Thrombectomy Improves Functional Independence in Medium-Vessel Occlusion Stroke

Addressing Medium-Vessel Occlusions in Acute Ischemic Stroke

While endovascular thrombectomy is the standard of care for acute ischemic stroke from large-vessel occlusion, its utility in medium-vessel occlusions has been a subject of considerable debate [1, 2]. These more distal occlusions account for a large proportion of ischemic strokes, yet evidence from prior trials and meta-analyses has been inconsistent, creating a clinical equipoise [3, 4, 5, 6]. Some analyses suggested a benefit for thrombectomy in anterior circulation medium-vessel occlusions, while others found no clear functional advantage and a heightened risk of hemorrhagic complications [4, 5, 3, 6]. For example, one meta-analysis involving over 1,200 patients reported that thrombectomy was associated with a significantly higher rate of symptomatic intracranial hemorrhage (risk ratio = 3.3, 95% confidence interval: 1.8-5.9, P < 0.01) without a corresponding improvement in functional independence [3]. This uncertainty has left a critical gap in clinical guidance for patients who present with moderate-to-severe deficits from these specific strokes.

Study Design and Patient Cohort

To address this gap, investigators conducted an open-label, randomized trial across 48 centers in China, employing a blinded outcome assessment to minimize evaluation bias. The study enrolled adults presenting within 24 hours of onset of a moderate-to-severe ischemic stroke, defined as a National Institutes of Health Stroke Scale (NIHSS) score of 6 or higher. The NIHSS scale ranges from 0 to 42, with higher scores reflecting greater neurologic impairment. All enrolled patients had strokes confirmed to be caused by an occlusion in a medium cerebral vessel. Participants were randomized in a 1:1 ratio to either endovascular thrombectomy plus standard medical management or medical management alone. The final analysis included 280 patients in the thrombectomy group and 283 in the control group. The cohort's median age was 71 years, 42.8% were women, and the median baseline NIHSS score was 10 (range, 3 to 36), confirming a population with significant neurologic deficits. Consistent with current practice, 36.6% of patients had received intravenous thrombolysis before randomization.

Defining Functional Outcomes and Safety Measures

The trial's primary outcome was initially planned as the overall shift in disability across the 90-day modified Rankin scale (mRS), a standard 7-point scale from 0 (no symptoms) to 6 (death). However, the analysis revealed a violation of the proportional-odds assumption. This statistical finding indicated that the treatment effect of thrombectomy was not uniform across the entire spectrum of disability, making a simple shift analysis potentially misleading. As prespecified in the protocol for such an event, the primary outcome was therefore switched to a more direct, binary measure: functional independence at 90 days. This was defined as achieving an mRS score of 0, 1, or 2, which corresponds to a patient having no significant disability and being able to manage their own affairs without daily assistance. To complete the clinical picture, the study also tracked two critical safety outcomes: the incidence of symptomatic intracranial hemorrhage and all-cause mortality at 90 days.

Thrombectomy's Impact on Functional Independence

The primary analysis demonstrated a clinically and statistically significant benefit for the intervention. At 90 days, 58.6% of patients in the thrombectomy group achieved functional independence (mRS score 0-2). This was substantially higher than the 46.6% of patients in the medical management control group who reached the same milestone. After adjusting for baseline variables, the data showed that patients treated with thrombectomy were significantly more likely to regain functional independence. The adjusted rate ratio for this outcome was 1.24 (95% confidence interval, 1.07 to 1.44; P = 0.004). This result indicates that for every 100 patients treated with medical management alone, treating 100 similar patients with thrombectomy would result in approximately 24 additional individuals achieving functional independence at 90 days, a finding with direct implications for long-term patient autonomy and quality of life.

Safety Profile: Hemorrhage and Mortality

The improved functional outcomes associated with thrombectomy were accompanied by a higher risk of a key complication. The incidence of symptomatic intracranial hemorrhage was 4.7% in the thrombectomy group, more than double the 2.2% incidence observed in the control group. This finding highlights a critical risk-benefit calculation for clinicians considering the procedure. Despite this elevated hemorrhage risk, however, the intervention did not lead to a significant increase in 90-day mortality. The mortality rate was 11.1% in the thrombectomy group compared to 10.2% in the control group. This suggests that while the procedural risk of hemorrhage is increased, it did not translate into a higher overall rate of death within the first three months post-stroke in this trial.

Clinical Implications and Study Context

This trial, known as ORIENTAL-MeVO, provides robust evidence supporting the use of endovascular thrombectomy for a specific and previously uncertain patient population: those with acute ischemic stroke from medium-vessel occlusion and moderate-to-severe neurologic deficits. The findings show that adding thrombectomy to standard medical management leads to a greater likelihood of functional independence at 90 days. Specifically, 58.6% of thrombectomy patients achieved an mRS score of 0-2, compared to 46.6% of controls (adjusted rate ratio, 1.24; 95% CI, 1.07 to 1.44). This benefit must be carefully weighed against a more than twofold increase in the risk of symptomatic intracranial hemorrhage, which occurred in 4.7% of thrombectomy patients versus 2.2% of controls. Importantly, this increased risk did not result in a statistically significant difference in 90-day mortality (11.1% vs. 10.2%). These data offer critical guidance for neurologists and interventionists making treatment decisions for this common type of stroke. The trial was registered as NCT06146790 on ClinicalTrials.gov and was funded by the National Natural Science Foundation of China and the Noncommunicable Chronic Diseases-National Science and Technology Major Project.

References

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2. Nogueira RG, Jadhav AP, Haussen DC, et al. Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct. New England Journal of Medicine. 2017. doi:10.1056/nejmoa1706442

3. Mortezaei A, Al-Saidi N, Taghlabi KM, et al. Endovascular thrombectomy for distal medium vessel occlusion stroke: A meta-analysis of randomized controlled trials.. Neurosurgical review. 2025. doi:10.1007/s10143-025-03835-0

4. Zhang X, Wang L, Chai Z, et al. Endovascular Therapy Versus Nonendovascular Therapy for Acute Ischemic Stroke With Distal Medium Vessel Occlusion: A Systematic Review and Meta-Analysis. Stroke. 2026. doi:10.1161/svin.125.001878

5. Loh EDW, Toh KZX, Kwok GYR, et al. Endovascular therapy for acute ischemic stroke with distal medium vessel occlusion: a systematic review and meta-analysis. Journal of NeuroInterventional Surgery. 2022. doi:10.1136/jnis-2022-019717

6. Chandak V, Raja F, S NH, et al. Abstract 4370746: Efficacy and Safety of Endovascular Therapy for Distal Medium Vessel Occlusion Stroke: A Systematic Review and Meta-Analysis of Comparative Studies. Circulation. 2025. doi:10.1161/circ.152.suppl_3.4370746