Cerebral Palsy

Definition

Cerebral palsy (CP), or static encephalopathy, is the name for a collection of movement disorders caused by brain damage that occurs before, during, or shortly after birth. A person with CP is often also affected by other conditions caused by brain damage.

Description

The affected muscles of a person with CP may become rigid or excessively loose. The person may lose control of muscles, or have problems with balance and coordination. A combination of these is also possible. Those with CP may be primarily affected in the legs (paraplegia or diplegia), or in the arm and leg of one side of the body (hemiplegia), or all four limbs may be involved (quadriplegia).

A person with CP may also be affected by a number of other problems, including a seizure disorder, visual deficits, hearing problems, mental retardation, learning disabilities, and attention-deficit hyperactivity disorder. None of these is necessarily part of CP, however, they may accompany the disorder.

CP affects approximately 500,000 children and adults in the United States, and is diagnosed in more than 6,000 newborns and young children each year. It is not an inherited disorder, and as of yet there is no way to predict with certainty which children will develop CP. It is not a disease, and is not communicable. CP is a nonprogressive disorder, which means that symptoms neither worsen nor improve over time. However manifestation of the symptoms may become more severe over time. For example, rigidity of muscles can lead to contractures and deformities that require a variety of interventions.

Causes

Cerebral palsy is caused by damage to the motor control centers of the brain. When the nerve cells (neurons) in these regions die, the appropriate signals can no longer be sent to the muscles under their control. The resulting poor control of these muscles causes the symptoms of CP.

The brain damage leading to CP may be caused by lack of oxygen (asphyxia), infection, trauma, malnutrition, drugs or other chemicals, or hemorrhage. In most cases it is impossible to determine the actual cause, although premature birth is recognized as a significant risk factor. It was once thought that difficult or prolonged delivery was responsible for many cases of CP, but most researchers now believe that the great majority of cases result from brain damage occurring before birth. The same injury that damages the motor areas can harm other areas as well, leading to problems commonly associated with CP.

If brain cells do not get enough oxygen because of poor circulation, they may die. Defects in circulation in the developing brain may cause CP in some cases. Asphyxia during birth is also possible, and about half of newborns known to have suffered asphyxia during birth (perinatal asphyxia) develop CP. However, asphyxia during birth is usually considered a symptom of an underlying neurological problem in a newborn, rather than its cause, and the resulting CP may be another sign of that problem. Asphyxia after birth can be caused by choking, poisoning (such as from carbon monoxide or barbiturates), or near-drowning.

The fetal brain may be damaged by an infection contracted by the mother. Infections correlated with CP include rubella (German measles), toxoplasmosis (often contracted from cat feces), cytomegalovirus (a herpes virus), and HIV (the virus that causes AIDS). Encephalitis and meningitis, infections of the brain and its coverings, can also cause CP when contracted by infants.

Physical trauma to the pregnant mother or infant may cause brain damage. Blows to the infant's head, as from a motor vehicle accident, violent shaking, or other physical abuse can damage the infant's brain. Maternal malnutrition may cause brain damage, as can the use of drugs, including cocaine or alcohol. Although these factors may cause CP, they may be more likely to cause mental retardation or other impairments.

Incompatibility between the Rh blood types of mother and child was once a major cause of athetoid CP, one type of movement impairment seen in cerebral palsy. In some cases, this incompatibility can cause the mother's defense (immune) system to attack and destroy the child's blood cells during pregnancy, a condition called erythroblastosis fetalis. High levels of a blood cell breakdown product called bilirubin in a child's circulation, leading to yellowish pigmentation of the skin caused by bile (jaundice) can result in brain damage. This condition is now rare because of testing procedures that identify potential Rh incompatibility, and treatment that prevents the mother's immune system from attacking the child's blood cells. Jaundice that does occur can be treated with special lights that help the breakdown of bilirubin. Blood transfusions for the child are also possible in extreme cases. Despite the virtual elimination of this cause of CP in the last few decades, CP rates have not declined, largely because of the increase of survival of premature babies.

Prematurity is one of the most significant risk factors for CP. About 7% of babies weighing less than three pounds at birth develop CP, and the risk increases dramatically as weight falls. Prematurity may increase the risk of CP because of the increased likelihood of hemorrhaging in the brain associated with low birth weight. Brain hemorrhage is most common in babies weighing less than four pounds at birth, and the risk increases as weight decreases. The hemorrhage may destroy brain tissue, either through asphyxia or release of toxic breakdown products.

Researchers in Sweden reported in 2002 that babies conceived through in vitro fertilization (IVF) were 3.7 times more likely to have CP than babies conceived naturally. Some of the reason can be attributed to a higher rate of twins, low birthweight, and premature births associated with IVF babies, but some single births also have higher rates of CP.

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