Do you start aspirin for patients with incidentally found intracranial vertebral stenosis?  

I'm not aware of any clinical trial evidence, but in this scenario, I would probably start with baby aspirin.

I'd start by asking why the MRA (or CTA) was done in this patient if it was found "incidentally". Then, I'd explore the patient's risk factors for cerebrovascular disease regarding primary prevention and whether they're controlled. So, my answer would be to avoid it until proven it is needed as seco...

Usually. Unless I think there's a non-atherosclerotic reason or if I think it's congenital.