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Microcephaly - Causes of Microcephaly

Microcephaly is a medical condition in whichunderweight and dwarfed. Development of motor
the circumference of the head is smaller thanfunctions and speech may be delayed.
normal because the brain has not developedHyperactivity and mental retardation are
properly or has stopped growing.common occurrences, although the degree of
Microcephaly can be present at birth or iteach varies. Convulsions may also occur.
may develop in the first few years of life.Motor ability varies, ranging from clumsiness
It is most often caused by geneticin  some  to  spastic quadriplegia in others.
abnormalities that interfere with the growth
of the cerebral cortex during the earlyCauses  of  Microcephaly
months of fetal development. It is
associated with Down's syndrome, chromosomalMicrocephaly can occur alone or in
syndromes, and neurometabolic syndromes.association with other health problems, and
Babies may also be born with microcephaly if,may occur from inheritance of an autosomal
during pregnancy, their mother abused drugsrecessive, or rarely, an autosomal dominant
or alcohol, became infected with agene. Acquired microcephaly may occur after
cytomegalovirus, rubella (German measles), orbirth due to various brain injuries such as
vermicelli (chicken pox) virus, was exposedlack  of  oxygen  or  infection.
to certain toxic chemicals, or had untreated
phenylketonuria (PKU). Babies born withMicrocephaly may be inherited but the gene is
microcephaly will have a smaller than normalconsidered to be extremely rare. In the
head that will fail to grow as they progressgeneral population, microcephaly due to
through  infancy.genetic factors occurs in 1 in 30,000 to
50,000 live births, and in 1 per 10,000
In many cases, microcephaly may not bebirths due to other causes. In some
evident by ultrasound until the thirdpopulations, frequency may be as high as 1 in
trimester, and, therefore, may not be seen on2,000  births.
ultrasounds performed earlier in pregnancy.
The diagnosis of microcephaly may be made atMicrocephaly can also be caused if the mother
birth or later in infancy. The baby's headhas an infection while pregnant or if she is
circumference is much smaller than normal.exposed to harmful substances during early
During the physical examination, thepregnancy, such as x-rays (a type of energy)
physician obtains a complete prenatal andor chemicals. Another cause of microcephaly
birth history of the child. In older babiesis if the bones of the skull come together
and children, the physician may also ask iftoo early. For genetic (inherited) causes of
there is a family history of microcephaly ormicrocephaly,  see  the  next  section.
other medical problems. The physician will
also ask about developmental milestones sinceMicrocephaly is either caused by exposure to
microcephaly can be associated with otherharmful substances during the fetal
problems,  such  as  mental  retardation.development, or it may be associated with
genetic problems or syndromes that may have a
Infants with microcephaly are born withtendency  to  run  in  families.
either a normal or reduced head size.
Subsequently the head fails to grow while theMicrocephaly most often occurs because of
face continues to develop at a normal rate,failure of the brain to grow at a normal
producing a child with a small head and arate. Skull growth is determined by brain
receding forehead, and a loose, oftenexpansion, which takes place during the
wrinkled scalp. As the child grows older, thenormal growth of the brain during pregnancy
smallness of the skull becomes more obvious,and infancy.
although the entire body also is often



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