The Pathogenesis of Transient Focal Cerebral Ischemia

The pathogenesis of certain types of focal cerebral ischemia, particularly episodes of focal cerebrovascular insufficiency, is not fully understood. Atherosclerosis, a relatively static process, commonly occurs without producing any neurologic phenomena. However, such episodes rarely occur in cerebral vascular systems unaffected by atherosclerosis. Atherosclerosis plus some transitory pathophysiologic event would explain the clinical events. A list of such events includes vasospasm, transitory systemic hypotension, kinking and external compression of vessels, transitory hypoglycemia, temporary shunts, and thrombosis and multiple emboli. The roles of polycythemia and anemia are mentioned. Evidence is presented that incriminates thrombosis or embolus formation (or both) as the process, secondary to atherosclerosis or associated with atherosclerosis, that produces the focal cerebral ischemia.