By Dr Ananya Mandal, MD
Cerebral palsy seems to affect the muscles and coordination but the actual cause and damage lies within the brain.
The cerebrum of the brain is responsible for important brain functions, such as motor coordination, movements, communication skills, memory and the ability to learn. This is the reason why children with epilepsy have difficulties in other learning and cognitive areas as well. Damage to the cerebrum can also cause problems with vision and hearing.
Causes of damage to the brain
It was believed earlier that brain damage that causes cerebral palsy occurs at birth as a result of the baby being temporarily deprived of oxygen (asphyxia). Asphyxia can sometimes occur during a difficult or complicated birth. However, studies have shown that this complication during birth is the cause of cerebral palsy in only about 5 to 10% babies with cerebral palsy.
Most of the cases of cerebral palsy are due to causes that affect a baby’s brain while still inside the womb. While adult brains are capable of withstanding injury and damage and have the ability to recover from them to a large extent, brains of babies, especially during the first six months of development, are particularly vulnerable. Any damage that occurs during this time can have serious and lifelong consequences.
Damage to a baby’s brain before birth
There are three basic ways in which a baby’s brain can be harmed before birth. These include:
Abnormal development of the brain
If the normal growth and development of the brain is impaired, there may be lasting consequences. The brain is particularly vulnerable during the first 20 weeks of a child's development. Development can be affected by mutations (alterations) in the genes that regulate brain growth, infection such as herpes, toxoplasmosis and cytomegalovirus and injury to the unborn baby's head.
Bleeding within the baby’s brain or intracranial hemorrhage
This can be dangerous for the baby as the brain may be deprived of blood and this may kill vital brain tissues and the blood itself may put a pressure of delicate brain structures and cause damage to the brain. Intracranial haemorrhage normally occurs in unborn babies when they have a stroke. This may occur if there are abnormalities in the baby's blood vessels like brain aneurysms. This may also occur if the mother has a high blood pressure or infection during pregnancy, particularly pelvic inflammatory disease.
Periventricular leukomalacia (PVL)
This refers to damage of the white matter of the brain. The white matter of the brain contains the nerve fibers while the grey matter contains the nerve cell bodies. The white matter consisting of the never fibers are covered in sheaths of fatty protein called myelin sheath. The white matter of the brain is responsible for directing communication between the thought-processing sections of the brain (grey matter) and the rest of the body.
When there is lack of blood supply to the white matter the child’s brain is deprived of oxygen. This damages brain cells that can have serious consequences in later life, as the white matter of the brain is responsible for transmitting signals to the muscles.
PVL may be caused by infections to the mother while pregnant. This commonly includes infections like rubella (German measles) and other infections commonly combined to form the TORCH complex (toxoplasmosis, other, rubella, cytomegalovirus, herpes simplex) infections).
PVL may also be caused if the mother has an abnormally low blood pressure, if the baby is born prematurely especially at six months of pregnancy or earlier or if the mother uses cocaine during her pregnancy.
Damage after birth
Some of the cases of cerebral palsy also occur due to brain damage after birth. The damage normally occurs during the first few months of a baby’s life. During this time the baby’s brain is incapable of withstanding and adapting to moderate degree of damage.
Damage can be caused by an infection of the brain, such as encephalitis or meningitis or even a traumatic head injury.
Risk factors for cerebral palsy
Some of the risk factors for cerebral palsy occurring due to damage before, during and after birth include:
Low birth weight – babies weighing less than 5½ pounds (2,500 grams) at birth, and especially those who weigh less than 3 pounds, 5 ounces (1,500 grams) have a greater risk.
Premature birth – babies born before 37th week of pregnancy, especially if they were born before the 32nd week of pregnancy have a greater risk.
Babies part of twin or multiple births have a greater risk.
Babies born from pregnancies resulting from the use of some infertility treatments have a greater chance of having cerebral palsy.
Neonatal jaundice and kernicterus – babies who develop severe jaundice immediately after birth are at risk. When severe jaundice goes untreated for too long, it can cause a condition called kernicterus that affects the brain of the baby.
Infections during pregnancy with viruses such as chickenpox, rubella (german measles), and cytomegalovirus (CMV), and bacterial infections such as infections of the placenta or fetal membranes, or maternal pelvic inflammatory diseases raise the risk of cerebral palsy.
Medical conditions of the mother including thyroid problems, intellectual disability, epilepsy, high or low blood pressure during pregnancy etc.
Complications at birth including rupture of placenta, uterine rupture, or problems with the umbilical cord during birth can cause oxygen deprivation to the baby leading to cerebral palsy.
Birth complications―Detachment of the can disrupt oxygen supply to the baby and result in CP.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)