Microcephaly

Abstract

Microcephaly is defined as a head circumference more than two standard deviations below the mean for gender and age. Congenital microcephaly is present at birth, whereas postnatal microcephaly occurs later in life. Genetic abnormalities, syndromes, metabolic disorders, teratogens, infections, prenatal, perinatal, and postnatal injuries can cause both congenital and postnatal microcephaly. Evaluation of patients with microcephaly begins with a thorough history and physical examination. In cases of worsening microcephaly or neurological signs or symptoms, neuroimaging, metabolic, or genetic testing should be strongly considered. Any further studies and workup should be directed by the presence of signs or symptoms pointing to an underlying diagnosis and are usually used as confirmatory testing for certain conditions. Neuroimaging with magnetic resonance imaging (MRI) is often the first diagnostic test in evaluating children with microcephaly. Genetic testing is becoming more common and is often the next step following neuroimaging when there is no specific evidence in the history or physical examination suggesting a diagnosis. Microcephaly is a lifelong condition with no known cure. The prognosis is usually worse for children who experienced an intrauterine infection or have a chromosomal or metabolic abnormality. Zika virus has rapidly spread since 2015, and maternal infection with this virus is associated with microcephaly and other serious brain abnormalities. Microcephaly has become much more prevalent in the news and scientific community with the recent emergence of Zika virus as a cause of congenital microcephaly.

Keywords: Zika virus; genetic abnormalities; head circumference; microcephaly; neuroimaging; syndromes.

Figure 1

Newborn Infant with congenital microcephaly.

Figure 2

Diagnostic approach to a child with microcephaly. *Testing for infections, genetic, metabolic, toxin, and endocrine disorders. MRI: magnetic resonance imaging; SD: Standard Deviation.