Narrowing of the carotid artery is generally caused by atherosclerosis – hardening of the arteries with plaque buildup. The affected area is usually the location in the neck where the artery splits into two branches. Your doctor will evaluate the benefits of repair by considering the risk factors involved. A "significant" narrowing of the artery is considered to be 50%, though surgery is generally not performed until the narrowing is greater than 60% or 70%. Your doctor will usually check for narrowing with a Duplex Ultrasound test; an MRI(A) or angiogram may also be useful in the diagnosis. Options for repair include surgery (endarterectomy) or angioplasty/ stenting.