Causes of Cerebral Palsy

Cerebral Palsy is one of the most common disabilities in the world. The United Cerebral Palsy Foundation estimates that there are currently 500,000 people living with cerebral palsy in the U.S. and another 16 million worldwide. Unlike some disabilities, the actual causes of cerebral palsy are fairly well understood.

Cerebral palsy is the result of damage or developmental abnormality in the cerebral cortex area of a baby’s developing brain. The cerebral cortex is one of the outer regions of the brain and it plays a key role in controlling body movement. The neurologic injury occurs during pregnancy or childbirth when the baby’s brain is not fully developed. Damage to the cerebral cortex during this stage causes the baby’s brain to develop abnormally.

The end result is that the child’s brain is not able to properly direct and control certain muscles in the body. The normal body movement signals from the cerebral cortex basically become scrambled. The baby’s arms and legs are structurally normal, but the brain is simply not able to move them correctly.

Although all cases of cerebral palsy are the result of this particular type of neurologic injury, the originating cause of the brain damage comes in several varieties. The various causes of brain damage resulting in cerebral palsy can be generally separated into 3 categories based on when the injury occurred: (1) prenatal; (2) childbirth; and (3) neonatal.

Prenatal Causes of Cerebral Palsy

Most cases of cerebral palsy are the result of injury to the baby’s brain that occurs sometime during pregnancy (the prenatal period). The Centers for Disease Control (CDC) estimates that almost 70% of cerebral palsy cases are the result of prenatal damage to the brain. These cases are sometimes referred to as “congenital.” During the prenatal period, there are number conditions and complications that are known to cause the type of brain damage that results in cerebral palsy. Below is a summary of the various prenatal causes of cerebral palsy.

• Developmental Abnormalities: Some cases of cerebral palsy are caused by genetic abnormalities or other conditions that interrupt the normal development of the baby’s brain during pregnancy. The 2 most common developmental abnormalities involve prenatal cell migration and prenatal myelin development. Disruption of brain cell migration or the formation of myelin insulation during early gestation can cause the brain the form abnormally and result in cerebral palsy. These developmental defects are usually caused by a combination of genetically inherited conditions and environmental factors. For example, excessive alcohol or drug use during pregnancy has been linked to these abnormalities.
• Maternal Viral Infections: New research has shown that maternal infections are one of the leading causes of prenatal brain injury leading to cerebral palsy. Certain types of viral infections in pregnant mothers, including rubella, chicken pox, and cytomegalovirus (CMV) have been linked to increased risks of cerebral palsy. This is because these particular infections prompt the mother’s system to release protein receptors called cytokines. During certain phases of pregnancy, excessive cytokines in the mother’s system can trigger inflammation in the head of the baby. The inflammation can actually injure the baby’s brain and eventually result in cerebral palsy.
• Chorioamnionitis: Chorioamnionitis is a somewhat different type of maternal infection that has also been shown to increase the chances of cerebral palsy. Chorioamnionitis is a bacterial infection during pregnancy that occurs in the fetal membranes or amniotic fluid. It usually occurs when bacteria in the mother’s vagina migrates upward into the uterus and membranes or amniotic fluid. If not promptly treated, chorioamnionitis can restrict the supply of oxygen and nutrients to the baby and cause injury to the brain. A recent study by the University of California showed that cerebral palsy was 4 times more when chorioamnionitis occurred.
• Prenatal Asphyxiation: Prenatal asphyxiation occurs when oxygen to the baby is restricted or cut off, causing cells in the brain to decay and die. Oxygen to the baby can be interrupted during pregnancy by a number of events or complications including umbilical cord compression, drug use, and membrane ruptures.
• Placenta Previa: Placenta previa is when the placenta covers the cervix which can cause the uterus to tear. This may cause bleeding which, in turn, can lead to a loss of oxygen and cerebral palsy.

Injury During Childbirth

About 20% of cerebral palsy cases are the result of damage to the baby’s brain (usually from oxygen deprivation) that occurs during the labor and delivery process. When the brain injury occurs during childbirth, it is almost always triggered by disruption of oxygen to the baby’s brain. There are a number of different complications or events that can occur during childbirth that can threaten the supply of oxygen to the baby, particularly if not handled promptly. The baby could become stuck in the birth canal; the umbilical cord could get twisted or pinched, or the fetal membranes could rupture. If not immediately identified and resolved, all of these events can cause brain damage a led to cerebral palsy in a matter of minutes. Injury to the baby’s brain during childbirth can also be caused by external trauma to the baby’s head.