Echogenic alteration in the raphe nuclei measured by transcranial sonography in patients with Parkinson disease and depression

BACKGROUND: Recently, several studies using transcranial sonography (TCS) have demonstrated reduced echogenicity of the mesencephalic midline in unipolar depression and patients with comorbid depression and Parkinson disease (PD). However, there is no consensus on the conclusion that raphe nuclei (RN) hypoechogenicity is associated with depression in PD. The methods used in previous studies lack quantitative and objective indicators to some extent; therefore, the present study used the level of platelet 5-hydroxytryptamine (5-HT) as an objective indicator of depression. Additionally, the reason for the reduced echogenicity of the brainstem raphe is still unclear. OBJECTIVES: The purpose of the present study was to assess the correlation between alterations in RN echogenicity and depressive symptoms in patients with PD using transcranial sonography (TCS). This information could provide a meaningful clinical reference for the antidiastole between depressive symptoms in PD and unipolar depression in patients with PD in whom depressive symptoms occur before motor symptoms. METHODS: TCS was performed in patients with PD, patients with PD and depression, patients with depression and no PD, and healthy controls. Using the red nucleus as a reference, the RN was rated from grades 0 to 1 (grade 0: invisible, slightly echogenic, or interrupted RN; grade 1: hyperechogenicity in the RN observed as a continuous line). RESULTS: The rate of abnormal RN (grade 0) was found to be 16.67% in patients with PD (5/30) and 14.29% in healthy controls (4/28). The presence of abnormal RN was significantly higher (χ(2) = 15.983, P < .05) in patients with depression and PD (40%, 12/30) and in patients with depression only (58.33%, 14/24) than in those without depression and healthy controls. No correlation was found between RN changes and depression severity (P > .05). There were no statistical differences in the concentration of platelet serotonin among the 4 groups (P > .05). CONCLUSIONS: TCS of the mesencephalic midline may be useful for detecting depression, which is an early symptom of PD. However, further neuropathological studies are needed to understand the principles underlying the use of platelet serotonin as a peripheral biomarker, as well as the connection between PD and depression.