Increased head circumference is when the measured distance around the widest part of the skull is larger than expected for the child's age and background.

A newborn's head is usually about 2 centimeters larger than the chest size. Between 6 months and 2 years, both measurements are about equal. After 2 years, the chest size becomes larger than the head.

A series of measurements over time that show an increased rate of head growth often can provide more valuable information than a single measurement that is larger than expected.

Increased pressure in the head (increased intracranial pressure) often accompanies increased head circumference. Symptoms associated with this condition include:

• Eyes moving downward
• Irritability
• Vomiting

See also: Bulging fontanelles

• Benign familial macrocephaly (family tendency toward large head size)
• Canavan disease
• Hurler syndrome
• Hydrocephalus (congenital, post-traumatic, or obstructive)
• Intracranial bleeding
• Morquio syndrome

The health care provider usually finds macrocephaly during a routine well-baby exam.

The health care provider will take a medical history and will perform a physical examination.

Medical history questions may include:

• Time pattern
  • When did you first notice that the baby's head seemed large?
  • Does the baby's head size seem to be increasing faster in proportion to the growth of the body?
• Location
  • Does the head seem larger all over?
  • Is the head growing more in a front-to-back pattern or in a side-to-side pattern?
• Other
  • What other symptoms are present (especially changes in brain or nervous system functions)?

Physical examination may include repeated measurements of the head circumference over a period of time to confirm that the head circumference is significantly increased. In some cases a single measurement is enough to confirm a significant increase.

Diagnostic tests may vary depending on the suspected cause, but often include:

• Head CT scan
• MRI of the head

After seeing your health care provider:

If your health care provider diagnosed the cause of increased head circumference, you may want to note that diagnosis in your personal medical record.