Research on preschoolers brain size and autism

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Research on preschoolers brain size and autism. While AADMD'ers are involved with adults with autism it behooves us to understand and appreciate the fundamental developmental anatomic changes in pediatric autism. This might have impact on future treatment approaches and outcome metrics.

Rick Rader, MD
AADMD VP of Public Policy and Advocacy

Study: Brain size signals certain type of autism
Nurse.com News
Tuesday November 29, 

In what researchers called the largest study of brain development in preschoolers with autism to date, 3-year-old boys with regressive autism, but not early onset autism, had larger brains than their healthy counterparts.

"The finding that boys with regressive autism show a different form of neuropathology than boys with early onset autism is novel," said study author Christine Wu Nordahl, a researcher at the University of California-Davis MIND Institute and an assistant professor in the Department of Psychiatry and Behavioral Sciences.

"Moreover, when we evaluated girls with autism separately from boys, we found that no girls — regardless of whether they had early onset or regressive autism — had abnormal brain growth."

Brain enlargement has been observed in previous studies of autism. However, prior to this study, little was known about how many and which children with autism have abnormally large brains.

"This adds to the growing evidence that there are multiple biological subtypes of autism, with different neurobiological underpinnings," said study author David G. Amaral, Beneto Foundation chairman, MIND Institute research director and University of California Distinguished Professor in the Department of Psychiatry and Behavioral Sciences.

Autism affects 1 in 110 children born today, according to the U.S. Centers for Disease Control and Prevention. It is diagnosed more frequently in male children than female children, at a ratio of 4 to 1.

The current study is one of the first published from data collected by the UC Davis MIND Institute Autism Phenome Project. The authors examined180 children between ages 2 and 4 who were enrolled in the APP. Of the participants, 114 had autism spectrum disorder; the remaining participants were 66 age-matched, typically developing "control" children. Of the children with autism, 54% were diagnosed with the regressive form — characterized by the loss of previously acquired language and social skills — and 46% with the non-regressive type.

Using magnetic resonance imaging scans, the researchers found that accelerated head growth and brain enlargement was consistently observed only in the subset of children diagnosed with regressive autism. Specifically, total brain volume in 3-year-old males with regressive autism was more than 6% larger than that of age-matched typically developing peers. Of boys with regressive autism, 22% had enlarged brains, as opposed to 5% of those without regressive autism.

Changes in brain size were not apparent in boys who did not experience a regression. Girls with autism, regardless of autism onset status, also did not show abnormal brain growth. The findings suggest that abnormalities in overall brain growth are specific to male children with the regressive type of autism, and that rapid brain growth may be a risk factor for regression, the researchers said.

While brain size was clearly larger at age 3, the study also determined when the precocious growth began, by examining records of head circumference that provide a reasonable estimate of brain size in young children. These analyses clearly indicated that brain growth diverged from normal at around 4 to 6 months of age. 

The researchers said this finding is of particular interest because many families believe that the trigger that led to their child's regression took place close to the time that the regression happened. But the data reported in this paper indicate that the process leading to the enlarged brain, which is presumably also associated with the onset of autism, started when the child was a newborn.

The study appeared Monday on the website of the Proceedings of the National Academy of Sciences. To download a PDF, visit http://bit.ly/tmePPz.