Characteristics of subcortical infarction due to distal MCA penetrating artery occlusion.

Objective: Isolated deep subcortical infarcts develop as a result of occlusion of the penetrating arteries from the internal carotid artery (ICA) and the proximal (M1) and distal middle cerebral artery (MCA). However, the clinical and neuroimaging characteristics of infarcts due to the occlusion of the distal MCA penetrating artery are unclear.
Methods: Consecutive patients with ischemic stroke or transient ischemic attack with magnetic resonance imaging (MRI) performed within 2days of onset were studied retrospectively. Using coronal MRI data, isolated deep subcortical infarcts were classified into two groups: 1) proximal group, described as being longer than they are wide, which were expected to be related to the occlusion of the ICA or M1 penetrating artery; and 2) distal group, described as oblong, which were expected to be associated with the occlusion of penetrating arteries from the distal MCA (M2/M3/M4).
Results: A total of 653 consecutive acute ischemic stroke patients (proximal group, 50 [7.7%]; distal group, 14 [2.1%]) were enrolled. Baseline clinical characteristics were not different between the 2 groups. Modified Rankin Scale scores were lower in the distal group than in the proximal group 3months after stroke onset (1.43±0.36 vs. 2.26±1.35, p=0.023). We measured the lengths of the infarcts in the X and Y directions using axial MRI. The X/Y ratio was larger in the distal group than in the proximal group (1.3±0.6 vs. 0.7±0.2, p<0.01), which indicated that distal MCA penetrating artery infarcts appear more oblong on axial MRI.
Conclusions: One cause for deep subcortical infarction is the occlusion of the distal MCA penetrating arteries, which occurs in 22% of patients with deep subcortical infarctions. These patients had better clinical outcomes than those with ICA and M1 penetrating artery infarctions. Distal MCA penetrating artery infarctions appear oblong on axial MRI.
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