Researchers have found that autism shows tell tale signs in babies as young as 6 months old — half a year or more before parents typically begin to notice symptoms of the condition. The results shed light on the fundamental differences in the brains of autistic children and could help lead to earlier detection and treatment, says co-author Geraldine Dawson, chief science officer at Autism Speaks, which helped fund the study in today's American Journal of Psychiatry.
According to the new study changes in the brain's communication pathways may take place silently, long before children begin to exhibit the diagnostic problems communicating and socializing, or exhibiting repetitive behaviours, Dawson says.
Dawson says eventually researchers may find a pattern in these brain scans that could allow them to spot which high-risk babies are likely to be autistic, and begin intensive behavioural therapy, which is most effective when begun early. Even if babies get into treatment by age 1½, Dawson says, “there has been a long period of time when the baby's brain has been developing abnormally,” which could make the child's behaviour harder to change.
Autistic children start showing symptoms at age 1 or 2, and kids typically aren't diagnosed until an average age of 5. Many parents perceive their child's symptoms appeared suddenly, a phenomenon that helped contribute to the now-debunked idea that autism is caused by vaccines, says autism researcher Christine Wu Nordahl, from the University of California-Davis MIND Institute, who wasn't involved in the new report. “A lot of the kids in this study, they looked pretty good socially at six months,” says senior author, Joseph Piven, director of Carolina Institute for Developmental Disabilities in Chapel Hill. “But by 12 months of age, it was almost as if someone had pulled the curtain down.” Overall, about one in 110 American children has an autism spectrum disorder, according to the Centers for Disease Control and Prevention.
In the study, researchers performed brain scans, using MRIs, of 92 babies with an older, autistic sibling. Studies show that younger siblings of one autistic child have a nearly 20% risk of being diagnosed with the condition. Researchers scanned the babies' brains at ages 6 months, 1 year and 2 years of age, creating three-dimensional pictures depicting changes over time in the brain's “white matter,” which include bundles of nerve fibres and their protective coatings. These fibre tracks act like communication paths or highways between brain regions, Dawson explained.
Fractional anisotropy (FA) revealed that the two groups differed in white matter fibre tract development — pathways that connect brain regions. FA measures white matter organization and development by tracking water molecule movement through brain tissue. Between infants who did develop autism versus infants who did not, significant differences were found in FA trajectories in 12 of the 15 tracts that were studied. Specifically, babies who later developed autism had elevated FA at six months but then had slower change over time. By 24 months of age, infants with autism had lower FA values than infants without autism. “Their brains aren't organizing as rapidly,” says first author Jason Wolff, also of the Carolina Institute. “This evidence, which implicates multiple fibre pathways, suggests that autism is a whole-brain phenomenon not isolated to any particular brain region,” Wolff said.
Twenty-eight children went on to develop autism. When researchers looked at their scans, they saw key differences in the way that these pathways developed, Piven said. At age 6 months, these pathways were more developed than those of typically developing children. By the time children were 2, the autistic kids' brain development had fallen behind.
Nordahl called the study “remarkable” and a “great first step.” But she notes that the absolute differences among the children are small. The findings need to be repeated by other researchers before doctors can begin to create a reliable early detection system.
The study has other limitations, says Charles Nelson, a professor of pediatrics and neuroscience at Harvard Medical School. The findings would be stronger if researchers compared them to those of a control group of normal-risk children, who don't come from families with other autistic children. He questioned why 30% of the high-risk children were diagnosed with autism, a rate that's 50% higher than expected. Nelson also notes that it can be hard to definitively diagnose autism at age 2, and that a child's diagnosis can change over time.
Autism Speaks is funding research into exercises that parents can perform with their babies to stimulate language and social development, in an effort to reinforce and strengthen those brain connections. In these exercises, whose results aren't yet known, she says researchers teach parents to play with babies in simple ways they hope will diminish the child's symptoms by “changing the course of brain development.”
According to Dr. Nancy Minshew, director of the NICHD Collaborative Program of Excellence in Autism at the University of Pittsburgh, who was not involved in the study, the current findings suggest that a child might have autism long before he or she begins to show outward signs. “Parents and primary care physician determination of onset of autism or ASD in the second or third year of life is not an accurate assessment of onset,” said Minshew. “This adds to the evidence that autism develops on its own, so to speak, and not because parents did something or did not do something to cause autism.”
Researchers reveal cellular foundations of functional brain networks in humans