A DTI tractography study of young children with autism

Background: Accelerated brain growth in autism has been amply documented in the first 2-4 years of life (1-4). Several studies used DTI to examine white matter structure in subjects with autism (5-7), yet most studies were performed with older children or adults. In our earlier work, we presented the first evidence of over restriction of white matter in young children with autism, providing quantitative information regarding white matter integrity (8). Objectives: To examine white matter integrity in young children with autism using DTI tractography. Methods: DTI data was acquired for subjects who met ADI-R and ADOS criteria for autism (AUT, n=8, age: 2.78±0.66) and typically developing control subjects (TD, n=9, age: 2.47±0.67). Three major fiber bundles were extracted: the corpus callosum, the cortico-spinal tract (cst) and the superior longitudinal fasciculus (slf). Further segmentation of the corpus callosum (cc) was conducted according to the method in Witelson (9). Streamline fiber tracking method based on fiber assignment by continuous tracking (FACT) was applied using DTI Studio software (Johns Hopkins University, Baltimore, MD, USA). For the tracking of white matter fibers, the multiple regions of interest method was applied. Mean diffusivity, FA, eigen values (0,1,2), axial and radial diffusivities were calculated for each fiber segment and were compared between the groups. Results: Although results did not reach statistical significance, consistently higher eigen values for the AUT group were found in the body of cc (Witelson2, 3 and 4), whereas, lower eigen values were found in the slf right and left. No between groups difference were detected in eigen values in the cst fibers. No differences in FA were found in any region. Conclusions: A distinct trend was detected in the eigen values, but not in the FA. Further exploration needs to be done in order to substantiate these results.