Autism and MRI Physical Biomarkers

Minor physical anomalies (MPAs) commonly occur in those with autism.  I have previously published a post on a study outlining the type and prevalence of these anomalies in a series of case of autism and austim spectrum disorder.

One of the MPAs noted in the 1970s in autism spectrum disorder is an increased intraorbital distance (distance between the eyes).   This abnormality also noted as hypertelorism has been noted in a variety of brain developmental abnormalities as well as in some normal individuals.

The brain developmental correlates of hypertelorism have not been studied extensively.  It is possible that developmental hypertelorism may reflect brain developmental variations linked to clinical disorders.

Cheung et al and colleagues from the University of Hong Kong and Harvard School of Dental Medicine recently published a brain MRI study of intraorbital distance in autism spectrum disorder in PloS One.  This study examined the correlation of intraorbital distance with a variety of brain structural measurements.

Thirty six children between the ages of 7 and 16 years with autism spectrum disorder were compared to a group of 55 developmentally normal children matched by age and gender.  The two groups were in the normal intelligence range with the verbal IQ of the autism spectrum group 112 compared to a verbal IQ of 117 in the control group.

Magnetic resonance imaging scans were used to accurately measure the intraorbital distance.  This measurement was then compared with brain structure volumes.

Intraorbital distance correlated with several brain regions volumes in the autism spectrum group but not in the control group.  The areas with increased volume correlating with intraorbital distance in the autism spectrum group included:

• Bilateral amygdala
• Bilateral medial temporal lobe regions
• Left inferior frontal cortex lobes

Amygdala developmental abnormalities have previously been noted in studies of autism.  The medial lobe appears to be important in social and language skills developments.

The authors note the possible relationship between intraorbital distance and brain development in this statement from the manuscript discussion section: 

     "The inference is that in this group, the growth of midline bony and brain regions are tightly linked; that is, regions involved in the regulation of socialization, emotion and memory appear to enlarge with the visual system".

These finding suggest that MRI intraorbital distance may be a potential biomarker for autism spectrum disorders.   Additional longitudinal studies of intraorbital distance and brain development in children may provide additional support for the findings in this cross-sectional studies.

Image of intraorbital distance measurement in autism from Cheung et al distributed under the terms of Creative Commons Attributions License which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 

Cheung C, McAlonan GM, Fung YY, Fung G, Yu KK, Tai KS, Sham PC, & Chua SE (2011). MRI study of minor physical anomaly in childhood autism implicates aberrant neurodevelopment in infancy. PloS one, 6 (6) PMID: 21687660