Investigations
Any patient with symptoms suggestive of carotid disease should undergo investigation. Simply listening for the presence of a bruit (a whooshing noise heard over the artery when listening with a stethoscope) is not enough.
Possible investigations include duplex scanning, CT scan, MRI scan and angiography. Of these, duplex scanning is the most widely used because it is not invasive, it is cheap and reliable and can be repeated frequently.
Duplex scanning
This is ultrasound scanning, which gives an image of the artery, combined with doppler which allows blood flow to be measured. Jelly is put on the neck and a probe rubbed over it.
The following picture shows a typical duplex machine. The video shows the image that is obtained. To start with the carotid arteries can be seen with blood flowing in them (these vessels are all normal). Then the doppler component is shown - the blood flow is represented as a graph and allows the measurement of blood speed. Blood flowing through a narrowing gets faster - this can be used to estimate the degree of narrowing (stenosis).
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Duplex scanner |
Video of carotid duplex. Move mouse over it to start. The common carotid is on the right and the internal carotid is on the top. The beginning of this artery is wider and is known as the carotid bulb. |
Angiography
This is used infrequently - only when there is doubt on the duplex. The duplex is not very good at looking at very tight narrowing and may diagnose these as a blockage. Sometimes an angiogram is needed to see if this is really the case. The following picture shows an angiogram with narrowing at the base of the internal carotid artery.
CT and MRI scans
These are not commonly used to look at the arteries. MR angiography is sometimes used to assess a very tight stenosis.
CT scanning is used to image the brain to look for evidence of stroke.
