Location of single subcortical infarction due to middle cerebral artery atherosclerosis: proximal versus distal arterial stenosis

Background: Atherosclerotic middle cerebral artery (MCA) disease may produce subcortical infarction either in the upper part (corona radiata, CR) or in the lower area (internal capsule, IC) of the pyramidal tract. The study aimed to see whether the location of MCA stenosis (proximal vs distal) determines the location of subcortical infarction. Methods: 62 consecutive patients who developed an acute (<72 h) infarction either on the CR or IC confirmed by diffusion-weighted MRI due to corresponding focal MCA M1 stenosis assessed by MR angiography were studied. The distance between the MCA origin and the centre of stenotic portion (S) and that between the MCA origin and its bifurcation site (M) were measured. Based on the S/M ratio, stenotic lesions were divided into "proximal' and "distal'. The relationship between the location of arterial stenosis and the location of infarcts was analysed. Results: Thirteen of 31 patients (41.9%) with proximal M1 stenosis had IC lesions, while 26 (83.9%) of 31 patients with distal stenosis had CR lesions (p = 0.025). The S/M ratio in patients with the CR infarcts (mean (SD) 0.65 (0.21) was significantly greater than in those with the IC infarcts (0.48 (0.23)) (p = 0.007). In addition, the National Institutes of Health Stroke Scale score at admission was higher in patients with proximal M1 stenosis than in those with distal stenosis (6 vs 3.5; p = 0.04). Conclusions: The results suggest that perforating arteries arising from the distal M1 segment are related to infarcts involving the upper part of pyramidal tract, while those from proximal segment are related to lower lesions.