Does large vessel occlusion affect clinical outcome in stroke with mild neurologic deficits after intravenous thrombolysis?

BACKGROUND: Large vessel occlusion (LVO) is associated with poor functional outcome in acute ischemic stroke. Given the uncertainty whether LVO has the same significance in mild and severe stroke, we compared functional outcomes after intravenous thrombolysis, based on severity and LVO.

METHODS: Ischemic stroke patients were thrombolyzed in less than 4.5 hours after onset between 2007 and 2013. LVO was defined as occlusion of one of the following arteries: internal carotid, middle cerebral (M1/M2), anterior cerebral (A1), posterior cerebral (P1), basilar, or vertebral (V4) arteries on prethrombolysis computed tomography angiography. Mild stroke was defined as baseline National Institutes of Health Stroke Scale (NIHSS) score 0-6. Favorable outcome was defined as modified Rankin Scale (mRS) score 0-1 at 3 months or equal to the prestroke mRS.

RESULTS: There were 175 acute stroke patients, median age 74 years (interquartile range [IQR], 64-83), median baseline NIHSS = 11 (IQR, 5-16), and 63 of 175 patients (36%) with mild stroke. LVO was associated with worse outcome in severe stroke (age-adjusted odds ratio [OR] of favorable outcome, .42; 95% confidence interval [CI], .19-.93; P = .033) and mortality (age-adjusted OR, 3.52; 95% CI, 1.08-11.48; P = .037). Although the difference in favorable outcome between mild stroke patients with and without LVO was not significant (55.6% vs. 74.1%, P = .262; age-adjusted OR of favorable outcome, .42; 95% CI, .1-1.84; P = .251), the similarity of effects across both subgroups cannot be excluded (LVO-by-stroke severity interaction test, P = .906).

CONCLUSIONS: LVO is associated with worse functional outcome and mortality in severe stroke after intravenous thrombolysis. Although significant association between LVO and outcome in mild stroke was not found, there were similar effects on outcome and a larger study might well confirm a relationship.