Gray matter abnormalities in autism spectrum disorder revealed by T2 relaxation

Objective: To perform quantitative T2 relaxation measurements to evaluate cerebral water content in children with autism. Methods: Sixty 2- to 4-year-old children with autism spectrum disorder (ASD), 16 age-matched children with idiopathic developmental delay (DD), and 10 children with typical development (TD) were scanned on a 1.5 T GE MRI scanner to obtain dual-echo fast spin echo images (2.5 mm thick, 0-mm gap). Images were segmented into gray and white matter and used to mask regions of interest for calculating T2 for each tissue type. Analysis of variance, covarying for age and sex, was used to compare T2 between groups, and correlations were used to compare T2 to IQ measures. Results: Children with ASD had prolonged cortical gray matter T2, but white matter T2 was not significantly different, compared with the children with TD. T2 was prolonged in cortical gray matter and white matter in children with DD compared with children with ASD or TD. Significant interactions between T2 measures and IQ were not observed. Conclusions: Prolonged gray and white matter T2 in the children with developmental delay likely represents a delay in neuronal development and maturation. Prolonged T2 in gray matter, but not white matter, observed in children with autism spectrum disorder may signify abnormal developmental processes specific to autism.