Bigger Not Always Better

Autism brain changes at thirty seven months of age

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) While all there are many unknown contributing factors that go into the development of autism spectrum disorders, research is starting to show that there are concrete differences in brain structure between autistic children and their unaffected peers.

The area of the brain associated with emotional reactions, known as the amygdala, is thought to be involved with autism spectrum disorders (ASD).  

A new study investigates the growth of the adolescent amygdala in order to gain insight on an autism symptom time table. This study, available through the Archives of General Psychiatry, suggests that increased amygdala development occurs around three years of age.

"Look for signs of autism as early as three years of age."

Christine Nordahl, Ph.D., assistant professor of psychiatry and behavioral science at the University of California at Davis Medical Center, and her team found abnormal growth in the amygdala “present by 37 months of age in ASD.”

Dr. Nordahl and her team explain, “The amygdala continues to grow at an increased rate, but substantial heterogeneity exists in amygdala and total cerebral volume growth patterns.”

Nordahl and her team worked with one hundred and thirty-two boys, eighty-five with ASD with the remainder acting as controls. Magnetic resonance imaging of all patients provided individualized insights into brain differences while one-year follow-up images of seventy participants provided scans for growth comparisons. Amygdala and total cerebral volume (TCV) were both evaluated.

“The amygdala was larger in children with ASD at both time points, but the magnitude of enlargement was greater at time 2,” Dr. Nordahl notes. “The TCV was also enlarged in the children with ASD by the same magnitude at both time points.” Even while controlling for TCV, or total cerebral volume, the amygdala enlargement remained significantly larger in both collections.

Moreover, the findings implicate that amygdala growth between ages three and four is significantly faster in children with autism than in healthy controls, while growth in the total volume of the cerebral cortex remained constant amongst all participants.

This research is one of the first studies published from data collected at the UC Davis MIND Institute under their Autism Phenome Project (APP). The goal of APP is to recruit and enroll a large population of young children in order to collect autism information and explore genetic markers associated with the disorder.

The studies of young children do not involve sedatives, but Nordahl notes, “Obtaining MRI scans in 3-year-old children without the use of sedation may seem quite challenging. But, by working closely with the parents, we actually were successful more than 85 percent of the time.

Patience on the part of everyone and the dedication of the families was critical for our success.”

Within a previous study, available online at UC Davis, young boys with regressive autism exhibited abnormal brain growth unique to their form of ASD as well as their gender.

The study found that twenty-two percent of boys with regressive autism, as opposed to five percent without, had enlarged brains.

These findings support the importance of early diagnosis and treatment of autism spectrum disorders.

Previous studies suggest that early treatment helps patients develop helpful habits in order to live a healthy and happy lifestyle, and its important to talk to your pediatrician if noticing mental health struggles within your child.

Reviewed by: 
Review Date: 
January 4, 2012
Last Updated:
January 4, 2012