Corpus Callosum Differences Seen Between Autistic Boys and Girls‏

NEW YORK (Reuters Health) - Magnetic resonance imaging (MRI) shows sex differences in corpus callosum neuroanatomy in preschoolers with autism spectrum disorder (ASD), researchers say.

"Our study adds to a growing body of evidence that there are differences between boys and girls with autism," said Dr. Christine Wu Nordahl, of the University of California, Davis in Sacramento, in email to Reuters Health. "These differences may affect how boys and girls are diagnosed with autism, as well as potentially the types of treatments or interventions that boys and girls with autism receive."

"The ultimate goal," she added, "is to understand the biological and behavioral differences between boys and girls with autism to try to understand the cause(s) of autism in boys and girls and to develop better treatments."

As reported May 13 online in Molecular Autism, Dr. Wu Nordahl and colleagues examined images from 112 male and 27 female children with ASD and a further 87 typically developing controls.

Relative to their sex-specific controls, both males and females with ASD had smaller regions dedicated to fibers projecting to superior frontal cortex. However, males with ASD had a smaller callosal region dedicated to orbitofrontal cortex, and females with ASD had a smaller callosal region dedicated to anterior frontal cortex. There were also sex differences in diffusion properties of callosal fibers.

Commenting by email, Dr. Meng-Chuan Lai, guest editor of this issue of the journal and coauthor of an accompanying editorial, told Reuters Health, "This important finding adds to previous observations in adults, further suggesting that male-female neurobiological differences in autism are present early in life."

Dr. Lai, of Cambridge University, UK, added, "This emphasizes the need to consider sex and gender as key moderating factors in the neurodevelopment of individuals with autism."

Dr. Wu Nordahl and colleagues observed that "additional studies are underway to relate these findings to the behavioral manifestations of ASD."

In fact, on May 16, the team presented the results of a further study examining behavioral differences at the International Society for Autism Research Meeting in Salt Lake City, Utah.

"We don't yet know enough about females with autism because most research studies do not have equal numbers of females and males with autism in their samples," Dr. Wu Nordahl added. "This is not surprising given that there are so many more males with autism than females. We need to do a better job of trying to recruit females with autism into our studies so that we can fully explore differences between males and females with autism."

However, in a statement, Dr. Wu Nordahl noted that in the preliminary behavioral study, "differences between girls with autism and typically developing girls are much larger than differences between boys with autism and typically developing boys."

"In other words, girls with autism deviate further from typically developing girls than boys with autism relative to typically developing males, suggesting that girls with autism have more severe social impairments than boys."