As long as a patient has ONE carotid artery
open, they can live a long, normal life with a completely closed carotid artery. The body can send blood to the brain through the open carotid artery as well as the vertebral artery
The blockage in the closed artery quickly becomes "set" and won't move.
When the artery FIRST closes, the patient may have a stroke
or a TIA
Most vascular surgeons won't operate on an occluded carotid artery. The risk of causing a stroke from the surgery is very high.