Describe the features of a carotid artery dissection.?

Arterial tear: An uncommon cause of stroke, but among younger patients, it is one of the most common. Sometimes spontaneously, sometimes after an activity that involves sudden torsion to the neck, a tear may form along the three layers that constitute the arterial wall. This tear causes turbulent blood flow and predisposes to clot formation. These clots can then cause a stroke by blocking important arteries.

Long smooth stenosis: On arteriography a long smooth stenosis is seen. On cta of the neck, the narrowing and the false lumen ( torn layer of the vessel) are seen. Mra also gives information about age of the dissection and shows the torn layers as cta does.