Mechanism of dissecting aneurysm formation

Lateral and cross-sectional schematic view of the carotid artery.
(A) Aneurysmal dilatation of the vessel related to a hemorrhage between the media and the adventitia (subadventitial dissection).
(B) Communication between the arterial lumen and the dissection cavity or disappearance of the hematoma may lead to the formation of an extraluminal pouch or a fusiform dilatation.