Symptomatic spontaneous internal carotid artery dissection is responsible for up to 20% of strokes in patients under age 45 years. A carotid artery dissection occurs when arterial walls separate and create a false lumen. Risk factors include neck trauma, recent infection, family history, smoking, hypertension, oral contraceptives, migraine headaches, and connective tissue disease. Dissections can produce local pain, facial paralysis, and pupillary defects. Treatment includes anticoagulation and, in the event of pharmaceutical failure or recurrence, surgery.