A clot would have probably meant being on
Warfarin. A carotid artery dissection does not directly cause a
stroke, dissection means tear, so what likely happened is that the tear clotted, separated from the injury and traveled to the brain. While BP could make it easier to dislodge the clots your doctor should have discussed the reasons behind the stroke and BP. He must not be on Warfain, since that would need to be checked every couple of weeks to keep his INR within acceptable ranges.