Microcephaly

An abnormally small head due to failure of brain growth. In precise terms, microcephaly is a head circumference that is more than 2 standard deviations below the normal mean for age, sex, race, and gestation. (Some authorities define microcephaly as more than 3 standard deviations below the mean.) Microcephaly may be congenital (present at birth) or it may become evident in the first few years of life when the head fails to grow while the face continues to develop at a normal rate, producing a child with a small head, a relatively large face, and receding forehead. As the child grows older, the smallness of the head becomes more obvious. Microcephaly is often equated with developmental delay and mental retardation. However, not all children with microcephaly are mentally retarded. The development of motor skills and speech may be delayed. Convulsions may also occur in some cases. Motor ability may be impaired and range from clumsiness in some children to spastic quadriplegia in others. Microcephaly stems from a wide variety of problems that can cause abnormal growth of the brain including infections, radiation, medications, chromosome abnormalities and genetic diseases. Congenital microcephaly may follow intrauterine infections such as with rubella, cytomegalovirus (CMV) and toxoplasmosis. It is part of many chromosomal abnormalities and other syndromes including: {{}}Chromosome abnormalities — such as trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome), the Wolf-Hirschhorn syndrome, the cat cry syndrome, and partial deletion of long arm of chromosome 13, Contiguous gene syndromes — such as the Miller-Dieker syndrome. Langer-Giedion syndrome, Prader-Willi syndrome, and the aniridia-Wilms tumor syndrome. Genetic disorders — such as the Johanson-Blizzard syndrome, Seckel syndrome, and the Smith-Lemli-Opitz syndrome. Environmental insults — such as maternal PKU (mothers who have poorly controlled PKU during pregnancy) and the fetal alcohol syndrome. There is no specific treatment for microcephaly. Treatment is symptomatic and supportive. On the average, life expectancy for individuals with microcephaly is reduced and the prognosis for normal brain function is poor. The prefix "micro-" is derived from the Greek "mikros"

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Abnormal smallness of the head; applied to a skull with a capacity below 1350 ml. Usually associated with mental retardation. SYN: microcephalia, microcephalism, nanocephalia, nanocephaly. [micro- + G. kephale, head]

- encephaloclastic m. complex growth disturbances in the brain as a result of regressive changes in fetal life.

- schizencephalic m. dysgenic process resulting in focal cerebral defects.

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mi·cro·ceph·a·ly -'sef-ə-lē n, pl -lies a condition of abnormal smallness of the head usu. associated with mental retardation

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n.

abnormal smallness of the head in relation to the size of the rest of the body: a congenital condition in which the brain is not fully developed. Compare macrocephaly.

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mi·cro·ceph·a·ly (mi″kro-sefґə-le) [micro- + cephaly] abnormal smallness of the head, usually associated with mental retardation. Called also nanocephaly. microcephalic, microcephalous adj