About cerebral palsy
Before and during the first six months of life, a child’s brain is especially vulnerable. It lacks the recovery capacity of an adult brain, so any problems during this period can have very serious and irreversible consequences.
Cerebral palsy is one such consequence.
It is the result of brain damage that occurs either during pregnancy, during birth or very soon after, with various possible factors that can cause it.
Causes of cerebral palsy
There is no single cause for cerebral palsy; it can differ from one patient to the next. In some cases, the cause can never be determined.
At the most basic level, two problems can cause cerebral palsy:
- Developmental malformations – where the brain does not develop properly
- Neurological damage – where there is an injury to a developing brain
Developmental malformations are when some kind of abnormality has impeded the brain’s standard process of development, for example:
- The brain may fail to produce the standard amount of brain cells
- The cells in the brain may be unable to communicate with each other normally
- The cells may fail to populate the correct parts of the brain
It is possible for these developmental malformations to be the result of genetic defects, where inherited genes suffer from abnormalities. However, it is not always fully understood why some of the malformations occur.
Neurological damage to a developing brain is an injury that can occur before, during and after childbirth. Several factors can contribute to this:
- An infection, fever or high blood pressure during pregnancy
- Injury to the foetus
- Premature birth
- Traumatic birth
Those factors can cause damage to the child’s brain in the following ways:
- Bleeding in the brain – If the mother has high blood pressure during pregnancy, there is a risk of blood clots in the placenta that can cause broken or blocked blood vessels in the child’s brain
- Head trauma
- Infection of the nervous system, for example, meningitis
- Lack of oxygen – This could occur if the umbilical cord becomes wrapped around the child’s neck, or if the placenta detaches, or even if the mother’s blood pressure drops very low thus starving the brain of oxygen. The longer that the child’s brain is deprived of oxygen, the more severe the damage
- Poisoning from drugs and other toxic substances consumed by the mother
- Severe jaundice
Areas of the brain that are affected
Cerebral palsy is categorised into three main groups. This is covered in further detail in our types of cerebral palsy section, though here we discuss the regions of the brain that may cause cerebral palsy if significantly damaged.
Spastic cerebral palsy
Spastic cerebral palsy is caused by an upper motor neurone lesion in the brain. This means that there is damage to the outer layer of the brain (a region known as the cerebral cortex), which is responsible for movement control. This is the most common area of the brain to be affected by injury, hence why spastic cerebral palsy is the most common type of cerebral palsy.
The cerebral cortex houses the motor cortex, a strip-like area that stretches across both hemispheres of the brain from ear to ear, rather like a headband. This is also an important area of the brain for controlling voluntary muscle movements. The exact site of injury to the motor cortex determines which part (and how much) of the body is affected by the muscle stiffness that defines spastic cerebral palsy.
Athetoid cerebral palsy
Athetoid cerebral palsy generally occurs before the cerebrum region of the brain is fully matured. In a healthy brain, the cerebrum is the most highly developed and largest area, making up around two thirds of the brain’s total mass. The condition is the result of a malfunction or injury to the brain’s extrapyramidal tracts, a network descending from the cerebrum and housed in the basal ganglia that transmits signals to the body for involuntary reflex reactions and coordination.
Damage to this part of the brain tends to occur when it has been starved of oxygen, either during pregnancy or shortly after. Any damage to the extrapyramidal tracts after this period is usually the result of trauma or infection.
One further way in which athetoid cerebral palsy can be caused is when an excessive amount of a substance called bilirubin accumulates in the grey matter of a newborn baby’s central nervous system, crossing the blood-brain barrier, ultimately causing severe jaundice. If this is not treated quickly, irreversible brain damage will occur.
Ataxic cerebral palsy
Damage to the cerebellum region at the base of the brain is responsible for ataxic cerebral palsy. The cerebellum is important for motor control in that rather than initiating movement, it controls coordination. This is what differentiates the condition from the damage that causes both spastic and athetoid cerebral palsy.
In most cases, the damage to the cerebellum occurs prior to birth, through either injury or maternal infection. However, children can acquire ataxic cerebral palsy, most likely the result of infections such as meningitis, but also through complications during delivery or severe head trauma.
It is estimated that no cause is ever found for 80% of prenatal ataxic cerebral palsy cases.
Early signs of cerebral palsy
It is not always possible to diagnose cerebral palsy immediately at birth. In some cases, there will be some obvious signs of brain damage and abnormal muscle tone whereas in others, the signs of cerebral palsy only will reveal themselves gradually over time and will ultimately need treatment.
Complications such as a traumatic birth, severe jaundice and infections are warnings that the risk of cerebral palsy is increased for the child and may be diagnosed at a later date. Furthermore, although congenital cerebral palsy is present at birth, it can take up to two years before any signs of cerebral palsy are displayed. In these cases, it is best noticeable when the child’s development and growth milestones are delayed, or in some cases not reached at all.
The following is an example of how some early signs of cerebral palsy may be displayed by a child. Please note that this is only a basic guide; it is not definitive and there may be other reasons why the child is displaying such signs:
2 – 5 months old: When picked up, the child may have problems controlling their head and may cross their legs in a “scissors” gait.
6 – 9 months old: The child may only be able to reach for objects with one hand whilst the other clenches like a fist. Meanwhile, they still may not be able to control their head when picked up.
10+ months old: The child may be unable to support itself when sitting. They may also be unable to crawl properly, most likely dragging one arm and leg.
12+ months old: The child may be unable to stand, even with support. In severe cases, they may not be able to crawl at all.
2(+) years old: The child may still be unable to walk and have problems when attempting to grasp objects.
Find out more in our types of cerebral palsy section.