What Causes Cerebral Palsy
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.
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 centres 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 foetus in the uterus, to cause damage to the developing nervous system. Other infections that can cause brain injury in the developing foetus include cytomegalovirus and toxoplasmosis. There is relatively recent evidence that placental and perhaps other maternal infection can be associated with cerebral palsy.
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, the yellow-coloured pigments can build up and cause jaundice. Severe, untreated jaundice can damage brain cells.
In this blood condition, the mother’s body produces immune cells called antibodies that destroy the foetus’s blood cells, leading to a form of jaundice in the newborn.
Severe oxygen shortage in the brain or trauma to the head during labour 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 labour 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.
What are the Risk Factors?
Research scientists have examined thousands of expectant mothers, followed them through childbirth, and monitored their children’s early neurological development. As a result, they have uncovered certain characteristics, called risk factors, which increase the possibility that a child will later be diagnosed with cerebral palsy:
Babies with cerebral palsy are more likely to present feet first, instead of head first, at the beginning of labour.
Complicated Labour and Delivery
Vascular or respiratory problems of the baby during labour and delivery may sometimes be the first sign that a baby has suffered brain damage or that a baby’s brain has not developed normally. Such complications can cause permanent brain damage.
Low Apgar Score
The Apgar score (named for anaesthesiologist Virginia Apgar) is a numbered rating that reflects a newborn’s condition. To determine an Apgar score, doctors periodically check the baby’s heart rate, breathing, muscle tone, reflexes, and skin colour in the first minutes after birth. They then assign points; the higher the score, the more normal the baby’s condition. A low score at 10-20 minutes after delivery is often considered an important sign of potential problems.
Low birth “eight and Premature Birth
The risk of cerebral palsy is higher among babies who weigh less than 2500 grams (5 lbs., 7 1/2 oz.) at birth and among babies who are born less than 37 weeks into pregnancy. This risk increases as birth weight falls.
Twins, triplets, and other multiple births are linked to an increased risk of cerebral palsy.
Nervous System malformations
Some babies born with cerebral palsy have visible signs of nervous system malformation, such as an abnormally small head (microcephaly). This suggests that problems occurred in the development of the nervous system while the baby was in the womb.
Maternal Bleeding or Severe Proteinuria Late in Pregnancy
Vaginal bleeding during the sixth to ninth months of pregnancy and severe proteinuria (the presence of excess proteins in the urine) are linked to a higher risk of having a baby with cerebral palsy.
Maternal hyperthyroidism, mental retardation, or seizures Mothers with any of these conditions are slightly more likely to have a child with cerebral palsy.
Seizures in the newborn
An infant who has seizures faces a higher risk of being diagnosed, later in childhood, with cerebral palsy.
Knowing these warning signs helps doctors keep a close eye on children who face a higher risk for long-term problems in the nervous system. However, parents should not become too alarmed if their child has one or more of these factors. Most such children do not have and do not develop cerebral palsy.
Early signs of cerebral palsy usually appear before 3 years of age, and parents are often the first to suspect that their infant is not developing motor skills normally. Infants with cerebral palsy are frequently slow to reach developmental milestones, such as learning to roll over, sit, crawl, smile, or walk. This is sometimes called developmental delay.
Some affected children have abnormal muscle tone. Decreased muscle tone is called hypotonia; the baby may seem flaccid and relaxed, even floppy. Increased muscle tone is called hypertonia, and the baby may seem stiff or rigid. In some cases, the baby has an early period of hypotonia that progresses to hypertonia after the first 2 to 3 months of life. Affected children may also have unusual posture or favour one side of their body.
Parents who are concerned about their baby’s development for any reason should contact their specialist, who can help distinguish normal variation in development from a developmental disorder.
How is Cerebral Palsy Diagnosed?
Doctors diagnose cerebral palsy by testing an infant’s motor skills and looking carefully at the infant’s medical history. In addition to checking for those symptoms described above — slow development, abnormal muscle tone, and unusual posture — a specialist also tests the infant’s reflexes and looks for early development of hand preference.
Reflexes are movements that the body makes automatically in response to a specific cue. For example, if a newborn baby is held on its back and tilted so the legs are above its head, the baby will automatically extend its arms in a gesture, called the Moro reflex, that looks like an embrace. Babies normally lose this reflex after they reach 6 months, but those with cerebral palsy may retain it for abnormally long periods. This is just one of several reflexes that a physician can check.
Doctors can also look for hand preference — a tendency to use either the right or left hand more often. When the doctor holds an object in front and to the side of the infant, an infant with hand preference will use the favoured hand to reach for the object, even when it is held closer to the opposite hand. During the first 12 months of life, babies do not usually show hand preference. But infants with spastic hemiplegia, in particular, may develop a preference much earlier, since the hand on the unaffected side of their body is stronger and more useful.