Endovascular Thrombectomy for Acute Basilar Artery Occlusion: Latest Findings and Critical Thinking on Future Study Design

Abstract

Randomized controlled trials (RCTs) have demonstrated powerful efficacy of endovascular thrombectomy (EVT) for large vessel occlusion in the anterior circulation. The effect of EVT for acute basilar artery occlusion (BAO) in the posterior circulation remains unproven. Here, we highlight the latest findings of observational studies and RCTs of EVT for BAO, with a focus on the predictors of functional outcomes, the limitations of recent RCTs, and critical thinking on future study design. Pooled data from large retrospective studies showed 36.4% favorable outcome at 3 months and 4.6% symptomatic intracranial hemorrhage (sICH). Multivariate logistic regression analysis revealed that higher baseline NIHSS score, pc-ASPECTS < 8, extensive baseline infarction, large pontine infarct, and sICH were independent predictors of poor outcome. Two recent randomized trial BEST (Endovascular treatment vs. standard medical treatment for vertebrobasilar artery occlusion) and BASICS (Basilar Artery International Cooperation Study) failed to demonstrate significant benefit of EVT within 6 or 8 h after stroke symptom onset. The limitations of these studies include slow enrollment, selection bias, high crossover rate, and inclusion of patients with mild deficit. To improve enrollment and minimize risk of diluting the overall treatment effect, futile recanalization and re-occlusion, optimal inclusion/exclusion criteria, including enrollment within 24 h of last known well, NIHSS score ≥ 10, pc-ASPECTS ≥ 8, no large pontine infarct, and the use of rescue therapy for underlying atherosclerotic stenosis, should be considered for future clinical trials.

Endovascular versus Medical Management of Acute Basilar Artery Occlusion: A Systematic Review and Meta-Analysis of the Randomized Controlled Trials

“…Despite a high frequency of ICAD, a subgroup analysis showed no treatment effect modification based on the presence of ICAD with a significant benefit in ICAD-related LVOs [ 19 ]. This is similar to prior studies that showed that, compared to patients without ICAD, patients with ICAD who received rescue treatment achieved similar rates of successful recanalization, favorable outcome, sICH, and mortality at 90 days [ 16 , 39 ].…”

“…The generalizability of these findings need to be considered as three of the trials were completed in China and Asians are known to have high rates of ICAD [ 40 ]. However, as mentioned, prior studies showed that patients with ICAD who received rescue treatment achieved similar rates of successful recanalization and favorable outcome, compared to patients without ICAD [ 16 , 39 , 41 ]. Data on the percentage of ICAD were not available in the BAOCHE trial and we were unable to compare outcomes of patients with ICAD and without ICAD in this meta-analysis.…”

“…ICAD, which is considered a potential cause of EVT failure in acute BAO stroke [ 16 , 38 ], was present in approximately 52% of patients in BEST (56% in the EVT group and 49% in the control group) [ 18 ], in approximately half of the patients in the ATTENTION trial leading to high rates of intracranial angioplasty +/- stenting (39%) [ 19 ], and over half of patients in the BAOCHE trial (intracranial stenting or angioplasty in 54%) [ 20 ]. Despite a high frequency of ICAD, a subgroup analysis showed no treatment effect modification based on the presence of ICAD with a significant benefit in ICAD-related LVOs [ 19 ].…”

“…EVT was reported with good clinical outcomes in acute BAO with rates of favorable functional outcome (modified Rankin Scale [mRS] score 0–3) at 90 days ranging between 32% to 40% in two prospective studies [ 14 , 15 ]. However, these studies were limited by selection bias, unblinded 90-day assessments, and heterogeneous treatment approaches [ 14 - 16 ]. Over the last three years, four randomized controlled studies (RCTs) reached different conclusions regarding the efficacy of EVT in acute BAO stroke [ 17 - 20 ].…”

“…14,15 However, these studies were limited by selection bias, unblinded 90-day assessments, and heterogeneous treatment approaches. [14][15][16] Over the last three years, four randomized controlled studies (RCTs) reached different conclusions regarding the efficacy of EVT in acute BAO stroke. [17][18][19][20] In 2020 and 2021, the BEST (Basilar Artery Occlusion Endovascular Intervention versus Standard Medical Treatment) and BASICS (Basilar Artery International Cooperation Study) trials demonstrated that in patients with BAO, there was equivocal benefit of EVT as compared to medical management (MM).…”