cpontis,
thanks for the post.
Its a difficult question. There is a lot of debate over the care of asymptomatic carotid stenosis. There is some data that suggest that carotid revascularization can potentially decrease the risk of stroke. Currently, the debate has increased even more with the advancement of carotid stenting which provides a less invasive option for treating carotid stenosis. Either option needs to be weighed against the risk and benefit of the procedure which would take into account your mothers full medical history.
The stneosis itself isnt probably causing memory loss but might be a marker for previous sroke or intracranial vascualr disease. If you wanted to be evaluated here at the Cleveland Clinic, Drs Jay Yadav, Samir Kapdia, Deepak Bhatt or Chris Bajzer all perform the carotid stenting and would be able to evaluate your mother.
good luck