Effect of Stenosis Severity on Outcomes After Rescue Stenting for Acute Middle Cerebral Artery Occlusions: a Real-world Multicenter Analysis

PURPOSE: Rescue stenting (RS) can achieve durable recanalization in cases of acute large vessel occlusion due to underlying intracranial artery stenosis (ICAS), but its clinical effects may be influenced by procedural factors. This study aimed to evaluate whether the severity of stenosis affects the outcomes after RS. METHODS: In this multicenter retrospective study, patients with acute middle cerebral artery occlusion and underlying ICAS were divided into two groups based on the treatment they received: mechanical thrombectomy (MT) + RS (n = 172) or MT-only (n = 131). Inverse probability of treatment weighting was used to balance baseline characteristics. We systematically evaluated stenosis thresholds from 40% to 90% to identify the optimal cutoff that best differentiated treatment effects on the 90-day modified Rankin Scale (mRS) score and safety outcomes, including symptomatic intracranial hemorrhage (sICH). RESULTS: A stenosis severity of 75% was identified as the optimal cutoff for effect modification. While RS improved recanalization rates overall, its effect on the 90-day mRS score was beneficial only in patients with > 75% stenosis compared to MT-only (Average Treatment Effect (ATE) -0.98, 95% CI -1.73 to -0.22; p = 0.01). In contrast, it showed a detrimental effect in those with < 75% stenosis (ATE 1.08, 95% CI 0.32 to 1.83; p = 0.005). Furthermore, RS increased the rate of sICH regardless of ICAS severity. CONCLUSIONS: The clinical benefit of RS is contingent on the underlying stenosis severity, providing favorable outcomes in patients with high-grade stenoses only. ICAS severity should also be considered for treatment decisions, though these findings require validation in prospective controlled studies.