Increased Echogenicity of the Substantia Nigra in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder

BackgroundRecent neurobiological models on attention-deficit/hyperactivity disorder (ADHD) as well as findings from imaging studies suggest a crucial involvement of dopaminergic midbrain nuclei, especially the substantia nigra (SN), in the pathogenesis of ADHD symptoms. The current study aimed to investigate whether alterations in the sonographic features of the SN could serve as a biological marker in ADHD patients.MethodsThe current study employed transcranial sonography in 29 children and adolescents with ADHD and 27 healthy control participants to assess midbrain abnormalities in ADHD.ResultsThe ADHD patients showed an increase in echogenic size of the SN that was correlated with symptoms of inattention, hyperactivity, and impulsivity but not oppositional or dissocial symptoms. Hyperechogenicity, defined as echogenic size above the 90th percentile in the control group, was present in 48% of ADHD patients.ConclusionsOur findings indicate an increased vulnerability of the nigrostriatal system in ADHD. Transcranial sonography could be successfully used in the future to explore whether ADHD patients with distinct SN hyperechogenicity constitute a specific subgroup or whether hyperechogenicity relates functionally to differences in reward processing, learning, and motor function.