I often encounter patients who say, “Doctor, I’m worried about a brain attack, let’s take a cranial CT for me. After learning that the cranial CT is normal, they feel that everything is fine and they should eat and smoke as usual. Or head CT report cavity infarction is nervous abnormal, in fact, both attitudes are not right. A normal cranial CT only means that you have not had a stroke yet, but it does not tell you whether you are likely to have a stroke in the future and how to prevent it. Many patients have severe atherosclerosis and luminal stenosis in the carotid artery or the arterial ring at the base of the brain, but the cranial CT is completely normal, and even the cranial MRI can be completely normal, so you cannot rest on your laurels just because the cranial CT or cranial MRI is normal. The presence of a luminal infarct on cranial CT, i.e., “lacunar infarction,” indicates that there is a lesion in the microscopic arteries of the brain, which requires attention, but there is no need to be overly anxious. The most important test that should not be overlooked is ultrasound of the cerebral arteries, including carotid ultrasound and TCD, both of which are non-invasive and relatively inexpensive, and can determine whether the carotid arteries and the arterial rings at the base of the brain are smooth and unobstructed. Once the problem is detected by ultrasound, further tests are necessary and then more aggressive medication or even surgical intervention is required to truly prevent stroke. To check for aneurysms or vascular malformations, it is necessary to have an MRI, which can be done to screen for them with MRI non-invasive angiography.