Impact of Middle Cerebral Artery Branching Patterns on Mechanical Thrombectomy Outcomes for M1 Occlusion

Anatomical variations in the middle cerebral artery affect outcomes of mechanical thrombectomy in M1 occlusion cases. However, the relationship between middle cerebral artery branching patterns-specifically trifurcation and bifurcation-and mechanical thrombectomy outcomes remains unclear. This study investigated that relationship and attempted to identify optimal mechanical thrombectomy strategies for trifurcation patterns. We retrospectively analyzed patients treated with mechanical thrombectomy for M1 occlusion at our institution between 2019 and 2024. Patients were categorized into bifurcation and trifurcation groups based on middle cerebral artery branching patterns, and differences in outcomes between the groups were analyzed. In the trifurcation group, further analysis compared characteristics between patients with and without successful recanalization, defined as a modified Thrombolysis in Cerebral Infarction score of 2b-3. Among 98 patients (trifurcation, n = 21; bifurcation, n = 77), the trifurcation group showed lower successful recanalization rates (57% vs. 91%, p = 0.001) and higher procedural complication rates, including distal thrombus migration (62% vs. 36%, p = 0.047) and symptomatic intracerebral hemorrhage (38% vs. 14%, p = 0.027), compared with the bifurcation group. A multivariate modified Poisson regression demonstrated that the trifurcation pattern was independently associated with reduced successful recanalization (relative risk = 0.22; 95% confidence interval, 0.09-0.53; p = 0.001). In trifurcation cases, contact aspiration achieved higher successful recanalization rates than the combined technique (100% vs. 44%, p = 0.009). Moreover, in combined technique cases, direct contact between the aspiration catheter and thrombus significantly improved recanalization rates (77% vs. 0%, p < 0.001) without increasing complications. Trifurcation anatomy hindered effective clot engagement by the aspiration catheter because of narrow M2 diameters and large branching angles, resulting in lower successful recanalization rates compared with bifurcation.