Henry Barnett showed benefit for patients who had 70% or greater narrowing of the carotid artery with symptoms localizing to that side to have surgery rather than medical management alone. The benefit is overall stroke
rate and death. The risks of surgery are bleeding in the brain, stroke
, infection, and not uncommonly mild facial weakness.
Sorry to hear about your father's overall decline. I can understand how you are looking for anything to potentially make him better.