My mother's TIA was caused by a narrowing of an artery in the brain, and she was also pretty much told there was nothing to be specifically about that artery because of where it is. I know they changed up some meds to hopefully ward off future problems, but I don't know the details.

What did they tell you about the cancer pathology report on your thyroid? I'd personally be more concerned about that at this point. I would want to know if they are certain they got all of it, if I need further treatment to be sure it is all gone, etc.

I would definitely get my GP to investigate the hospital reports and be sure everything is being addressed. That's where a good GP can be your best ally.