Cerebral microbleeds and cognition in patients with symptomatic small vessel disease.

Background and Purpose: Cerebral microbleeds (CMBs) are common in cerebral small vessel disease. They may cause cognitive impairment, possibly via white matter tract disruption but previous studies have produced inconsistent results. We determined whether CMB number and location are associated with impaired cognition in symptomatic small vessel disease and whether any association was independent of other magnetic resonance imaging markers of small vessel disease.
Methods: One hundred sixteen patients with lacunar stroke and radiological leukoaraiosis were studied. Neuropsychological assessment was performed. CMBs on gradient echo images were assessed using the Brain Observer Microbleed Rating Scale criteria. Magnetic resonance imaging measures, including diffusion tensor imaging, were also analyzed. Associations between cognitive function and the presence, number, and location of CMBs were determined.
Results: CMBs were present in 46 (39.7%) patients. CMB number correlated weakly with executive function (r=0.22; P=0.022) but not with other cognitive indices. CMBs count in the top decile (≥ 9 CMB, N=12) was more strongly associated with poor executive function; this association remained significant after controlling for T2-lesion load, brain volume, lacune count, and mean diffusivity (b=-0.51; P=0.043).
Conclusions: In symptomatic small vessel disease, CMB number was weakly associated with executive dysfunction. There seemed to be a threshold effect with the association being largely accounted for by an association of impaired executive function with high CMB count. No association of CMBs with other cognitive domains, including processing speed, was found.