Macrocephaly

What is macrocephaly?  

Macrocephaly, also known as macrocrania, means “large head.” If your child is diagnosed with macrocephaly, this means that their head circumference (the measurement around the widest part of the head) is greater than the 98th percentile on the growth chart.  

What causes macrocephaly?  

There are multiple conditions that cause macrocephaly. Some of the most common causes include: 

• Familial macrocephaly – child inherits a large head from family members 
• Benign enlargement of the subarachnoid spaces (BESS) – extra cerebrospinal fluid on the outside of the brain that does not cause pressure inside the head 
• Hydrocephalus – a buildup of fluid in the brain causing pressure inside the head 

What are the signs/symptoms of macrocephaly? 

If your child has a benign case of macrocephaly, they may not have any symptoms other than a large head. However, other possible signs and symptoms may include delayed developmental milestones, prominent veins on the scalp, fullness of the anterior fontanelle (soft spot on your baby’s head), or downward gaze of the eyes.  

How is it diagnosed? 

Some tests may include head circumference measurement, physical exam including a detailed head and neurologic exam, and imaging tests such as ultrasound, MRI, or CT of the brain.  

When should I call the clinic? 

Call the clinic if your child has: 

• Rapidly increasing head size 
• A bulging or tense soft spot (anterior fontanelle) 
• Persistent vomiting 
• Excessive irritability 
• Excessive sleepiness 
• Abnormal eye movements including fixed downward gaze of the eyes 

What else do I need to know?  

Treatment will differ depending on the cause of macrocephaly. Familial macrocephaly does not typically require treatment or routine neurosurgery follow up. Benign enlargement of the subarachnoid spaces usually requires brain MRIs and neurosurgery follow up every few months until the anterior fontanelle closes. Hydrocephalus requires surgical intervention and follow up will vary. Follow up with the neurosurgery team per their recommendations.  

Questions? 

This information is not specific to your child but provides general information. If you have any questions, please call the Neurosurgery Clinic at 651-220-5230.  

Reviewed 9/2023

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