Transcranial Doppler ultrasound, see through cerebrovascular disease

Author: Jia Lingyun, Chief Physician, Xuanwu Hospital, Capital Medical University

Reviewer: Chief Physician of Huayang Capital Medical University Xuanwu Hospital

Aunt Liu has been feeling dizzy and having headaches lately. She refused to go dancing even when her friends asked her to. She is listless all day. Many of her friends are worried about her and asked her to go to the hospital for a checkup.

Aunt Liu went to the hospital to consult a doctor, who recommended a transcranial Doppler ultrasound examination. What is a transcranial Doppler ultrasound? What is so magical about this examination?

1. Transcranial Doppler Ultrasound - Non-invasive Cerebrovascular Examination Method

Transcranial Doppler ultrasound is a noninvasive cerebrovascular examination method. Due to its advantages such as easy operation and non-invasiveness, it has been widely used in clinical practice. It is mainly used to judge and screen diseases related to stroke. It has good diagnostic or monitoring value for both hemorrhagic stroke and ischemic stroke.

Figure 1 Copyright image, no permission to reprint

This examination is particularly suitable for patients whose vascular function changes are inconsistent with vascular structure changes. For example, some patients have severe vascular stenosis, but their cerebrovascular regulation function is good and they do not have related symptoms; some patients have angiography or vascular ultrasound examination results showing no abnormalities in vascular structure, but the actual cerebrovascular function is abnormal. Performing transcranial Doppler ultrasound examinations on these patients can help doctors develop individualized treatment plans and prevent the occurrence of related diseases.

The routine examination sites of transcranial Doppler ultrasound are the patient's temporal window, ocular window and occipital window. The temporal window is the weakest area of ​​the skull and sound waves can easily penetrate it, so the temporal window is the best position to examine the arteries of the cerebral hemisphere; the occipital window is to examine the access path of the patient's posterior circulation vertebral-basilar artery; the ocular window can examine the arterial blood flow signals of the patient's ophthalmic artery and the internal carotid artery located in the intracranial section.

Figure 2 Copyright image, no permission to reprint

2. What are the detection methods of transcranial Doppler ultrasound?

There are two types of transcranial Doppler ultrasound detection methods commonly used in clinical practice.

1. Carbon dioxide vasomotor reactivity test During the examination, the doctor will ask the patient to hold his breath or hyperventilate for a certain period of time to record the changes in the patient's cerebral blood flow, blood pressure and carbon dioxide under different breathing conditions and calculate the patient's breath-holding index. The breath-holding index can reflect the patient's cerebral vascular reserve function.

2. Cerebral blood flow autoregulation function test When the patient lies flat, the dynamic changes of cerebral blood flow under the conditions of blood pressure, electrocardiogram and end-tidal carbon dioxide can be monitored in real time. After data analysis, the parameters of cerebral blood flow autoregulation function are obtained, which can reflect the ability of cerebral blood flow to maintain stability, that is, the ability of cerebral blood flow autoregulation, to a certain extent.

The role of transcranial Doppler ultrasound examination

1. Check the stenosis or occlusion of the intracranial artery and extracranial carotid artery, and determine the compensation of collateral circulation and the location and degree of stenosis. According to the difference in arterial blood flow velocity and spectrum morphology, the intracranial artery can be divided into mild stenosis, moderate stenosis, severe stenosis or occlusion according to the severity of the lesion.

2. Monitoring cerebral blood flow microemboli can detect and quantify the number of microemboli in real time.

3. Performing a bubble test can help diagnose congenital patent foramen ovale or pulmonary arteriovenous malformation, and is suitable for screening patients with headaches and unexplained cerebral infarction.

4. Detect cerebrovascular function. Mainly check the large blood vessels located in the intracranial base arterial ring, and screen for large artery atherosclerotic stenosis and occlusive lesions, moyamoya disease, and arteritis-related large vessel lesions.

5. To evaluate the occurrence, development and changes in cerebral hemodynamics during the treatment and recovery of cerebral vasospasm after subarachnoid hemorrhage.

6. Perform intraoperative monitoring, such as intravascular stent implantation, carotid endarterectomy, vascular bypass surgery, cardiac surgery, etc., to monitor cerebral blood flow and microemboli in real time, and assess the risk of perioperative cerebral embolism, thrombosis, and blood reperfusion injury.

In summary, transcranial Doppler ultrasound has certain value in the diagnosis of cerebrovascular diseases. It is a convenient and non-invasive examination method that can not only diagnose the location and degree of vascular stenosis, but also monitor whether the patient has diseases such as cerebral vasospasm. In addition, the monitoring role of transcranial Doppler ultrasound during surgery cannot be ignored.

Therefore, for many patients who suffer from dizziness and headaches like Aunt Liu in life, doctors will recommend a transcranial Doppler ultrasound examination to rule out cerebrovascular disease.