Retinal microvascular function is associated with the cerebral microcirculation as determined by intravoxel incoherent motion MRI Maud van Dinther a, b, *, Paulien H.M. Voorter c, d, Miranda T. Schram d, e, Tos T.J.M. Berendschot d, f, g, Alfons J.H.M. Houben b, e, Carroll A.B. Webers d, f, Robert J. van Oostenbrugge a, b, d, Walter H. Backes b, c, d, Julie Staals a, b, Jacobus F.A. Jansen c,

a - Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands
b - CARIM - School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
c - Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, the Netherlands
d - MHeNs - School for Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands
e - Department of Internal Medicine, Maastricht University Medical Center, Maastricht, the Netherlands
f - Department of Ophthalmology, Maastricht University Medical Center, Maastricht, the Netherlands
g - NUTRIM – School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, the Netherlands
h - Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands

A B S T R A C T
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 prop­
erties, 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.