Mechanical Thrombectomy for M2 Segment Occlusion in Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

BACKGROUND: The safety and benefit of mechanical thrombectomy (MT) in the treatment of acute ischemic stroke (AIS) patients with M2 segment middle cerebral artery occlusions remain uncertain.OBJECTIVE: To investigate the benefit of mechanical thrombectomy for M2 occlusion compared with M1 oc-clusion in patients with AIS. -METHODS: The PubMed, Embase, and Cochrane Library databases were searched from inception to April 2021 to identify relevant articles. The main results comprised 90 -day functional independence (modified Rankin Score from 0-2), successful recanalization (thrombectomy in cere-bral infarction [TICI] 2b/3), mortality, and rates of symp-tomatic intracerebral hemorrhage after using modern thrombectomy devices. Odds ratios (ORs) were generated for binary variants. ReviewManager 5.3 software was used.RESULTS: Ultimately, a total of 14 trials were included, with 3454 participants enrolled. MT for M2 occlusion had a higher rate of 3-month functional independence than M1 occlusion, but the difference was nonsignificant (OR: 1.19, 95% confidence interval [CI]: 0.98 to 1.46). The TICI2b/3 scores (OR: 0.71, 95% CI: 0.58-0.88) in M2 oc-clusion were remarkably lower than those in M1. The mortality and symptomatic intracerebral hemorrhage rates were comparable between the 2 groups. When comparing M2 and M1 occlusions, we found that there was no significant difference between stent retriever and aspiration in the modified Rankin Score (0-2) after AIS, but aspiration exerted an eminently higher recana-lization rate with regard to TICI2b/3 (OR: 0.77, 95% CI: 0.61-0.96).CONCLUSIONS: Compared with M1 occlusion, patients with M2 occlusion treated by MT demonstrated similar clinical outcomes in this study. Moreover, there was no difference between stent retriever and aspiration in treat-ing M2 occlusion in terms of functional independence at 90 days. However, aspiration exerted a conspicuously higher recanalization rate in M2 occlusion than in M1 occlusion.