Cerebral Microbleeds and Cognition
Jose Gutierrez, MD, MPH
Patel B, Lawrence AJ, Chung AW, Rich P, MacKinnon AD, Morris RG, et al. Cerebral Microbleeds and Cognition in Patients With Symptomatic Small Vessel Disease. Stroke. 2013; 44: 356-36.
Leukoaraiosis, lacunar strokes, perivascular spaces, and cerebral microbleeds (CMB) are considered markers of brain small vessel disease (SVD). Although sometimes found incidentally, the significance of these MRI finding has been the focus of multiple studies. In this article, Patel et al. explored the association of CMB with cognitive function in a clinical sample of patients with lacunar stroke.
The authors collected demographic, clinical and radiographic data from 116 patients with acute stroke who were admitted to three hospitals in South London. Brain MRI images were analyzed to obtain counts of lacunar strokes and CMB as well as grey and white matter volumes, T2-lesion load, and DTI values. The first analysis included demographic and clinical predictors of the CMB count. They found that markers of other SVD manifestations were the only predictors of CMB. Interestingly, there was trend for greater prevalence of CMB in those taking statins. Using CMB as a continuous variable, the authors did not find any correlation between the cognitive indices included in this study. However, categorizing the CMH count in upper deciles vs. not, there was an association between those with the highest CMB count and impaired executive function. This association remained significant, although with reduced intensity, after controlling for covariates. Although CMB in the basal ganglia and the frontal region were correlated with worse executive function, this association became non-significant after controlling for covariates.
The authors acknowledged important limitations, which include the biased sample used for this study and the limited applicability to other groups. The lack of prospective data hinders inferences about causality. Additionally, the multivariate models did not include cardiovascular risk factors and no mention of reliability measures could be found in the manuscript.
Markers of SVD are frequently found in populations with stroke and in populations with high prevalence of cardiovascular risk factors. Some questions remain unanswered: should markers of SVD be used to improve the cardiovascular risk stratification? Are these markers revelatory of a deleterious interaction between cardiovascular risk factors and reparative mechanisms in the microvasculature? If CMB are proven independent markers of a worse cognitive function, are the mechanisms leading to CMB so unique that would warrant a different approach to the traditional, evidenced-based cardiovascular prevention? This study is an intriguing starting point to broaden the discussion about the implications of these frequent markers of SVD.