microcephaly
n. a condition 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 disability, delayed motor functions 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 will have normal intelligence and a head that will grow bigger, although it will still be below the normal growth curves for
head circumference. See also primary microcephaly. Compare macrocephaly. —microcephalic
adj.