Fractal analysis of retinal vessels suggests that a distinct vasculopathy causes lacunar stroke

Objectives: Lacunar stroke accounts for 25% of all ischemic stroke and may represent the cerebral manifestation of a systemic small vessel vasculopathy of unknown etiology. Altered retinal vessel fractal dimensions may act as a surrogate marker for diseased cerebral vessels. We used a cross sectional study to investigate fractal properties of retinal vessels in lacunar stroke Methods: We recruited patients presenting with lacunar stroke and patients with minor cortical stroke as controls. All patients were examined by a stroke expert and had MRI at presentation. Digital retinal photographs were taken of both eyes. Mono and multifractal analyses were performed with custom written semi-automated software. Results: We recruited 183 patients (17 were excluded with poor photographic quality) leaving 166 patients (86 with lacunar and 80 with cortical stroke). The mean age was 67.3 years (SD 11.5 years). The patients with lacunar stroke were younger but the prevalence of diabetes, hypertension and white matter hyperintensities did not differ between the groups. The mean Dbox (monofractal dimension) was 1.42 (SD 0.02), the mean D0 (multifractal dimension) 1.67 (SD 0.03). With multivariate analysis, decreased Dbox and D0 (both representing decreased branching complexity) were associated with increasing age and lacunar stroke subtype after correcting for hypertension, diabetes, stroke severity and white matter hyperintensity scores. Conclusions: Lacunar stroke subtype and increasing age are associated with decreased fractal dimensions suggesting a loss of branching complexity. Further studies should concentrate on longitudinal associations with other manifestations of cerebral small vessel disease.