Cerebral artery piracy syndrome is a condition in which the pressure in the distal cerebral artery is significantly reduced due to severe stenosis and occlusion of the aortic arch and nearby large arteries caused by various reasons, and the siphoning effect causes blood flow from other nearby cerebral arteries to reverse to supply the artery with lower pressure to compensate for its blood supply. The blood supply to the stolen cerebral artery is significantly reduced, and the corresponding cerebral tissue becomes ischemic with clinical symptoms, which is called cerebral artery steal syndrome. Clinical manifestations There are 3 types of subclavian artery piracy syndrome When the narrowing or occlusion of the subclavian artery or unnamed artery on one side steals the blood flow from the contralateral vertebral artery due to siphoning, and enters the subclavian artery through the affected side to supply the affected upper limb, symptoms of insufficient blood supply to the vertebrobasilar artery appear during the activity of the affected upper limb, such as episodes of dizziness, rotation of vision, diplopia, unstable walking, unclear speech, difficulty in eating, and fainting. In severe cases, symptoms of internal carotid artery ischemia, such as hemiparesis, numbness and discomfort of the hemianesthesia and dysphonia. Atherosclerosis is the common cause, followed by arteritis. 2. Internal carotid artery piracy syndrome When the internal carotid artery is occluded on one side and the contralateral internal carotid artery is compensated by counterflow, the contralateral ischemic symptoms appear, such as hemiparesis, hemianesthesia and dysphonia; or the vertebrobasilar artery is compensated by counterflow and the symptoms of insufficient blood supply to the vertebrobasilar artery appear, such as episodes of dizziness, rotation of vision, diplopia, unstable walking, unclear speech, difficulty in eating, fainting, etc. 3. Vertebrobasilar artery steal syndrome When the vertebrobasilar artery is significantly narrowed and stenosed or occluded, it can cause the internal carotid artery system to compensate for blood flow and symptoms of internal carotid artery ischemia, such as hemiparesis, numbness and discomfort of the partial body sensation and difficulty in pronunciation. Diagnosis 1. Significant reduction or disappearance of arterial pulsation in the affected upper extremity, blood pressure below 20mHg on the healthy side; 2. Diagnosis can be confirmed by cerebral angiography, which reveals a backflow of contrast into the affected vessel. Treatment Surgery, such as endovascular stenting, vascular bypass surgery, endovascular stripping, etc., can be considered for severe ischemic symptoms.