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Among all the neurologic diseases of adult life, stroke ranks first in frequency and importance. The common mode of expression of stroke is a relatively sudden occurrence of a focal neurologic deficit. Both of these features, acute onset and signs of damage in a limited region of the brain, separate stroke from most other forms of neurologic disease. Strokes are broadly categorized as ischemic or hemorrhagic. Ischemic stroke, the most common type, is due to occlusion of a cerebral blood vessel and causes cerebral infarction. These are categorized on the basis of the cause of vascular occlusion, the main ones being cerebral embolism, atherosclerosis, and occlusion of small vessels within the substance of the brain. The second broad category is hemorrhage, which occurs either within the substance of the brain, called intracerebral hemorrhage; or blood contained within the subarachnoid spaces called subarachnoid hemorrhage. The causes of hemorrhagic stroke (generally called cerebral hemorrhage or intracerebral hemorrhage) are numerous and include chronic hypertension, coagulopathies that arise endogenously or because of anticoagulant medications, vascular malformations of the brain, and hemorrhage that occurs within the area of an ischemic stroke. A subtype that has distinctly different characteristics from other hemorrhagic strokes is subarachnoid hemorrhage, which has fewer causes, the most common being the rupture of a developmental aneurysm arising from the vessels of the circle of Willis, but also includes arteriovenous malformations (AVMs) and other less common processes.
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The causes of stroke are so numerous that the listing given in Table 33-1 offers only a guide to the remainder of this chapter. Knowledge of the major causes of stroke by each epoch of age is particularly helpful, as certain types of cerebrovascular disease occur predominantly in childhood and young adults, a subject taken up in a later section and summarized in Table 33-2. In addition to the two broad categories of stroke, there are diverse disorders of blood vessels, such as vasculitis, dissection, and venous occlusion and a multitude of syndromes that are considered in the category of “cerebrovascular disease” and are discussed in this chapter.
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