Microstructural Abnormalities in the Combined and Inattentive Subtypes of Attention Deficit Hyperactivity Disorder: a Diffusion Tensor Imaging Study

Previous research has demonstrated that there are specific white matter abnormalities in patients with attention deficit/hyperactivity disorder (ADHD). However, the results of these studies are not consistent, and one of the most important factors that affects the inconsistency of previous studies maybe the ADHD subtype. Different ADHD subtypes may have some overlapping microstructural damage, but they may also have unique microstructural abnormalities. The objective of this study was to investigate the microstructural abnormalities associated with two subtypes of ADHD: combined (ADHD-C) and inattentive (ADHD-I). Twenty-eight children with ADHD-C, 28 children with ADHD-I and 28 healthy children participated in this study. Fractional anisotropy (FA), radial diffusivity (RD) and axial diffusivity (AD) were used to analyze diffusion tensor imaging (DTI) data to provide specific information regarding abnormal brain areas. Our results demonstrated that ADHD-I is related to abnormalities in the temporo-occipital areas, while the combined subtype (ADHD-C) is related to abnormalities in the frontal-subcortical circuit, the fronto-limbic pathway, and the temporo-occipital areas. Moreover, an abnormality in the motor circuit may represent the main difference between the ADHD-I and ADHD-C subtypes.