July 24, 2002 ST. PAUL, MN -- Children with autism exhibit abnormal brain development during the very early years of life, according to two separate studies published in the current issue of Neurology, the scientific journal of the American Academy of Neurology.
Both studies used MRI (magnetic resonance imaging) scanning technology to analyze brain volume in those with autism, and age-matched control groups.
In the first study, which set out to explore anatomical differences in the brains of very young autistic children, the brain volume measurements of 45 autistic children, ages 3 and 4, were compared with those of 26 children with typical development and 14 children with developmental delay. "We found that the autistic children had significantly increased cerebral volumes compared to typically developing children and developmentally delayed children," according to study author Stephen R. Dager, MD, with the University of Washington School of Medicine in Seattle, WA. The average cerebral volume -- including measures of the cerebrum, cerebellum, amygdala, and hippocamus -- was 10 percent larger in autistic children than in typically developing children. The difference was 12.5 percent between autistic and developmentally delayed children. He said the study shows that abnormal brain development processes occur very early in autistic children.
Dager said more research is now underway to better ascertain the causes of the abnormalities as well as the disease's progression. The children in the study will undergo brain reimaging at age 6 to 7 years old, which will make it possible to track changes in behavioral symptoms and corresponding brain volume.
The study was supported by a grant from the National Institute of Child Health and Human Development and the National Institute on Deafnesss and Communication Disorders, and the Cure Autism Now Foundation (CAN).Using a separate sample, researchers at the same university hypothesized that brain growth among autistic patients is rapid in the early years of life, but brain size decreases slightly around age 12, about the same time that normally developing children experienced a growth spurt in cerebral volume. The study showed that by adolescence and adulthood, brain volume levels out to normal size.
The study measured cerebral volume and head circumference of 67 autistic children and adults and 83 healthy controls, ranging in age from 8 to 46 years old. Among those with autism age 12 and under, average brain volume was 5 percent larger than in the controls. By age 12, there was no difference in volume, but head circumference was 1 to 2 percent greater in autistic individuals than controls, whether children or adults. "This increased head circumfrence among adults as well as children with autism is further suggestion of accelerated growth in brain volume among autistic children," according to study author Elizabeth H. Aylward, Ph.D.
Aylward ventured that the accelerated brain growth in children with autism may be a sign of increased numbers of neurons and premature growth of synapses. She acknowledged that the lack of participants under age 8 was a limitation of the study because they were unable to determine when the brain enlargement began.
### The study was supported by the National Institute for Neurological Disorders and Stroke (NINDS) and the University of Pittsburgh's Collaborative Programs of Excellence in Autism.
The American Academy of Neurology, an association of 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. For more information about the American Academy of Neurology, visit its web site at http://www.aan.com.
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