BACKGROUND: Endovascular treatment (EVT) of stroke with large-vessel occlusion is known to be safe and effective. The effect of EVT for occlusion of medium or distal vessels is unclear.

METHODS: We randomly assigned participants with an isolated occlusion of medium or distal vessels (occlusion of the nondominant or codominant M2 segment of the middle cerebral artery [MCA]; the M3 or M4 segment of the MCA; the A1, A2, or A3 segment of the anterior cerebral artery; or the P1, P2, or P3 segment of the posterior cerebral artery) to receive EVT plus best medical treatment or best medical treatment alone within 24 hours after the participant was last seen to be well. The primary outcome was the level of disability at 90 days, as assessed with the modified Rankin scale score.

RESULTS: A total of 543 participants (women, 44%; median age, 77 years) were included in the analysis: 271 were assigned to receive EVT plus best medical treatment and 272 to receive best medical treatment alone. The median score on the National Institutes of Health Stroke Scale (range, 0 to 42, with higher scores indicating more severe symptoms) at admission was 6 (interquartile range, 5 to 9). Intravenous thrombolysis was given to 65.4% of the participants. The predominant occlusion locations were the M2 segment (in 44.0% of the participants), M3 segment (in 26.9%), P2 segment (in 13.4%), and P1 segment (in 5.5%). In the comparison between EVT plus best medical treatment and best medical treatment alone, no significant difference in the distribution of modified Rankin scale scores was observed at 90 days (common odds ratio for improvement in the score, 0.90; 95% confidence interval, 0.67 to 1.22; P = 0.50). All-cause mortality was similar in the two groups (15.5% with EVT plus best medical treatment and 14.0% with best medical treatment alone), as was the incidence of symptomatic intracranial hemorrhage (5.9% and 2.6%, respectively).

CONCLUSIONS: In persons with stroke with occlusion of medium or distal vessels, EVT did not result in a lower level of disability or a lower incidence of death than best medical treatment alone. (Funded by the Swiss National Science Foundation and others; DISTAL ClinicalTrials.gov number, NCT05029414.).