@brihug This is exactly what happened, and what was explained to, my well-aged father who was 85 at the time he had an endarterectomy. The vascular surgeon told him his right side was fully occluded, and therefore inoperable. The left still had 10% passage, and she offered to bypass that with a vein stripped from his ankle. My dad opted for MAID three weeks ago, but due to failing health with other problems. He continued to invest on line and did very well, so his cognition did not suffer as a result of the one side being fully shut off. Note that there are other smaller arteries running up the back of the neck that an take up some of the needed flow, in addition to the bypassed left side in my Dad's case. So, while it's a distinct and lamentable bummer to lose one carotid's flow, it isn't an end-game catastrophe.