ST. PAUL, Minn. -- Children with autism have altered brain anatomy thought to be due to abnormal brain development, according to a study published in the August 22, 2006, issue of Neurology, the scientific journal of the American Academy of Neurology.
The study compared 60 autistic children to 16 children with developmental delay and 10 children with typical development. All of the children were age two to four.
Using magnetic resonance imaging scans (MRI), the researchers measured the transverse relaxation (T2) of cortical gray and white matter in the children's brains. T2 relaxation is a measure of how tightly bound, or mobile, water is in brain tissue and has been used to measure the temporal progression of brain maturation. The researchers found that the autistic children had differences in the gray matter of their brains compared to the children with typical development.
"One of the more consistent brain findings associated with autism has been enlarged brain size," said study author Stephen Dager, MD, of the University of Washington School of Medicine in Seattle. "In contrast to current theories which suggest the enlarged brains are due to accelerated early growth tied to a more advanced stage of brain maturation, gray matter T2 relaxation findings were in the opposite direction. These results suggest that the mechanism or mechanisms responsible for larger brains in autism are different from more rapid growth."
The results were also different from the children with developmental delays, who demonstrated evidence for alterations of both gray and white matter.
"An important consideration is that our findings point toward a different research strategy to elucidate abnormal mechanisms underlying brain development in autism," Dager said. "These findings suggest altered gray matter cellular structure and/or pathologic brain processes such as inflammation early in the developmental course of autism."
Dager cautions that these tests cannot be used as a diagnostic tool to determine if a child has autism.
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The study was supported by grants from the National Institute of Child Health and Human Development and the National Institute on Deafness and Communication Disorders and the National Institute of Mental Health.
The American Academy of Neurology, an association of more than 19,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating, and managing disorders of the brain and nervous system such as Alzheimer's disease, epilepsy, Parkinson disease, multiple sclerosis, and stroke. For more information about the American Academy of Neurology, visit www.aan.com.