1. What type of disease is smog?
It is a chronic developmental, non-inflammatory, cerebrovascular occlusive disease of unknown origin, firstly proposed by two scholars in 1957, characterized by spontaneous progressive occlusion of the internal carotid artery, the anterior cerebral artery and the proximal middle cerebral artery in the bed synapse, and the appearance of a large number of mesh-like collateral vessels in the skull base. These abnormal vessels look like “smoke” on cerebral angiography, so it is named smog disease.
2. What is the incidence of smog?
Smoke disease mainly occurs in Asian countries, with Japan being the most common. It also occurs in various parts of the world and in various ethnic groups. In Japan, the annual incidence rate is 0.35/100,000, and the ratio of men to women is 1:1.7.
3. What are the characteristics of the onset of smog?
There are two peak ages for the onset of smog, 1 – 10 years old and the other is 30 – 40 years old. In Japan, it is more common in women, and in China, it is more common in men, and some patients have family history. The onset of symptoms is mostly bleeding in adults and ischemia or seizures in children.
4. What causes can lead to the onset of the disease?
The etiology and pathogenesis of smog is still inconclusive. It is generally believed to be associated with chronic inflammation of the central nervous system. However, studies have suggested several possibilities.
(1) Genetic factors: 6-10% of patients with smog have a family history of the disease, and the mode of inheritance is polygenic or autosomal dominant with low epistasis. Two familial smog-related loci on chromosome 6 have been successfully localized.
(2) Inflammatory and immune responses: Studies have shown that the vascular histological changes in smog are similar to those caused by other autoimmune lesions that lead to vasculitis, which also suggests that smog may be some kind of immune disease.
(3) In addition, environmental factors also have an impact on the development of the disease. Radiation and some specific infections have been found to be important causes of this disease.
5.What are the clinicopathological changes of smog?
The basic pathological changes of smog disease: the stenotic segment of the internal carotid artery and its branch vessels show endothelial cell hyperplasia, intimal thickening, intravascular elastic plate flexion and thickening, which may break with the progression of the disease, and the proliferation and degeneration of the smooth muscle cells in the middle membrane, leading to the narrowing and even occlusion of the lumen of the vessel.
Due to the stimulation of long-term ischemia, there is an extensive network of abnormal vessels in the ring of Willis arteries and its surrounding trunk arteries with the surrounding cerebral cortex, basal ganglia, thalamus and dura mater. For smoldering neovascularization, the pathology manifests as thin-walled dilated or occluded small arteries due to recent thrombosis or after vessel wall landing, with or without elastic tissue degeneration and fibrosis, meanwhile, tiny aneurysms are often seen in these small arterial networks.
6.What are the clinical manifestations of smog disease?
(1) Smoke disease in adolescents and children: transient ischemic attack and ischemic stroke are the main manifestations. Bleeding is less frequent. Ischemia mainly manifests as reversible neurological dysfunction, sensory abnormalities, seizures or acute hemiparesis, headache, involuntary-like choreographic movements, etc. There is a general decrease in IQ.
(2) Adult patients: Mostly symptoms of cerebral hemorrhage, including intracerebral hemorrhage, ventricular hemorrhage, and subarachnoid hemorrhage. There may be headache, coma, hemiparesis, and sensory impairment. In addition, cerebral ischemia is also a common symptom in committed patients, but the age of ischemia is relatively young.
7.What are the examination means?
Including head CT, MRI and MRA, TCD, DSA examination, etc. Once the diagnosis is confirmed, local cerebral blood flow can also be measured by SPECT to help determine the treatment plan and evaluate the effect of surgery.
8.Diagnostic criteria of smog disease?
The radiological diagnostic criteria for smog disease are
1, stenosis and occlusion of the terminal internal carotid artery and the beginning segments of the middle and anterior cerebral arteries.
2, abnormal vascular network near the occlusion visible in the filling phase of the skull base artery.
3, bilateral involvement. The diagnosis is established when all three of these conditions are met and systemic disease is excluded. If a unilateral lesion is shown, it is considered to be a possible smoker’s disease.