Retinal microvascular function is associated with the cerebral microcirculation as determined by intravoxel incoherent motion MRI

Background and aims: The easily accessible retinal vessels provide a unique opportunity to study a proxy for cerebral small vessels. Associations between retinal vessel diameters and macrostructural brain white matter changes have already been demonstrated. Alterations in microvascular function, likely precede these structural abnormalities. We examined whether retinal microvascular function is related to cerebral microvascular properties, assessed by the intravoxel incoherent motion (IVIM) effect in brain MRI. Methods: Seventy participants (age 60 ± 8 years, 41% women) from the population-based Maastricht Study underwent brain IVIM diffusion imaging (3 Tesla) to determine the microvascular measures f (perfusion volume fraction) and D* (pseudo-diffusion of circulating blood). The retinal arteriolar and venular dilation response to flicker light stimulation were measured by a dynamic vessel analyzer. Linear regression analysis was used to investigate associations between retinal vasoreactivity and IVIM measures in white matter hyperintensities (WMH), normal-appearing white matter (NAWM) and cortical gray matter (CGM). Results: More retinal arteriolar dilation was significantly associated with stronger pseudo-diffusion (D*) in the NAWM and CGM (β 0.280 [95% CI 0.084–0.475], and β 0.310 [95% CI 0.091–0.528], respectively), but not with the cerebral blood volume fraction (f). No associations were observed between retinal venular dilation response and cerebrovascular IVIM measures. Conclusions: Variations in retinal arteriolar microvascular function and microcirculatory properties in the brain are linked. The retina could serve as a proxy for early detection of brain microvascular dysfunction.