Structural abnormality of the substantia nigra in children with attention-deficit hyperactivity disorder

Background Structural abnormality of the substantia nigra can be detected by transcranial sonography in neuropsychiatric disorders such as Parkinson disease and restless legs syndrome. We investigated echogenicity of the substantia nigra as a potential structural marker for dysfunction of the nigrostriatal dopamine system in children with attention-deficit hyperactivity disorder (ADHD). Methods We used a blinded design and determined echogenicity of the substantia nigra by use of transcranial sonography in 22 children with ADHD and 22 healthy controls matched for age and sex. Results The echogenic substantia nigra area was significantly larger in ADHD patients than in healthy controls ( F1,42 = 9.298, p = 0.004, effect size = 0.92). We found no effects of age or sex. Limitations Owing to a lack of dimensional assessment, we could not analyze the correlation between echogenicity and clinical symptoms. Conclusion Our results support the hypothesis that the nigrostriatal dopaminergic system is abnormal in children with ADHD.