Children with autism spectrum disorder (ASD) have distinct brain chemical changes that differ from children with other developmental delays as well as typically developing children, according to researchers at the University of Washington. And these changes seem to resolve themselves after 10 years of age.
“In autism, we found a pattern of early chemical alterations at the cellular level that over time resolved – a pattern similar to what others have seen with people who have had a closed head injury and then got better,” said Stephen R. Dager, M.D., a UW professor of radiology and adjunct professor of bioengineering and associate director of UW’s Center on Human Development and Disability.
This finding gives new insight to efforts aimed at improving early detection and intervention.
“The brain developmental abnormalities we observed in the children with autism are dynamic, not static. These early chemical alterations may hold clues as to specific processes at play in the disorder and, even more exciting, these changes may hold clues to reversing these processes,” said Dager.
During the study, researchers analyzed brain chemistry among three groups of children: those with a diagnosis of ASD, those with a diagnosis of developmental delay, and those considered typically developing. The researchers used magnetic resonance spectroscopic imaging, a type of MRI, to measure tissue-based chemicals in three age groups: 3-4 years, 6-7 years and 9-10 years.
One of the chemicals measured, N-acetylaspartate (NAA), is thought to play an important role in regulating synaptic connections and myelination. Its levels are lower in people with conditions such as Alzheimer’s, traumatic brain injury or stroke. Other chemicals examined in the study were choline, creatine, glutamine/glutamate and myo-inositol, which help with brain tissue integrity.
One important finding included changes in gray matter NAA concentration. In scans of the 3- to 4-year-olds, NAA concentrations were low in both the ASD and developmentally delayed groups.
By 9 to 10 years of age, however, NAA levels in the ASD children had caught up to the levels of the typically developing group, while low levels of NAA persisted in the developmentally delayed group.
“A substantial number of kids with early, severe autism symptoms make tremendous improvements. We’re only measuring part of the iceberg, but this is a glimmer that we might be able to find a more specific period of vulnerability that we can measure and learn how to do something more proactively,” said Annette Estes, Ph.D., a co-author of the study and director of the UW Autism Center. She is an associate professor of speech and hearing sciences.
Study co-author Dr. Dennis Shaw, a UW professor of radiology and director of MRI at Seattle Children’s, said that the study findings “parallel some of the early brain structural differences we and others have found on MRI that also appear to normalize over time in children with autism. These chemical findings will help to better establish the timing and mechanisms underlying genetic abnormalities known to be involved in at least some cases of autism.”
This study also suggests that developmental delay and autism spectrum disorder are distinct disorders having different underlying brain mechanisms and treatment considerations, Dager said.
“Autism appears to have a different pathophysiology and different early biological course than idiopathic (arising spontaneously or from an obscure or unknown cause) developmental disorder.
“There are differences in their underlying biological processes; this supports the notion that ASD is different from developmental delay and challenges the notion that the increasing prevalence of autism merely reflects a re-categorization of symptoms between autism and intellectual disabilities,” he said.
The findings were reported July 31 in the Journal of the American Medical Association Psychiatry.