Callosal morphology in high functioning adolescents with autism spectrum disorders and its relation to symptomatology

Background: Previous studies of subjects with autism spectrum disorders (ASDs) have demonstrated abnormalities of structural brain connectivity, particularly in the corpus callosum. 

Objectives: The present study sought to examine corpus callosum morphology among adolescents with high functioning ASDs and its correlation with autism symptomatology. 
Methods: T1-weighted MP-RAGE MRI volumes were acquired at 3T from 16 males with a high functioning ASD (diagnosed using DSM-IV criteria as well as scores from the Autism Diagnostic Interview and the Autism Diagnostic Observation Schedule) and from 17 typically developing males matched group-wise on age and IQ.  The midsagittal area of the corpus callosum was quantified and parcellated into 7 subdivisions based on a previously developed methodology.  

Results: No group differences in corpus callosum area were found; however, when accounting for group differences in total white matter volume, the corpus callosum was relatively larger among the adolescents with ASD.  Within the ASD group, corpus callosum area was negatively correlated with autism symptomatology.  Specifically, posterior regions of the corpus callosum were negatively correlated to measures of stereotyped behavior.

Conclusions: Intact corpus callosum area, but reduced white matter volumes may indicate aberrant connectivity in ASD.  Moreover, variation in corpus callosum area may be related to autism symptoms.