Introduction: Endovascular mechanical thrombectomy (MT) has revolutionized our ability to treat the significant cost-of-life associated with large intracranial vessel strokes (1,2). The use of MT in strokes arising from occlusions of distal branches of these vessels, however, is not well-established as these subjects were woefully underrepresented in the original randomized-controlled trials of MT.

Methods: We investigate the safety and efficacy of MT in treating distal circulation (DC) strokes via a direct comparison to MT for proximal circulation (PC) strokes. A retrospective review was conducted of patients presenting with DC and PC strokes who received MT at our tertiary referral center between 2010 and 2018.

Results: Out of 453 patients who were treated with MT, 73 patients had a DC occlusion which most commonly involved the M2 artery (89%, n=68). Most subjects were treated with thrombectomy using combined stent retriever and aspiration (72%, n=55). Mortality rate of DC strokes was 8% (n=6) and independent functional status (modified Rankin Scale<2) was achieved in 59% of patients at three-month follow-up (Figure 1). Rates of mortality and independent functionality were equivocal between proximal and distal stroke cohorts. PC strokes were five-times more likely to demonstrate adequate radiographic revascularization (Thrombolysis in Cerebral Infarction score>2b) compared to DC strokes (OR:5.69, 95% CI:1.22-26.5, p<0.05; Figure 2). Periprocedural complications were comparable between treatment groups though distal embolization was higher in the DC cohort (7% vs. 2%, p<0.05) and symptomatic intracranial hemorrhage was higher in the PC cohort (0% vs. 6%, p<0.05; Figure 3).

Conclusions: Mechanical thrombectomy is a safe treatment option for DC strokes. The beneficial effects of MT on morbidity and mortality arising from DC strokes were comparable to the well-documented outcomes of MT for PC strokes. Though distal intracranial vessels supply small and variable brain regions we demonstrate that the benefits of MT intervention outweigh the risks.

Patient Care: There is a significant unmet need in treating strokes originating from distal branches of intracranial vessels. While mechanical thrombectomy has been established as one of the most effective treatments for acute ischemic stroke in large, proximal intracranial vessels, its efficacy in treating occlusions in distal branches of these same vessels is not well understood. Our research provides data that supports the use of mechanical thrombectomy as a safe and effective procedure in alleviating the mortality and morbidity caused by distal circulation strokes.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of mechanical thrombectomy for treating acute ischemic stroke of distal intracranial vessels. 2) Identify the strengths and weaknesses of treating distal circulation strokes with mechanical thrombectomy. 3) Discuss in small groups the future research that is needed to make mechanical thrombectomy the standard of care for distal circulation strokes.

References: 1.Goyal M, Menon BK, Van Zwam WH, et al. Endovascular thrombectomy after large-vessel ischaemic stroke: A meta-analysis of individual patient data from five randomised trials. Lancet. 2016;387(10029):1723-1731. doi:10.1016/S0140-6736(16)00163-X 2.Saver JL, Goyal M, Bonafe A, et al. Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke. N Engl J Med. 2015;372(24):2285-2295. doi:10.1056/NEJMoa1415061