Diffusion Tensor Imaging Study Of The White Matter Fasciculus Related To Social Communicatin Impairment In Young Children With Autism Spectrum Disorders

Objective：To study the microstructural features of the white matterfasciculus related to social communication impairment in younger childrenwith autism spectrum disorders (ASD) by measuring fractional anisotrophy(FA) and average diffusion coefficient (ADC) through diffusion tensorimaging (DTI), and to explore the microstructural change of the whitematter fasciculus with the age increasing.Materials and methods：Sixteen ASD children (14males and2females, age ranging from1.5to5.6years with the mean age of3.2±1.4years old) and10typical development children (7males and3females, ageranging from1.5to5.7years with the mean age of3.4±1.4years old) wereincluded in this study. All participants underwent single-shot echo-planarDTI scan. FA map, ADC map and colour code map were respectivelyreconstructed through the original DTI data by using FuncTool softwarefixed in the post-processing work station. The regions of interest (ROI)were determined according to Fiber Tract-Based Atlas of Human White Matter Anatomy by Johns Hopkins University. The ROIs related to socialcommunication impairment included cingulum, uncinate fascicules,splenium, body and genu of corpus callosum, inferior fronto-occipitalfasciculus, and inferior longitudinal fasciculus. The mean FA and ADCvalue were obtained by drawing2-3ROIs, with the area of each ROI35mm2to45mm2. To compare the difference of FA and ADC between ASDpatients and typical development children, the independent sample t testwas applied, and P<0.05were considered to have statistic significance.Pearson linear regression analysis was used to determine the relationshipbetween FA (ADC) and the age in ASD group, as well as in typicaldevelopment children group.Results：FA in the splenium of corpus callosum（P=0.030）, the rightcingulum (P=0.037) was found significantly higher in ASD group than inthe control group. ADC in the splenium of corpus callosum（P=0.015）andthe left cingulum (P=0.026) decreased significantly in ASD patientscomparing with the typical development children. For most of the fibersboth in ASD and control group, FA increased and ADC decreased with theage increasing. Comparing with the controls, ASD group showed a slow FAincreasing (ADC decreasing) trend in some fibers, while a fast FAincreasing (ADC decreasing) trend in other fibers.Conclusion：(1) DTI which can accurately locate and evaluate theintegrity of white matter fiber tracts is an ideal method to investigate the underlying neuroanatomical structures in ASD.(2) The FA of white matterfibers was higher in small-age ASD than in controls, suggesting thatexcessive myelination could occur in the early stage of ASD.(3) FA inmost brain regions increased along with the age growth. Comparing withthe controls, however, FA increasing amplitude with the age growth wasnot synchronous in different brain regions of ASD.