Effect of the locations of middle cerebral artery occlusion on outcomes after intravenous thrombolysis in patients with acute ischemic stroke

Objective To investigate the effect of the location of middle cerebral artery (MCA) occlusion on outcomes after intravenous thrombolysis with recombinant tissue plasminogen activator (rtPA) in patients with acute ischemic stroke. Methods The consecutive patients with stroke of acute MCA occlusion treated with rtPA intravenous thrombolysis within 4.5 h after onset were included. The locations of MCA occlusion were divided into either a proximal MCA segment (proximal M1 segment) or a distal MCA segment (distal M1 segment, M2 segment and more distally). Early neurological improvement was defined as National Institutes of Health Stroke Scale (NIHSS) score improvement ≥4 points from baseline or NIHSS 0 point at 24 h after thrombolysis. They were divided into a good outcome group (0-2) and a poor outcome group (3-6) according to the modified Rankin Scale (mRS) scores. Results A total of 70 patients with MCA occlusion were enrolled in the study, including 22 (31.4%) with proximal MCA occlusion and 48 (68.6%) with distal MCA occlusion; 52 (74.3%) with good outcome and 18 (25.7%) with poor outcome. The proportion of atrial fibrillation (χ2=4.541, P=0.033), the NIHSS scores on admission (t=5.192, P=0.026) and 24 h after thrombolysis (t=5.365, P=0.024) in the proximal MCA occlusion group were higher than those in the distal MCA occlusion group. The proportion of early neurological improvement in the proximal MCA occlusion group was significantly lower than that in the distal MCA occlusion group (χ2=9.434, P=0.002), and the incidence of symptomatic intracranial hemorrhage (χ2=9.563, P=0.002) and the mortality rate within 7 d (χ2=14.491, P<0.001) were significantly higher than those in the distal MCA occlusion group. The time from onset to thrombolysis (t=6.346, P=0.014), NIHSS scores on admission (t=4.498, P=0.038) and at 24 h after thrombolysis (t=4.866, P=0.028), and the proportion of proximal MCA occlusion (χ2=18.710, P<0.001) in the poor outcome group were significantly longer or higher than those in the good outcome group. Multivariate logistic regression analysis showed that the proximal MCA occlusion (odds ratio [OR] 14.385, 95% confidence interval [CI] 2.525-81.925; P=0.003), longer time from onset to thrombolysis (OR 12.927, 95% CI 2.624-61.748; P=0.002), higher NIHSS score at 24 h after thrombolysis (OR 3.492, 95% CI 1.027-11.880; P=0.045) were the independent predictors for poor outcome at 90 d. Conclusions There are differences in the outcomes after intravenous thrombolysis in patients with MCA occlusion at different locations. The locations of MCA occlusion, time from onset to thrombolysis, and NIHSS score at 24 h after thrombolysis, and age are the independent predictors for the outcomes after intravenous thrombolysis in patients with acute MCA ischemic stroke. Key words: Stroke; Brain Ischemia; Middle Cerebral Artery; Thrombolytic Therapy; Tissue Plasminogen Activator; Treatment Outcome