The Relationship Between Changes Of White-matter In Limbic System And Depression In Patients With Parkinson’s Disease

Background and Objective:Parkinson’s disease(PD) is a chronic progressive degenerative disease of the central nervous system. It is common in the elderly. And the main clinical symptoms always include the resting tremor, bradykinesia, rigidity, as well as the postural balance disorders. With the further research of PD, most scholars have found that various non-motor symptoms is also an important part of the clinical manifestations apart from the movement symptoms, such as anxiety, depression, sleep disorders and so on. Depression is one of the most prominent non-motor symptoms and often appears in early-stage PD. It not only can increase the severity of other clinical symptoms, but also accelerate the progression of the disease. It is an independent risk factor that causes a serious decline in the quality of life in patients with PD. However, the pathogenesis of depression in patients with PD remains unclear. Some studies show that depression in patients with PD is closely related to the changes of white-matter in the emotional projection loop. This is thought to be one of the potential mechanisms of pathogenesis.Recently, the emergence and rapid development of diffusion tensor imaging provid a security, objective, non-invasive, convenient means for the in vivo study of white-matter. DTI can be used to quantitatively measure the strength and direction of the anisotropic diffusion of water molecules along the nerve fibers in 3D space. Fractional anisotropy is the most commonly used index to measure the degree of anisotropic diffusion. White-matter within normal brain tissue has a high degree of anisotropy, FA is larger, when its fine structure damaged, FA will be reduced. So FA can be used to assess the full extent and continuous case of white-matter. Presently, the whole brain, part of the brain lobe or a particular brain structure are analysised in abroad study of DTI in PD patients with depression, but there is no specific research on the limbic system, and little domestic research.This study was designed to investigate the prevalence of depression in patients with PD and to assess the integrity of white-matter in limbic system in PD patients with depression by diffusion tensor imaging. In addition, to further explore the relationship between FA values of white-matter with abnormal changes and the severity of depression in patients with PD. It could increase the possibility for deeply understanding the pathogenesis of depression in patients with PD and provide the evidence for diagnosis, treatment and prognosis of it. Methods:A total of 73 patients with idiopathic PD and 20 healthy volunteers were enrolled in this study, those gender, age, education level were matched each other. All subjects’ general information was collected. They were assessed by Genatric Depression Scale(GDS-30) and Hamilton Depression Scale(HAMD-17) to screen for the severity of depression. Then, patients with PD were divided into three groups: those without depression(nd PD), with mild depression(md PD) and with mod-severe depression(msd PD). All subjects were also assessed by Mini-Mental State Examination(MMSE), Unified Parkinson’s Disease Rating Scale motor part(UPDRS-Ⅲ),and Hoehn-Yahr staging(H&Y)to judge their cognitive status, motor function and severity of the disease. They were inspected by MRI+DTI. The bilateral boundaries of frontal orbital, medial temporal, midbrain tegmentum, anterior cingulate bundle, medial dorsal thalamus and amygdala were manually sketched out. Fractional anisotropy(FA) of each region of interest(ROI) was measured and underwent statistical analysis. Spearman correlation analysis was examined betwween FA of ROIs that showed a statistically significant difference and the severity of depression in 3 groups of PD patients. Results:1.35 subjects(47.9%) associated with depression in the total patients of PD, of which 32.9% patients with mild depression, 10.9% patients with moderate depression, 4.1% patients with severe depression, and 15% patients with mod-severe depression in all. The prevalence of depression in patients with early-stage PD was 47.6%, of which 38.1% patients with mild depression, these were higher than in patients with advanced-stage PD(P<0.05).2.Compared with the healthy control group, FA of bilateral amygdale, left midbrain tegmentum, left frontal orbital decreased in nd PD group; FA of bilateral amygdale, left midbrain tegmentum, left frontal orbital,bilateral medial dorsal thalamus and bilateral anterior cingulate bundles decreased significantly in md PD group; except the bilateral medial temporal and right midbrain tegmentum, FA of each ROI in msd PD group was lower(P<0.05). Compared with the nd PD group, FA of left frontal orbital,left medial dorsal thalamus and bilateral anterior cingulate bundles decreased in md PD group; FA of bilateral frontal orbital, bilateral medial dorsal thalamus and bilateral anterior cingulate bundles obviously decreased in msd PD group(P<0.05). FA of left frontal orbital, left medial dorsal thalamus and left anterior cingulate bundles in msd PD group was lower than that in md PD group.3.FA of left frontal orbital, left medial dorsal thalamus and left anterior cingulate bundles had a negative correlation with the severity of depression in patients with PD. Conclusion:1.The prevalence of depression is high in early-stage PD and mild depression is always considered the main type.2.The abnormal changes of white-matter in limbic system have occurred already in PD patients with depression, this may be one of the potential mechanisms of pathogenesis.3.Abnormal changes of partial white-matter in limbic system are associated with the severity of depression in patients with PD, it can provide the evidence to early detect, prevent and treatment the depression in patients with PD and to assess the severity of depression in whom.