Cerebrovascular Disease

Cerebrovascular Disease

A stroke or cerebrovascular accident (CVA) occurs when the blood supply to a part of the brain is suddenly interrupted by occlusion (called an ischemic stroke -- approximately 90% of strokes), by hemorrhage (called a hemorrhagic stroke -- about 10% of strokes) or other causes. Ischemia is a reduction of blood flow most commonly due to occlusion (an obstruction). On the other hand, hemorrhagic stroke (or intracranial hemorrhage), occurs when a blood vessel in the brain bursts, spilling blood into the spaces surrounding the brain cells or when a cerebral aneurysm ruptures. The mortality and long-term morbidity prognosis is generally worse for hemorrhagic strokes than for ischemic strokes. A small proportion of strokes are watershed strokes caused by hypoperfusion (usually due to hypotension) or other vascular problems including vasculitis.

Cerebrovascular accident or stroke (also called brain attack) results from sudden interruption of blood supply to the brain, which precipitates neurologic dysfunction lasting longer than 24 hours. Stroke are either ischemic, caused by partial or complete occlusions of a cerebral blood vessel by cerebral thrombosis or embolism or hemorrhage (leakage of blood from a vessel causes compression of brain tissue and spasm of adjacent vessels). Hemorrhage may occur outside the dura (extradural), beneath the dura mater (subdural), in the subarachnoid space (subarachnoid), or within the brain substance itself (intracerebral).

Risk factors for stroke include transient ischemic attacks (TIAs) - warning sign of impending stroke - hypertension, arteriosclerosis, heart disease, elevated cholesterol, diabetes mellitus, obesity, carotid stenosis, polycythemia, hormonal use, I.V., drug use, arrhythmias, and cigarette smoking. Complications of stroke include aspiration pneumonia, dysphagia, constractures, deep vein thrombosis, pulmonary embolism, depression and brain stem herniation.

Pathophysiology

Neurons and glia die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. These damaged cells can linger in a compromised state for several hours. With timely treatment, these cells can be saved. Intriguingly, when the brain cells suffer the ischemia, they begin to fill up with free zinc ions which are released from some of their proteins, especially metallothionein, which can release 7 zinc ions per molecule. This released zinc is a major player in the ensuing death of the brain cells. Drugs that buffer the zinc and reduce the level of free zinc are already being tested to reduce brain cell death after stroke.

Impact of Psychosocial Factors and Stroke Onset

In theory, psychosocial risk factors for stroke should be similar to those that have been demonstrated in coronary heart disease. Both conditions arise from vascular disease that can involve thrombosis, hemorrhage, coagulation disorders, and various disease processes that lead to ischemia. However, many of the psychosocial risk factors that have been found to be robust predictors of heart disease have not been clearly demonstrated in stroke.

This constitutes something of a puzzle. An example is the work on stress. Factors such as work stress, stressful life events, and so forth have produced very mixed results. Some studies suggest an increased risk for ...