Brain Cortical Volume and Thickness Abnormalities in Autism Spectrum Disorder Aged 2-4 Years: a Structural MRI Comparative Study.

Purpose: To examine the brain morphological characteristics of 2-to-4-year-olds with ASD, including cortical and subcortical regions, and to investigate their associations with clinical behaviors.

Methods: A total of 43 toddlers with ASD aged 2-4 years, 44 age- and gender- matched toddlers with developmental delay (DD) and 18 typically developing (TD) children were recruited. All participants underwent whole-brain high-resolution MRI and clinical assessments. Brain structural data were analyzed using Surface-Based Morphometry with FreeSurfer. Linear mixed-effects models were employed to identify differences in brain regions between groups and to explore their links with clinical behaviors.

Results: Compared to TD group, ASD group demonstrated increased cortical thickness and volume, particularly within the frontal and parietal brain regions (FDR, p < 0.05). When compared to DD, ASD group exhibited a distinction in the increased cortical volume within the posterior frontal lobe and middle-post cingulate (FDR, p < 0.05). DD children had increased cortical thickness and cortical volume in the superior parietal gyrus compared to TD (FDR, p < 0.05). In the ASD + DD group, increased cortical thickness of the superior frontal sulcus was correlated with lower adaptive behavior, while reduced nucleus accumbens volume and increased cortical thickness of the superior frontal sulcus and precentral sulcus were associated with decreased language development (FDR, p < 0.05).

Conclusion: Our study found widespread brain abnormalities in young children with ASD, notably altered cortical volume and thickness in frontal and parietal lobes. These findings may serve as important indicators of altered brain development trajectories in this population.