Many patients diagnosed with smog are very confused: Why do I have smog? I pay close attention to my diet and exercise, but why do I have this disease that I have never heard of? In fact, smog is a rare disease not only in China, but also in the world, and its low incidence determines the lack of public awareness of the disease. Some scholars explain it as congenital, because some smog patients have similar diseases in their families, while others believe it is an acquired cause of this occlusive cerebrovascular disease. Therefore, there is no definite conclusion in the medical community about the cause of smog, so from this perspective, unlike other common diseases that can be prevented, smog is not preventable, but can only wait until it is detected and then receive effective treatment. In some local hospitals, there are also many doctors who do not understand this disease, and because of the limited medical equipment, many patients with smog are missed and misdiagnosed, thus not getting timely and effective treatment for smog. So what are the diagnostic criteria? The first gold standard is DSA, which is a cerebral angiography, and the second is MRA/MRI. If these tests clearly show stenosis or occlusion at the end of the internal carotid artery and/or the proximal end of the anterior cerebral artery and middle cerebral artery, and if an abnormal vascular network can be seen near the stenosis or occlusion, the diagnosis of smog can be confirmed.