Alterations in the white matter fiber tracts of preschool-aged children with autism spectrum disorder: an automated fiber quantification study.

Background: Little is known about the precise impaired patterns of white matter (WM) fiber tracts in preschool-aged children with autism spectrum disorder (ASD). Thus, we used diffusion tensor imaging (DTI)-based automated fiber quantification (AFQ) to explore the changes in WM fiber tracts in preschool-aged children with ASD and its correlation with the severity of clinical manifestations. Methods: A total of 43 pediatric ASD and 42 age- and sex-matched typical developing children were examined with DTI. AFQ was used to quantify 100 nodes of 16 specific WM fiber tracts. The DTI metrics, including fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), were compared between the two groups. Correlation analysis was performed to evaluate whether abnormal DTI metrics correlated with the Childhood Autism Rating Scale. Results: Compared with typical developing children, at the entire level, the ASD group exhibited a decreased FA [P=0.04 after false discovery rate (FDR) correction] and an increased MD (P=0.048 after FDR correction), and RD (P=0.024 after FDR correction) in the left inferior longitudinal fasciculus (ILF). A decreased FA (P=0.02 after FDR correction) and an increased RD (P=0.024 after FDR correction) were shown in forceps minor. An increased MD (P=0.016 after FDR correction) and RD (P=0.026 after FDR correction) were shown in the left inferior frontal-occipital fasciculus (IFOF). At the point-wise level, significantly decreased FA, and increased MD and RD were observed in the anterior part of forceps minor, left IFOF, and posterior part of left ILF in the ASD group (all P<0.05 after FDR correction). Furthermore, there was a negative correlation between FA of the posterior part of left ILF and the Childhood Autism Rating Scale within the ASD group (r=-0.475, P<0.001). Conclusions: Preschool-aged children with ASD displayed a site-specific propensity for WM fiber tract impairment, mainly in the left cerebral hemisphere. The decreased integrity for the posterior part of the left ILF may reflect the severity of autistic symptoms.