SEATTLE, July 22 (UPI) -- Autistic children show abnormal brain growth during their first few years of life, two new studies released Monday reveal.
Both studies used magnetic resonance imaging or MRI technology that provides a window into the brains of children with this particular developmental disorder. The findings show physiological changes in the brain that could help explain the roots of autism, a condition with no known specific cause.
In the first study, researchers led by Dr. Stephen R. Dager of the University of Washington School of Medicine in Seattle compared brain images of 45 autistic kids ages 3 and 4 to those of 26 children with normal development and another 14 children with delayed development but no specific diagnosed disorder. They measured the volume of four keys parts of the brain -- the cerebellum, the cerebrum, the amygdala and the hippocampus.
Scans revealed all four regions of the brain were 10 percent larger in the autistic children compared to the average kids. The difference was 12.5 percent between the autistic kids and the children who were delayed developmentally.
"What we were surprised about was that the children with the more severe expression of the autism disorder, they had disproportionate enlargement of the amygdala," Dager told United Press International. The amygdala is a region associated with emotion -- it sometimes is called the center of fear. One of the characteristics of autism is difficulty expressing a range of emotions. "That was something we hadn't predicted," Dager said.
The children will undergo brain re-imaging at ages 6 and 7 to track whether any physiological changes in the brain correspond with behavior symptoms, Dager added.
In a separate study from the same university, researchers measured cerebral volume and head circumference of 67 autistic children and adults and compared them to 83 individuals ranging in ages 8 to 46 who did not have autism.
The study found among the children age 12 and under, brain volume among autistics averaged 5 percent greater than those who were not autistic. By age 12, there were no differences in brain volume, but head circumference was slightly higher -- autistic children and adults showed a 1 to 2 percent greater head circumference compared to the other group.
Lead researcher Elizabeth H. Alyward said her findings indicate accelerated brain growth among autistic patients could explain why they have increased head circumference. However, it is unclear when this brain enlargement begins.
"I think it's quite exciting to be able pin down specific areas brain that are abnormal," Dr. G. Robert DeLong, a professor of pediatric neurology at Duke University Medical Center in Durham, N.C., told UPI. "I think it's a step forward."
Autism is increasing in the United States, DeLong said, which may be due to doctors recognizing the condition earlier. It is estimated between one in 500 and one in 1,000 children have autism. How the disease starts remains unclear. When asked whether autism could start in the mother's womb, DeLong said, "We honestly don't know. There's some evidence it might start in utero, but there's also evidence of some changes in the first year of life."
Both studies are published in the July issue of Neurology, the journal of the American Academy of Neurology.
(Reported by Katrina Woznicki, UPI Science News, in Washington)