Vl carotid bilat post tia found:l internal carotid stenosis 50-79% by velocity. f/u with neck contrast mra, shows nothing normal study! how can it be?

Angio: If there is no obvious source for TIA other than carotids and with two conflicting studies of the carotids , then if it highly suspicious to be carotid in origin then you need to have conventional angiogram ( catheterization ) which is the gold standard or at least a third study with ct angiogram.

Velocity accurate: Most likely accurate ultrasound. Repeat at 6 months. Unlikely a dissection with resolution- but possible. Or increased flow after tia? Would be unusual. Mra has value but some limitations of stenosis measurements.