Diffusion tensor imaging in autism spectrum disorder: a review

Abstract

White matter tracts of the brain allow neurons and neuronal networks to communicate and function with high efficiency. The aim of this review is to briefly introduce diffusion tensor imaging methods that examine white matter tracts and then to give an overview of the studies that have investigated white matter integrity in the brains of individuals with autism spectrum disorder (ASD). From the 48 studies we reviewed, persons with ASD tended to have decreased fractional anisotropy and increased mean diffusivity in white matter tracts spanning many regions of the brain but most consistently in regions such as the corpus callosum, cingulum, and aspects of the temporal lobe. This decrease in fractional anisotropy was often accompanied by increased radial diffusivity. Additionally, the review suggests possible atypical lateralization in some white matter tracts of the brain and a possible atypical developmental trajectory of white matter microstructure in persons with ASD. Clinical implications and future research directions are discussed.

Figure 1

Illustration of the diffusion tensor ellipsoid representing anisotropic diffusion in an area of white matter (cartoon region at top). Maps at the bottom are examples of FA, MD, AD and RD.

Figure 2

Key features of the 48 empirical studies reviewed in the present paper, including sample size, how participants were diagnosed with ASD, how participant groups were matched, the types of DTI measures reported in the studies, the DTI methods, and the b-values used for data acquisition.

Figure 3

Studies that have shown decreased fractional anisotropy (FA) in persons with ASD (compared to persons with typical development) in the splenium, body, or genu of the corpus callosum.

Figure 4

Tractography of a typically developing cingulum (green), superior longitudinal fasciculus (blue), arcuate fasciculus (red), and uncinate fasciculus (purple).