Efficacy of Mechanical Thrombectomy in Medium Vessel Occlusions of the MCA in the Extended Time Window

Background Mechanical thrombectomy (MT) has significantly improved outcomes in acute ischemic stroke (AIS) due to large vessel occlusions (LVOs) up to 24 hours post-onset. The effectiveness of MT for medium vessel occlusions (MeVOs) in the M2 or M3 segments of the middle cerebral artery beyond 6 hours is less investigated. Methods This retrospective study analyzed 80 patients who underwent MT for primary, isolated M2 or M3 segment occlusions between January 2020 and August 2023. Patients were categorized by time from stroke onset to groin puncture into two groups: ≤6 hours (n=61) and >6 hours (n=19). Outcomes assessed included clinical severity (NIH Stroke Scale [NIHSS]), functional outcomes (modified Rankin Scale [mRS]), symptomatic intracranial hemorrhages (sICH), and reperfusion success (modified Thrombolysis in Cerebral Infarction [mTICI] scale). Results Mean onset-to-puncture time was 192±57 minutes for the ≤6 hours group and 611±327 minutes for the >6 hours group. Baseline NIHSS scores were 9.5 (IQR 9) and 7 (IQR 8), respectively (p=0.418). While the NIHSS improvement was greater in the ≤6 hours group (median: −5 vs. −2; p=0.028), both groups showed significant improvement from baseline NIHSS scores (p6 hours group (84.2% vs. 96.7%; p=0.084), with more attempts (2.37 vs. 1.66; p=0.024). Conclusion MT for M2 and M3 segment occlusions in the MCA shows benefits beyond 6 hours from stroke onset, with earlier treatment yielding greater improvement. Extending MT’s treatment window could be valuable for MeVOs in the MCA.