Autistic children
show abnormal brain growth during their first few years of life, two new
studies released 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.
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