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. We attempted to see whether the location of MCA stenosis (proximal vs. distal) determines the location of subcortical infarction.
Methods: We studied 62 consecutive patients who developed an acute (< 72 hr) infarction either on the CR or IC confirmed by diffusion-weighted MRI due to corresponding focal MCA M1 stenosis assessed by MR angiography. We measured the distance between the MCA origin and the center of stenotic portion (S) and that between the MCA origin and its bifurcation site (M). Based on S/M ratio, stenotic lesions were divided 'proximal' and 'distal'. The relationship between the location of arterial stenosis and the location of infarcts was analyzed.
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 (0.65±0.21, mean±SD) was significantly greater than in those with the IC infarcts (0.48±0.23) (p=0.007). In addition, the NIHSS 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: Our results suggest that perforating arteries arising from distal M1 segment are related with infarcts involving the upper part of pyramidal tract, while those from proximal segment are related to lower lesions.