A simple checklist for behavioral signs and symptoms is all that is used by specialists to diagnose a child with an autism spectrum disorder. Although it is one of the fastest growing diagnoses among toddlers, there are no medical tests to screen for the disorder.
But a new study adds to mounting evidence that measuring brain activity during infancy could help determine whether a baby might be at higher risk of developing autism.
Researchers used electroencephalography, or an EEG, to measure the brain waves of nearly 80 babies from the time they were 6 months old until they reached age 2. Researchers found those who were already known to be at higher risk for autism -- those who had an older sibling on the spectrum -- showed a different brain wave pattern than those with no known risk for the disorder.
Current tests to diagnose autism look at a child's change in behavior, which often becomes apparent when a child reaches around 2 years old. Many experts say the earlier they can diagnose and start behavioral therapies, the easier it will be to manage the disorder.
"This is why predictive markers will be so valuable," said Sarah Paterson, director of the infant and toddler research program within the Center for Autism Research at the Children's Hospital of Philadelphia.
According to the study, at as early as 9 months old, many of the infants that were already shown to be at greater risk for autism showed abnormal activity in the front left side of the brain, which is involved in language and social development.
"Just as you can observe certain behaviors after a certain point that indicate a child has autism, this process is really bringing it back a little," said William Bosl, research scientist at Children's Hospital in Boston, instructor of pediatrics at Harvard medical school, and author of the study.
He said that the different brain wave pattern seen in the children with great risk factors "seems to be highly correlated with behaviors that will develop later."
According to Geraldine Dawson, chief science officer at Autism Speaks, at 9 months old, autism experts are already looking for physical symptoms that show a lack of what she called, "joint attention skills."
"Infants begin paying attention to where others are looking and using early gestures to share information with others," Dawson said. "A lack of joint attention is one of the earliest signs of autism."
But it's hard to detect these physical symptoms in some infants, especially in children as young as 9 months old, she said. The ability to show a lack of social development before there are outward symptoms could help experts intervene earlier, Dawson said.
Previous research has studied magnetic resonance imaging, or MRIs, and even magnetoencephalography, or MEGs, to see if changes in brain waves could potentially detect whether a child has autism.
But while initial results seemed promising, follow-up research could not reproduce consistent results. And, as with EEGs, the findings are still too preliminary to convince some experts that the procedure will become a way to detect autism in children younger than 2 years old.
"Each is promising, but like all things in science, the devil is in the details," Patterson said. "The history of science is littered with initial findings that don't hold up, or are less exciting with further study."
In fact, while the findings of this latest study seem to add to growing evidence that brain wave patterns may be a predictive marker for the disorder, researchers did not follow the infants to see if they went on to actually develop autism.
And until studies find a potential parallel between brain wave patterns and a subsequent diagnosis of autism, many experts are not convinced EEGs are able to lead experts to diagnose autism any earlier.
"The test tells us no more clinically than knowing that a child has a sibling with autism," said Catherine Lord, director of the University of Michigan autism and communication disorder center.
Still, Lord said it is interesting to see that there are slight neurological differences in children whose siblings are on the spectrum. Previous studies suggest that children whose older siblings have an autism spectrum disorder have up to a 10 percent chance of developing autism.
This study, she said, is one of many that suggests brain activity is different among those who have a family history of autism. But it's hard to tell what the difference means, if anything, for a child's chances of developing autism, she said.
"We have to be careful to take ... studies such as these for what they are, basic research with potentially very important implications, not clinical findings," Lord said.