Abstract
Perivascular Spaces (PVS) become increasingly visible with advancing age on brain MRI, yet their relationship to morphological changes in the underlying microvessels remains poorly understood. Retinal and cerebral microvessels share morphological and physiological properties. We compared computationally-derived PVS morphologies with retinal vessel morphologies in older people. We analysed data from community-dwelling individuals who underwent multimodal brain MRI and retinal fundus camera imaging at mean age 72.55 years (SD=0.71). We assessed centrum semiovale PVS computationally to determine PVS total volume and count, and mean per-subject individual PVS length, width and size. We analysed retinal images using the VAMPIRE software suite, obtaining the Central Retinal Artery and Vein Equivalents (CRVE and CRAE), Arteriole-to-Venule ratio (AVR), and fractal dimension (FD) of both eyes. We investigated associations using general linear models, adjusted for age, gender, and major vascular risk factors. In 381 subjects with all measures, increasing total PVS volume and count were associated with decreased CRAE in the left eye (volume β=-0.170, count β=-0.184, p<0.001). No associations of PVS with CRVE were found. The PVS total volume, individual width and size increased with decreasing FD of the arterioles (a) and venules (v) of the left eye (total volume: FDa β=-0.137, FDv β=-0.139, p<0.01; width: FDa β=-0.144, FDv β=-0.158, p<0.01; size: FDa β=-0.157, FDv β=-0.162, p<0.01). Increase in PVS number and size visible on MRI reflect arteriolar narrowing and lower retinal arteriole and venule branching complexity, both markers of impaired microvascular health. Computationally-derived PVS metrics may be an early indicator of failing vascular health and should be tested in longitudinal studies.
Highlights
Perivascular spaces (PVS) are known as Virchow–Robin spaces, and are seen with increasing clarity on brain magnetic resonance imaging (MRI) in older subjects, in small vessel disease (SVD), stroke, dementia and other neurological disorders [1]
PVS numbers have been reported to increase with age, with other brain SVD features [5], and with vascular risk factors, especially hypertension, in common brain disorders including stroke, mild cognitive impairment, and dementia including of vascular subtype ([1,50])
MRI scans that could not be processed successfully mainly contained motion artefacts that appeared as parallel lines similar to PVS
Summary
Perivascular spaces (PVS) are known as Virchow–Robin spaces, and are seen with increasing clarity on brain MRI in older subjects, in small vessel disease (SVD), stroke, dementia and other neurological disorders [1]. The method by Ballerini et al [11,12] was able to segment PVS in the centrum semiovale and enabled quantification of several PVS features including the total count and total volume per individual subject’s brain, plus the size, length, width, shape and direction of each individual PVS. All these can be analysed as mean or median per individual subject [11] or per brain region. We compared computationally-derived PVS morphologies with retinal vessel morphologies in older people
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