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.
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."