Parents of new babies may expect that pediatricians will check their baby's length and weight. But they may not expect that doctors will pull out a tape measure to check the size of a new baby's head. Baby head measurements are just as important for tracking growth as height and weight are. But what does it mean when a baby has a head that is larger than most?
The medical term for a large head is "macrocephaly." Most of the time, it isn't a serious condition, so parents don't need to worry about it. But in rare cases, it can be a sign that your baby has other health conditions.
"While most children with large heads are completely healthy, early evaluation helps identify the small number who may need imaging or treatment for underlying conditions," says Aria Fallah, MD, a pediatric neurosurgeon at UCLA Health.
Learn more about macrocephaly and what it means.
What Is Macrocephaly?
The simple definition of the word macrocephaly is "large head." It's a measurement that shows that a baby's head size is greater than the 97th percentile. This means that the baby's head is bigger than 97% of other babies of the same age and sex.
Sometimes, doctors spot macrocephaly during an ultrasound before the baby is born. In other cases, it's something that they notice when they measure the baby at routine exams during the baby's first year of life. Your pediatrician may have you see a doctor called a neurologist (who specializes in nervous system conditions) if your child has macrocephaly.
Should I Worry if My Baby Has a Big Head?
Not all cases of macrocephaly are a sign that something is wrong. One of the most common reasons for macrocephaly is something that doctors call "benign familial macrocephaly." In other words, big heads run in your family.
A doctor might figure out if a baby's big head is passed down through their family by measuring the heads of the parents. The doctor will also check the baby's head, particularly the fontanelles (soft spots that are normal for babies). If everything is fine, there is nothing you need to do. The doctor will probably ask you to come back in a few months or if any other symptoms arise.
Average head circumference of newborns
A newborn's head circumference is a measurement around the widest area of their head. On average, a newborn's head circumference is about 13 3/4 inches (35 centimeters). Boys tend to have slightly larger heads than girls, but the average difference is under half an inch (1 centimeter).
Symptoms of Macrocephaly
If your baby has benign familial macrocephaly, their only symptom likely will be a larger than average head. Many children with large heads are healthy.
But if an underlying health condition causes macrocephaly, the baby also might have symptoms such as:
- Tightness or bulging of the soft spot on the head where the bones haven't fully formed
- Fast growth of the head
- Bulging veins in the head
- Unusual eye movements, such as an ongoing downward gaze
- Unexplained projectile vomiting
- Less hunger than usual
- Irritability that gets worse over time or extreme sleepiness
- High-pitched cry like the baby is in pain or discomfort
- Developmental delays, meaning a child is slow to reach milestones in areas such as moving, speaking, and learning compared to other children of the same age
Some babies with macrocephaly also have other conditions, such as epilepsy or autism.
If a baby with a large head has concerning symptoms, doctors will first need to figure out if the size of the head is due to an enlarged brain, excess fluid in the skull, or an overgrowth of the skull bones. They will use imagining tests such as an MRI or CT scan to answer these questions. After that, they may need to do blood tests or genetic testing to reach a final diagnosis.
“What matters most is the trend in head growth over time and whether it's accompanied by neurological symptoms,” Fallah says.
Macrocephaly Due to Hydrocephalus
Hydrocephalus is sometimes called "water on the brain." It refers to a buildup of excess cerebrospinal fluid around the brain. Sometimes, when this happens to babies, it's not a problem. Doctors call it "benign extra-axial collections of infancy" or "benign external hydrocephalus." Children typically outgrow the condition by early childhood. Still, your doctor will want to follow up with you regularly to keep an eye on your baby.
There are times when hydrocephalus is dangerous. The pressure of the fluid can lead to brain injuries. Your baby may need surgery to ease the pressure and lower the risk of lasting brain damage.
Macrocephaly vs. hydrocephalus
Hydrocephalus is one of the conditions that can cause macrocephaly. It can lead to symptoms such as a bulge on the soft spot of the baby's head, a downward gaze, vomiting, and sleepiness. It also can lead to developmental troubles. Surgery is often the treatment when hydrocephalus causes macrocephaly. Babies who have macrocephaly due to other causes may need treatments other than surgery.
Congenital Macrocephaly?
It's a term that means your baby was born with microcephaly. You might also hear it called primary macrocephaly.
Benign familial macrocephaly, in which having a big head runs in the family, is a common reason for congenital macrocephaly.
Sometimes, macrocephaly is a symptom of an underlying genetic condition. Some of the conditions include:
Sotos syndrome
This condition causes rapid physical growth before birth and for the first several years of life. In addition to macrocephaly, the shape of the head is longer than is typical. People with this condition also tend to have developmental delays.
Cowden syndrome
This condition results in noncancerous growths that appear on a person's body. People with Cowden syndrome may have a high risk of certain cancers later in life.
Gorlin syndrome
Also known as basal cell nevus syndrome, this condition results in a large head, distinctive facial features, and pitted skin on the hands and feet. Gorlin syndrome causes benign tumor growth. People who have it have a significant risk of basal cell skin cancer as young adults.
Fragile X syndrome
Fragile X syndrome happens because a person's body doesn't make a particular protein needed for brain development. It causes developmental delays, learning and intellectual disabilities, and social-emotional difficulties.
Tuberous sclerosis
This condition causes noncancerous tumors to form in various body parts, such as the skin, brain, eyes, kidneys, heart, and lungs. Some children have mild symptoms, while others have serious ones. It depends on where the tumors form and how large they are.
Neurofibromatosis type 1 (NF1)
This condition causes certain skin changes and tumors on nerve tissue. The tumors usually are not cancer. The symptoms tend to be mild, but NF1 can lead to other health concerns such as learning disabilities, vision loss, pain, and heart and blood vessel conditions.
Genetic conditions like this don't have a cure. Instead, your doctor will help you manage the symptoms that your child has. This might include medical treatment as well as therapy to help with physical or developmental delays. You and your doctor can make a plan to serve your child's particular needs best.
Macrocephaly isn't always present at birth. Sometimes, it happens after a baby is born. You might hear this called secondary macrocephaly. It can be due to conditions such as:
- Hydrocephalus that becomes worse
- Irregular buildups of fluid near the brain called subdural fluid collections
- Brain tumors
- Irregular blood vessels in the head
- Brain infections such as meningitis and encephalitis
- Growing pressure inside the skull called increased intracranial pressure
How Is Macrocephaly Diagnosed?
A doctor might discover macrocephaly during pregnancy, while your baby is in your womb. Or they might find out that your baby has macrocephaly sometime after birth.
During pregnancy. A common imaging test called ultrasound can help doctors find out if the fetus has macrocephaly. The test is often done in the late second trimester or the early third. Ultrasound uses sound waves to make pictures of your baby in the womb, letting the doctor check on your baby's health and development.
After birth. The doctor measures your child's head circumference during routine checkups called well-child visits. They compare the measurement to those of other children of the same age and sex based on an expected growth chart. If the doctor decides that your child's head is larger than average, they also take into account the size of close relatives' heads (including parents and grandparents) to find out if macrocephaly runs in your family.
If the doctor says your child has macrocephaly, you may be referred to a neurologist. The neurologist may ask you questions about your little one's symptoms, health history, and development. Your answers could provide clues about a possible underlying cause. Your child also gets a physical exam to check for possible macrocephaly symptoms such as tightness or bulging of any remaining soft spot on the head, large veins in the head, a downward gaze, and poor weight gain due to a lack of hunger.
Your child may need imaging tests as well. These might include:
- MRI, which can make detailed pictures of the inside of the head by using magnets, radio waves, and a computer
- Ultrasound, which can help check the brain using sound waves if soft spots on your child's skull haven't fully closed
- CT scan, which uses X-rays and might be done if your doctor doesn't get enough information from an ultrasound
If the doctor thinks that a genetic condition might be the cause of your child's macrocephaly, they may refer you to another doctor called a geneticist. The geneticist may do blood tests to check for the signs of these conditions.
Macrocephaly Treatment
Macrocephaly treatment depends on the cause. Examples of causes and their treatments include:
Benign familial macrocephaly. Your child likely won't need any treatment.
Genetic conditions tied to macrocephaly. Your child might need various treatments. These could include different types of therapy that help with movement, everyday tasks, speech, language, and behavior.
Hydrocephalus. Your child might need surgery to ease the pressure of fluid buildup on the brain.
Brain tumor. Treatment options may include surgery to remove the tumor, chemotherapy, or radiation.
If your baby has developmental delays due to macrocephaly, contact your state's early intervention services as soon as possible. This is a type of support that might help your child reach important milestones and make the most of their abilities.
Also, make sure your child gets all of the follow-up checkups that their doctor recommends. The doctor may refer you to other specialists if your child has macrocephaly complications such as lazy eye (amblyopia), trouble speaking, or misaligned teeth.
Takeaways
Macrocephaly is the medical term for a large head. Most often, it isn't a serious condition. Rarely, it might be a clue of an underlying health problem. If treatment is needed, the right treatment depends on the underlying cause.
Macrocephaly FAQs
What is the main cause of macrocephaly?
There isn't a main cause. But the most frequent explanation is benign familial megalencephaly.
Is there a cure for macrocephaly?
There's no cure for macrocephaly, which has various causes. When macrocephaly has an underlying cause that takes a toll on health, treatments are available to help.
Can macrocephaly be normal?
Yes. For many people with macrocephaly, having a big head simply runs in families and doesn't cause health problems. This is called benign familial macrocephaly.
Does macrocephaly mean autism?
No, but there is a partial link between the two.
