Pathophysiology of extracranial cerebral arterial stenosis--a critical review.

phenomenon of stenosis in extracranial cerebral arteries, its effects on normal blood flow patterns and the biological and clinical implications for the extracranial cerebral circulation. Stenosis, generally defined as a narrowing or constriction, is of particular interest because of its potential to decrease blood flow. Stenosis of the extracranial cerebral vessels is of clinical concern because the disordered flow patterns which can result may lead to exacerbation of the stenosis itself or contribute to problems in the distal vasculature. Transient cerebral ischemia, stroke, thromboembolism and post stenotic dilatation have all been reported in association with stenosis. In this paper an introduction to the principles of normal blood flow is provided, followed by a discussion of the pathophysiological effects of stenosis. The final section considers ideas relevant to clinical aspects of extracranial cerebral arterial stenosis. Normal Arterial Blood Flow Patterns Flow through a blood vessel normally obeys Pouiseuilles' law and proceeds in an orderly fashion as predicted by theoretical considerations derived from studies of basic fluid mechanics. Some of the principles of fluid mechanics which will be used in the discussion of blood flow through a stenosis, are reviewed here. 1 " 5