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Probing the Brain in Autism Using fMRI and Diffusion Tensor Imaging
Published on: September 12, 2011
Brain volume findings in 6-month-old infants at high familial risk for autism
Heather Cody Hazlett1, Hongbin Gu, Robert C McKinstry
1Carolina Institute for Developmental Disabilities and the Department of Psychiatry, University of North Carolina, Chapel Hill, USA. hcody@med.unc.edu
Insights
Brain scans of 6-month-old infants at high risk for autism showed no significant differences in brain volume or head circumference compared to controls. Further longitudinal studies are needed to determine if early brain differences emerge later in development.
Area of Science:
- Neuroscience
- Developmental Psychology
- Pediatric Radiology
Background:
- Autism Spectrum Disorder (ASD) is associated with brain enlargement in early childhood.
- Head circumference studies suggest postnatal brain overgrowth around 1 year of age.
- Limited neuroimaging data exists for infants younger than 2 years, especially those at high familial risk for ASD.
Purpose of the Study:
- To investigate early brain volume differences in 6-month-old infants with a high familial risk for autism.
- To systematically examine brain structure using magnetic resonance imaging (MRI) before age 2.
- To identify potential early biomarkers for autism spectrum disorder.
Main Methods:
- Cross-sectional analysis of the Infant Brain Imaging Study (IBIS) cohort.
- Comparison of brain volumes (intracranial, cerebrum, cerebellum, lateral ventricles) at 6 months of age.
- Inclusion of 98 high-risk infants and 36 low-risk controls; assessment for radiologic abnormalities.
Main Results:
- No statistically significant group differences were found in head circumference.
- No significant differences in intracranial, cerebrum, cerebellum, or lateral ventricle volumes between high-risk and control infants.
- No radiologic abnormalities were detected in either group.
Conclusions:
- Early magnetic resonance imaging (MRI) at 6 months did not reveal group differences in brain volume or head circumference in infants at high familial risk for autism.
- The absence of detected abnormalities does not rule out their presence in infants who later develop autism.
- Longitudinal follow-up of the IBIS cohort is crucial to determine if brain volume differences emerge over time in infants who develop autism.
Objective:
Individuals with autism as young as 2 years have been observed to have larger brains than healthy comparison subjects. Studies using head circumference suggest that brain enlargement is a postnatal event that occurs around the latter part of the first year. To the authors' knowledge, no previous brain imaging studies have systematically examined the period prior to age 2. In this study they used magnetic resonance imaging (MRI) to measure brain volume in 6-month-olds at high familial risk for autism.
Method:
The Infant Brain Imaging Study (IBIS) is a longitudinal imaging study of infants at high risk for autism. This cross-sectional analysis compared brain volumes at 6 months of age in high-risk infants (N=98) and infants without family members with autism (N=36). MRI scans were also examined for radiologic abnormalities
Results:
No group differences were observed for intracranial, cerebrum, cerebellum, or lateral ventricle volume or for head circumference.
Conclusions:
The authors did not observe significant group differences for head circumference, brain volume, or abnormalities in radiologic findings from a group of 6-month-old infants at high risk for autism. The authors are unable to conclude that these abnormalities are not present in infants who later go on to receive a diagnosis of autism; rather, abnormalities were not detected in a large group at high familial risk. Future longitudinal studies of the IBIS study group will examine whether brain volume differs in infants who go on to develop autism.
