Is a thrombus in carotid life threatening?

Yes: Thrombus is clot. Most carotid disease is detected as plaque thickening the wall of the artery, and if severe can send small emboli (clots) to the brain causing a stroke or ministroke.The only frank carotid thrombosis I have seen was one day after endarterectomy, eating breakfast one minute, not talking the next. Prompt re-operation brought her back to full function, no deficits.

Stroke Threatening: Atherosclerosis, in the artery walls, starts in childhood, asymptomatic for decades because artery wall thickens & enlarges. Most events & narrowing due to plaque rupture & clots. Primary driver lipoproteins (not cholesterol), blood sugar & BP + others. However, once clot present, high risk of stroke. At the same time most are missed if no symptoms occur & scar down, rarely near totally resolve.