Pathophysiology
Clinical meaning
Carotid artery dissection (CAD) is a potentially catastrophic vascular condition in which a tear develops in the tunica intima (innermost layer) of the internal carotid artery, allowing blood to enter the arterial wall and create a false lumen (intramural hematoma) between the intimal and medial layers. This intramural hematoma expands within the vessel wall, progressively narrowing the true lumen and reducing cerebral blood flow, or may extend subadventitially to form a pseudoaneurysm. Carotid artery dissection is responsible for approximately 10-25% of ischemic strokes in young and middle-aged adults (under 50 years), making it a critical diagnosis that requires rapid recognition and intervention. The arterial wall consists of three concentric layers: the tunica intima (endothelial cells resting on a basement membrane and internal elastic lamina), the tunica media (smooth muscle cells embedded in an extracellular matrix of elastin and collagen fibers that provide structural integrity and vasomotor tone), and the tunica adventitia (the outermost connective tissue layer containing the vasa vasorum that supply the outer wall). In carotid dissection, the initiating event is a breach of the intimal layer, which can...