Endovascular Therapy for Isolated M2 Occlusion in Patients with Ischemic Stroke: A Propensity Score-Matched Analysis

Endovascular therapy (EVT) is an established treatment for large vessel occlusion in patients with acute ischaemic stroke; however, its efficacy for medium vessel occlusions, particularly isolated M2 segment occlusions, remains uncertain. As M2 occlusions are relatively proximal among medium vessel occlusions and can cause disabling neurological deficits, clarifying the role of EVT is clinically important. In this study, we aimed to evaluate the efficacy and safety of EVT compared with best medical management (BMM) in patients with acute isolated M2 occlusion using data from a multicentre registry.

We analysed the data of patients from a multicentre stroke registry who had an isolated M2 occlusion, had arrived within 24 h of onset, and were functionally independent before stroke. Data on baseline demographics, vascular risk factors, stroke characteristics, and treatment were collected. Propensity score matching generated 100 well-balanced pairs of EVT- and BMM-treated patients. The primary outcomes were favourable functional outcomes (modified Rankin Scale [mRS] score of 0-2 or 0-1) and mortality at discharge and 3 months. The secondary outcomes included neurological improvement or deterioration and haemorrhagic complications during hospitalisation.

Among 594 eligible patients (EVT, n = 118; BMM, n = 476), data from 100 matched pairs were analysed. At 3 months, good functional outcomes (mRS score of 0-2: 49% EVT vs. 46% BMM) and mortality (7% vs. 9%) were comparable, with consistent findings at discharge. EVT was associated with higher rates of any intracranial haemorrhage (46% vs. 21%), although the symptomatic intracranial haemorrhage rates were identical (5%). In exploratory subgroup analyses, a significant interaction with onset-to-door time was observed for mRS score of 0-2 (p = 0.03), whereas no significant interaction was detected for mRS score of 0-1 or mortality.

In this multicentre registry of patients with isolated M2 occlusion, EVT was not associated with superior functional outcomes or reduced mortality, compared with BMM. Although exploratory analyses suggested possible heterogeneity of treatment effect according to clinical factors, such as time from onset, these findings should be interpreted cautiously. Overall, the results highlight the heterogeneity of M2 occlusions and underscore the need for adequately powered randomised trials to inform individualised treatment decisions.