Abstract T P23: Posterior Circulation CT Angiography Collaterals Predict Outcome of Endovascular Acute Ischemic Stroke Therapy for Basilar Artery Occlusion

Abstract

Background & Purpose: The outcomes of patients with acute ischemic stroke (AIS) due to basilar artery occlusion (BAO) are poor. Endovascular therapy (EVT) improves rates of recanalization. We hypothesized that good collateral patterns by pre-treatment CT Angiography (CTA) would predict favorable outcome after EVT. Methods: We conducted a retrospective chart review of patients presenting with AIS due to BAO in a tertiary care stroke center during a four-year period. BAO was diagnosed by CTA in all cases, who received EVT as standard of care. Admission stroke severity was documented using NIHSS-score. Pretreatment collateral score (CS) for posterior circulation was defined as follows: 0 - no posterior communicating artery (PCOM), 1- unilateral PCOM, 2- bilateral PCOM. Complete recanalization was defined by Thrombolysis in Cerebral Infarction (TICI) scores of 2b or 3. Favorable outcome was defined as modified Rankin Scale score (mRS) of 0-2 at three months. Results: Our study population consisted of 15 AIS patients (age range; 31-84 years, median admission NIHSS-score: 21, range 2-38 points) who underwent EVT. Systemic thrombolysis was administered in 4 patients (27%). Seven of 15 patients (47%) had bilateral PCOMs, while unilateral PCOM was diagnosed in 2 cases (13%). Patients with bilateral PCOMs tended to have less severe stroke (p=0.199) at admission in comparison to patients with absent/unilateral PCOM (median NIHSS-score 18 vs. 28 points). The rate of favorable outcome was higher in patients with bilateral PCOMs (71%) in comparison to patients with absent or unilateral PCOM (0%; p=0.014). Patients with bilateral PCOMs tended to have higher recanalization in comparison with patients with absent/unilateral PCOM (86% vs. 33%, p= 0.076). CONCLUSION: Presence of bilateral PCOMs on pre-treatment CTA is associated with lower baseline stroke severity, higher rates of complete recanalization and favorable outcome in patients with AIS due to BAO who are treated with EVT. Future prospective studies including a larger sample of patients are required to define the potential association of posterior circulation collateral status with favorable outcome in this subgroup of ischemic stroke patients.