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Cerebral palsy may have genetic causes, Canadian study suggests

Emily Diamond, whose four-year-old son Bennett Ross has cerebral palsy, can understand parents’ need for answers, even though she knows exactly what caused Bennett’s condition: She had a major traumatic event while pregnant.

McGill University Health Centre

A new Canadian study has uncovered surprising evidence of possible genetic causes for cerebral palsy.

The study, published in the scientific journal Nature on Monday, is overturning decades of firmly held beliefs about the disorder, and could lead to significant policy changes.

Cerebral palsy is a catch-all term for a wide variety of symptoms, but it is generally characterized by non-progressive impaired movement, speech and reflexes, and can in some cases include seizures. It's most often caused by complications during birth such as asphyxiation or head trauma, which lead to brain damage.

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Genetic causes were rarely – if ever – seriously considered, according to Dr. Stephen Scherer, one of the study's authors. "Nobody really wanted us to do this [study], because they were told over the years that genetics doesn't have a role."

"We did it anyway," he said.

The researchers tested the genes of 115 children with cerebral palsy, and the genes of their parents too. They found that almost 10 per cent of the kids had large chromosomal abnormalities. Of that group, 70 per cent did not share the abnormalities with their parents.

The 10 per cent with abnormalities was a big surprise, Dr. Scherer said.

"This was shocking," he said. "When I told a bunch of people in the clinical genetics unit, they literally fell off their chairs."

Dr. Maryam Oskoui, the lead author of the study, said the findings are laying the groundwork for new avenues of research that, up until this study, had been woefully underexplored.

"It opens up this door. I really see that in the next 10 years, the research into genetic causes of [cerebral palsy] is going to exponentially increase," she said.

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The study focused on a particular kind of genetic abnormality called copy number variants, or CNVs. Discovered by Dr. Scherer in 2004, CNVs are large chunks of DNA that are deleted or copied. Humans inherit two copies of their genes, one from each parent, and CNVs occur when one of those copies is deleted or copied, leaving either one or three genes in place where there would normally be two.

Everyone has CNVs, Dr. Scherer said, but certain ones seem to be linked with diseases such as muscular dystrophy and autism. This new study links CNVs, though not specific genes, to cerebral palsy.

"Some of these kids have massive CNVs that affect dozens and hundreds of genes," Dr. Scherer said.

Dr. Jan Gorter, director of CanChild, a centre for childhood disability research run through McMaster University, said the study's inclusion on the clinical perspective was refreshing.

"It starts off with a clinical question, addressing the needs of parents with children who are born with cerebral palsy … There was a better rationale to start this specific genetic search," he said.

Dr. Oskoui said she is hoping the study changes the status quo in a few ways. Primarily, she hopes it will lead to more genetic screening of children diagnosed with cerebral palsy.

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"There are clear guidelines … but specifically for genetic testing, they say there's strong evidence that we not do genetic testing routinely … We should be doing genetic testing on them," she said.

Genetic screening will allow parents to better understand the cause of their child's condition, Dr. Oskoui said. For parents, that kind of information is invaluable.

Emily Diamond, whose four-year-old son Bennett Ross has cerebral palsy, can understand parents' need for answers, even though she knows exactly what caused Bennett's condition: She had a major traumatic event while pregnant.

"It's not going to change anything," she said. "But I think the unknown is far worse than knowing why, even if it's as simple as 'He's got the markers for it.'"

Bennett's symptoms are mostly mobility-related. He uses a wheelchair bound, and can't speak. He communicates with his eyes, mostly by looking at pictures of the words "yes" and "no." He wasn't part of the study, and its findings wouldn't have changed his therapy, but Ms. Diamond said she still can see how important the study might be for others.

"We really don't know what they're going to achieve," she said. "We hope for the best and prepare for the worst, and go on that way."

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