Location of the Susceptibility Vessel Sign on T2*-Weighted MRI and Early Recanalization within 1 Hour after Tissue Plasminogen Activator Administration

BACKGROUND We have recently reported that the susceptibility vessel sign (SVS) at the proximal portion of the horizontal (M1) middle cerebral artery (MCA) on T2*-weighted MRI is a strong predictor for no early recanalization after intravenous recombinant tissue plasminogen activator (t-PA) therapy. However, it is unclear whether the presence of the SVS at other locations, such as distal M1, the vertical portion (M2) of the MCA, and distal branches (MCA distal), is a predictor for no early recanalization in acute ischemic stroke patients. METHODS The SVS was defined as a hypointense signal of the MCA on T2*-weighted MRI on admission. The locations of the SVS were classified as M1 proximal, M1 distal, and MCA distal. M1 proximal SVS was defined as an SVS at the origin of the M1. M1 distal SVS was any M1 SVS not including the origin of the M1. MCA distal SVS was an SVS further away from M1. Early recanalization was defined as a new appearance of at least one of the distal branches on MRA within 1 h after t-PA therapy. A good outcome at 3 months was defined as a modified Rankin Scale (mRS) score of 0-1. RESULTS Consecutive acute stroke patients admitted to our stroke center and treated with t-PA between October 2005 and October 2012 were enrolled. There were 158 patients [median age, 78 (71-84) years; 84 (53%) males; median National Institutes of Health Stroke Scale score, 16 (10-20)]. Internal carotid artery occlusion was seen in 18 (72%) of the 25 patients with M1 proximal SVS, in 3 (14%) of the 22 patients with M1 distal SVS, in 4 (9%) of the 44 patients with MCA distal SVS, and in 18 (27%) of the 67 patients with No SVS (p < 0.001). Twenty-four (96%) of the 25 patients with M1 proximal SVS had no early recanalization, while 16 (73%) of the 22 patients with M1 distal SVS, 25 (57%) of the 44 patients with MCA distal SVS, and 36 (54%) of the 67 patients with No SVS had no early recanalization (p < 0.001, 0.140, and 0.846, respectively, compared to the patients with No SVS). Multivariate analysis showed that only M1 proximal SVS was significantly associated with no early recanalization (odds ratio 16.80, 95% confidence interval 2.04-138.17, p = 0.009). Among the 95 patients with a premorbid mRS score of 0-1, none (0%) of the 16 patients with M1 proximal SVS, 5 (36%) of the 14 patients with M1 distal SVS, 12 (48%) of the 25 patients with MCA distal SVS, and 13 (33%) of the 40 patients with No SVS achieved a good outcome (p = 0.011, 1.000, and 0.295, respectively, compared to the patients with No SVS). CONCLUSION M1 proximal SVS on T2*-weighted MRI is a strong predictor for no early recanalization, and all patients with it had a poor outcome. However, M1 distal SVS and MCA distal SVS were not predictors for no early recanalization, and half of the patients had a poor outcome.