Mechanism of Stroke According to the Severity and Location of Atherosclerotic Middle Cerebral Artery Disease.

BACKGROUND AND PURPOSE: Strategy for secondary prevention of ischemic stroke depends on the mechanism of stroke. The aim of this study was to compare the stroke mechanism according to the location and severity of middle cerebral artery (MCA) disease.

METHODS: We analyzed acute ischemic stroke patients within 7 days of onset with symptomatic MCA disease. The location of MCA disease was classified into proximal MCA M1 (pMCA) and distal MCA M1/proximal M2 (dMCA). The mechanism of stroke was categorized according to the pattern of ischemic lesion: local branch occlusion, artery-to-artery embolism/hemodynamic infarction, in situ-thrombosis, or a combined mechanism. The mechanism and imaging characteristics of stroke were compared according to the location and severity. The factors associated with the stroke mechanism were also investigated.

RESULTS: A symptomatic MCA disease was observed in 126 patients (74 pMCA and 52 dMCA). The mechanism of stroke differed according to the location (p < 0.001); the combined mechanism was most common in pMCA disease (54.1%), especially in those who presented with MCA occlusion and with a susceptible vessel sign. Artery-to-artery embolism/hemodynamic infarction was most common in dMCA disease (46.2%). A longer length of stenosis was observed in local branch occlusion than in other mechanisms (p = 0.04) and was an independent factor associated with local branch occlusion (OR=1.631, 95% CI=1.161-2.292; p = 0.005).

CONCLUSIONS: The mechanism of stroke differed according to the location of MCA disease: occlusion caused by plaque rupture with combined mechanism of stroke type was predominant in pMCA. Longer length of stenosis was associated with local branch occlusion.