Brain enlargement may be characteristic of autism

December 05, 2005

CHICAGO - Magnetic resonance imaging (MRI) has found evidence of brain enlargement in a relatively large sample of children with autism, compared with children who do not have the disorder, according to a study in the December issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Autism is a complex neurodevelopmental disorder defined by social deficits, abnormalities in communication, and stereotyped, repetitive behaviors. While the neuroanatomical basis of this condition is not yet known, numerous lines of evidence suggest that abnormalities in brain volume may be characteristic of autism, according to background information in the article.

Heather Cody Hazlett, Ph.D., of the University of North Carolina, Chapel Hill, and colleagues examined brain volume and head circumference (HC) in children with and without autism. They analyzed data from an ongoing MRI study on 51 children with autism - aged 18 to 35 months - and a comparison group made up of 25 children without autism (14 with typical development, and 11 with developmental delay without evidence of a pervasive developmental disorder). Retrospective longitudinal HC measurements were also gathered from medical records on a larger sample of 113 children with autism and 189 control children, from birth to age three years.

"Significant enlargement was detected in cerebral cortical volumes but not cerebellar volumes in individuals with autism," the authors report. "Enlargement was present in both white and gray matter, and it was generalized throughout the cerebral cortex."

The cerebral cortex of the brain is responsible for the processes of thought, perception, and memory, among other functions. The cerebellum is a structure that controls complex motor functions. Gray matter (GM) represents information processing centers in the brain, while white matter (WM) represents connections between those processing centers.

"[In children with autism] head circumference appears normal at birth, with a significantly increased rate of HC growth appearing to begin around 12 months of age," the authors write.

"The findings from this study confirm the presence of generalized cerebral cortical GM and WM brain volume enlargement at age two in individuals with autism," they conclude. "Given the strong relationship between HC and brain volume, the onset of this enlargement appears likely to be during the postnatal [after birth] period and may begin as late as the latter part of the first year of life."
(Arch Gen Psychiatry. 2005;62:1366-1376. Available pre-embargo to the media at

Editor's Note: This work was supported by grants to co-authors Guido Gerig, Ph.D., and Joseph Piven, M.D., from the National Institutes of Health, Bethesda, Md.

For more information, contact JAMA/Archives Media Relations at 312/464-JAMA (5262) or e-mail

The JAMA Network Journals

Related Autism Articles from Brightsurf:

Autism-cholesterol link
Study identifies genetic link between cholesterol alterations and autism.

National Autism Indicators Report: the connection between autism and financial hardship
A.J. Drexel Autism Institute released the 2020 National Autism Indicators Report highlighting the financial challenges facing households of children with autism spectrum disorder (ASD), including higher levels of poverty, material hardship and medical expenses.

Autism risk estimated at 3 to 5% for children whose parents have a sibling with autism
Roughly 3 to 5% of children with an aunt or uncle with autism spectrum disorder (ASD) can also be expected to have ASD, compared to about 1.5% of children in the general population, according to a study funded by the National Institutes of Health.

Adulthood with autism
The independence that comes with growing up can be scary for any teenager, but for young adults with autism spectrum disorder and their caregivers, the transition from adolescence to adulthood can seem particularly daunting.

Brain protein mutation from child with autism causes autism-like behavioral change in mice
A de novo gene mutation that encodes a brain protein in a child with autism has been placed into the brains of mice.

Autism and theory of mind
Theory of mind, or the ability to represent other people's minds as distinct from one's own, can be difficult for people with autism.

Potential biomarker for autism
A study of young children with autism spectrum disorder published in JNeurosci reveals altered brain waves compared to typically developing children during a motor control task.

Autism often associated with multiple new mutations
Most autism cases are in families with no previous history of the disorder.

State laws requiring autism coverage by private insurers led to increases in autism care
A new study led by researchers at the Johns Hopkins Bloomberg School of Public Health has found that the enactment of state laws mandating coverage of autism spectrum disorder (ASD) was followed by sizable increases in insurer-covered ASD care and associated spending.

Autism's gender patterns
Having one child with autism is a well-known risk factor for having another one with the same disorder, but whether and how a sibling's gender influences this risk has remained largely unknown.

Read More: Autism News and Autism Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to