OBJECTIVE: To investigate the potential of composite inflammatory markers, including the neutrophil-to-lymphocyte ratio (NLR), in predicting outcomes in patients with posterior circulation large vessel occlusion who underwent mechanical thrombectomy (MT). METHODS: We included patients who underwent MT for posterior circulation large vessel occlusion between February 2016 and December 2021. We then assessed composite inflammatory markers on day 1 post-MT. The primary outcome was the modified Rankin Scale score at 3 months (favorable score: 0-3). The primary safety measure was 3-month mortality. Receiver operating characteristic (ROC) curve analysis determined each marker's predictive values and optimal cutoff values. Multivariable regression analysis assessed the relationship between markers and outcomes. RESULTS: We included a total of 137 patients (median age: 71 years, 26% female, median National Institutes of Health Stroke Scale score: 23). NLR demonstrated the best predictive value for the prognosis of patients with posterior circulation large vessel occlusion who underwent MT. ROC analysis identified an optimal NLR cutoff of 12.5 (area under curve [AUC]: 0.741, 95% CI: 0.652-0.830) for favorable outcomes and 14.1 (AUC: 0.764, 95% CI: 0.662-0.865) for predicting death. Multivariate analysis determined an NLR <
12.5 as an independent predictor of favorable post-MT outcomes (odds ratio [OR]: 10.43, 95% CI: 3.85-28.29, P <
0.001), and NLR <
14.1 as an independent predictor of post-MT survival (OR: 0.09, 95% CI: 0.03-0.25, P <
0.001). CONCLUSIONS: Among the assessed markers, NLR emerged as the strongest predictor of clinical outcomes following MT for posterior circulation large vessel occlusion.