- Amy Sniderman, MD
- Cleveland Clinic Foundation Cleveland, Ohio
- Baxter PS,
- Rigby AS,
- Rotsaert M,
- Wright I
- Zitelli BJ,
- Davies HW
- Head Circumference for Age Tables, Infants Ages Birth–36 Months- Selected Percentiles. Accessed July 2010at: http://www.cdc.gov/growthcharts/
- Ashwal S,
- Michelson D,
- Plawner L,
- Dobyns WB
Dr Sniderman has disclosed no financial relationships relevant to this In Brief. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
Measurement of the head circumference is a routine yet critical part of newborn, infant, and toddler health supervision care. Abnormal head growth may indicate a medical or developmental problem and often leads practitioners to further evaluation.
Normal head circumferences in term infants range from 32 to 38 cm. Microcephaly is defined as a head circumference 2 standard deviations (SDs) below the mean for age and sex or roughly less than the 2nd percentile. Conversely, macrocephaly is defined as a head circumference greater than 2 SDs above the mean or greater than the 98th percentile. Bright Futures recommendations state that head circumference measurements should be obtained at each health supervision visit from birth to 24 months of age, but the Centers for Disease Control and Prevention growth charts extend to 36 months.
Microcephaly can present as primary or acquired. Causes of primary microcephaly include autosomal dominant and autosomal recessive genetic disorders; trisomy 13, 18, and 21; various syndromes, including Cornelia de Lange syndrome, Smith-Lemli-Opitz syndrome, and Rett syndrome; inborn errors of metabolism; and hypothyroidism. Acquired microcephaly is distinguished by a normal head circumference at birth, followed by development of microcephaly in subsequent months or years, usually due to lack of brain development or growth. Causes of acquired microcephaly include sequelae from stroke, meningitis, or encephalitis; other infections, such as toxoplasmosis, rubella, cytomegalovirus, and herpes; in utero teratogen exposure; and hypoxic-ischemic encephalopathy. One study from England (Baxter PS, et al, 2009) noted three different patterns of head growth in infants …