Smoldering disease is a spontaneous unilateral or bilateral progressive occlusive disease of the terminal segment of the internal carotid artery (distal to the siphon) and its major branches, which appears as a network of small vessels on the floor of the brain, acting as a compensatory blood supply. As the disease progresses, the middle cerebral artery, the beginning of the anterior cerebral artery and the basilar artery can be involved. The natural prognosis for smoldering disease is very poor, with 73% of children developing severe neurological deficits or dying within two years, and the prognosis for adults is similar. The clinical manifestations of the pediatric and adult forms are distinct. In children, cerebral ischemia is most common (approximately 81%), with some transient ischemic attacks and 40% reversible ischemic neurological deficits or cerebral infarction. Alternating transient ischemic attacks on the affected side are the characteristic manifestation of smog. Exertion or hyperventilation is often the trigger for the onset of the disease, which may be a decrease in partial pressure of carbon dioxide, causing cerebral vasoconstriction. It can also manifest as seizures, progressive cognitive impairment, and involuntary movements, and generally stabilizes after the age of 10 years. Adult cerebral hemorrhage is more common (about 60%), and 70%-80% of hemorrhages are due to rupture of “smoldering” vessels causing hemorrhage in the basal ganglia, thalamus, or ventricles.