Posterior circulation ischemia refers to transient ischemic attack (TIA) of the carotid artery system and cerebral infarction in the posterior circulation. Synonyms include ischemia of the vertebrobasilar system, TIA of the posterior circulation with cerebral infarction, vertebrobasilar artery disease, and vertebrobasilar thromboembolic disease. Given that MRI diffusion-weighted imaging reveals that about half of posterior circulation TIAs have definite infarct changes and the boundary between TIA and cerebral infarction is becoming increasingly ambiguous, it is beneficial for clinical operation to cover posterior circulation TIAs with cerebral infarction by posterior circulation ischemia. 1. Main etiology and pathogenesis of posterior circulation ischemia (1) Atherosclerosis is the most common vascular pathological manifestation of posterior circulation ischemia. The mechanisms leading to posterior circulation ischemia include: large artery stenosis and occlusion causing hypoperfusion, thrombosis and arterial-derived embolism. Atherosclerosis occurs in the beginning and intracranial segments of the vertebral arteries. (2) Embolism is the most common pathogenesis of posterior circulation ischemia, accounting for about 40% of emboli, which mainly originate from the heart, aorta and vertebral basilar artery. The most common sites of embolism are the intracranial segment of the vertebral artery and the distal basilar artery. (3) Penetrating small artery lesions include vitreous lesions, microaneurysms and atherosclerotic lesions at the initiation of small arteries, which preferably occur in the pontocerebrum, midbrain and thalamus. (2) Major risk factors for posterior circulation ischemia Similar to carotid system ischemia, in addition to non-adjustable age, sex, race, genetic background, family history, and personal history, the main factors are lifestyle (diet, smoking, lack of activity, etc.), obesity and various vascular risk factors, the latter including hypertension, diabetes, hyperlipidemia, heart disease, stroke, history of TIA, carotid artery disease and peripheral vascular disease. Cervical spine osteophytes are not the main cause of posterior circulation ischemia: It was previously thought that turning the head and neck could cause the osteophytes to compress the vertebral artery, resulting in posterior circulation ischemia and dizziness/vertigo due to the sensitivity of the vestibular nucleus to ischemia. This model of hypothesis instead of evidence is a major cause of confusion in the diagnosis of inadequate blood supply to the vertebrobasilar artery. In contrast, clinical studies have demonstrated that cervical osteophytes are by no means a major risk factor for posterior circulation ischemia, as there is no significant difference in the degree of cervical osteophytes between middle-aged and elderly populations with or without posterior circulation ischemia, and only vascular risk factors differ; serial dynamic vertebral arteriograms have only seen isolated arterial compression due to osteophytes; Doppler ultrasonography after turning the neck has not been performed between those with or without posterior circulation symptoms The rate of extracranial compression of the vertebral artery did not differ between those with or without posterior circulation symptoms.