In atherosclerosis, cholesterol and other fatty substances collect in arteries, causing narrowing or blockages. Risk factors for atherosclerosis include high blood pressure, diabetes, and high cholesterol levels. The carotid arteries are large blood vessels in either side of the neck that bring blood to the brain. Atherosclerosis-related blockages in the carotid arteries (carotid artery stenosis) can lead to low blood flow to the brain and conditions called transient ischemic attacks (TIAs) or stroke. With a TIA, blockage of blood flow to the brain is temporary and the brain suffers no permanent damage. With a stroke, blockage of the blood flow lasts long enough that a section of brain tissue dies. People who have TIAs or stroke can have problems in their memory and thinking (cognitive impairment). It is unknown whether carotid artery stenosis that is not severe enough to result in a TIA or stroke also cause cognitive impairment.