Genetics causes 1 in 4 cerebral palsy cases

A large Chinese study has re-affirmed growing evidence that genetics and not birth asphyxia is often responsible for cerebral palsy.

“Birth asphyxia is a label that’s never been proven,” says Alastair MacLennan AO, Head of the Australian Collaborative Cerebral Palsy Research Group at the Robinson Research Institute at University of Adelaide, and co-author of the study published overnight in Nature Medicine.

“We are showing birth asphyxia is a myth.”

The world’s largest study of cerebral palsy (CP) genetics was conducted in China which had more than 1000 children in a studiable cohort.

The research found the mutations were significantly higher in CP cases labelled at birth with perinatal asphyxia – a lack of blood flow to a baby’s brain before, during, or right after birth.

The findings, which are consistent with smaller studies globally, indicate that “at least some portion of the perinatal asphyxia events seen in individuals with CP are very probably related to improper brain development due to underlying genetic variants,” according to the authors.

“24.5% of Chinese children in the study had rare genetic variations linked to cerebral palsy,” says co-author Jozef Gecz, Head of Neurogenetics at the University of Adelaide Medical School and the Robinson Research Institute.

“This revelation mirrors our earlier findings in our Australian cerebral palsy cohort, where up to one third of cases have genetic causes.

“Our research shows at least some babies who experience birth asphyxia and are diagnosed with CP may have improper brain development as a result of the underlying genetic variants rather than a lack of oxygen.

“Crucially, clinically actionable treatments were found in 8.5% of cases with a genetic cause. It is exciting to see how genetic pathways to cerebral palsy inform tailored treatments for these individuals.”

Cerebral palsy is the most common physical motor disability in children. It is estimated to affect 1.6 in every 1,000 live births globally.

In CP, damage or abnormalities inside the developing brain disrupt its ability to control movement and maintain posture and balance.

Symptoms often emerge during infancy and early childhood and can range from mild to severe. They also commonly occur in association with epilepsy, autism, and intellectual disability.

In a collaboration between Fudan  and Zhengzhou Universities in China, researchers conducted genetic sequencing on 1,578 Chinese children (505 girls and 1,073 boys) with CP. In the children who had experienced birth asphyxia they identified 81 genes with causative mutations.

All the genes are known to play important roles in neural and embryonic development. For example, 5 are associated with spastic paraplegia, 3 have been associated with neonatal encephalopathy; and 3 are involved in molecular pathways relevant to central nervous system development.  

“A lack of oxygen at birth is often claimed to be the cause of CP in medical litigation following a diagnosis and this has led to the presumption that the condition is preventable with better obstetrics or midwifery. This is simply not the case,” says MacLennan.

“These results highlight the need for early genetic testing in children with cerebral palsy, especially those with risk factors like birth asphyxia, to ensure they receive the right medical care and treatment.

“All children with cerebral palsy merit modern genetic screening as early and customised interventions really can make a difference and improve their long-term outcomes.”

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