A new study from Norway suggests there may be a genetic link to cerebral palsy, the most common cause of physical disability in children. Published in the July 15 journal BMJ, the study is the first to investigate cerebral palsy over a broad range of family relationships.
“Our data suggest that cerebral palsy includes a genetic component,” wrote the researchers in their report, “with a stronger recurrence among relatives with closer genetic relationship.”
Cerebral palsy affects approximately two in 1,000 live births. The condition originates from damage to the developing brain, “the causes of which are still largely unknown,” wrote the authors in the study’s introduction. Known risk factors in pregnancy include preterm delivery, multiple fetuses, prenatal infection, birth asphyxia and abnormal intrauterine growth.
For this study, researchers analyzed data from more than 2 million births in Norway between 1967 and 2002. Using national registries and family links, they identified 3,649 cases of cerebral palsy among single and twin births.
The investigators found an occurrence of 1.8 cases of cerebral palsy for every 1,000 children born during the study period. The rate of occurrence for the condition in single births was 1.7 per 1,000 children and 5.1 for every 1,000 among twin births. If one twin had cerebral palsy, there was a 15 times increased risk the other twin would have it too.
The researchers also found that if a child had cerebral palsy, siblings born at a later date had a six to nine times greater risk of having the condition. Half siblings had up to a three times greater risk.
Where a first cousin was affected, there was evidence of a 1.5 times greater risk to other family members. The children of parents who had cerebral palsy had a 6.5 times greater risk of having the condition than those whose parents were not affected by cerebral palsy.
In an editorial that accompanied the BMJ article, Peter Rosenbaum, MD, a pediatrician and professor at McMaster University in W. Hamilton, Ontario, noted that parents rightly want to know why their child has neurological impairments. If the disability is the result of delivery complications, then having more children may be an easier decision. If the parents know there is a genetic component, they have the knowledge they need to make an informed choice about having more children.
For parents who have a family member with cerebral palsy, Rosenbaum wrote that while a 15-fold increased risk of cerebral palsy is significant in relative terms, the actual risk is small. “This information should provide some reassurance to families in which cerebral palsy is already present,” he said.