Incompleteness of the Circle of Willis Correlates Poorly with Imaging Evidence of Small Vessel Disease. A Population-based Study in Rural Ecuador (the Atahualpa Project)

BackgroundStudies looking for an association between incompleteness of the Circle of Willis (CoW) and small vessel disease (SVD) markers are scarce and conflicting. We aimed to evaluate this association in an unbiased population-based study conducted in Atahualpa (rural Ecuador).MethodsAtahualpa residents 60 years of age or more were identified during a door-to-door survey and invited to undergo magnetic resonance imaging for identification of SVD markers, including white matter hyperintensities (WMHs), strokes, and deep microbleeds. Magnetic resonance imaging (MRA) was used for classifying the CoW according to the presence or absence of one A1 segment of the anterior cerebral artery or one or both P1 segments of posterior cerebral arteries.ResultsOf 311 eligible persons, 258 were enrolled. Mean age was 70 ± 8 years, 59% were women, and 74% had a poor cardiovascular health (CVH) status. Of these, 172 patients (67%) had WMH, 40 patients (16%) had SVD-related strokes, and 23 patients (9%) had deep microbleeds. MRA revealed a complete CoW in 157 persons (61%). Persons with SVD markers were older than those without markers (P < .0001). A poor CVH status was noted in 79% of persons with at least 1 SVD marker and in 65% of those with no markers (P = .02). Logistic regression models showed no association of incompleteness of the CoW with any marker of SVD—alone or in combination—after adjusting for age, sex, and CVH status.ConclusionsLack of association between incompleteness of CoW and SVD markers suggest that genetically determined variants in the intracranial vasculature are not responsible for the high prevalence of SVD among native South American populations.