Impact of First-pass Effect for M2 Segment of Middle Cerebral Artery Occlusion

Although the efficacy of endovascular therapy for large-vessel occlusion is well-established, its effectiveness in the M2 segment of middle cerebral artery occlusion remains uncertain. This study aimed to identify which M2 segment of middle cerebral artery occlusion cases may benefit from endovascular therapy by focusing on the first-pass effect, which refers to patients who underwent endovascular therapy and achieved complete reperfusion after 1 pass. The study analyzed computed tomography perfusion imaging using the Rapid Processing of Perfusion and Diffusion software. In this retrospective study, we analyzed 71 patients with M2 segment of middle cerebral artery occlusion who underwent endovascular therapy after computed tomography perfusion imaging using the Rapid Processing of Perfusion and Diffusion software. The patients were divided into 2 groups: the first-pass effect group (n = 15) and the No first-pass effect group (n = 56). The first-pass effect group showed a significantly higher proportion of patients with a modified Rankin Scale score of 0-2 at 90 days than the No first-pass effect group (80.0% vs. 39.3%; adjusted odds ratio: 12.6, 95% confidence interval: 1.27-125.5). Among Rapid Processing of Perfusion and Diffusion-derived parameters, a median Hypoperfusion Intensity Ratio, an index of collateral status, was significantly lower in the first-pass effect group, with a suggested threshold of <0.22. In patients with M2 segment of middle cerebral artery occlusion, achieving first-pass effect was associated with better neurological outcomes. First-pass effect was more likely when Hypoperfusion Intensity Ratio was ≤ 0.22, suggesting this parameter may guide treatment decisions.