Diffusion Tensor Imaging Along the Perivascular Space Index in Different Stages of Parkinson’s Disease

Background: To evaluate the glymphatic system activity in patients with Parkinson’s disease (PD) using the Diffusion Tensor image analysis along the perivascular space (DTI-ALPS) methods. Methods: 71 patients with idiopathic PD and 36 age- and sex-matched normal controls (NCs) were recruited. PD patients were divided into early (n=35) and late (n=36) subgroups, based on Hoehn and Yahr (HY) Stages. We calculated the diffusivity along the perivascular spaces (ALPS) as well as projection fibers and association fibers separately, to acquire the ALPS-index. Enlarged perivascular spaces (EPVS) and periventricular white matter hyperintensities (PVWMH) were also rated. Differences in ALPS-index between the PD and NCs and between two PD subgroups and NCs were compared. In addition, a multivariate logistic regression analysis was conducted to investigate the association between ALPS-index and clinical variables. Results: PD patients revealed lower ALPS-index than NCs (p = 0.010). Late PD group exhibited significant lower ALPS-index than NCs (p = 0.006). However, there were no markedly differences in ALPS-index between NCs and early PD, and between two PD subgroups. In early PD group, there was a significantly positive correlation between ALPS-index and MMSE score (β= 0.021, p = 0.029), and a negative correlation between ALPS-index and EPVS score (β= -0.050, p = 0.034, after controlling for multiple variables. In late PD group, ALPS-index was inversely associated with age (β= -0.012, p = 0.004). Conclusions: Impairment of glymphatic system is involved in Parkinson’ disease. DTI-ALPS index could be a promising biomarker of glymphatic system in PD.