Macrocephaly

What is macrocephaly?

The term macrocephaly means “large head.” If your infant has macrocephaly, they have a head circumference that’s much larger than others of the same age and sex. Technically, your child’s head circumference (measurement around the widest part of their head) is greater than the 97th percentile. This means their head is larger than 97% of children of the same age and sex.

Macrocephaly can be a sign of a condition that requires treatment. However, your baby’s larger head size might also be something that runs in your family, and is harmless and doesn’t need to be treated. This condition is called benign familial macrocephaly.

How common is macrocephaly?

Macrocephaly is diagnosed in about 2% to 5% of the U.S. population.

What are the symptoms of macrocephaly?

Common signs and symptoms include:

• Rapid head growth.
• Bulging veins on your child’s head.
• Developmental delays (not reaching learning milestones).
• A downward gaze of your child’s eyes.
• Firm or bulging spaces between the bones of your child’s skull where bone formation isn’t yet complete.
• Poor appetite.
• Having other conditions along with macrocephaly, such as epilepsy or autism.

If your child has benign familial macrocephaly, they won’t have symptoms other than an unusually large head circumference.

What causes macrocephaly?

Causes of macrocephaly range from benign (harmless) to severe. If your child has benign familial macrocephaly, they simply have a larger-than-normal-sized head. Their larger head size is inherited and is similar to the head size of another family member.

However, there are other, more harmful causes of macrocephaly, some are congenital (born with), while others may develop over time. These include:

• An enlarged brain (megalencephaly).
• Fluid on your child’s brain (hydrocephalus). This is an increase in cerebrospinal fluid (CSF). Extra CSF pushes their brain against the inside of their skull increasing the pressure on their brain.
• Bleeding in your child’s brain, including from arteriovenous malformation.
• Overgrowth of skull bones (cranial hyperostosis).
• Brain tumors.
• Chronic (long-lasting) hematomas. Hematomas are pockets of blood that can be caused by head injuries of force, such as from falls or shaking.
• Brain infection, like meningitis, encephalitis or an abscess.
• Genetic disorders, including achondroplasia, fragile X syndrome, neurofibromatosis type 1, PTEN hamartoma tumor syndrome (including Cowden syndrome), Gorlin syndrome and Greig cephalopolysyndactyly syndrome.
• Increased intracranial pressure.

How is macrocephaly diagnosed?

Before birth

Your healthcare provider can determine if your baby has macrocephaly before they’re born by reviewing the results of routine ultrasound tests done late in your second trimester or early in your third trimester.

After birth

Your child’s healthcare provider will measure your baby’s head circumference during each well-child visit, up to the first five years of life. Your child’s healthcare provider will compare your child’s head size to an expected growth chart of children of the same age and sex. They’ll also consider the head size of birth parents and grandparents.

If macrocephaly is found, the next step is to determine the cause. Their healthcare provider will perform several types of exams and tests.

Neurologic exam

During a neurologic exam, your child’s healthcare provider will:

• Ask you questions and/or conduct tests to determine your child’s developmental history and current state.
• Ask about any history of brain or nervous system trauma (head injury) to your child.
• Ask if you developed an infection during pregnancy or if your baby developed an infection (such as meningitis) after birth. This can lead to hydrocephalus.
• Ask if your baby has been vomiting, is increasingly irritable or shows signs of a headache (noticeable by changes in usual behavior, crying that can’t be comforted). These are signs of increased pressure on their brain.
• Ask if your child has a history of seizures.

Physical exam

During a physical exam, in addition to measuring your child’s head circumference, your healthcare provider will look for:

• The space between the bones of their skull (called fontanels). These spaces, or soft spots, are where bone formation isn’t yet complete. They allowed your baby’s skull to be pliable during birth. The fontanel at the back of their head usually closes by age 2 or 3 months. The fontanel at the front of their head closes between age 9 months and 18 months of age. A wide, full and firm fontanel is a sign of increased intracranial pressure.
• Large scalp veins on your baby’s head. This is a sign of increased blood volume in the blood vessels in their brain.
• A downward gaze of your child’s eyes (rather than moving or staring ahead). This is called setting-sun eye phenomenon in infancy, or sundowning in infants, and is a sign of increased pressure on their brain.
• Lack of weight gain. Having a poor appetite and not gaining weight, called “failure to thrive,” can sometimes be associated with a brain issue.

Imaging tests

Imaging tests may include:

• Ultrasound. This may be the first imaging test your child’s healthcare provider orders because it’s safe (doesn’t involve radiation), quick and easy to do, and doesn’t require sedation. This imaging test can show most brain structures if your child’s brain fontanel (especially the front-of-skull fontanel) hasn’t closed.
• Computed tomography (CT). This imaging test shows changes in brain tissue. Because radiation is used in CT, your child’s healthcare provider might order it if an ultrasound doesn’t provide enough information or when sedation isn’t possible.
• Fast magnetic resonance imaging (MRI). This special version of MRI is a quick test that doesn’t require sedation. It can reveal extra fluid in your child’s brain.

What are the complications of macrocephaly?

Complications include:

• Brainstem compression from an oversized brain not having enough room within your child’s skull.
• Hydrocephalus, which can lead to death if not treated quickly.
• Seizures and epilepsy.
• Developmental delays.
• Abnormal brain function.

How is macrocephaly treated?

Treatment depends on the underlying cause.

Benign familial macrocephaly and benign enlargement of the subarachnoid space in infancy (BESSI)

• If your child has no neurologic symptoms, is meeting developmental milestones and has a family history of a larger-sized head, it’s likely that head size is hereditary (runs in the family) and no treatment is needed.
• BESSI is also a harmless (benign) condition. In this condition, there’s extra cerebrospinal fluid in areas of their brain, but it’s not causing harm and resolves on its own without treatment.

Macrocephaly associated with genetic causes

• Ongoing treatment may be needed, which includes physical therapy, occupational therapy, speech and language therapy, and behavioral therapy.

Fluid buildup in the brain or brain bleed

• Surgery is needed to relieve the fluid buildup or stop the brain bleed.

Brain tumor

• Treatment may include surgery, chemotherapy, radiation and steroids.

Can macrocephaly be prevented?

Macrocephaly is a term that means “large head.” The word doesn’t denote a harmful condition. A large head can be a completely normal and healthy condition if a large head size is typical in your family. Your child’s healthcare provider will determine if a medical condition is causing the macrocephaly.

There’s nothing that can be done to prevent macrocephaly. However, there are treatments to help manage many of its causes.

What can I expect if my child has macrocephaly?

If your child has a larger-sized head but has otherwise met normal developmental milestones and a normal neurologic exam, the macrocephaly is often harmless and the outcome is good. No treatment is needed. This is usually the case if your child is diagnosed with benign familial macrocephaly.

If your child has macrocephaly due to an underlying cause, what to expect depends on the specific cause. Your child’s treatment plan will be specialized for them.

When should I call my doctor?

Contact your child’s healthcare provider right away if you notice:

• A bulging soft area on your infant’s head.
• Lack of interest in eating.
• Vomiting.
• Unusual eye movements.
• Being more sleepy than usual.
• Being extra irritable.

These symptoms could mean that your infant's condition could be changing and your child’s healthcare provider will want to investigate and determine if treatment is needed.

How much does a child’s head grow during childhood?

Here’s a simple chart of average head circumference increase by age:

What’s the difference between macrocephaly and megalencephaly?

Macrocephaly is a broader term. It simply means an unusually large head. It includes megalencephaly as a possible cause. Megalencephaly is a distinct term that means an unusually large brain.

What is “benign extra-axial collections of infancy”?

This condition, also called benign external hydrocephalus, means there’s a small amount of fluid between your infant’s brain and skull. It’s very common in children with large heads. It usually doesn’t require treatment. Your child’s healthcare provider will closely follow your child. Usually, children outgrow this condition.

A note from Cleveland Clinic

Macrocephaly is a word that means your baby has a larger than normal head circumference. Macrocephaly is often present at birth. The cause can be harmless if you have other family members with larger heads and there aren’t any other signs or symptoms present. But macrocephaly can also be a sign of a serious condition. Your child’s healthcare provider will do a careful physical and neurologic exam and order any necessary imaging tests of your child’s head. Based on the findings, your child’s healthcare provider can determine the cause and develop an appropriate treatment plan.