Transient ischemic attack (TIA), cerebral infarction and cerebral hemorrhage are the three main clinical symptoms of smog. Adults (mostly over 40 years of age) have essentially a 50/50 split between ischemic and hemorrhagic symptoms. In most of the literature, smog is defined as a chronic progressive rare disease, and broadly speaking it has an ever worsening course. The question that has been on the minds of many people is, at what point does the progression of smog disease stop? Before answering this question, let’s first understand what is smog? Smog is also known as moyamoya disease because it was discovered in Japan. It is caused by progressive narrowing or occlusion of the end and major branches of the internal carotid artery, and in order to relieve the blood supply to the brain, many capillary-like abnormal blood vessels proliferate at the base of the skull, which appear like smoke under cerebral angiography. When it reaches the sixth stage, some patients with smog have formed a good compensatory environment in the brain, and the smog-like vessels in the brain have basically dissipated, so the chance of brain infarction is very small, but they should not be relaxed and should be treated in time. In summary, it is unclear to what extent the symptoms of smog disease will stop developing, and it is recommended to go to a regular hospital for diagnosis and treatment as soon as possible after the body develops symptoms similar to brain infarction. The etiology of smog is complex, and the true cause of its onset is not clear. At present, based on clinicopathological studies, it is tentatively believed that the disease may be related to genetic factors, infection and immune response, but there is still a lack of reliable scientific basis, and the specific cause of the disease still needs to be further studied by medical experts in the future.