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Simeon A. Boyadjiev Boyd

, MD, University of California, Davis

Last full review/revision May 2020| Content last modified May 2020
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Macrocephaly (megacephaly) is a head circumference > 2 standard deviations above the mean for age (1, 2).

There are two types:

  • Disproportionate macrocephaly

  • Proportionate macrocephaly

In disproportionate macrocephaly, the head is larger than appropriate for the child's size; affected children are at risk of autism spectrum disorders, developmental disability, and seizures.

In proportionate macrocephaly, the head appears appropriately sized for the body (ie, the large head is associated with a large stature), and an overgrowth syndrome (eg, growth hormone excess) should be considered.

Abnormal macrocephaly may be due to an enlarged brain (megalencephaly), hydrocephalus, cranial hyperostosis, or other conditions. These conditions may be the result of genetic disorders or disorders the child acquired before or after birth (3).

Evaluation should include a 3-generation family history, developmental and neurologic assessment, examination for limb asymmetry and cutaneous lesions, and brain MRI. Sometimes disproportionate macrocephaly is familial and not associated with other anomalies, complications, or developmental delays; this form is transmitted in an autosomal dominant pattern, so at least one parent has a large head circumference. The diagnoses to be considered include neurofibromatosis type 1, Fragile X syndrome, Sotos syndrome, and lysosomal storage disorders.

General references

  • 1. Cogulu O, Aykut A, Kutukculer N, et al: Two cases of macrocephaly and immune deficiency. Clin Dysmorphol 16(2):81–84, 2007. doi: 10.1097/MCD.0b013e3280464ee6.

  • 2. Fenichel, Gerald M: Clinical Pediatric Neurology: A Signs and Symptoms Approach, ed. 6. Philadelphia, Saunders/Elsevier, 2009, p. 369.

  • 3. Strassburg HM: Macrocephaly is not always due to hydrocephalus. J Child Neurol 4 Suppl:S32–S40, 1989. doi: 10.1177/0883073889004001s07.

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