macrocephaly /mak′rōsef″əlē/ [Gk, makros + kephale, head] , a congenital anomaly characterized by abnormal largeness of the head and brain in relation to the rest of the body, resulting in some degree of cognitive impairment and growth delay. The head is more than two standard deviations above the average circumference size for age, sex, race, and period of gestation, with excessively wide fontanels; the facial features are usually normal. The condition may be caused by some defect in formation during embryonic development, or it may be the result of progressive degeneration processes, such as Schilder’s disease, Greenfield’s disease, or congenital lipoidosis. In macrocephaly there is symmetric overgrowth at the head without increased intracranial pressure, as differentiated from hydrocephalus, in which the lateral, asymmetric growth of the head is caused by excessive accumulation of cerebrospinal fluid, usually under increased pressure. Specific diagnostic tests may be necessary to differentiate the two conditions. Treatment is primarily symptomatic, with health care concentrated specifically on helping parents learn to care for a child who experiences developmental and cognitive delays. Also called macrocephalia, megalocephaly. Compare microcephaly. See also hydrocephalus. −macrocephalic, macrocephalous, adj., −macrocephalus, n.
