In its early stages, carotid artery disease often doesn't produce any signs or symptoms. The condition may go unnoticed until it's serious enough to deprive your brain of blood, causing a stroke or TIA.

Signs and symptoms of a stroke or TIA include:

• Sudden numbness or weakness in the face or limbs, often on only one side of the body
• Sudden trouble speaking and understanding
• Sudden trouble seeing in one or both eyes
• Sudden dizziness or loss of balance
• Sudden, severe headache with no known cause

Carotid artery disease is caused by a buildup of plaques in arteries that deliver blood to your brain. Plaques are clumps of cholesterol, calcium, fibrous tissue and other cellular debris that gather at microscopic injury sites within the artery. This process is called atherosclerosis.

Carotid arteries that are clogged with plaques are stiff and narrow. Clogged carotid arteries have trouble delivering oxygen and nutrients to vital brain structures that are responsible for your day-to-day functioning.

Factors that increase your risk of carotid artery disease include:

• High blood pressure. Excess pressure on artery walls can weaken them and make them more vulnerable to damage.
• Tobacco use. Nicotine can irritate the inner lining of your arteries. Smoking also increases your heart rate and blood pressure.
• Diabetes. Diabetes lowers your ability to process fats efficiently, placing you at greater risk of high blood pressure and atherosclerosis.
• High blood-fat levels. High levels of low-density lipoprotein cholesterol and high levels of triglycerides, a blood fat, encourage the accumulation of plaques.
• Family history. Your risk of carotid artery disease is higher if a relative has atherosclerosis or coronary artery disease.
• Age. Arteries become less flexible and more prone to injury with age.
• Obesity. Excess weight increases your chances of high blood pressure, atherosclerosis and diabetes.
• Sleep apnea. Spells of stopping breathing at night may increase your risk of stroke.
• Lack of exercise. It contributes to conditions that damage your arteries, including high blood pressure, diabetes and obesity.

Carotid artery disease causes about 10 to 20 percent of strokes. A stroke is a medical emergency that can leave you with permanent brain damage and muscle weakness. In severe cases, a stroke can be fatal.

Carotid artery disease can lead to stroke through:

• Reduced blood flow. A carotid artery may become so narrowed by atherosclerosis that not enough blood is able to reach portions of your brain.
• Ruptured plaques. A piece of a plaque may break off and flow to smaller arteries in your brain. The plaque fragment may get stuck in one of these smaller arteries, creating a blockage that cuts off blood supply to part of your brain.
• Blood clot blockage. Some plaques are prone to cracking and forming irregular surfaces on the artery wall. Your body reacts as if to an injury and sends blood cells that help the clotting process to the area. The result can be a large clot that blocks or slows blood flow to the brain, causing a stroke.