Most diagnostic and imaging tests for cerebrovascular disease are designed to detect carotid artery disease (CAD) before it results in a stroke. Unlike hemorrhagic disease, which has symptoms, this form of cerebrovascular disease often progresses for years with no symptoms, and it accounts for about 95 percent of cerebrovascular disease. Tests to detect carotid artery disease include:

• Physical examination. When a stethoscope is placed on the neck an abnormal sound of blood flow may be heard, called a bruit (pronounced: BRU-ee). When the level of atherosclerosis in the carotid arteries is severe a bruit is less common, making it an unreliable test by itself. However, anytime a significant bruit is heard, more tests are necessary to determine the nature and seveity of the condition.
  
  
• Carotid duplex ultrasound. This test refers to the use of ultrasound to generate an image of the carotid arteries in the neck and blood flow through the arteries. This is a highly accurate test when performed by vascular ultrasound technicians who specialize in vascular testing (known as RVTs or Registered Vascular Technicians) and in a laboratory that carries the I.C.A.V.L. accreditation.
  
  Carotid duplex ultrasound has become the most important test in the diagnosis and follow-up of CAD. The test involves lying relatively still in a reclining chair for about 30 minutes. It is noninvasive, requires no medication, is painless and is virtually risk-free. Most vascular specialists use this test without any others (e.g., angiogram, magnetic resonance angiogram, described below). In centers without “full-time” vascular specialists or an accredited ultrasound facility, arteriograms and MRA provide excellent imaging. Procedures and risks involved in cartoid ultrasound are similar to those of an echocardiogram.
  
  
• Carotid angiogram. Before ultrasound was perfected, minimally invasive angiograms (also called arteriograms) were the only way to diagnose and develop a treatment plan for carotid artery disease. They remain highly accurate tests in showing the severity and location of a carotid lesion as well as showing all of the vessels before and after the lesion. This test is primarily used when the physician needs to have an understanding of the vessels beyond the area where the lesion is located. An angiogram involves a catheter, which is inserted through the skin (usually in the groin) and advanced through the blood vessels to the neck area. At that point, a contrast medium (dye) is injected and x-rays are taken to show a picture of the arteries. Though the area being imaged is different, a carotid angiogram is similar in terms of procedures and risks to a cerebral angiogram.
  
  
• Magnetic resonance angiogram (MRA). This type of magnetic resonance imaging (MRI) involves using the natural properties of the blood (e.g. flow direction, water content) to produce images in a scanner. For this test, patients lie flat on a scanner table that goes through a small tunnel where the images are obtained. Some patients may have a difficult time being enclosed in a small space or staying still for the required time. For these patients, a mild sedative may be given or the test may be performed in an open MRI scanner. Patients with pacemakers and other metal implants cannot have a magnetic resonance scan.
  
  This nonivasive or minimally invasive test is appealing for the diagnosis of CAD because it produces images similar to a carotid angiogram, sometimes without using a contrast medium. For that reason it is also very low risk. However, the test may not be able to produce clear images of arteries that have turbulent blood flow, which is common with CAD. This renders the test less accurate than an ultrasound or angiogram. MRA is often used when more information about blood vessels in the brain is needed or to confirm a questionable ultrasound result.
  
  MRA technology is advancing very rapidly and its role in carotid disease may become more prominent in the future as physicians learn how to differentiate different kinds of arterial plaque. However, MRA technology is not available at all medical facilities.
  
  
• Computed tomography arteriography (CT-A). Also known as multi-slice computed tomography (MSCT), this is a relatively new technique that uses a CT scanner to generate pictures of the carotid arteries. The test is nearly identical to a carotid angiogram except that the contrast medium is put into the veins instead of the arteries and therefore has a lower risk of complications. CTA is being studied as a means to detect blockages in the coronary arteries in place of the more invasive cardiac catheterization.

Imaging techniques are also allowing physicians to better describe the characteristics of carotid plaque. For example, many researchers classify plaque as homogeneous or heterogeneous. Homogeneous plaque has a smooth surface and is basically the same texture throughout. Heterogeneous plaque has an irregular surface with areas of hemorrhage. Studies have found that heterogeneous plaque may be prevalent among individuals who have had a stroke or transient ischemic attack.

It is believed that therapy for carotid artery disease will eventually be influenced by such characteristics of carotid plaque, in addition to the degree of narrowing (stenosis) of the carotid artery.