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

Abstract

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 (F(1,42) = 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.

Fig. 1

Typical transcranial sonography findings. In the butterfly shaped mesencephalic brainstem (circled by the dotted line), the ipsilateral echogenic substantia nigra can be seen (full line). The echogenic area indicated by the substantia nigra area was regular in control participants (A) but was enlarged in patients with attention-deficit hyperactivity disorder (B).

Fig. 2

Scatterplot of substantia nigra echogenicity (left and right side combined) versus age. A visual inspection indicates no relevant effect of age on the findings. There are no outliers that would have caused the group differences.