Objective:To study the microstructural features of the white matter fasciculus in young children with autism spectrum disorders(ASD) by measuring fractional anisotrophy(FA) and average diffusion coefficient(ADC) through diffusion tensor imaging(DTI). Methods:Sixteen ASD patients aged from 1.5 to 5.6 years(mean 3.2±1.4) and 10 typical development children aged from1.5 to 5.7 years(mean 3.4±1.4) were included in this study.DTI was performed on all patients. The regions of interest(ROI) was determined according to Fiber Tract-Based Atlas of Human White Matter Anatomy by Johns Hopkins University. The ROIs included cingulum

uncinate fascicules

splenium

body and genu of corpus callosum

inferior fronto-occipital fasciculus

and inferior longitudinal fasciculus.The mean FA and ADC values were obtained by drawing 2-4 ROIs.The differences of FA and ADC between ASD patients and typical development children were statistically analyzed. Results:FA in the splenium of corpus callosum(0.66 ±0.07) and the right cingulum(0.31±0.03) were significantly higher in ASD group than in control group(0.58±0.09

P=0.030;0.27±0.06

P=0.037).ADC in the splenium of corpus callosum(1.00 ±0.09) and the left cingulum(0.84 ±0.04) decreased significantly in ASD patients comparing with the typical development children(1.15±0.18

P=0.015;0.88±0.04

P=0.026). Conclusion:The FA of some white matter fibers is higher in young children ASD than in the controls

suggesting that abnormal excessive development of white matter possibly exist at the early stage of ASD.