Carotid artery stenosis (atherosclerotic) is a cerebrovascular disease commonly seen in middle-aged and elderly people, which can clinically cause ischemic cerebrovascular diseases such as transient ischemic attack and even cerebral infarction. Atherosclerotic plaque itself can cause arterial stenosis, while cerebral artery embolism caused by microemboli shed from plaque is a more important pathogenic factor. What ischemic cerebrovascular diseases can be caused by carotid stenosis? 1. Transient ischemic attack (TIA): TIA refers to sudden transient neurological impairment caused by focal cerebral ischemia, which recovers within 24 hours after the onset. Clinical manifestations include sudden onset of upper or/and lower limb weakness, temporary limb numbness, transient monocular vision loss, etc. TIA is the golden opportunity for treatment before the occurrence of cerebral infarction. 2.Reversible ischemic neurological impairment (RIND): RIND is the neurological impairment caused by focal cerebral ischemia for more than 24 hours, which can be recovered within several days~3 weeks. 3. Cerebral infarction: It is a general term for ischemic stroke. Cerebral infarction is a focal cerebral ischemia that causes ischemic necrosis of brain tissue, resulting in irreversible neurological deficits such as hemiparesis, hemianesthesia and aphasia. In fact, due to the concept and conditions, a considerable number of TIA patients in China often neglect the necessary systematic examination, which eventually leads to the occurrence of cerebral infarction. Therefore, for patients with TIA that may be caused by carotid artery stenosis, the following examinations should be performed: 1. Carotid ultrasonography: It can initially determine the presence and degree of carotid artery stenosis. 2. 2, Magnetic resonance angiography (MRA): MRA is highly sensitive and specific for carotid stenosis, but the degree of stenosis is often overestimated by conventional MRA. 3.CT angiography (CTA): The three-dimensional images reconstructed by CTA can observe carotid artery stenosis from different directions, levels and angles. 4.Digital subtraction angiography (DSA): DSA is the “gold standard” for the diagnosis of carotid stenosis and is superior to other tests in determining the location, extent, and degree of stenosis. Its disadvantage is that it is somewhat invasive. What can be done to prevent carotid artery stenosis from developing into cerebral infarction? Surgical treatment and medical treatment are generally available. The first treatment is preventive treatment of stroke risk factors such as hypertension, diabetes mellitus and hyperlipidemia, as well as smoking and alcohol cessation and exercise. Surgical treatment aims to remove or stabilize atherosclerotic plaques, improve cerebral ischemia and prevent cerebral infarction. The main methods are: carotid endarterectomy, carotid stenting and intracranial and extracranial artery bypass grafting. 1.Carotid endarterectomy: At present, this technique is mature, and the main indications include: ① Symptomatic carotid stenosis: for symptomatic patients with carotid stenosis ≥ 70%, carotid endarterectomy can reduce the 5-year incidence of cerebral infarction by 16%. (ii) Asymptomatic carotid stenosis: prophylactic treatment of asymptomatic patients with carotid stenosis ≥ 70% will reduce the incidence of cerebral infarction. ③Carotid stenosis with cerebral infarction: the annual recurrence rate of patients with cerebral infarction due to carotid stenosis is 5%-20%, and the 5-year recurrence rate can reach 50%. If carotid endarterectomy is taken after the first cerebral infarction, the annual recurrence rate can be reduced to 2%. 2.Carotid stenting: Since the 1990s, with the development of endovascular interventional technology, carotid stenting has come into being. In North America, Professor Loftus proposed the criteria of “high-risk” patients for stenting, including post-surgical stenosis, post-radiotherapy stenosis, patients with pacemakers, and patients with recent myocardial infarction. 3.Intracranial and extracranial artery bypass surgery: For patients with cerebral ischemia and hypoperfusion who are not treated by internal medicine, individual scholars advocate intracranial and extracranial artery bypass surgery. Intracranial and extracranial artery bypass surgery is to make the blood from the extracranial artery flow into the intracranial artery through the bridging vessel to improve cerebral ischemia.