Rationale: There are no randomized trials examining the best treatment for acute basilar artery occlusion (BAO) in the 6-24 hour time window.

Aims: To assess the safety and efficacy of thrombectomy for stroke due to BAO in patients randomized within 6-24 hours from symptom onset or time last seen well.

Sample size: For an estimated difference of 20% in proportions of the primary outcome between the two groups, 318 patients will be included for 5% significance and 90% power with a planned interim analysis after 2/3 of the sample size (212 patients) have achieved the 90 days follow-up.

Methods and design: A prospective, multi-center, randomized, controlled, open-label and blinded-endpoint trial. The randomization employs a 1:1 ratio of mechanical thrombectomy with the detachable Solitaire thrombectomy device and best medical therapy (BMT) versus BMT alone.

Study outcomes: The primary outcome will be the proportion of patients achieving modified Rankin Scale (mRS) 0-3 at 90 days. Key secondary outcomes are: dramatic early favorable response, dichotomized mRS score (0-2 versus 3-6 and 0-4 versus 5-6) at 90 days, ordinal (shift) mRS analysis at 90 days, infarct volume at 24 hours, vessel recanalization at 24 hours in both treatment arms, and successful recanalization in the thrombectomy arm according to the modified thrombolysis in cerebral infarction (mTICI) classification defined as mTICI 2b or 3. Safety variables are mortality at 90 days, symptomatic intracranial hemorrhage rates at 24 hours, and procedure related complications.

Discussion: Results from this trial will indicate whether mechanical thrombectomy is superior to medical management alone in achieving favorable outcomes in subjects with acute stroke caused by BAO presenting within 6 to 24 hours from symptom onset.