What to know about macrocephaly

Macrocephaly is the term for an unusually large head. An infant with macrocephaly will have a larger head than most other infants of the same age and sex.

In many cases, this condition is benign or harmless. In other cases, it may indicate an underlying medical condition, such as a genetic syndrome or a brain tumor.

In this article, learn about the causes of macrocephaly and how doctors diagnose and treat the potential underlying medical conditions.

What is macrocephaly?

A child with an unusually large head may have macrocephaly
A child with an unusually large head may have macrocephaly.

Macrocephaly means big head, and it is the name for a condition in which an infant or child has an abnormally large head size.

For a doctor to diagnose macrocephaly, the measurement of the head around its widest part needs to be larger than the 98th percentile.

Macrocephaly may sometimes be a sign of an underlying condition that requires treatment.

In other cases, it may occur due to genetics, including a family history of macrocephaly. If this is the case, the condition will be harmless.


Genes are responsible for many cases of macrocephaly. When an infant with a large head has a family history of larger-than-average head sizes, doctors will diagnose them with benign familial macrocephaly.

Infants with benign familial macrocephaly will not experience any symptoms other than a large head and will have no additional health concerns.

However, there are several potential causes of macrocephaly that require medical attention, one of which is a fluid buildup on the brain. Extra fluid can put pressure on the brain, increasing the risk of many health complications.

The severity of the condition depends on the amount of fluid present. When there is a significant fluid buildup in the brain, which is called hydrocephalus, the underlying cause is likely to require treatment to prevent further problems.

Other causes of macrocephaly include:

  • bleeding in the brain
  • brain tumors
  • certain metabolic conditions
  • some types of infection
  • Alexander disease
  • Greig cephalopolysyndactyly syndrome
  • Sotos syndrome
  • chronic hematomas and other lesions
  • other genetic syndromes

Signs and symptoms

macrocephaly is often harmless
While macrocephaly is often harmless, it can lead to a buildup of fluid in the brain.

The primary sign of macrocephaly is an unusually large head. In cases of benign familial macrocephaly, this will be the only symptom.

If an infant has an underlying condition that is causing the macrocephaly, they will present with additional symptoms. These may include:

  • delays reaching developmental milestones
  • a fast-growing head
  • comorbidity with other conditions, such as autism
  • mental disorders

A doctor will typically continue to monitor the infant after the diagnosis. The doctor will also ask parents or caregivers to watch for the following signs:

  • excessive sleepiness
  • unusual eye movement
  • poor feeding
  • vomiting
  • a bulging soft spot
  • excessive irritability


Doctors can usually diagnose macrocephaly during a routine physical examination.

As part of a physical examination for a baby or young child, the doctor will measure the head circumference. They will do this at each checkup, and any time there is a concern. If the doctor notes a rapid increase in head size over time, this can lead to a diagnosis.

If a doctor thinks that an infant has macrocephaly, they will often order imaging tests, such as a CT scan, ultrasound, or MRI.

These tests will help the doctor to determine if there is a fluid buildup in the brain, which could cause pressure and other complications.

Some symptoms of increased pressure on the brain include:

If a child with macrocephaly has additional symptoms, these may help the doctor to diagnose other health conditions. Other symptoms may include:

  • vision problems
  • bulging veins
  • a bulging soft spot on the top of the head


Speech and language therapy can help children with macrocephaly
Speech and language therapy can help children whose macrocephaly stems from a genetic condition.

The treatment for macrocephaly will vary depending on the underlying cause. An infant with benign familial macrocephaly will not usually require any treatment.

Infants whose macrocephaly stems from a genetic condition may require life-long treatment and support, including:

  • occupational therapy
  • behavioral therapy
  • speech and language therapy
  • physical therapy

An infant who has a fluid buildup or bleeding in the brain will often require prompt surgery to reduce the pressure and prevent further complications.

Doctors may use a variety of methods to treat a brain tumor, including:


The outlook largely depends on the underlying condition causing the macrocephaly. Infants with benign familial macrocephaly have a good outlook and will not usually experience any complications.

A child who has macrocephaly as a result of an underlying condition, such as a brain tumor or a genetic syndrome, will require an individualized treatment plan.

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