Middle Cerebral Artery M2 Occlusions: Impact of Segment Dominance and Benefit of Direct Aspiration for the First-Pass Effect

Background and Purpose: Endovascular thrombectomy (EVT) for acute ischemic stroke (AIS) with M2 segment occlusion of the middle cerebral artery (MCA) is debatable. This study assessed the efficacy, safety, and functional outcomes of EVT in M2 occlusion patients, examining differences in outcomes based on the dominance of the occluded segment (DomM2 vs. Non-DomM2). Methods: A prospective cohort of 108 patients with AIS resulting from M2 segment occlusion of the MCA who underwent EVT was analyzed. We compared demographic, clinical, angiographic, and clinical outcome data (National Institutes of Health Stroke Scale [NIHSS] score at 24 h and modified Rankin Scale [mRS] score at 3 months) between patients with or without DomM2. The primary endpoint was the first-pass effect (FPE), defined as achieving modified Thrombolysis in Cerebral Infarction 2c-3 after one pass. We examined the symptomatic hemorrhagic transformation, 3-month functional outcomes, and mortality rates. Results: Seventy-five patients (69.44%) had DomM2. FPE rates (48.48% for DomM2; 42.66% for Non-DomM2, p = 0.521), final successful recanalization rate, and functional outcomes were comparable between subgroups. Direct aspiration yielded a higher FPE rate (56.25%). FPE was associated with lower NIHSS scores at discharge (median, 2 [interquartile range 0-4] vs. 5 [1-10]; p < 0.001) and higher 3-month functional independence (83.33% vs. 60.34%; p < 0.001). Direct aspiration independently predicted FPE, with a 75% likelihood compared to stent retriever (p = 0.007). Conclusions: EVT is a safe and effective treatment for acute M2 occlusion regardless of the dominance of the M2 segment. Direct aspiration used as a frontline technique increases the likelihood of FPE.