THEDoppler echo or transcranial doppler is a test that allows you to observe the blood circulation about large vessels of the brain (cerebral arterial trunks).

It is an important consideration in the balance sheet of neurovascular diseases.

Why have a transcranial Doppler ultrasound?

Transcranial Doppler is a simple, non-invasive, and painless test that allows you to view the main blood vessels in the brain. It is therefore widely used, especially in emergency departments in neurology and for many indications, among others:

• Evaluation of a head trauma
• diagnosis of a occlusion or stenosis vascular (narrowing) in the brain
• followed by a cerebral embolism
• vascular monitoring during surgery
• monitoring of arteriovenous malformations in the brain
• diagnosis of brain death.

When ultrasound passes through the blood stream, it is possible to study the “Doppler effect”, which makes it possible to determine the speed and direction of the blood flow in the vessels, as well as its character, homogeneous or turbulent (in anomaly, for example).

The Doppler effect is often compared ?? the variations in sound that we hear when a car passes quickly in front of us: the sound seems more acute when the car approaches and then more serious when it moves away, which can allow the vehicle to regain the speed of the vehicle. Likewise, the frequency difference between the ultrasound emitted by the probe and the ultrasound received makes it possible to measure the speed of the red blood cells.

In the case of the transcranial examination, it may be an exclusive Doppler or an ultrasound-Doppler. In the first case, the analysis of the Doppler effect is done acoustically, with a mobile device. In the second case, an image is obtained with a conventional ultrasound device, making it possible to visualize the intracranial vessels, before the Doppler measurement.

The examination is painless and takes place like any ultrasound, using a probe placed on the skin in contact with the area to be explored. Three areas allow ultrasound to enter the skull:

• la temporal pathway : in terms of times
• la occipital tract, on the back of the skull
• la transorbital approach, through the eye

These different routes make it possible to visualize different arteries. The middle cerebral artery, also called the sylvian artery, is the most important from a functional point of view (60% to 70% of cerebral blood flow).

Doppler ultrasound can be used to detect abnormalities in the flow of blood in the blood vessels. In the event of head trauma, in particular, this examination makes it possible to detect the patients most at risk and thus to set up an appropriate monitoring and treatment method, when they arrive at the emergency room.