Inclusion Criteria- Stroke or TIA in the vertebrobasilar territory
- Conventional or CT angiographic demonstration of ≥50% stenosis or occlusion of extracranial or intracranial vertebrobasilar artery
- Symptoms within 60 days of enrollment
- Age 18 and above
- Able to provide informed consent
Exclusion CriteriaNeurologic criteria:
- Major disabling stroke prohibiting the ability to return for follow-up assessment
- Any neurological disease which would confound follow-up assessment
- Any severe co-morbidity condition with less than 12 month life expectancy
- Known cardiac disease associated with cardioembolic risk specifically atrial fibrillation, prosthetic valves, endocarditis, left atrial/ventricular thrombus, cardiomyopathy with EF<25%, cardiac myxoma
- Blood dyscrasias, specifically polycythemia vera, essential thrombocytosis, sickle cell disease
- Non-atherosclerotic disease vertebrobasilar disease including dissection, fibromuscular dysplasia, vasculitis, radiation induced vasculopathy
- Unilateral vertebral stenosis or occlusion
- Unable or unwilling to undergo MRI or cerebral angiography or CTA
- Pregnancy concurrent participation in an interventional trial for treatment of vertebrobasilar disease.
- Renal dysfunction will be exclusionary if it precludes angiography. No subjects will be excluded based upon gender, race, ethnic group, religion or socioeconomic status. Children will not be recruited as atherosclerotic VBD is a condition that affects adults primarily in later life and is not a disease that occurs or is relevant in children.