The Brain

Agenesis of Corpus Callosum Linked to Autism

April 29, 2014 | by Lisa Winter

Photo credit: Life Science Databases, via Wikimedia Commons

The corpus callosum is a wide bundle of over 200 million axons which link the right and left hemispheres of the brain. During development, this important bridge is not always formed correctly and can either be malformed or partially or completely absent. This condition is referred to as Agenesis of Corpus Callosum (AgCC). A group of researchers have established a link between AgCC and autism. The announcement comes from the lab of Ralph Adolphs of Caltech, and the paper published in the journal Brain.

Though severing the corpus callosum can alleviate seizures in those with severe epilepsy, a rare defect which first presents during the first trimester of pregnancy leaves some without that structure, or with one that was not completely or correctly formed. AgCC typically isn’t fatal, but those with the condition may have delayed developmental milestones, social difficulties, memory issues, and/or cognitive impairments. These are also many of the same symptoms of autism.

This isn’t the first time a connection between AgCC and autism has been made, but this is the first time that both groups have been directly compared. Over the span of about 10 years, the researchers had participants from both groups complete tasks based in social behavior and abstract thinking. Some of these experiments were recorded, allowing researchers to go back and watch the tapes again to analyze the behavior. In addition to social function, they also measured intelligence.

"When we made detailed comparisons, we found that about a third of people with AgCC would meet diagnostic criteria for an autism spectrum disorder in terms of their current symptoms," said Lynn Paul, lead author of the study, in a press release.

There are differences between the two groups, however. While symptoms of autism usually present early on in life, those with AgCC don’t start showing symptoms until the pre-pubescent years when the brain undergoes developmental changes. While being a pre-teen is typically awkward enough, those with AgCC are more likely to display social awkwardness.

This information has researchers and physicians in a good position to begin a new line of research. As ultrasound technology has advanced, it has been made possible to diagnose AgCC while the baby is still developing. This would allow researchers to monitor behavior and brain morphology through MRI throughout life and compare it to the timeline of a child with autism.

"If we can identify people with AgCC already before birth, we should be in a much better position to provide interventions like social skills training before problems arise," Paul continues in the press release. "And of course from a research perspective it would be tremendously valuable to begin studying such individuals early in life, since we still know so little both about autism and about AgCC." 

[Hat tip: Katie Neith, Caltech News]

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