Lesion patterns and stroke mechanism in atherosclerotic middle cerebral artery disease: early diffusion-weighted imaging study.

BACKGROUND AND PURPOSE Patterns and mechanisms of stroke in patients with atherosclerotic middle cerebral artery (MCA) disease remain unclear. We sought to identify lesion patterns and stroke mechanisms associated with MCA disease using early diffusion-weighted imaging (DWI). METHODS We reviewed 185 acute ischemic stroke patients who had (1) symptomatic lesions located in the unilateral MCA territory on DWI performed within 48 hours of symptom onset, and (2) either corresponding MCA disease, internal carotid artery disease, or cardioembolism. Acute DWI lesion patterns were classified as (1) single (small perforator <2 cm; large perforator > or =2 cm; pial; large territorial; border-zone) and (2) multiple. RESULTS MCA disease was diagnosed in 63 patients, 32 (50.8%) of whom showed multiple lesions. Concomitant perforator and pial infarcts (14/63, P<0.001), concomitant perforator, pial, and border-zone infarcts (9/63, P<0.001), and single small perforator infarcts (12/63, P=0.001) were identified more often in patients with MCA disease than in those with cardioembolism or internal carotid artery disease. Small perforator infarcts were more common in patients with milder stenosis than with severe stenosis or occlusion of MCA (P<0.001). Whether they occurred singly or in addition to other lesions, pial infarcts were identified more often in patients with severe stenosis or occlusion of MCA (P=0.001). CONCLUSIONS Perforating artery infarcts, whether single or occurring in addition to pial or border-zone infarcts, are lesion patterns specific for MCA disease. This suggests that local branch occlusion and coexisting distal embolization may be a common stroke mechanism in patients with MCA disease.