There are two carotid arteries, left and right. The left is a direct branch of the aorta, the right originates from a primary branch of the aorta called the brachiocephalic artery. The artery then divides into the internal and the external carotid artery. The internal carotid artery flows directly to the brain. The external carotid artery supplies the face. This fork is a common site for atherosclerosis, an inflammatory buildup of plaque that can narrow the common or internal carotid artery. The plaque can be stable and asymptomatic, or it can be a source of embolization. Emboli (small pieces of atheroma) may break off from the plaque and travel through the circulation to blood vessels in the brain, blocking these vessels causing ischemia (loss of blood flow). This ischemia can either be temporary giving a transient ischemic attack (small temporary stroke), or permanent resulting in a major stroke. The carotid disease accounts for roughly one-third of all strokes.
Clinically, the risk of stroke from carotid stenosis can be evaluated prior to developing symptoms by a screening carotid ultrasound in at-risk patients. The degree of narrowing plus the presence or absence of symptoms is part of the evaluation. Transient ischemic attacks (TIAs), strokes that last less than 24 hours, are a warning sign. They can be followed by severe permanent strokes, particularly within the first 48 hours. TIAs by definition last less than 24 hours and usually take the form of a weakness or loss of sensation of a limb or the trunk on one side of the body, or loss of sight (amaurosis fugax) in one eye. Less common symptoms are arterial sounds (bruits), or ringing in the ear (tinnitis). Headaches, dizziness, loss of balance are rarely if ever signs of carotid disease. If you meet the criteria for surgery, the most accepted form of treatment is surgical repair by carotid endarterectomy and patch angioplasty. Carotid stenting is available for certain patients and at certain centers. The perioperative stroke rate (risk for stroke as a result of the procedure) for open surgery is roughly 2% and for stenting of its 4%. Although carotid therapy is intended to reduce your risk of the stroke there is a small stroke risk associated with therapy. The risk is lower for patients who have never had a stroke and higher for patients who have had a stroke or have a disease of both arteries.