Thrombectomy for M2 Strokes Outperforms M1 After Propensity Matching — Benefit Concentrated in Moderate-to-Severe Deficits

After propensity matching, M2 occlusion thrombectomy yielded good functional outcome (90-day mRS ≤2) in 51.9% vs 30.8% for M1 (OR 2.32, 95% CI 1.01–5.3; p=0.04), with lower mortality. Benefit concentrated in NIHSS ≥6 — possibly explaining neutral medium-vessel RCT results.

• Retrospective propensity-matched cohort (Top-Gear repository); 171 eligible patients reduced to 52 per group after matching on age, sex, baseline mRS, NIHSS, tPA use, and recanalization passes — small matched sample limits precision.
• Early neurological improvement (ENI) was rare in mild M2 strokes (NIHSS ≤5) but occurred in 75% of moderate and 65.6% of severe M2 cases; among M2 patients with ENI, 64.5% reached mRS ≤2 at 90 days vs only 33.3% of M1 patients with ENI.
• Key limitation: single-repository retrospective design with modest post-matching n; external validity uncertain, and the study cannot exclude residual confounding despite PSM.

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