Depression in Parkinson's disease: brainstem midline alteration on transcranial sonography and magnetic resonance imaging

Recent studies using transcranial sonography (TCS) have provided evidence o f alterations in the mesencephalic midline structures in patients with unip olar depression and depression in Parkinson's disease (PD), suggesting an i nvolvement of the basal limbic system in primary and secondary mood disorde rs. This study tested the hypothesis of brainstem midline abnormality in de pression and investigated 31 PD patients by magnetic resonance imaging (MRI ) and TCS. Signal intensity of the pontine and mesencephalic brainstem midl ine was rated on T2- weighted images and measured by relaxometry. In additi on, two blinded investigators assessed the echogenicity of the brainstem mi dline by TCS. The severity of motor symptoms and depression were graded ind ependently using standard research scales. Rating of signal intensity and T 2 relaxometry of the pontomesencephalic midline structures revealed signifi cant difference between depressed and nondepressed PD patients (P < 0.05). This corresponded to a significant reduction in mesencephalic midline echog enicity of depressed PD patients on TCS images. No correlation was found be tween raphe signal intensity, T2 relaxation times, or TCS echogenicity and the severity of motor symptoms or depression. This study is the first to sh ow changes in signal intensity and T2 relaxation time of the pontomesenceph alic midline structures on MRI in depressed PD patients confirming previous TCS findings. As these midline structures comprise fiber tracts and nuclei of the basal limbic system, che findings may support the hypothesis of an alteration in the basal limbic system in mood disorders.