Combination Antithrombotic Treatment for Prevention of Recurrent Ischemic Stroke in Intracranial Atherosclerotic Disease

Inclusion Criteria: 1. Age ≥ 40 years 2. Recent brain ischemia attributed to intracranial atherosclerotic stenosis of 30-99% as evidenced by CT or MR angiography, occurring between 7 to 100 days prior to randomization and consisting of either: 1. a high-risk TIA defined as TIA with motor and/or speech involvement or 2. an ischemic stroke 3. Written informed consent consistent with local regulations governing research in human subjects Exclusion Criteria: 1. Indication for DAPT for \> 90 days on guideline recommendations or investigator ́s judgment; e.g., cardiac stenting. 2. Indication for chronic anticoagulation based on guideline recommendations or investigator ́s judgment; e.g. patient with prosthetic mechanical valve, venous thromboembolism, hypercoagulable state 3. Atrial fibrillation or a history of atrial fibrillation 4. Intracranial arterial occlusion (e.g. 100% stenosis) responsible for the acute brain ischemia 5. Intracranial arterial stenosis secondary to causes other than atherosclerosis 6. Extracranial carotid artery disease ipsilateral to the qualifying brain ischemia with a plan for carotid revascularization 7. Intraluminal thrombus 8. Subdural hematoma within 12 months of randomization 9. Previous spontaneous hemorrhagic stroke (e.g. intracerebral or subarachnoid hemorrhage) 10. Traumatic brain hemorrhage within 1 month of randomization 11. Contraindication for MRI scan (e.g. pacemaker incompatible with MRI) 12. Advanced kidney disease (recent estimated GFR \<30 ml per minute) 13. Modified Rankin Scale (mRS) \>=4 at entry 14. Platelet count less than 100,000/mm3 at enrolment or other bleeding diathesis 15. Uncontrollable hypertension with systolic BP/ diastolic BP consistently above180/100mmHg after treatment 16. Known hypersensitivity to either ASA or rivaroxaban 17. Life expectancy less than 6 months 18. Concomitant use of strong inhibitors of both cytochrome P450 isoenzyme 3A4 (CYP3A4) and P-glycoprotein (P-gp), i.e., human immunodeficiency virus protease inhibitors and the following azole-antimycotics agents: ketoconazole, itraconazole, voriconazole, or posaconazole, if used systemically 19. Female of childbearing potential who are not surgically sterile, or, if sexually active not willing to use adequate contraceptive measures with a failure rate less than 1% per year (e.g., prescription oral contraceptives, contraceptive injections, intrauterine device, double-barrier method, male partner sterilization) before entry and throughout the study, as well as pregnant or breast-feeding women 20. Inability to adhere to study procedures 21. Close affiliation with the investigational site; e.g. a close relative of the investigator, dependent person (e.g., employee or student of the investigational site) 22. Previous randomization to this study or participating in a study with an investigational drug or medical device at the time of randomization 23. Antiphospholipid antibody syndrome