When and how does CP strike?

by Kari Williamson 22 March 2013

There is still great uncertainty surrounding the causes of cerebral palsy (CP), but new research suggests that the brain injury which leads to CP in infants with low birth weight occurs before they are born.

Ordsky CP.In premature children the causes are often a combination of several risk factors; whereas in infants born at full term, it could be the child’s inherent abilities to withstand unfortunate events at birth that cause some children to develop CP and others not.

In addition there seems to be a correlation between high prevalence of CP and low neonatal death rates in some Norwegian counties.

“There could be several explanations for this,” says PhD candidate Magne Stoknes at the Department of Laboratory Medicine, Children’s and Women’s Health (LBK), NTNU. One explanation could be that more children that already have a brain injury before birth are saved that otherwise would not have survived.

“Survival rates were higher in smaller counties, but these counties also had a higher prevalence of CP, which could suggest that the distance to hospital may be of some relevance. But we cannot say for certain whether the correlation is due to differences in quality or external factors.”

Individual factors.

  • CP affects around 120 children in Norway every year. About 8000 people in Norway have CP.
  • CP is caused by damage to the brain’s motion control centre and can occur during pregnancy, birth and up to an age of two to three years.
  • Known risk factors include: Premature birth, infections during pregnancy, illness in the mother, fertility treatment, multiple births, disease in the placenta, low birth weight (small for gestational age – SGA), abnormal positioning of the foetus, preterm rupture of membranes, induced labour and lack of oxygen (hypoxia) in the newborn.

When looking at the risk factors present during pregnancy and around birth in children with CP, there are no clear factors that can be singled out, and often there are different combinations of risk factors. It is also not clear when in the pregnancy CP occurs:

“The background for a child developing brain injury leading to cerebral palsy is complex. There are probably several risk factors that independently or combined contribute to a process that leads to brain injury, and these risk factors operate together in a certain order of events (so-called causal pathways).

“In addition some children seem to be more vulnerable to the various combinations of risk factors, so that there are different combinations of risk factors leading to CP in individual children,” Stoknes explains.

Still a puzzle

The research nevertheless offers a new piece to a larger puzzle, but there are still many pieces left to be found before we with certainty can say something about why some children develop CP and how this could be prevented.

Stoknes says the research team now wishes to continue with larger studies that look even closer at how different risk factors come together to contribute to brain injury which again causes CP.

The studies

Stoknes’ research is based on three studies. The first study which looked at low birth weight at full term included 400,488 Norwegian children born in the period 1996-2003, where 36,604 had low birth weight. Of these 104 did not live and 69 developed CP.

The second study, which looked at how risk factors were combined, included 176,979 children born in the period 1996-98, where 241 developed CP.

In the last study where the share of neonatal deaths was compared with the prevalence of CP in surviving children, the researchers used data from 468,443 children born in the period 1996-2003, where 1020 were diagnosed with CP.


Magne Stoknes will defend his thesis “Novel Approaches to the Study of Risk Factors for Cerebral Palsy” on 8. April 2013 at 12.15 in ØHA11 at NTNU.

The trial lecture will take place at 10.15.


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