Transcranial Doppler

What is Transcranial Doppler?

Transcranial Doppler (TCD) is a non-invasive ultrasound method used to examine the blood circulation within the brain. This is similair to the well-known carotid ultrasound study that is used to exam the arteries in the neck.

A transcranial Doppler study (TCD) is a safe, painless test that evaluates the blood flow to and in your brain. This test uses high-frequency sound waves that you can’t hear or feel. As the sound waves bounce off blood vessels, information is sent to a computer screen. Analyzing the information helps your doctor look for problems that might keep your brain from  getting enough oxygen.

Your doctor might use a TCD study to assess:

  • Whether arteries are narrowed by plaque (fatty buildup) or by one or more tiny blood clots.
  • Whether anticoagulation medication is working to dissolve blood clots in the arteries
  • Whether arteries have gone into spasm (tightened up).
  • This can happen after an aneurysm (weakened part)of a blood vessel bursts.

The TCD test is also used to monitor blood flow in the brain during surgery or after a head injury.

Why might I need a TCD?

Your doctor might recommend this test if:

  • You have had a stroke or a TIA (mini-stroke), with symptoms such as numbness or weakness, confusion, trouble seeing, headache, or loss of coordination
  • You have had a brain aneurysm
  • You have frequent migraines (very bad headaches)
  • You have unexplained blood clots in your system
  • You have unexplained low blood oxygen levels
  • You have had a head trauma
  • You are having surgery that can affect blood flow to the brain

What happens during a TCD study?

A TCD study takes about an hour. Here’s what happens:

  • Getting ready: You’ll either lie down on a padded exam table or sit in a chair. The technician will prepare the area to be tested by putting a small amount of gel on the skin.
  • During a TCD study that looks for blood vessel narrowing or spasms, the technician will move a hand-held device called a transducer on your skin. Depending on what the  doctor is looking for, the test will include one or more of the areas below.
    ––The sides of your head above your ears
    –– Under your chin
    ––The hollows in the back of your neck (you’ll sit or lie on your side and hold your head down)
    –– On your closed eyelids (don’t worry — the gel won’t hurt your eyes, and the transducer is moved very lightly over the skin)
  • During a TCD study that looks for tiny blood clots, the technician will hold a transducer against your head (or you will wear a headset) and the technician will listen to the  arteries inside your brain for up to an hour.

What happens after the test?

After either type of test, here’s what happens:

  • Preparing to leave. The gel will be wiped off. If you had an IV, it will be removed.

Getting the results. Your doctor will analyze the test. You’ll get the results in a later appointment. Potential benefits Risks and potential complications Alternatives A TCD

  • Identify whether spasms, clots, or plaque are blocking blood flow to the brain
  • Identify whether you have an abnormal opening inside your heart TCDs and bubble studies are very safe.

Risks include:

  • Minor pain or infection at the IV site (during a bubble study)
  • Stroke or blood clot in the lungs (extremely rare)

Alternatives to TCD may include:

  • MRI, CT scan

Talking with your doctor about the test

The listsbelow are the most common potential benefits, risks and alternatives for TCD and bubble studies, but other benefits or risks may apply in your unique medical situation.  Talking with your doctor is the most important part of learning about the test. If you have questions, be sure to ask.

Potential Benefits:

A TCD study can:

  • Identify whether spasms, clots, or plaque are blocking blood flow to the brain
  • Identify whether you have an abnormal opening inside your heart

Risks and potential complications:

TCDs are very safe.

Risks include:

  1. Minor pain or infection at the IV site (during a bubble study)


Alternatives to TCD may include:

  • MRI, CT scan

Indications for a TCD ultrasound examination of children and adults include but are not limited to:

1. Evaluation of sickle cell disease to determine stroke risk.​

2. Detection and follow-up of stenosis or occlusion in a major intracranial artery in the circle of Willis or vertebrobasilar system, including monitoring and potentiation of thrombolytic therapy for acute stroke patients.​​

3. Detection of cerebral vasculopathy.​

4. Detection and monitoring of vasospasm in patients with spontaneous or traumatic subarachnoid hemorrhage.​

5. Evaluation of collateral pathways of intracranial blood flow, including after intervention.​

6. Detection of circulating cerebral microemboli or high-intensity transient signals (HITS)​

7. Detection of right-to-left shunts.​

8. Assessment of cerebral vasomotor reactivity (VMR).​

9. As an adjunct to the clinical diagnosis of brain death.​

10. Intraoperative and periprocedural monitoring to detect cerebral thrombosis, embolization, hypoperfusion, and hyperperfusion.​

11. Assessment of arteriovenous malformations, before and after treatment.​

12. Detection and follow-up of intracranial aneurysms.​

13. Evaluation of positional vertigo.

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