Clinical Results of Mechanical Thrombectomy in Middle Cerebral Artery M2 Segment Compared to M1 Segment: A Single-Stroke Center Cohort Study

Abstract

Sufficient evidence has not yet been established for mechanical thrombectomy in middle cerebral artery M2 segment occlusion, unlike in the case of M1 occlusion. This study aimed to compare the treatment results of M2 and M1 segment occlusions in our cases. We retrospectively investigated cases in which mechanical thrombectomy was performed for occlusion of the middle cerebral artery segments M1 and M2 from July 2014 to April 2021. They were divided into cases with M1 segment occlusion (M1 group) and cases with M2 segment occlusion (M2 group), and patient background, preoperative NIHSS, use of rt-PA, treatment time, recanalization rate as TICI score, frequency of intracranial hemorrhage, and modified Rankin scale (mRS) after 3 months were compared. In addition, factors contributing to an mRS 3-6 after three months were examined using logistic regression analysis. During the study period, 128 patients (mean age 75.9 years, male 52.3%) were enrolled in this study, the M1 group was 86 cases (67.1%) in the M2 group and 42 (32.9%). There was no difference in age between the two groups, and the patients in the M2 group were older (74.5 years vs. 78.7 years, P = 0.03). Onset to recanalization time (259.5 minutes vs 235.5 minutes; P = 0.25), recanalization rate (TICI 2b ≤; 89.5% vs 83.3%; P = 0.4) and hemorrhagic transformation (34.9% vs 28.6%; P = 0.24) were no difference. In multivariate analysis, age (OR 1.08, 95% CI 1.03 – 1.13; P<0.01), preoperative mRS (OR 3.53, 95% CI 1.84 – 6.78; P<0.01), hemorrhagic transformation (OR 7.62, 95% CI 2.51 – 23.20; P<0.01) were associated with mRS 3-6 after 3 months and the occlusion arteries were not associated. In mechanical thrombectomy for M2 segment occlusion, the recanalization rate and hemorrhagic complications are equivalent to M1 segment occlusion. In the multivariate analysis, the difference in occluded arteries was not associated with poor prognosis. According to our results, mechanical thrombectomy for M2 segment occlusion appears to be a useful treatment option.