Altered white matter microstructure in children with attention-deficit/hyperactivity disorder

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Pediatric Neurology

Background:

• Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder.
• Macrostructural brain alterations are documented in ADHD, but white matter microstructure in preadolescent children remains understudied.
• White matter undergoes significant maturation during childhood, potentially confounding interpretations of adolescent/adult findings.

Purpose of the Study:

• To investigate white matter microstructure differences in preadolescent children with ADHD compared to healthy controls.
• To identify potential early neuroimaging biomarkers for ADHD.
• To explore the role of white matter microstructure in the early pathophysiology of ADHD.

Main Methods:

• Diffusion tensor imaging (DTI) was used to create mean fractional anisotropy (FA) maps via tract-based spatial statistics.
• FA, mean diffusivity (MD), axial diffusivity, and radial diffusivity were compared between 16 children with ADHD and 20 healthy children (aged 7-9 years).

Main Results:

• Children with ADHD exhibited decreased FA in multiple white matter regions, including frontoparietal, frontolimbic, cerebellar, corona radiata, and temporo-occipital areas.
• ADHD was associated with altered MD in specific tracts: lower in the posterior internal capsule and frontoparietal regions, and higher in frontolimbic regions.
• Differential patterns of axial and radial diffusivity were observed in ADHD, correlating with white matter maturation stages.

Conclusions:

• ADHD in preadolescent children is characterized by widespread atypical white matter microstructure, indicating altered structural brain connectivity.
• Abnormalities in later-maturing frontolimbic pathways, potentially due to delayed myelination, were identified in children with ADHD.
• These findings suggest that white matter microstructure disruptions are integral to the early pathophysiology of ADHD.