| Microcephaly is a medical condition in which the | | | | skull becomes more obvious, although the entire |
| circumference of the head is smaller than normal | | | | body also is often underweight and dwarfed. |
| because the brain has not developed properly or has | | | | Development of motor functions and speech may be |
| stopped growing. Microcephaly can be present at | | | | delayed. Hyperactivity and mental retardation are |
| birth or it may develop in the first few years of life. | | | | common occurrences, although the degree of each |
| It is most often caused by genetic abnormalities that | | | | varies. Convulsions may also occur. Motor ability |
| interfere with the growth of the cerebral cortex | | | | varies, ranging from clumsiness in some to spastic |
| during the early months of fetal development. It is | | | | quadriplegia in others. |
| associated with Down's syndrome, chromosomal | | | | Causes of Microcephaly |
| syndromes, and neurometabolic syndromes. Babies | | | | Microcephaly can occur alone or in association with |
| may also be born with microcephaly if, during | | | | other health problems, and may occur from |
| pregnancy, their mother abused drugs or alcohol, | | | | inheritance of an autosomal recessive, or rarely, an |
| became infected with a cytomegalovirus, rubella | | | | autosomal dominant gene. Acquired microcephaly may |
| (German measles), or vermicelli (chicken pox) virus, | | | | occur after birth due to various brain injuries such as |
| was exposed to certain toxic chemicals, or had | | | | lack of oxygen or infection. |
| untreated phenylketonuria (PKU). Babies born with | | | | Microcephaly may be inherited but the gene is |
| microcephaly will have a smaller than normal head | | | | considered to be extremely rare. In the general |
| that will fail to grow as they progress through | | | | population, microcephaly due to genetic factors |
| infancy. | | | | occurs in 1 in 30,000 to 50,000 live births, and in 1 per |
| In many cases, microcephaly may not be evident by | | | | 10,000 births due to other causes. In some |
| ultrasound until the third trimester, and, therefore, | | | | populations, frequency may be as high as 1 in 2,000 |
| may not be seen on ultrasounds performed earlier in | | | | births. |
| pregnancy. The diagnosis of microcephaly may be | | | | Microcephaly can also be caused if the mother has an |
| made at birth or later in infancy. The baby's head | | | | infection while pregnant or if she is exposed to |
| circumference is much smaller than normal. During the | | | | harmful substances during early pregnancy, such as |
| physical examination, the physician obtains a complete | | | | x-rays (a type of energy) or chemicals. Another |
| prenatal and birth history of the child. In older babies | | | | cause of microcephaly is if the bones of the skull |
| and children, the physician may also ask if there is a | | | | come together too early. For genetic (inherited) |
| family history of microcephaly or other medical | | | | causes of microcephaly, see the next section. |
| problems. The physician will also ask about | | | | Microcephaly is either caused by exposure to harmful |
| developmental milestones since microcephaly can be | | | | substances during the fetal development, or it may |
| associated with other problems, such as mental | | | | be associated with genetic problems or syndromes |
| retardation. | | | | that may have a tendency to run in families. |
| Infants with microcephaly are born with either a | | | | Microcephaly most often occurs because of failure of |
| normal or reduced head size. Subsequently the head | | | | the brain to grow at a normal rate. Skull growth is |
| fails to grow while the face continues to develop at | | | | determined by brain expansion, which takes place |
| a normal rate, producing a child with a small head and | | | | during the normal growth of the brain during |
| a receding forehead, and a loose, often wrinkled | | | | pregnancy and infancy. |
| scalp. As the child grows older, the smallness of the | | | | |