APA Dictionary of Psychology

n. a congenital disorder in which the circumference of the head is more than two standard deviations below the mean for age, gender, race, and gestation. It may be present at birth or develop in the first few years of life. The condition is associated with Down syndrome and other chromosomal syndromes; neurometabolic syndromes; maternal PKU; and prenatal exposure to drugs or alcohol, cytomegalovirus, rubella (German measles), varicella (chicken pox) virus, and certain toxic chemicals. Depending on the severity of their accompanying syndrome, children with microcephaly may have intellectual developmental disorder, delayed motor functionst, and speech, facial distortions, dwarfism or short stature, hyperactivity, seizures, difficulties with coordination and balance, and other brain or neurological abnormalities. Some children with microcephaly have typical intelligence and experience growth in head size, although the size will still be below the normal growth curves for head circumference. See also primary microcephaly. Compare macrocephaly. —microcephalic adj.