Frequency and pathogenesis of silent subcortical brain infarction in acute first-ever ischemic stroke.

OBJECTIVES We have often observed silent subcortical brain lesions on CT or MRI in first-ever ischemic stroke, but there is little published information on the relationship of these lesions to stroke subtypes. Here, we describe the incidence of MRI-detected silent subcortical brain lesions, including infarctions and white matter lesions, in a series of patients with first-ever ischemic stroke classified according to stroke subtypes. We also discuss the pathogenesis of these silent subcortical lesions. PATIENTS We evaluated 171 patients with acute first-ever ischemic stroke. METHODS The subjects were divided into three groups: lacunar, atherothrombotic and cardioembolic infarction groups. We evaluated silent subcortical brain infarction (SSBI), enlargement of perivascular space (EPS), and other white-matter lesions using MRI. RESULTS Hypertension was observed in 67.6% of lacunar infarction, 57.1% of atherosclerotic infarction, and 54.1% of cardioembolic infarction. SSBI was more frequently observed in lacunar infarction than the others (lacunar vs. atherothrombotic vs. cardiogenic infarction, 81.5% vs. 44.4% vs. 42.1%, p=0.006). High-grade EPS (grade 2 or higher) was also observed more frequently in lacunar infarction than in the others (lacunar vs. atherothrombotic vs. cardiogenic infarction, 63.3% vs. 24.2% vs. 0%, p<0.001). Scheltens' score of silent subcortical lesions was significantly higher in lacunar infarction than in the others. CONCLUSIONS The frequency of silent subcortical ischemic brain lesions was significantly higher in lacunar infarction than in atherosclerotic or cardioembolic infarction. We suggest that the pathogenesis of silent subcortical ischemic brain lesions is common to that of lacunar infarction, that is, small-vessel vasculopathy.