M2 vessel occlusion characteristics and outcome after endovascular therapy: A post-hoc pooled analysis of MR CLEAN MED, NO-IV and LATE.

PurposeEndovascular treatment (EVT) of M2-segment occlusions in acute ischemic stroke patients is still under debate. The impact of different M2 vessel occlusion characteristics on the outcomes of EVT remains unclear. We evaluated the association between M2 occlusion characteristics and clinical and safety outcomes following EVT.MethodsThis is a retrospective pooled post-hoc analysis of data from the MR CLEAN MED, MR CLEAN NO-IV and MR CLEAN LATE trials, including patients who underwent EVT for M2 occlusions. We classified M2 occlusions on CTA images by location (proximal/distal), vessel dominance, affected branch (superior/inferior) and hemisphere. The primary outcome was the 24-hour National Institutes of Health Stroke Scale (NIHSS) score. Secondary outcomes included ΔNIHSS, a 90-day modified Rankin Scale (mRS) score, EVT procedural characteristics and safety outcomes. We adjusted for relevant prognostic factors.Results181 patients with endovascular-treated M2 occlusions were included. There were no significant differences in 24-hour NIHSS or ΔNIHSS between proximal and distal occlusions. Ordinal shift analysis of mRS showed similar outcomes for proximal and distal M2 occlusions (cOR 1.32, 95% CI 0.70-2.49). Vessel dominance, affected branch and hemisphere did not significantly influence the NIHSS, ΔNIHSS or 90-day mRS. More symptomatic intracranial haemorrhages were seen in EVT of inferior branch occlusion (9.1% versus 2.1%, p = 0.02).ConclusionIn patients with endovascular-treated M2 occlusions, our study suggests no significant differences in clinical outcomes based on occlusion location, vessel dominance, affected branch or hemisphere; however, confirmation from larger studies is required. Notably, the increased rate of symptomatic haemorrhage in EVT of inferior branch occlusions needs further exploration.