Cerebrovascular accident

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.

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.

Related Topics:
Neurons - Glia - Oxygen - Nutrient

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