TCD is used to initially determine cerebrovascular disease in high-risk patients through non-invasive and radiation-free examinations. If the patient’s blood flow rate increases significantly with murmurs, it suggests the presence of cerebral vascular stenosis. Further CTA or MRA examinations or even cerebral angiography should be performed to confirm the disease and then determine the treatment plan, such as surgery, interventional therapy, or conservative medication. If the blood flow is slowed down, the heart and large blood vessels should be examined to check whether there is any narrowing or occlusion of blood vessels, which leads to insufficient blood supply to the brain.