Cyanosis or necrosis of the fingers is an ischemic symptom of the upper limbs in the clinical manifestations of subclavian artery steal syndrome: the common ones are intermittent dyskinesia, upper limb weakness, pain and sensory abnormalities in that order, and very rarely cause cyanosis or necrosis of the fingers. So how to diagnose the disease clinically? 1, generally more common in males than females, and the age is mostly above 50 years old. It is more common in those with left-sided damage. This may be due to the large angle formed by the left subclavian artery at the beginning of the aorta, which is susceptible to blood flow impulse and causes atherosclerosis. The syndrome may present with neurological symptoms of inadequate vertebrobasilar artery supply and ischemic symptoms of the upper extremities. Symptoms of inadequate carotid artery supply are rare and are seen only in patients with stenosis of the head and arm trunk or bilateral subclavian arteries. The most common symptoms of insufficient vertebral-basilar artery supply are, in order, vertigo, light paralysis of limbs, sensory abnormalities, bilateral visual impairment, ataxia, diplopia, syncope, and, rarely, intermittent claudication, dysphonia, dysphagia, tinnitus, convulsions, headache and mental disorders. Rarely, dropattack may occur, which is an episode of sudden loss of muscle strength in the lower extremities without aura and a fall, which may be unconscious and recover quickly, probably due to ischemia in the region of the medullary vertebral crossings. Generally patients with this syndrome, it does not cause permanent nerve damage. 3.Ischemic symptoms of upper limbs are intermittent dyskinesia, upper limb weakness, pain and sensory abnormalities in order, and rarely cause cyanosis or necrosis of fingers. General signs (1) Blood pressure: The blood pressure of the affected upper extremity is reduced, and the difference in systolic blood pressure between the two upper extremities can be 20-150 mmHg, mostly 20-70 mmHg. From the angiography, the degree of symptoms and the frequency of attacks, the difference in blood pressure is not related to the degree of damaged blood vessel stenosis. (2) Pulse: Most of the radial arteries on the affected side are weakened or absent, and some of the brachial or subclavian artery pulses are also weakened or absent. In addition, the pulses on the affected side are delayed, which is due to the distance from the contralateral vertebral artery to the affected vertebral artery and then to the wrist. (3) Vascular murmur in the supraclavicular region: most systolic murmurs can be heard, and movement of the affected limb may aggravate the murmur.