When the internal carotid artery is occluded on one side, it may cause the blood of the contralateral internal carotid artery to flow into the affected side via the anterior communicating artery; or the blood of the vertebral basilar artery to flow into the internal carotid artery via the posterior communicating artery on the same side; thus, the limb on the same side as the occluded vessel may become paralyzed or have sensory impairment, or the clinical manifestations of insufficient blood supply to the vertebral basilar artery, such as hemiplegia, hemianesthesia, aphasia, etc. The treatment of this disease may include endarterectomy, vascular bypass (bypass), intracranial and extracranial arterial anastomosis, etc., to improve the insufficient blood supply. Vasodilators and antihypertensive drugs are contraindicated because they may lead to aggravation of the phenomenon of “blood theft”. In addition, symptomatic treatment can be combined. Vertebral basilar artery theft syndrome: The vertebral artery is a major blood vessel supplying blood to the brain. When it is occluded, especially when both left and right vertebral arteries are occluded, it can generally steal blood from the internal carotid artery system through the vascular network. If the intracerebral vascular network is sound and there is no diffuse disease in the cerebral arteries, the patient may be asymptomatic. If the blood supply of the internal carotid artery itself is faulty and cannot satisfy the “blood theft” of the vertebral artery, the patient may experience symptoms of cerebral insufficiency such as mild hemiparesis and aphasia. Cerebral hemispheric artery blood theft syndrome: this is less common, it can occur in cerebrovascular malformation, brain tumor and cerebral infarction during the acute phase of inappropriate treatment, local brain tissue blood “theft” and produce a series of psychoneurological symptoms. If the “blood theft” phenomenon is recurrent and the symptoms are severe, endarterectomy, endovascular stenting or revascularization are required. It is inappropriate to use vasodilators and blood pressure-lowering drugs to prevent blood theft from worsening.