What Is Cerebral Palsy?
Cerebral palsy (CP) is a broad term used to describe a group of chronic "palsies" -- disorders that impair control of movement due to damage to the developing brain. CP usually develops by age 2 or 3 and is a nonprogressive brain disorder, meaning the brain damage does not continue to worsen throughout life. However, the symptoms due to the brain damage often change over time -- sometimes getting better and sometimes getting worse. CP is one of the most common causes of chronic childhood disability.
About 10,000 infants are diagnosed with CP and up to 1,500 preschoolers in the U.S. are recognized as having it each year. The United Cerebral Palsy Association estimates that more than 764,000 Americans have CP.
Between 35% and 50% of all children with CP will have an accompanying seizure disorder and some level of mental retardation. They also may have learning disabilities and vision, speech, hearing, or language problems.
Much remains unknown about the disorder's causes, but evidence supports theories that infections, birth injuries, and poor oxygen supply to the brain before, during, and immediately after birth result are common factors. Premature infants are particularly vulnerable. Severe illness (such as meningitis) during the first years of life, physical trauma, and severe dehydration can cause brain injury and result in CP.
What Causes Cerebral Palsy?
Congenital cerebral palsy results from brain injury during a baby's development in the womb. It is present at birth, although it may not be detected for months. It is responsible for CP in about 70% of the children who have it. An additional 20% are diagnosed with congenital cerebral palsy due to a brain injury during the birthing process. In most cases, the cause of congenital cerebral palsy is unknown. Some possible causes are:
- Infections during pregnancy that may damage a fetus' developing nervous system. These include rubella (German measles), cytomegalovirus (a herpes-type virus), and toxoplasmosis (an infection caused by a parasite that can be carried in cat feces or inadequately cooked meat). Other infections in pregnant women that may go undetected are being recognized now as an important cause of developmental brain damage in the fetus.
- Severe jaundice in the infant. Jaundice is caused by excessive bilirubin in the blood. Normally, bilirubin is filtered out by the liver. But often, newborns' livers need a few days to start doing this effectively, so it's not uncommon for infants to have jaundice for a few days after birth. In most cases, phototherapy (light therapy) clears up jaundice, and there are no lasting health effects. However, in rare cases, severe, untreated jaundice can damage brain cells.
- Rh incompatibility between mother and infant. In this blood condition, the mother's body produces antibodies that destroy the fetus's blood cells. This, in turn, leads to a form of jaundice in the newborn and may cause brain damage.
- The physical and metabolic trauma of being born. This can precipitate brain damage in a fetus whose health has been threatened during development.
- Severe oxygen deprivation to the brain or significant trauma to the head during labor and delivery.
According to the United Cerebral Palsy Association, about 10% of children with CP in the U.S. acquire the disorder after birth. It results from brain damage in the first few months or years of life. CP often follows infections of the brain, such as bacterial meningitis or viral encephalitis, or it may be the result of a head injury.
Some risk factors that increase the possibility that a child will later be diagnosed with CP include:
- Breech births (with the feet, knees, or buttocks coming out first).
- Vascular or respiratory problems in the infant during birth.
- Physical birth defects such as faulty spinal bone formation, groin hernias, or an abnormally small jaw bone.
- Receiving a low Apgar score 10 to 20 minutes after delivery. An Apgar test is used to make a basic, immediate determination of a newborn's physical health. For the test, the infant's heart rate, breathing, muscle tone, reflexes, and color are evaluated and given a score from 0 (low) to 2 (normal).
- A low birth weight (less than 2,500 grams, or 5 lbs. 7.5 oz.) and premature birth (born less than 37 weeks into pregnancy).
- Being a twin or part of a multiple birth.
- A congenital nervous system malformation, such as an abnormally small head (microcephaly).
- Seizures shortly after birth.
Mothers who had bleeding or severe proteinuria (excess protein in the urine) late in their pregnancy have a higher chance of having a baby with CP, as do mothers who have hyperthyroidism or hypothyroidism, mental retardation, or seizures.
Not all children who are exposed to these risk factors develop CP. However, parents and doctors should be aware of these risks and watch an at-risk child's development carefully.