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Brain injury as a result of oxygen deprivation either due to hypoxic or anoxic mechanisms is generally termed hypoxic/anoxic injury (HAI). 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.
A closely related disease to brain ischemia is brain hypoxia. Brain hypoxia is the condition in which there is a decrease in the oxygen supply to the brain even in the presence of adequate blood flow. If hypoxia lasts for long periods of time, coma, seizures, and even brain death may occur.
Prolonged hypoxia induces neuronal cell death via apoptosis, resulting in a hypoxic brain injury. [34] [35] Oxygen deprivation can be hypoxic (reduced general oxygen availability) or ischemic (oxygen deprivation due to a disruption in blood flow) in origin. Brain injury as a result of oxygen deprivation is generally termed hypoxic injury.
Brain ischemia is insufficient blood flow to the brain, and can be acute or chronic. Acute ischemic stroke is a neurological emergency typically caused by a blood clot blocking blood flow in a vessel in the brain. [15] Chronic ischemia of the brain may result in a form of dementia called vascular dementia. [16]
Reperfusion injury, sometimes called ischemia-reperfusion injury (IRI) or reoxygenation injury, is the tissue damage caused when blood supply returns to tissue (re-+ perfusion) after a period of ischemia or lack of oxygen (anoxia or hypoxia).
The ischemic (ischaemic) cascade is a series of biochemical reactions that are initiated in the brain and other aerobic tissues after seconds to minutes of ischemia (inadequate blood supply). [1] This is typically secondary to stroke, injury, or cardiac arrest due to heart attack.
Immediately following the event, blood flow and therefore oxygen transport is reduced locally, leading to hypoxia of the cells near the location of the original insult. This can lead to hypoxic cell death ( infarction ) and amplify the original damage from the ischemia ; however, the penumbra area may remain viable for several hours after an ...
Focal and diffuse brain injury are ways to classify brain injury: focal injury occurs in a specific location, while diffuse injury occurs over a more widespread area. It is common for both focal and diffuse damage to occur as a result of the same event; many traumatic brain injuries have aspects of both focal and diffuse injury. [ 1 ]