Investigation of thrombectomy technique for M2 occlusion based on the M1–M2 bifurcation angle

PurposeThe efficacy of mechanical thrombectomy (MT) for M2 occlusion remains uncertain, partly due to recanalization challenges owing to anatomical factors and hemorrhagic complications. This study investigated the best method for M2 occlusion based on the M1-M2 bifurcation angle.MethodsWe retrospectively evaluated the clinical data of 134 consecutive patients with M2 occlusion who underwent MT. The M1-M2 angle was measured between the conterminous (M2) and immediately proximal (M1) vessel segments with respect to the occlusion site. Patients were divided into the acute- and obtuse-angle groups. For each angle, we investigated the stent retriever (SR), contact aspiration (CA), and combined technique (CT) of MT.ResultsThere were 64 and 70 obtuse- and acute-angle cases, respectively. Univariate analysis showed no significant difference in the M1-M2 angle between the groups, but there was a trend toward increased intracranial hemorrhage in the obtuse-angle group (56% vs. 41%, p = 0.09). CA was significantly associated with lower postoperative subarachnoid hemorrhage incidence in the obtuse-angle group (CA vs. SR vs. CT: 9% vs. 39% vs. 50%, p = 0.02). In the acute-angle group, CT was significantly superior in number of passes (CT vs. SR vs. CA: 1.4 vs. 1.8 vs. 2.4, p = 0.03), puncture-recanalization time (48.5 vs. 59.1 vs. 69.4, p = 0.04), and modified first-pass effect (mFPE; 67% vs. 48% vs. 21%, p = 0.01). No association was observed between the first-line technique and clinical outcomes for any angle.ConclusionProcedure results varied according to the M1-M2 bifurcation angle. For treating M2 occlusion, the bifurcation angle should be considered in the choice of technique.