Macrocephaly (megacephaly) is a head circumference > 2 standard deviations above the mean for age (1, 2).
(See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders and Overview of Congenital Craniofacial Abnormalities.)
There are two types of macrocephaly:
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).
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
Diagnosis
Prenatally, ultrasound
Postnatally, physical examination, including measurement of head circumference and cranial MRI
Genetic testing
Prenatally, the diagnosis of macrocephaly sometimes is made with routine ultrasonography done in the late second or early third trimester.
Postnatally, 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.
A clinical geneticist should evaluate affected patients even in cases of apparent isolated congenital anomaly. Chromosomal microarray analysis, specific gene tests, or broader gene panel tests should be considered in the evaluation of patients with macrocephaly. If the results of these tests are nondiagnostic, whole exome sequencing analysis is recommended.
Developmental assessment should be done to identify need for any intervention to optimize developmental outcome.
Treatment
Surgical repair
Currently, the majority of these craniofacial anomalies are treated surgically with the goal of restoring function and improving cosmetic appearance. Treatment and management are best done in tertiary medical centers by multidisciplinary teams capable of addressing all symptoms caused by the congenital anomaly.
Secondary complications (eg, increased intracranial pressure, amblyopia, dental misalignments, speech difficulties) should be managed by the appropriate specialists.
