Social Brain Abnormalities in Very Young Children with Autism

Background: Anatomo-functional abnormalities in the regions of the ‘social brain’ (superior temporal sulcus, orbito-frontal cortex, amygdala and fusiform gyrus) have previously been described in autism spectrum disorders (ASD. These results concern school aged children, adolescents and adults.

Objectives: Here, we investigated whether these abnormalities could be detected earlier, before the age of 5 years

Methods: Regional cerebral blood flow (rCBF) was measured at rest with positron emission tomography (PET) in 22 children with ASD (18 boys, mean age: 3.8 ± 0.6 years, mean IQ: 60 ± 15) and 11 non-autistic mentally retarded children (mean age: 7.2 ± 2.3 years, mean IQ: 52± 23). The ASD diagnosis was based on DSM IV-R and ADI-R criteria. rCBF was determined from the distribution of radioactivity measured with high-resolution PET camera (ECAT - Exact - HR+ - 962) after bolus intravenous injections of H₂O¹⁵. Images were analyzed using SPM2 software (http://www.fil.ion.ucl.ac.uk/spm/).

Results: We found in children with ASD a significantly hypoperfusion in the right temporal lobe (p<0.001, corrected), centred on the superior temporal sulcus, associated to a less significant and less extended hypoperfusion in left temporal gyrus, cingular gyrus and bilateral inferior frontal gyri (p<0.001, uncorrected). In addition, temporal hypoperfusion was detected individually in 82% of autistic children.

Conclusions: PET and voxel-based image analysis revealed a dysfunction of temporal lobes and frontal and limbic regions in very young children with ASD (<5 years old). As these interconnected regions are important components in social cognition, we can postulate an early dysfunction of a social cortical network including temporal, frontal and cingular regions in autism