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Explainer: what is cerebral palsy?

Research in cerebral palsy has historically lagged behind other medical areas. EPA/Kerim Okten

Cerebral palsy (CP) is the most common physical disability, affecting 35,000 Australians, or one in 500 people. It is estimated that one Australian child is born with cerebral palsy every 15 hours.

We know CP is caused by injury to the developing brain, which affects the part of the organ responsible for movement. This injury usually occurs before birth, but we often don’t know the cause.

CP is a life-long condition and can vary in severity from very mild, where people can walk and climb stairs, through to extremely severe, which leaves no independent mobility. People with cerebral palsy usually have a normal lifespan but experience the effects of ageing earlier.

How does CP affect movement?

Cerebral palsy can affect the body in different ways:

  • one in four people CP with are unable to walk
  • three in four experience chronic pain
  • half have an intellectual disability
  • one in three have epilepsy.

In most cases, there is involuntary muscle tightness, known as spasticity. Quadriplegia involves all four limbs, while diplegia affects the movement of the legs.

Another common form of CP is hemiplegia, the inability to move either the right or left side of the body, which can also be caused by strokes.

What are the causes of CP?

In the past, it was assumed that most cerebral palsy resulted from a lack of oxygen during birth. But we now know that this is the case for only a small minority.

Most cerebral palsy occurs during pregnancy, with extremely premature birth a major risk factor for the condition.

Thankfully, the rate of cerebral palsy has been declining in preterm babies in developing countries such as Australia and Holland, probably as a result of expert neonatal intensive care.

Mothers are now administered steroids prior to the preterm birth and the premature infants are given caffeine after birth to remind them to breathe during the first few weeks of life.

Half the children diagnosed later with cerebral palsy, however, were born on time and were well at birth. There often isn’t an obvious cause in such cases, but there are many known risk factors.

Statistical risk factors include the failure of the baby to thrive during pregnancy, having an abnormal placenta, a family history of cerebral palsy or other neurological conditions.

Other known associations include birth defects, maternal thyroid disease and infections. In the past, severe neonatal jaundice due to problems with the rhesus blood group caused cerebral palsy.

But this has been virtually eradicated, due to anti D therapy – although other causes of jaundice can still be damaging.

Another 10% of cerebral palsy results from a damaging event following birth such as meningitis, road accidents, near drownings and non-accidental injury.

How is CP treated?

There are many effective therapies including casting (holding a muscle in a stretched position with a plaster cast, which helps lengthen the shortened muscles associated with cerebral palsy), muscle strengthening and Botox (which is injecting into over-active or spastic muscles to provide a window for therapy to work on strengthening under-active muscles).

A new type of activity-based physical therapy called goal-directed training is also delivering results. We know from research among elite athletes and musicians that the brain forms efficient nerve connections and dedicates more space to tasks that are carried out repetitively and successfully. This appears to be the case in cerebral palsy as well.

Another therapy that appears to help is called constraint-induced movement, which can also be used in infants who have had a stroke. It involves constraining the unaffected arm in a mitt and challenging the weaker arm with appropriate tasks.

Next steps in CP research

Recent research has focused on early diagnosis of CP to help decrease the rate of complications such as hip dislocation or scoliosis of the spine.

In premature babies, a drug called magnesium sulphate has been shown to decrease the rate of cerebral palsy by 30% in babies of less than 30 weeks gestation. And scientists have just started testing whether magnesium sulphate can also help babies born between 30 and 34 weeks of gestation.

Another exciting recent finding shows that cooling full-term infants who are clearly unwell at birth, and showing signs of neurological abnormality, may decrease the risk of cerebral palsy.

Other protective therapies which are about to be trialled in humans include melatonin and erythropoietin, which have shown promising results in animal trials.

But while hundreds of Australians have sought expensive risky and unproven stem cell therapy in developing countries, research is still at an early stage in reputable laboratories.

Research in cerebral palsy has historically lagged behind other medical areas. But recently growth in the number and quality of studies offers hope for prevention, better interventions to improve the quality of life of people living with this condition and, hopefully, one day a cure.

See more Explainer articles on The Conversation.

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