Silent Cerebral Microbleeds on T2*-Weighted MRI

BACKGROUND AND PURPOSE: Gradient-echo T2*-weighted MRI is uniquely sensitive to detect silent, old hemosiderin deposits, but the clinical significance of such "microbleeds" remains to be determined. Therefore, we investigated the incidence and the number of microbleeds among different stroke subtypes and the correlation with stroke recurrence and the severity of leukoaraiosis. METHODS: This study consisted of 213 patients (73.5+/-9.1 years old, 104 men and 109 women), who were classified according to stroke subtypes into atherothrombotic infarction (24 patients), cardioembolic infarction (23 patients), lacunar infarction (66 patients), intracerebral hemorrhage (35 patients), and control (65 patients) groups. Gradient-echo T2*-weighted MRI was performed with a 1.5 T system, and asymptomatic microbleeds were located and counted. RESULTS: The incidence and the number of microbleeds were significantly greater in patients with intracerebral hemorrhage (71.4% and 9.1+/-13.8, respectively) and lacunar infarction (62.1% and 7.4+/-16.1) compared with patients with cardioembolic infarction (30.4% and 2.5+/-5.6), atherothrombotic infarction (20.8% and 0.63+/-1.53), and controls (7.7% and 0.09+/-0.34). There was a correlation between the number of microbleeds and the severity of periventricular hyperintensity (r=0.626, P<0.0001). There was also a correlation between the number of microbleeds and the number of intracerebral hemorrhages (r=0.689, P<0.0001) or lacunar infarctions (r=0.514, P<0.0001). The locations of microbleeds were subcortical white matter (31.8%), thalamus (24.8%), basal ganglia (19.8%), brain stem (12.0%), and cerebellum (11.7%). CONCLUSIONS: The findings suggest that microbleeds on T2*-weighted MRI are an indicator of advanced small artery disease of the brain with an increased risk for bleeding. This result should be taken into consideration when treating patients with stroke, and further studies are required.