News Alert: Early Brain Overgrowth Linked to Autism

Early Brain Overgrowth Linked to Autism

By Drucilla Dyess

Last updated on May 03, 2011

The continuing quest to find methods for earlier detection of autism has yielded further progress. Results of a long-term magnetic resonance imaging (MRI) study by researchers from North Carolina at Chapel Hill have confirmed that early brain overgrowth is characteristic among children with autism prior to the age of two.

In 2005, Heather Cody Hazlett, Ph.D., of the department of psychiatry at the Carolina Institute for Developmental Disabilities, and her colleagues, compared the brains of 59 children diagnosed with autism to those of 38 children who did not have the disorder and were used as the control group.

Among the control group were typically developing children, as well as children with developmental delay and low IQ. All of the children in the analysis ranged in age from 18 to 35 months. The study results showed that children with autism have brains up to 10 percent larger than children without autism.

The research team continued to track the study participants, and at ages four to five years, there remained a total of 38 of the autistic children and 21 among the control group who were available for additional MRI scans. The later scans indicated that those children who had enlarged brains at age two continued to have enlarged brains at ages four and five. However, the rate of growth noted was not increased in comparison with brains of children without autism, indicating that although autistic brains are bigger, their rate of growth is relatively normal after reaching the age of two years.

On average, the autistic children had 6 percent more total brain volume and 9 percent more volume in the cerebral cortex, which is the area of the brain containing the “newest” sprouting of neurons. This multi-functional brain region handles the receipt of signals and input from the environment, processes memory and attention, and more.

Although previous research has indicated that head circumference and brain enlargement are characteristic among children with autism, it has remained unclear as to when abnormal changes begin to occur. The results of the new research have now moved science one step closer to determining the actual onset of these changes. Prior studies have offered only indirect evidence that abnormal brain growth begins around the age of one year, which is about the same time that abnormal behaviors begin to become apparent. At some point prior to reaching two years of age, it seems that autistic children experience a surge in brain growth that is strongly associated with later behavioral and developmental difficulties.

According to Dr. Joseph Piven, a psychiatrist and director of the Carolina Institute for Developmental Disabilities, and a senior author of the study, “This study strongly suggests that much of the enlargement in the brains of children with autism takes place before the age of two. And the results suggest a mechanism not thought of before in autism, that there is increased production of neurons in the [cerebral cortex] of the brain.”

In conclusion, the study authors noted, “Direct evidence of the timing of early brain volume overgrowth in autism will focus future studies on this narrow window of brain development, providing important insights into potential underlying neural mechanisms and highlighting a potentially important period for early intervention and possible prevention.”

The outcome of the research provides a new understanding of the critical early stages of autism that could pave the way for early intervention, and possibly even reversal of the abnormal development that leads to social and behavioral difficulties associated with autism.

Details of the study can be found in the May Archives of General Psychiatry.