Definition of Terms
As discussed below, the term stroke is applied to a sudden focal
neurologic syndrome, specifically the type due to cerebrovascular
disease. The term cerebrovascular disease designates any abnormality
of the brain resulting from a pathologic process of the blood
vessels. Pathologic process is given an inclusive meaning—
namely, occlusion of the lumen by embolus or thrombus, rupture
of a vessel, an altered permeability of the vessel wall, or increased
viscosity or other change in the quality of the blood flowing
through the cerebral vessels. The vascular pathologic process may
be considered not only in its grosser aspects—embolism, thrombosis,
dissection, or rupture of a vessel—but also in terms of the
more basic or primary disorder, i.e., atherosclerosis, hypertensive
arteriosclerotic change, arteritis, aneurysmal dilation, and developmental
malformation. Equal importance attaches to the secondary
parenchymal changes in the brain resulting from the vascular
lesion. These are of two main types—ischemia, with or without
infarction, and hemorrhage—and unless one or the other occurs,
the vascular lesion usually remains silent. The only exceptions to
this statement are the local pressure effects of an aneurysm, vascular
headache (migraine, hypertension, temporal arteritis), multiple small
vessel disease with progressive encephalopathy (as in malignant hypertension
or cerebral arteritis), and increased intracranial pressure
(as occurs in hypertensive encephalopathy and venous sinus thrombosis).
Also, persistent acute hypotension may cause ischemic necrosis
in regions of brain between the vascular territories of cortical
vessels, even without vascular occlusion. The many types of cerebrovascular
diseases are listed in Table 34-1, and the predominant
types during each period of life, in Table 34-2.
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