What is transcranial Doppler ultrasound?
The transcranial (through the skull) Doppler ultrasound test uses reflected sound waves—the same used to see the fetus during pregnancy—to measure how blood is flowing through the blood vessels in the brain. The test does not require entering the body (it is noninvasive). Transcranial Doppler ultrasound is often done together with carotid Doppler ultrasound.
How does transcranial Doppler ultrasound work?
Transcranial Doppler ultrasound works the same way as carotid Doppler ultrasound, except it is done on the head instead of the neck. A small hand-held device (called a probe) is placed lightly on your head, where it gives off ultrasound waves that pass into the body and bounce off the arteries and the red blood cells moving through them, like an echo. The echo from the moving blood is detected by the device. A computer converts the echoes into moving images of the insides of the blood vessels in the brain. Colors in the graphs may be used to show the speed and direction of blood flow.
Who might have a transcranial Doppler ultrasound?
The most common use of transcranial Doppler is to perform daily checks in patients who have had sudden bleeding in the space around the brain (subarachnoid hemorrhage) to make sure that the blood vessels in the brain are not constricting (vasospasm). Vasospasm usually appears 3 to 21 days after subarachnoid hemorrhage and can cause another stroke or death.
In patients with blocked-vessel (ischemic) stroke, transcranial Doppler ultrasound is most often used to monitor blood flow during and after procedures such as carotid endarterectomy or carotid stenting. Transcranial Doppler ultrasound can detect blood clots and make sure blood is flowing properly throughout the brain during the procedure. This type of monitoring helps reduce complications.5 The test is convenient to use during and after procedures to reduce stroke risk because it is safe to use continuously, accurately shows blood flow in real time, and is portable, allowing doctors to monitor blood flow at the patient’s bedside.
If you have had a blocked-vessel stroke you may have a transcranial Doppler ultrasound test to determine the location and the amount of narrowing in the blood vessels inside your brain. Other tests such as angiography and MRA can also be used to obtain this information, but ultrasound may be used first because it is fast and easy. Which tests you undergo will depend on the preferences of you and your doctor, the availability of the tests at your hospital, and which treatments you may be eligible for.