Cerebral palsy is not one
disease with a single cause, like chicken pox or measles. It is a
group of disorders with similar problems in control of movement, but
probably with different causes. When physicians try to uncover the
cause of cerebral palsy in an individual child, they look at the form
of cerebral palsy, the mother's and child's medical history,
and onset of the disorder.
In the United States, about 10 to 20 percent of children who have
cerebral palsy acquire the disorder after birth. (The figures are
higher in underdeveloped countries.) Acquired cerebral palsy
results from brain damage in the first few months or years of life and
can follow brain infections, such as bacterial meningitis or viral
encephalitis, or results from head injury -- most often from a motor
vehicle accident, a fall, or child abuse.
Congenital cerebral palsy, on the other hand, is present at
birth, although it may not be detected for months. In most cases, the
cause of congenital cerebral palsy is unknown. Thanks to research,
however, scientists have pinpointed some specific events during
pregnancy or around the time of birth that can damage motor centers in
the developing brain. Some of these causes of congenital cerebral
palsy include:
Infections during pregnancy. German measles, or rubella, is
caused by a virus that can infect pregnant women and, therefore, the
fetus in the uterus, to cause damage to the developing nervous system.
Other infections that can cause brain injury in the developing fetus
include cytomegalovirus and toxoplasmosis. There is relatively recent
evidence that placental and perhaps other maternal infection can be
associated with cerebral palsy.
Jaundice in the infant. Bile pigments, compounds that are
normally found in small amounts in the bloodstream, are produced when
blood cells are destroyed. When many blood cells are destroyed in a
short time, as in the condition called Rh incompatibility (see below),
the yellow-colored pigments can build up and cause jaundice. Severe,
untreated jaundice can damage brain cells.
Rh incompatibility. In this blood condition, the mother's body
produces immune cells called antibodies that destroy the fetus's blood
cells, leading to a form of jaundice in the newborn.
Severe oxygen shortage in the brain or trauma to the head during labor
and delivery. The newborn infant's blood is specially equipped to
compensate for low levels of oxygen, and asphyxia (lack of oxygen
caused by interruption in breathing or poor oxygen supply) is common
in babies during the stresses of labor and delivery. But if asphyxia
severely lowers the supply of oxygen to the infant's brain for lengthy
periods, the child may develop brain damage called hypoxic-ischemic
encephalopathy. A significant proportion of babies with this type of
brain damage die, and others may develop cerebral palsy, which is then
often accompanied by mental impairment and seizures.
In the past, physicians and scientists attributed most cases of
cerebral palsy to asphyxia or other complications during birth if they
could not identify another cause. However, extensive research by NINDS
scientists and others has shown that very few babies who experience
asphyxia during birth develop encephalopathy soon after birth.
Research also shows that a large proportion of babies who experience
asphyxia do not grow up to have cerebral palsy or other neurological
disorders. Birth complications including asphyxia are now estimated to
account for about 6 percent of congenital cerebral palsy cases.
Stroke. Coagulation disorders in mothers or infants can produce
stroke in the fetus or newborn baby. Bleeding in the brain has several
causes -- including broken blood vessels in the brain, clogged blood
vessels, or abnormal blood cells -- and is one form of stroke.
Although strokes are better known for their effects on older adults,
they can also occur in the fetus during pregnancy or the newborn
around the time of birth, damaging brain tissue and causing
neurological problems. Ongoing research is testing potential
treatments that may one day help prevent stroke in fetuses and
newborns.
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