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Other effects that may result from brain ischemia are stroke, cardiorespiratory arrest, and irreversible brain damage. An interruption of blood flow to the brain for more than 10 seconds causes unconsciousness, and an interruption in flow for more than a few minutes generally results in irreversible brain damage. [ 5 ]
Watershed strokes are caused by ischemia or a lack of blood flow to the brain. [2] There are several causes of ischemia, including embolism and atherosclerosis.There are several conditions that can predispose someone to watershed stroke by increasing the likelihood that insufficient blood supply will be able to reach the brain.
Cerebral infarction, also known as an ischemic stroke, is the pathologic process that results in an area of necrotic tissue in the brain (cerebral infarct). [1] In mid to high income countries, a stroke is the main reason for disability among people and the 2nd cause of death. [2]
It is more likely to result in death or major disability than ischemic stroke or subarachnoid hemorrhage, and therefore constitutes an immediate medical emergency. Intracerebral hemorrhages and accompanying edema may disrupt or compress adjacent brain tissue , leading to neurological dysfunction.
The brain sustains irreversible injury after about 20 minutes of ischemia. [4] Even after blood flow is restored to the brain, patients can experience hours-days of hypotension, hypoxemia, impaired cerebrovascular autoregulation , brain edema, fever, hyperglycemia and/or seizures which further insult brain tissue. [ 5 ]
Hypoxic ischemic encephalopathy (HIE) is a condition that occurs when the entire brain is deprived of an adequate oxygen supply, but the deprivation is not total. While HIE is associated in most cases with oxygen deprivation in the neonate due to birth asphyxia , it can occur in all age groups, and is often a complication of cardiac arrest .
Ischemia: A decrease or restriction of circulating blood flow to a region of the brain which deprives neurons of the necessary substrates (primarily glucose); represents 80% of all strokes. A thrombus or embolus plugs an artery so there is a reduction or cessation of blood flow.
Ischemia is the loss of blood flow to the focal region of the brain. This produces heterogeneous areas of ischemia at the affected vascular region, furthermore, blood flow is limited to a residual flow. Regions with blood flow of less than 10 mL/100 g of tissue/min are core regions (cells here die within minutes of a stroke).