BACKGROUND: In patients with acute ischemic stroke caused by a proximal 
intracranial arterial occlusion, intraarterial treatment is highly effective for 
emergency revascularization. However, proof of a beneficial effect on functional 
outcome is lacking.
METHODS: We randomly assigned eligible patients to either intraarterial 
treatment plus usual care or usual care alone. Eligible patients had a proximal 
arterial occlusion in the anterior cerebral circulation that was confirmed on 
vessel imaging and that could be treated intraarterially within 6 hours after 
symptom onset. The primary outcome was the modified Rankin scale score at 90 
days; this categorical scale measures functional outcome, with scores ranging 
from 0 (no symptoms) to 6 (death). The treatment effect was estimated with 
ordinal logistic regression as a common odds ratio, adjusted for prespecified 
prognostic factors. The adjusted common odds ratio measured the likelihood that 
intraarterial treatment would lead to lower modified Rankin scores, as compared 
with usual care alone (shift analysis).
RESULTS: We enrolled 500 patients at 16 medical centers in The Netherlands (233 
assigned to intraarterial treatment and 267 to usual care alone). The mean age 
was 65 years (range, 23 to 96), and 445 patients (89.0%) were treated with 
intravenous alteplase before randomization. Retrievable stents were used in 190 
of the 233 patients (81.5%) assigned to intraarterial treatment. The adjusted 
common odds ratio was 1.67 (95% confidence interval [CI], 1.21 to 2.30). There 
was an absolute difference of 13.5 percentage points (95% CI, 5.9 to 21.2) in 
the rate of functional independence (modified Rankin score, 0 to 2) in favor of 
the intervention (32.6% vs. 19.1%). There were no significant differences in 
mortality or the occurrence of symptomatic intracerebral hemorrhage.
CONCLUSIONS: In patients with acute ischemic stroke caused by a proximal 
intracranial occlusion of the anterior circulation, intraarterial treatment 
administered within 6 hours after stroke onset was effective and safe. (Funded 
by the Dutch Heart Foundation and others; MR CLEAN Netherlands Trial Registry 
number, NTR1804, and Current Controlled Trials number, ISRCTN10888758.).