Abstract 122: Stroke Patterns And Causative Mechanisms Of Ischemia In Patients With Symptomatic Intracranial Atherosclerotic Stenosis

Abstract

Background/objectives: Putative mechanisms of stroke in intracranial atherosclerotic stenosis (ICAS) include hypoperfusion, artery-to-artery embolism or perforator occlusion, each of which may be characterized by different stroke patterns on neuroimaging. Our aims are to determine: 1) the different stroke patterns in patients with ICAS; 2) the correlation of angiographic factors (collaterals, degree and location of stenosis) with stroke patterns; and 3) if the patterns of recurrent stroke in the same territory are similar to qualifying strokes. Methods: From the WASID dataset, we selected patients with a stroke at baseline who had conventional angiographic information on collaterals (n=136), and patients with a recurrent stroke in the territory during follow-up (n= 47). We categorized stroke patterns as follows: for anterior circulation-subcortical (SC), cortical (C), territorial (T), borderzone (BZ) and multiple (M); for posterior circulation,-subcortical (SC), cortical (C), cerebellar (CB) and multiple (M). We defined an embolic mechanism if C, T, CB or multiple were present. The association between stroke patterns and collateral grade assessment (ASITN/SIR), location and degree of stenosis, and treatment assignment (warfarin vs aspirin) was analyzed using Chi-Square and McNemar’s tests. Results: Anterior circulation patterns (n=72) at baseline were: 14(19%) SC, 5(7%) T, 2(29%) C, 12(17%) BZ and 20(28%) M. All isolated BZ stroke patterns were located in internal borderzone region. BZ pattern was equally distributed among patients with no collaterals (5/40=12%) vs. patients with collaterals (7/32=22%) (p= 0.29) and among patients with moderate (8/43=19%) vs. severe stenosis (4/29=14%) (p=0.59). Posterior circulation patterns (n= 64) at baseline were: 25(39%) SC, 5(8%) C, 10(16%) CB and 24(38%)M. Embolic stroke pattern at baseline was the most frequent (85/136=62.5%). Among patients with a recurrent stroke in the territory (n=47), embolic pattern was also the most frequent (32/47, 68%). The probability of having a recurrent embolic stroke pattern was related to stenosis degree (81% in severe vs 50% in moderate stenosis, p= 0.03), collateral grade (83% with collaterals vs 53% no collaterals, p= 0.09), and previous embolic stroke pattern (74 % who had baseline embolic stroke vs 25% who had baseline non-embolic stroke,p= 0.01). Having a recurrent embolic stroke pattern was not influenced by treatment assignment (67% treated with warfarin vs 69% treated with aspirin, p=0.85). Conclusions: Artery-to-artery embolism seems to be the most frequent mechanism of stroke in ICAS patients and was not modified by antithrombotic treatment. Isolated BZ infarcts were less frequent, and were not related to poor collaterals or more severe stenosis.