Abstract
BackgroundAutism spectrum disorders (ASD) are associated with widespread alterations in white matter (WM) integrity. However, while a growing body of studies is shedding light on microstructural WM alterations in high-functioning adolescents and adults with ASD, literature is still lacking in information about whole brain structural connectivity in children and low-functioning patients with ASD. This research aims to investigate WM connectivity in ASD children with and without mental retardation compared to typically developing controls (TD).MethodsDiffusion tensor imaging (DTI) was performed in 22 young children with ASD (mean age: 5.54 years) and 10 controls (mean age: 5.25 years). Data were analysed both using the tract-based spatial statistics (TBSS) and the tractography. Correlations were investigated between the WM microstructure in the identified altered regions and the productive language level.ResultsThe TBSS analysis revealed widespread increase of fractional anisotropy (FA) in major WM pathways. The tractographic approach showed an increased fiber length and FA in the cingulum and in the corpus callosum and an increased mean diffusivity in the indirect segments of the right arcuate and the left cingulum. Mean diffusivity was also correlated with expressive language functioning in the left indirect segments of the arcuate fasciculus.ConclusionsOur study confirmed the presence of several structural connectivity abnormalities in young ASD children. In particular, the TBSS profile of increased FA that characterized the ASD patients extends to children a finding previously detected in ASD toddlers only. The WM integrity abnormalities detected may be relevant to the pathophysiology of ASD, since the structures involved participate in some core atypical characteristics of the disorder.
Highlights
Autism spectrum disorders (ASD) are associated with widespread alterations in white matter (WM) integrity
After Magnetic resonance imaging (MRI)/Diffusion tensor imaging (DTI) acquisition, six patients were excluded due to 8) anomalies detected by MRI; 9) insufficient image quality; 10) for children under 48 months, lack of follow-up after 48 months of chronological age confirming the clinical diagnosis of ASD
fractional anisotropy (FA) differences between groups Young children with autism spectrum disorder had a significant increase of FA in a lot of WM areas
Summary
Autism spectrum disorders (ASD) are associated with widespread alterations in white matter (WM) integrity. There is increasing evidence that the heterogeneity and complexity of core and associated ASD symptoms can be explained as a fundamental impairment in brain connectivity [1,2,3]. In this perspective, diameter, myelination, interaxonal spacing and coherence of directional alignment of fibers within WM tracts [6,7,8], while MD represents a directionally independent measure of the average diffusivity that reflects the degree of myelination, interstitial space and axonal density [9]. Among whole-brain approaches, a further innovative method of analysis is tract-based spatial statistics (TBSS) [10]. This analysis method provides some advantages with respect to traditional voxel-based analysis (VBA), since it does not require smoothing and it allows for a higher spatial comparability
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