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The sac à mains two vertebral arteries supply the medulla. It is not uncommon for one of the arteries to be hypoplastic. In such instances, occlusion of the sole arterial supply for the medulla may produce ignificant bilateral disturbances. Sometimes, in occlusion of the subclavian arery, proximal to the origin of the vertebral,sacs à mains exercise of the upper limb results in siphoning of blood from the vertebral to the distal part of the subclavian. This retrograde flow of blood from the vertebral artery renders the brainstem ischemic and symptoms of basilar insufficiency develop (subclavian steal syndrome).In occlusions of branches of the vertebral sac en cuir artery supplying the lateral aspect of the medulla s characteristic syndrome called the lateral medullary syndrome occurs (Wallenberg's syndrome). This is perhaps the commonest mode of presentation of vertebral artery occlusion. The resultant neurological features consists of sensory impairment over the face, Horner's syndrome and ataxia on the ipsilateral side, and impaired sacs en cuir pain and temperature sensations on the contralateral side. In addition, vertigo, nausea, vomiting, dysphagia, hoarseness of voice, and hiccups also occur in many cases The anterior branches of the PCA supply the sensory nuclei of the thalamus through the thalamogeniculate branches sacs and parts of the basal ganglia through the thalamoperforate branches. Occlusion of these branches result in characteristic syndromes. Infarction of the thalamus causes severe sensory loss and mild hemiparesis contralaterally. After sometime, sensations begin to return and patient complains vente de sac of pain and hyperpathia. The term hyperpathia indicates an increased threshold to induce pain, but once pain is produced it is severe (thalamic syndrome of Dejerine and Roussy).Infarction of the midbrain results in ipsilateral third nerve palsy and contralateral hemiparesis (Weber's syndrome).sac main Sometimes ataxic tremors on the side of hemiparesis appear (ataxic hemiparesis). Hemiballismus, hemichoreoathetosis or tremors result due to occlusion of the thalamoperforate branches This supplies sac mains the medial surface of the anterior ¾ of the cerebral hemisphere nrl