Why Does Cerebral Palsy Happen?

How Common Is It?

Cerebral palsy is the most common lasting motor disorder of childhood; worldwide, it's seen in about 2–3 out of every 1,000 live births. This means you are not alone: everywhere in the world, there are millions of families who have set out on a journey similar to yours.

These frequency figures have stayed relatively stable over time; while advances in newborn care have reduced some causes (for example, kernicterus due to severe jaundice), the increased survival of extremely premature babies has offset this decline to some extent.

Causes by Timing

The brain injury that leads to cerebral palsy can happen in three periods: before birth, during birth, and in the first years after birth. Causes before birth include genetic and structural problems that affect the brain's development, certain infections during pregnancy, problems related to the placenta, and premature birth. A lack of oxygen during birth is an important cause, but contrary to what is commonly believed, only a portion of cerebral palsy cases are due to a problem during birth. Causes after birth include severe newborn jaundice (kernicterus), central nervous system infections, and serious head trauma.

The risk of cerebral palsy is higher in babies born prematurely; the reason is that the white matter — one of the most fragile parts of the brain — has not yet matured in premature birth. This form of injury is called periventricular leukomalacia (PVL), and it usually leads to a spastic diplegia picture in which the legs are more prominently affected. Nevertheless, a significant number of children with cerebral palsy were born at term.

In some cases, factors from more than one timing category can come together; for example, in a baby who was born prematurely and then had an infection in the newborn period, both prenatal/perinatal and postnatal factors may have played a role together.

How Does the Location of the Brain Injury Determine the Clinical Picture?

Damage in the white matter is often linked with leg-dominant spastic diplegia. Damage to the deep gray matter (basal ganglia and thalamus) is usually seen after severe oxygen deprivation or kernicterus and leads to a dyskinetic picture. Broad cortical-subcortical damage is often linked with a quadriplegic picture and more marked cognitive involvement. A one-sided, limited vascular injury, on the other hand, leads to hemiplegia. In some children, no clear damage can be found on imaging; this does not mean the diagnosis is wrong.

Why Does Knowing the Cause Matter?

When your doctor investigates the likely cause of your child's cerebral palsy, they are looking both for an explanation of the past and for information that will guide the future. In cases where the cause has not become clear, your doctor may recommend an MRI and, if needed, genetic or metabolic tests.

I'd like to give families an important reminder here: in a significant number of cerebral palsy cases, no single "culprit" cause can be found looking back; usually it's a matter of more than one factor coming together. Blaming yourself or the health team who cared for you during the birth is, most of the time, not a scientifically justified stance.

Genetic Counseling

When a genetic cause is found underneath the cerebral palsy, or is strongly suspected, a genetic counseling consultation can be helpful. In this consultation, the inheritance pattern of the condition found, the risk of recurrence in future pregnancies, and screening options for family members if any are discussed. Genetic counseling is a process that offers information — not one that imposes decisions — and helps the family make their own decisions in an informed way.

The Importance of the Time in the Womb

Getting regular prenatal care during pregnancy makes it possible to catch and manage some risk factors (infections, certain health problems) early; but this does not mean every case of cerebral palsy is preventable. Some causes (such as genetic factors or placental problems) cannot be foreseen or prevented with current medical knowledge. My purpose in sharing this is not to point blame at the past, but to help you know that doing your best for future pregnancies is enough.

Risk in Twin Pregnancies

Multiple pregnancies (twins, triplets) carry a higher risk of premature birth — and therefore of cerebral palsy — compared with single pregnancies; this risk can be even more marked especially in identical twins who share the same placenta. This information is one of the reasons families with multiple pregnancies are monitored more closely during the pregnancy.

Early Monitoring After Birth

For high-risk babies (premature, with a history of difficult birth, or who spent time in newborn intensive care), being included in a structured follow-up program after discharge is extremely valuable for catching possible developmental problems early. These follow-up programs usually include developmental assessments at regular intervals (such as at 3, 6, 12, 18, and 24 months).

The Risk of Cerebral Palsy in Another Child in the Family

In most cases of cerebral palsy, the risk of recurrence in siblings is close to that of the general population; but if an underlying genetic cause has been found, this risk can change. To get clear information on this, a genetic counseling consultation is recommended in cases where the cause has become clear.

The Limits of Prenatal Imaging

Routine ultrasound examinations done during pregnancy can't always show subtle structural differences in the brain; for this reason, a pregnancy that looks normal on prenatal follow-up is not a guarantee that cerebral palsy won't develop. This information is meant to help you understand the limits of current medical technology, not to point blame at the past.