Nov. 8, 2011 -- New research highlights some potentially important differences in the brains of children with autism.
The small study found that boys with autism had an average of 67% more brain cells called neurons in the prefrontal cortex region of their brains, when compared with children who did not have autism.
Located in the front of the brain beneath the forehead, the prefrontal cortex is responsible for "higher order" functions such as problem solving, emotions, and complex thought. These are some of the processes that are impaired in autism.
Most of these neurons develop before birth, which would go against the theory that certain vaccines or other environmental influences encountered after birth may cause autism.
The findings are published in TheJournal of the American Medical Association.
"It's a small study with a large impact," says study researcher Eric Courchesne, PhD, director of the National Institute of Health-University of California-San Diego School of Medicine Autism Center of Excellence in La Jolla, Calif. "This is an incredibly important discovery that tells us that something started going wrong in prenatal life in children with autism."
The CDC estimates that an average of one in 110 children in the U.S. has an autism spectrum disorder, a range of developmental disorders that affect the ability to communicate and relate to others.
Some children with autism do have overly large heads, and the new study showed that the brains of boys with autism weighed more than the brains of boys who did not.
"If their brain is too large, there may be too many brain cells. And now we know that the area that shows overgrowth is the prefrontal cortex and this very important for higher-order functions," Courchesne says.
Researchers examined the number and size of neurons among seven boys with autism and six boys without autism. The boys were aged 2 to 16 and had died between 2000 and 2006. They looked at neurons in two areas of the prefrontal cortex -- the dorsolateral (DL-PFC) and mesial (M-PFC).
Specifically, there were 79% more neurons in DL-PFC and 29% more in M-PFC among boys who had autism when compared with boys who did not.
If these findings are confirmed in larger groups of people, it may help researchers identify autism earlier than they can today. The diagnosis of autism is now made on the basis of behavioral assessment around age 2 or 3.
Early Autism Diagnosis
"Earlier intervention leads to improvement all the way around in children with autism. So the need for early diagnosis is there and this will be one of the signatures that will help identify kids at a much earlier age," Courchesne says.
Nicholas Lange, ScD, who co-authored an editorial on the new report, agrees. He is an associate professor of biostatistics at the Harvard University Schools of Medicine and Public Health in Boston.
"These neurons can be measured in a brain scan and this may help give the clinician more brain-based information to help clarify a diagnosis of autism," he says.
Today, the diagnosis is based on symptoms and behaviors, not blood tests, brain scans, or other tangible indicators.
Lange also points out that the diagnosis would be based on the number of brain cells in the prefrontal cortex, not head size.
A big head does not necessarily mean a child has autism, he says. "Many other things that have nothing to do with autism lead to big heads, including genetics. Just 20% of people with autism have big heads."
The fact that these neurons develop before birth is also telling, Lange says. "There are more neurons generated during fetal development in this small sample and this points toward a more precise genetic [cause] of the disorder."
Robert Ring, PhD, urges caution in interpreting the new findings. He is vice president for Translational Research at Autism Speaks, an autism advocacy and science group.
"The small size does limit our ability to draw any real conclusions, but it does raise a lot of interesting questions that warrant further investigation," he says.
For example, do non-autistic children with large heads also have a greater number of neurons in these regions of their brains? The findings are "an intriguing snapshot and really begs for replication in a larger sample."
Y. Jane Tavyev Asher, MD, tells WebMD there is more to diagnosing autism than measuring head size. If a parent is concerned that their child may have autism, get him or her evaluated right away, she says. Asher is a pediatric neurologist at Cedars-Sinai Medical Center in Los Angeles, Calif.
"The hallmark of autism is language delay. So if there is early language delay, shoot first and ask questions later," Asher says. "It is better to have started a little speech therapy and find out it's not autism, than to go from person to person being evaluated before starting speech."