some children.
• Movement and muscle problems: Such as increased muscle tightness or coordination difficulties.
• Seizures: Occur in some children.
• Feeding and growth difficulties: Particularly in more severely affected infants.

Many children with mild microcephaly have few or no additional problems, so the outlook is highly individual.

Causes

Microcephaly can arise from anything that interferes with normal brain growth before or after birth.

• Genetic conditions: Many inherited syndromes and chromosomal changes affect brain development and head size.
• Infections during pregnancy: Certain infections passed to the developing baby, including some viruses, can impair brain growth.
• Exposures in pregnancy: Alcohol, certain drugs, and some toxins can affect the developing brain.
• Lack of oxygen or injury: Severe oxygen shortage or brain injury around the time of birth.
• Metabolic and other disorders: Some metabolic conditions and severe malnutrition can slow brain growth after birth.

In some children no specific cause is found despite thorough testing.

Risk Factors

• A family history of microcephaly or related genetic conditions
• Infections during pregnancy that can affect the developing brain
• Alcohol or substance use during pregnancy
• Poorly controlled certain maternal health conditions during pregnancy
• Severe oxygen deprivation or brain injury around birth
• Significant malnutrition in early infancy

Diagnosis

Microcephaly is identified by measuring the head and then investigating the cause.

• Head circumference measurement: Compared against standard growth charts at birth and during routine checkups; repeated measurements show whether growth is keeping pace.
• Brain imaging: An ultrasound, MRI, or CT scan to look at the structure of the brain.
• Tests for infections: Blood and other tests to check for infections acquired during pregnancy.
• Genetic and metabolic testing: To identify inherited or metabolic causes.
• Developmental assessment: To understand a child's abilities and needs over time.

Treatment

There is no treatment that increases brain or head size, so care centers on supporting each child's development, managing complications, and treating any underlying or ongoing cause.

• Early intervention and therapies: Physical, occupational, and speech therapy to help a child reach their potential and build skills.
• Developmental and educational support: Individualized learning plans and special education services as needed.
• Seizure management: Anti-seizure medication for children who have seizures.
• Managing other issues: Support for feeding, muscle tightness, vision or hearing problems, and coordination difficulties.
• Family support: Counseling, resources, and genetic counseling where a genetic cause is found.

A team of specialists usually works together to tailor support to the individual child.

Prevention

Not all causes can be prevented, but some risks can be reduced before and during pregnancy.

• Attend regular prenatal care and follow vaccination and infection-prevention advice
• Avoid alcohol and non-prescribed drugs during pregnancy
• Take recommended prenatal vitamins, including folic acid, as advised
• Manage existing health conditions with your care team during pregnancy
• Seek genetic counseling if there is a family history of microcephaly or related conditions

When to See a Doctor

Routine well-child visits include head measurements, but contact your child's doctor if you notice that the head seems unusually small, is not growing, or if your child is not meeting developmental milestones. Seek prompt care if a child has:

• A seizure
• Significant feeding difficulties or poor weight gain
• A sudden change in alertness or new neurological symptoms

Early evaluation helps identify the cause and connect the child with supportive therapies as soon as possible.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Facts about Microcephaly.
2. MedlinePlus, U.S. National Library of Medicine. Microcephaly.
3. National Institute of Neurological Disorders and Stroke (NINDS).
4. World Health Organization (WHO).