Sensory Processing Disorders (SPD) affect 5-16% of children in the US, and have been shown to impair intellectual and social development due to disrupted processing and integration of sensory input. SPD exists both comorbidly with other neurpathologies such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), but often also exists in isolation. In our previous work, tract-based spatial statistics (TBSS) were used with diffusion tensor imaging (DTI) data of SPD subjects to demonstrate decreased white matter integrity in parieto-occipital white matter tracts.
Autism Spectrum Disorders (ASD) are typically clinically characterized by impaired communication, social interaction, and behavioral flexibility. However, the majority of individuals with ASD also exhibit sensory processing differences. It is valuable to characterize the similarities and differences in sensory processing deficits between sensory processing deficits within SPD and ASD for differential diagnosis and potentially for treatment planning.
We validate and expand upon previous white matter studies of ASD and our previous results in SPD by taking a tractographical approach to examining white matter tracts that we expect to be commonly and differentially affected in SPD vs ASD. Diffusion tensor imaging data was acquired in 16 boys with SPD, 15 boys with ASD, and 23 typically developing boys. Probabilistic fiber tractography was then used with this data to delineate white matter tracts of interest, and white matter structural integrity was assessed for each of these tracts using average values of fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity within each tract. Significant decreases in FA were found for both the SPD and ASD cohorts within the parieto-occipital tracts as compared with the control cohort, with the SPD cohort demonstrating surprisingly and pervasively more affected FAs. Significant decreases in FA were found for the ASD cohort, but not the SPD cohort, within the temporal white matter tracts.
These findings validate abnormal white matter as a biological basis for SPD, demonstrate differential white matter pathology between ASD and SPD, and suggest that tracts contributing to social and emotional processing (and implicated in ASD) are independent of sensory processing.