A Preliminary Study of MRI-derived Glymphatic System Indices in Early-Stage Normal Aging

Glymphatic system (GS), known to clear out waste products and metabolites from the central nervous system, has been implicated in many neurodegenerative diseases. However, due to the lack of noninvasive biomarkers, its role in the pathogenesis of normal ageing population is limited. Indicators based on magnetic resonance imaging (MRI) are the most promising methods for assessing GS impairments indirectly, this preliminary study was desired to evaluate whether the MRI-derived GS indices are age-related and to detect the associations among them.

52 clinically confirmed normal healthy volunteers aged 60.71±7.09 were retrospectively enrolled, including 31 female. MRI-derived GS indices, including quantitative volume fraction of perivascular spaces (PVS-VF), diffusion tensor imaging analysis along the perivascular space (ALPS), free water in white matter (FW-WM) and volume of choroid plexus (Chp) were used to estimate the difference in GS abnormalities between them. Correlation analyses were also conducted to explore the age-related GS indicators, and to detect the interrelationships among these GS indices in the early old age.

GS indices, including ALPS and FW showed age-related trends in this early old age, Pearson correlation analysis indicated that ALPS was negatively correlated with age (r = -0.300, p = 0.040), and FW-WM was positively correlated with age (r =0.520, p<0.001). Moreover, lower ALPS index was accompanying with larger fraction of FW and volume of Chp, as well as enlarged CSF; larger fraction of FW-WM was accompanied with larger volume of Chp, as well as CSF.

To some extent, age-related trends of ALPS and FW were present in early old age. Interrelationships among these GS indices may suggest that lower ALPS index, larger fraction of FW and volume of Chp may play important role in the pathogenesis of normal ageing population.