Baby's head being measured


Macrocephaly is a common reason for referral to Neurology or Neurosurgery, often noted during routine well-care visits with a child’s primary care provider. The incidence of macrocephaly is reported up to 5%(1). There are a number of reasons for macrocephaly, many benign, but others which require more urgent evaluation.

What is the definition of macrocephaly?

The American Academy of Pediatrics recommends measuring head circumference at each routine well-care visit through age 24 months. Standardized head circumference charts are available to plot head size for both children and young adults. There are also growth charts for children with special health care needs such as Down syndrome, Turner syndrome and others. Macrocephaly is defined as an occipitofrontal head circumference which is >2 standard deviations above the mean or 0.5cm above the 97th percentile for age and gender.

What are the causes of macrocephaly?

Several studies have demonstrated that the majority of macrocephaly cases (i.e. 60-80%) are due to benign etiologies such as familial macrocephaly or benign enlargement of the subarachnoid spaces (BESS).(2,3) Familial macrocephaly presents in an otherwise healthy and developmentally normal child with normal neurological examination and no other signs of overgrowth. One or both of the child’s parents often have large head size as well. You should ask the parents if they have difficulty finding hats that fit and measure their head size during a clinic visit. Benign enlargement of the subarachnoid spaces presents in infancy with macrocephaly in an otherwise developmentally normal child with normal neurological examination. The parents often have normal head size and imaging will reveal increased extraaxial fluid predominantly in the frontoparietal convexities. In these cases, the head size may demonstrate steady growth prompting imaging, but then stabilizes over early infancy.

There are a number of pathologic reasons for macrocephaly which must be considered. Often, these disorders will present with signs or symptoms to suggest underlying abnormalities such as hydrocephalus or brain overgrowth.

Symptoms suggesting urgent referral and imaging(4)

  • Impaired consciousness or excessive irritability
  • Persistent vomiting
  • Papilledema
  • Bradycardia
  • Seizures
  • Sunsetting (difficulty with upward gaze)
  • Tense fontanelle

Physical findings which may suggest underlying syndromic cause of macrocephaly

  • Dysmorphic features
  • Somatic overgrowth
  • Vascular malformations
  • Developmental delays or neurologic deficits
  • Skin lesions or skeletal anomalies

What should the workup of macrocephaly include?

The most important component of evaluation is a history to delineate signs/symptoms of increased intracranial pressure or other features to suggest underlying structural abnormality. Physical exam should also evaluate these signs as noted above. If the child is otherwise developmentally normal and without worrisome signs/symptoms, they can be followed closely for head growth over time. For children with abnormal exams or worrisome findings on history, imaging may be needed. Cranial ultrasound can be a useful and simple test in children with open fontanelles. This is reassuring if normal. For abnormal results, further imaging with CT or MRI brain is often needed. For children requiring urgent imaging due to signs/symptoms of increased intracranial pressure, CT is preferred. For older kids in which the fontanelles are closed, MRI will provide the best imaging, but may require sedation due to longer scan times and need to remain motionless. Other workup may include referral for eye exam to evaluate for papilledema, skeletal exam if there are concerns of abuse or overgrowth syndromes, and blood/urine testing for suspected metabolic etiologies.

When should you refer for evaluation?

Referral to a neurologist is warranted for children with macrocephaly and abnormal neurological examinations, developmental delays, seizures, and other signs/symptoms of underlying genetic or metabolic etiology. For children with imaging findings or signs/symptoms on exam of hydrocephalus, neurosurgery referral is appropriate. For children with signs/symptoms of increased intracranial pressure – emergent evaluation for imaging and treatment is necessary.

For more information on macrocephaly, you can visit the following resource.

DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995. Macrocephaly in children – approach to the patient;

[updated 2018 Oct 08; cited 2019 June 7]

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Contributing author

M. Scott Perry, MD
Medical Director, Neurology; Co-Director of the Jane and John Justin Neurosciences Center; Medical Director, Tuberous Sclerosis Complex Clinic

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Contact the Jane and John Justin Neuroscience Center at Cook Children’s to refer a patient or ask questions: 682-885-2500.


1. Top Magn Reson Imaging 2018, 27(4):197-217

2. Iran J Child Neurol 2013, 7(3):28

3. Pediatr Int 2018, 60(5):474

4. BMJ 2011, 343:d4191

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