Transcranial Doppler Ultrasound Examination-"Monitor" of Cerebrovascular Vessels

Author: Wang Juan, deputy chief physician, Peking University Third Hospital

Reviewer: Fan Dongsheng, Chief Physician, Peking University Third Hospital

The heart has a heart monitor, and blood pressure has a blood pressure monitor. The brain is the main component of the human central nervous system, which controls people's thinking, activities and language, and the cerebral blood vessels are responsible for transporting blood and oxygen to the central nervous system. If there is a problem with the cerebral blood vessels, the consequences will be disastrous.

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So, is there any instrument that can monitor cerebral blood vessels? The answer is yes, that is transcranial Doppler ultrasound (TCD). It is specially invented for cerebral blood flow, and can observe the changes of cerebral hemodynamics and pressure in real time, for a long time and dynamically. It is a monitor to check whether there are abnormalities in cerebral blood vessels.

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1. The main clinical applications of transcranial Doppler ultrasound examination

When screening patients in the outpatient clinic, it can sometimes be used to monitor cerebral blood vessels, thereby detecting lesions in the cerebral blood vessels themselves and whether there are abnormalities in the large blood vessels before the cerebral blood vessels. For example, when a patient has vulnerable plaques in the carotid artery, the plaques that are very easy to fall off will fall off during transcranial Doppler ultrasound examination. In this case, this plaque is a thrombus in the cerebral blood vessels. The sound reflected by the thrombus when encountering the ultrasound beam is different from the sound reflected by normal blood flow when encountering the ultrasound beam. It is a short and sharp whistle. At this time, the transcranial Doppler ultrasound examination can immediately identify this abnormal blood flow sound and display it on the computer screen in the form of a spectrum.

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By monitoring the number of blood clots over a period of time, it is possible to determine the patient's risk of cerebrovascular disease and assist clinicians in formulating appropriate treatment plans.

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2. Unexpected findings from transcranial Doppler ultrasonography

The middle-aged man in front of you suddenly felt weak in his right limbs while carrying heavy objects a few days ago, and the heavy objects on his shoulders fell off. After an MRI examination in the emergency room, he was diagnosed with cerebral infarction.

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The patient was very surprised at the time: "I am in good health and don't have high blood pressure or diabetes. How come I am paralyzed on one side?" The doctor explained: "The transcranial Doppler ultrasound bubble test found that you have a patent foramen ovale (PFO)."

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Normal people transfer nutrients with their mothers through the oval foramen in the heart during the fetal period, and the oval foramen should be closed at about 2 years old. However, the oval foramen of some people is not completely closed, and this abnormal pathway from right to left may cause cerebral infarction. So, what is a "rain curtain" level "PFO"? It was discovered during the transcranial Doppler ultrasound bubble test: activated saline is injected from the elbow vein of the arm. If the oval foramen in the heart is not completely closed and has a "heart", then the super-small gas emboli in the activated saline can enter the cerebral blood vessels through this "heart" with the venous blood. When transcranial Doppler ultrasound is used to monitor the patient's cerebral blood vessels, these artificial "emboli" can be captured. By counting the "emboli" and grading them, the more "emboli", the higher the level, which also means that the "heart" is larger. If there are so many emboli that you can't count them like rain, it is called level IV, that is, the "rain curtain" level. Therefore, having a "heart eye" is not necessarily a good thing. If a blood clot passes through this abnormal hole in the heart and blocks the cerebral blood vessels, it will cause cerebral infarction. In other words, this patient may have a "heart eye" in his heart, but don't worry, you can go to the neurology department for treatment. Neurologists have rich experience in treating this disease, and this patient can just follow the doctor's advice for treatment.