Intracranial Hemorrhage After Mechanical Thrombectomy: Proximal Versus Distal MCA M1 Occlusions

Intracranial hemorrhage (ICH) is a recognized complication of mechanical thrombectomy that may affect outcomes. Whether the occlusion site within the MCA M1 segment (proximal vs. distal) influences the risk and subtype distribution of post-procedural ICH remains uncertain. We compared the frequency and subtypes of ICH between proximal and distal MCA M1 occlusions and evaluated their impact on 90-day clinical outcomes.

We retrospectively analyzed consecutive patients from two stroke centers who underwent mechanical thrombectomy for isolated MCA M1 occlusion. Patients were classified as proximal or distal. Post-procedural ICH was assessed on 24-h non-contrast CT (or earlier if NIHSS worsened by ≥ 4 points) and categorized as hemorrhagic infarction (HI, Types 1-2) or parenchymal hematoma (PH, Types 1-2). Ninety-day outcomes were evaluated using the modified Rankin scale (mRS).

Among 178 patients (107 proximal, 71 distal), successful reperfusion (mTICI 2b-3) was achieved in 89.1%. HI was more frequent in proximal than distal occlusions (27.1% vs. 12.6%, p = 0.037), mainly due to HI1 (12.1% vs. 1.4%, p = 0.009). PH and symptomatic ICH rates were similar between groups. In logistic regression analysis, occlusion site was not an independent determinant of post-thrombectomy hemorrhage (OR 1.52, 95% CI 0.80-2.91, p = 0.20). At 90 days, functional outcomes did not differ significantly between groups (mRS 0-2: 39.2% proximal vs. 47.9% distal, p = 0.271).

Hemorrhagic infarction is more frequently observed in proximal MCA M1 occlusions, likely due to involvement of lenticulostriate arteries. However, this does not translate into a worse functional outcome.