Abstract TP23: Differentiated Para-Vascular Distribution of Amyloid Plaques in Normal versus Cognitively Impaired

Abstract

Introduction: The vascular contribution to Alzheimer’s disease (AD) and AD-related dementias is increasingly recognized. Scanning laser ophthalmoscopy (SLO) visualizes two important markers of cognitive dysfunction in the retina, vascular changes and amyloid plaque deposition. The relationship between retinal vascular changes and peri-vascular amyloid deposition in the continuum of neurodegeneration is imperfectly understood. In this exploratory topographic analysis of a cohort of subjects with normal and impaired cognition that underwent SLO, we investigated the retinal vascular-adjacent (para-vascular) amyloid plaque distribution and its correlation with cognitive measures. Methods: 34 subjects with cognitive decline underwent retinal SLO, brain magnetic resonance imaging and standard neuropsychometric testing. Retinal para-arteriolar and para-venular curcumin positive amyloid plaques were quantified in the supero-temporal retinal quadrant, in the first-, second- and third-order retinal vascular branches. The para-venous and para-arteriolar amyloid count were compared between patients with normal and impaired cognition, and their correlation with brain volumes and white matter hyperintensities was determined. Results: We analyzed retinal para-venous and para-arteriolar amyloid and vascular-structural parameters derived from 29 subjects, mean (SD) age 65(7), 48% female. Para-arteriolar plaque was higher than para-venular plaque in the entire cohort (p<0.0001). Secondary branch para-venular amyloid plaque count was higher in patients with impaired cognition, CDR ≥1 and MOCA ≤26. The para-arterial plaque count in the secondary branches significantly correlated with hippocampal volume and white matter hyperintensities scores. Conclusion: Our topographic analysis of the amyloid plaque distribution in retinal para-vascular regions shows higher amyloid accumulation in the para-arteriolar regions overall, and specifically in the secondary para-venular branches in patients with impaired cognition. Larger longitudinal studies are needed to study the temporal and spatial relationship between vascular dysfunction and para-vascular amyloid deposition in AD.