The gray matter abnormalities revealed by magnetic resonance imaging are inconsistent, especially in pediatric individuals with autism spectrum disorder (ASD) (age < 18 years old), a phenomenon possibly related to the core pathophysiology of ASD. The purpose of our meta-analysis was to identify and map the specific gray matter abnormalities in pediatric ASD individuals thereby exploring the potential effects of clinical and demographic characteristics of these gray matter changes. A systematic search was conducted to identify voxel-based morphometry studies in pediatric individuals with ASD. The effect-size signed differential mapping method was used to quantitatively estimate the regional gray matter abnormalities in pediatric ASD individuals. Meta-regression was used to examine the associations among age, gender, intelligence quotient, symptom severity and gray matter changes. Fifteen studies including 364 pediatric individuals with ASD (male = 282, age = 10.3 ± 4.4 years) and 377 healthy controls (male = 289, age = 10.5 ± 4.2 years) were included. Pediatric ASD individuals showed significant gray matter increases in the right angular gyrus, left superior and middle frontal gyrus, left precuneus, left inferior occipital gyrus and right inferior temporal gyrus, most of which involving the default mode network, and decreases in the left cerebellum and left postcentral gyrus. The meta-regression analysis showed that the repetitive behavior scores of the Autism Diagnostic Interview-Revised were positively associated with increased gray matter volumes in the right angular gyrus. Increased rather than decreased gray matter volume, especially involving the angular gyrus and prefrontal cortex may be the core pathophysiology in the early course of ASD.
Keywords: Autism spectrum disorder; Gray matter; Meta-analysis; Pediatrics; Signed differential mapping; Structural MRI.