transcranial ultrasonography; raphe nuclei; substantia nigra; Parkinson's disease; mental disorders; depression

The use of neuroimaging methods is one of the pillars of re-convergence of neurology and psychiatry. Transcranial ultrasonography of the brainstem parenchyma is a method widely clinically used in neurology while it has also started to bear first fruit in the field of mental disorders. Sonographic imaging mainly concerns structures of the brainstem. Reduced echogenicity of the brainstem raphe is related to unipolar major depressive disorder, the majority of organic depressive disorders and several anxiety disorders but not bipolar affective disorder. According to initial results, this could be the marker of good efficacy of serotoninergic antidepressants. Hyperechogenicity of substantia nigra, typical for Parkinson's disease, has also been frequently found in depressive states, and suggests shared etiopathogenic background. In addition, it is related to severity of medication-induced extrapyramidal syndrome in psychiatry. Verification and extension of these findings may provide clinically important markers for discrimination between unipolar and bipolar depression, a more personalized choice of an antidepressant and prediction of the risk of antipsychotic-induced extrapyramidal adverse effects. This article presents a detailed overview of brain sonographic findings when used at the interface between neurology and psychiatric border.