Neurovascular Ultrasound: Carotid and Transcranial Doppler Diagnostic Test
Carotid and transcranial Doppler are key tests used to evaluate patients who have had strokes or transient ischemic attacks (TIAs, or "mini strokes") or who are at risk for stroke. The Neurovascular Ultrasound Laboratory uses state-of-the art equipment to assess blood flow to the brain by ultrasound (a non-invasive method that measures blood flow and images blood vessels with high-frequency sound waves). These studies help to detect blood flow problems that can cause strokes in patients with prior stroke or TIAs or patients with cardiovascular risk factors — such as hypertension, high cholesterol, coronary artery disease, vascular disease, diabetes, and smoking — which also increase the risk of stroke.
Neurovascular ultrasound tests include:
- Carotid (extracranial) Doppler ultrasound, which is used to scan the carotid arteries in the front of the neck. These blood vessels can become blocked (occluded) or narrowed (stenotic) by atherosclerosis, raising a person's risk of stroke and TIAs. People with blocked or narrowed carotid arteries who have an elevated risk of stroke or TIA can be treated medically or surgically to enlarge the opening inside the artery and enhance the flow of oxygen-rich blood to the brain, reducing their risk of stroke.
- Transcranial Doppler (TCD) ultrasound is used to examine the arteries inside the skull to check for blockages and to assess the amount of blood flowing toward the brain.
Several specialized types of TCD are done in the Weill Cornell Neurovascular Ultrasound Lab to address specific issues that are important in some patients who have had a stroke or who are at risk for stroke:
- TCD can detect certain types of heart and lung problems that cause strokes, such as an abnormal opening between chambers of the heart (for example, a patent foramen ovale, or PFO). TCD can identify conditions in which clots that form in the legs or elsewhere in the body can bypass the lungs, which normally filter them out, and pass instead directly through the heart to arteries in the brain to cause a stroke. To look for these conditions, a TCD bubble study is performed to see if microscopic bubbles injected into a vein reach the arteries that supply the brain.
- A TCD emboli detection study is performed to detect and monitor tiny blood clots, also known as emboli, which travel from the heart or from arteries in the chest or neck and can cause strokes by lodging in the arteries that supply blood to the brain.
- Finally, a TCD vasoreactivity study can help to determine if blockages in the carotid arteries are so severe that they prevent the normal changes in blood flow that occur in reaction to different breathing patterns. Patients who do not have these normal reactive changes are likely to be at increased risk of stroke.
In all of these ultrasound studies, a small probe (about one-half inch in diameter) is placed on the patient's skin over the arteries to assess blood flow noninvasively. A small amount of gel is placed between the probe and the skin to create a smooth contact. The tests are all performed by Registered Vascular Technologists who have specialized training in these methods, and the tests are interpreted by neurologists with special expertise in stroke and neurovascular ultrasound