Although cerebral palsy appears to involve the muscles, it is caused by damage to the part of the brain that controls these muscles, called the cerebrum.
The cerebrum is also responsible for other important brain functions, such as communication skills, memory and the ability to learn. This is why some children with cerebral palsy also have learning and communication difficulties.
Damage to the cerebrum can also cause problems with vision and hearing.
How does brain damage occur?
In the past, doctors believed that the damage to the brain occurred during birth as a result of the baby being temporarily deprived of oxygen (asphyxia). Asphyxia can sometimes occur during a difficult or complicated birth.
However, a major research project carried out in the 1980s showed that asphyxia was only responsible for an estimated 5-10% of cases of cerebral palsy. Most cases occurred as a result of damage to the brain that happened before the child was born.
The adult brain is fairly adaptable and can recover from quite serious damage. But the brains of children, especially during the first six months of development, are particularly vulnerable. Any damage that occurs during this time can have serious and lifelong consequences.
Researchers believe there are three ways the brain can be damaged before birth. These are discussed below.
Periventricular leukomalacia (PVL)
Periventricular leukomalacia (PVL) refers to damage of the white matter of the brain. This part of the brain is made up of many nerve fibres that are protected by a white fatty protein, known as myelin. The white matter of the brain is responsible for directing communication between the thought-processing sections of the brain (known as grey matter) and the rest of the body.
It is thought the damage to the brain is caused by a reduction in the child’s blood supply. This reduced blood supply deprives the child’s brain of oxygen, damaging the brain cells. This damage has serious consequences in later life, as the white matter of the brain is responsible for transmitting signals to the muscles.
PVL can be caused by:
an infection caught by the mother, such as rubella (German measles)
the mother having abnormally low blood pressure
premature birth, especially if a child is born at six months of age or earlier
the mother using cocaine during her pregnancy
Abnormal development of the brain
Anything that changes or affects the normal development of the brain can lead to problems with the way it transmits information to the muscles, and therefore can cause cerebral palsy. The brain is particularly vulnerable during the first 20 weeks of a child’s development.
The development of the brain can be affected by:
mutations (alterations) in the genes that help the brain to develop
infection such as herpes, toxoplasmosis (an infection caused by a parasite) and cytomegalovirus (a herpes-type virus that most people have immunity to)
trauma or injury to the unborn baby’s head
Intracranial haemorrhage is bleeding in the brain. This can be dangerous because:
the brain can be deprived of blood, which can kill tissue
the blood itself can damage brain tissue
Intracranial haemorrhage normally occurs in unborn babies when they have a stroke. Strokes can be caused by:
pre-existing weaknesses or abnormalities in the baby’s blood vessels
the mother having high blood pressure
an infection during pregnancy, particularly pelvic inflammatory disease (an infection of the upper female reproductive organs)
Damage after birth
A few cases of cerebral palsy are caused by damage to the brain that occurs after birth.
The damage normally occurs during the first few months of a baby’s life, before the brain develops its ability to withstand and adapt to a moderate degree of damage.
Damage can be caused by an infection of the brain, such as meningitis, or as the result of a traumatic head injury.