The research is being done to determine if an investigational drug called "TS23" is safe and effective for the treatment of patients with an ischemic stroke that do not meet the criteria for standard treatments to remove the clot. The best dose of TS23 for these patients is unknown. Prior studies have shown that TS23 works without increasing safety concerns.

The purpose of this research study is to see whether ticagrelor and aspirin or rivaroxaban and aspirin compared to clopidogrel and aspirin will have the most success in preventing another stroke, bleed in the brain, or death in participants who have already had a stroke from a narrowed brain artery.

The purpose of the study is to compare the effects of apixaban (also known as Eliquis®) with aspirin in patients with atrial fibrillation and a recent brain hemorrhage to see which is better in preventing strokes and death.

Subjects will be in the research study for up to 3 years (minimum of 1 year). About 700 people will take part in this study at approximately 125 sites throughout the United States.

This is an ancillary study on the Phase 3 parent trial (CREST-2) in which patients with asymptomatic high grade carotid artery stenosis have enrolled to receive either a novel intensive medical management plan alone, or in combination with either Carotid Endarterectomy (CEA) or Carotid artery stenting (CAS). Patients enrolled in CREST-H will undergo a baseline MRI and some patients will also undergo a followup MRI at 1 year. The purpose is to determine whether cognition can be improved by revascularization among the subset of CREST-2 patients with hemodynamic impairment and mild cognitive impairment at baseline.

CREST-2 is two parallel multi-center randomized, observer-blinded endpoint clinical trials. One trial will assess treatment differences between intensive medical management alone compared to carotid endarterectomy procedure plus intensive medical management. The parallel trial will assess treatment differences between intensive medical management alone compared to carotid artery stenting plus intensive medical management. Intensive medical management will involve control of blood pressure, LDL cholesterol, cigarette smoking, and other vascular risk factors.