Here I would like to give you a general idea of smog in as simple and easy to understand language as possible. Etiology: The exact cause of smog is still unclear. Those with known causes, such as some atherosclerosis and intracranial vasculopathy caused by leptospirosis, can also cause smoke-like changes in blood vessels on angiographic images, which we call smog syndrome when the cause is known, but it is also commonly referred to as “smog state,” for example, in the United States. The essence of the lesion: smog is a chronic progressive occlusive disease of the cerebral blood vessels of unknown origin. For example, the neurons in our brain, which are responsible for various functions, are like crops in the field, the glial tissue is like the soil, and the cerebral blood vessels are like the irrigation channels. Under normal circumstances, the brain is well irrigated and the crops grow lushly. If the irrigation channels gradually blocked, then it will cause drought, the brain on the “drought”, the crops will lack of water, gradually withered and yellow (ischemia), or even in severe cases directly withered (infarction), this is the process of smog caused by cerebral ischemia and cerebral infarction. But our brain is very “smart”, when the main channel is blocked, it will automatically open some small “secondary channels” to relieve the “drought” downstream as much as possible, these secondary channels are what we see in the angiogram These are the “smoky vessels” we see in angiography. However, these smoke-like vessels are not original, and their walls are very thin and prone to rupture and bleeding. Once they rupture and bleed, they can cause “flooding” in the brain, which can drown crops and affect neurological function. Therefore, smog can cause both cerebral ischemia (drought) and cerebral hemorrhage (flooding). The principle of surgery: Surgery is to connect blood vessels outside the cerebral cortex to the brain. Bridging is to connect the superficial temporal artery outside the skull directly to the cortical vessels inside the skull. It is like drawing water from the Yangtze River to the Yellow River to relieve the drought in the Yellow River basin. A bridge improves the blood supply to the brain directly. Indirect surgery involves attaching muscle and meningeal tissues rich in extra-cortical blood supply to the surface of the cerebral cortex, from which the brain automatically draws blood vessels to form spontaneous anastomoses with the cortical vessels. This process usually takes about 4 months to 6 months. After the blood supply to the brain improves, the need for smoldering blood vessels will gradually diminish and, therefore, indirectly reduce the probability of cerebral hemorrhage. For those crops that have withered, they can usually be restored to life by improving irrigation. Crops that have already died will not help even if irrigation is restored. However, improved irrigation can reduce the risk of other crops dying again. Smoker’s disease often involves the blood supply to both hemispheres of the brain, and bilateral surgery is preferable. Our surgical approach: The 2011 Japanese guidelines for smog disease recommend direct bypass or a combination of procedures including direct bypass for adults, and both direct and indirect procedures for pediatric patients. For adult patients or older children, we use a combination of direct superficial temporal-middle cerebral artery bypass and cerebral-dural-muscular vascular fusion (STA-MCA bypass plus EDMS (first named by us in November 2007, see related literature)), and our patching area is relatively large, because the patching area is like the area of land planted. If you want to get a better harvest, you have to plant a larger area. Intraoperatively, we ensure the integrity of the middle meningeal artery and the deep temporal artery network, and that the cerebral cortex is not damaged. The advantage of this procedure is that the three vascular branches of the external carotid artery (superficial temporal artery, deep temporal artery, and middle meningeal artery) are maximally utilized. Nowadays, there is a saying of “a few hitchhikers and a few stickers” circulating among some patients, which sounds as if the larger the number, the better the effect, but in fact, the larger the number, the greater the damage to the original middle meningeal artery or deep temporal artery vascular network. As for the application of one or two superficial temporal artery branches, it depends on the patient’s capacity, and again, more is not better, and even certain special circumstances (less than 5%) encountered intraoperatively may force us to abandon direct bypass of our own accord: too great a difference in the diameter of the donor-recipient artery, too slender or thin recipient artery. These situations require careful microscopic examination and operator experience to determine, and too much reluctance can increase the risk. In summary, the specific procedure for each patient should be adjusted flexibly according to the actual conditions seen intraoperatively, and it is difficult to determine preoperatively based on DSA or MRI alone. For children under ten years of age, we will make a flexible decision based on the size and vascularity of the child, with an adult procedure for those close to adult size and a brain-dural-muscle vascular fusion for those smaller. Follow-up results show that the superficial temporal artery can form a spontaneous anastomosis with the cortical artery through the bone flap gap even without a direct bypass, relying on the compensatory capacity of pediatric patients greatly exceeding that of adults. The timing of surgery for smoldering disease is very selective, and the best results are achieved when surgery is performed during the stable phase of the disease. In the United States, at Harvard Children’s Hospital and other units, it has been found that children with smog are sometimes treated as emergencies. Some families (especially the young parents of small children) do not listen to the doctor’s advice rationally, but their emotions prevail over their reason, hoping for an unexpected miracle, and delaying the surgery until they are too sick to continue.