tailieunhanh - LAST MINUTE EMERGENCY MEDICINE - PART 6

Lưu thông phía sau, có nguồn gốc từ động mạch đốt sống, chịu trách nhiệm cho 20% còn lại của lưu lượng máu não. Các vùng được cung cấp: thân não, tiểu não, đồi thị, các trung tâm thính giác và tiền đình, cũng như các thùy trung gian thời gian | STROKE 297 The posterior circulation originating from the vertebral arteries is responsible for the remaining 20 of cerebral blood flow. The following regions are supplied brainstem cerebellum thalamus the auditory and vestibular centers as well as the medial temporal lobe and the visual occipital cortex. The anterior and posterior circulations communicate via the circle of Willis. When vessel occlusion occurs cerebral blood flow diminishes. A range of neuronal changes occurs from electrical silence to cell death. The extent and severity of a stroke depend on duration and degree of diminishment of cerebral blood flow to the affected region as well as the collateral flow to that region. Four major types of ischemic CVAs have been identified Thrombotic Intracranial thrombosis of large arteries especially at branch points. Etiologies include atherosclerosis dissection hemoglobinapathies and fibromuscular dysplasia. Embolic Large emboli may originate from the heart or large vessels. Cardiac sources include mural thrombi from atrial fibrillation ventricular aneurysm dilated cardiomyopathy valvular thrombi and atrial myxoma. Small vessel May result in lacunar infarcts. The causes include small emboli and lipohyalinosis. Miscellaneous Strokes of uncommon mechanisms or unknown etiologies comprise 40 of ischemic CVAs. TABLE 12-11 STROKE RISK FACTORS Prior CVA TIA Atherosclerosis Hypertension Cardiac Atrial fibrillation Dilated cardiomyopathy Ventricular aneurysm Atrial myxoma Coagulopathies Antiphospholipid antibody Protein C S Factor 5 Leidan OCP use Polycythemia Sickle cell disease Vasoconstriction Cocaine phenylpropanolamine Complex migraine Clinical Presentation In the most general terms stroke must be suspected in the setting of any acute neurological defect including a change in mental status. The patient s presentation depends on several factors mainly the etiology of the stroke vessel size and location of occlusion. 298 CHAPTER 12 NERVOUS SYSTEM DISORDERS Due to the