Decreased Rest Cerebral Blood Flow (CBF) in the Superior Temporal Sulcus (STS) in Children with Autism: An MRI-ASL Study

Background: The first results on brain rest functional abnormalities in ASD using positons emission tomography (PET) have described decreased cerebral blood flow (CBF) in children with ASD compared to controls in the temporal regions and particularly in the superior temporal sulcus (STS) (Zilbovicius et al., 2000; Ohnishi et al., 2000). In addition, multivariate classification analysis has shown that STS hypoperfusion allows to correctly classify individual images of children with ASD at rates of 86% (sensitivity: 88%, specificity: 75%) (Duchesnay et al., NeuroImage, 2011). This suggests that the decrease in CBF at the STS level predicts the diagnosis of autism in 86% of cases and could therefore become a useful biomarker in autism. However, PET has significant limitations such as injecting radioisotope products, which makes it unsuitable to study children. Nowadays it is possible to measure rest CBF using arterial spin labeling (ASL) sequence in MRI, without contrast nor radioactivity injections. Thus, ASL could replace the PET method, which had important limitations.

Objectives: To reproduce the results described with PET using ASL-MRI in order to develop a possible biomarker in autism using a non-invasive brain imaging method.

Methods: Twelve children with ASD (age = 11.2 ± 3 years, 7-16 years) and 28 typically developing (TD) children (age = 10.1 ± 2.5 years) participated in this study. The ASD diagnosis was based on DSM-IV and the ADI-R. All participants underwent MRI at the Pediatric Radiology Department at Necker Hospital, in Paris, and rest CBF measures were performed with the ASL sequence, which allows rest CBF measures based on marking arterial water spin. Image processing was performed using Statistical Parametric Mapping 8 (SPM8) (http://www.fil.ion.ucl.ac.uk/spm). A voxel-to-voxel analysis on the whole brain and without a priori hypothesis was performed comparing the ASL images of children with ASD to the control group of children. Further region of interest (ROI) analyses was performed on the bilateral superior temporal regions.

Results: Whole brain voxel-by-voxel analysis showed a significant decrease in rest CBF (p <0.05 FEW corrected for multiple comparisons) in the ASD group compared to the TD group in the left posterior STS. In addition, ROI analysis showed decreased rest CBF in children with ASD in left and right superior temporal regions.

Conclusions: The evidence of a decreased rest CBF within the STS by a non-invasive imaging MRI method could have a major impact on understanding the pathophysiological mechanisms underlying autistic behavior. In addition, if confirmed in a larger sample, STS hypoperfusion may become a biomarker in ASD for the evaluation of new therapeutic strategies.