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Brain ischemia has been linked to a variety of diseases or abnormalities. Individuals with sickle cell anemia, compressed blood vessels, ventricular tachycardia, plaque buildup in the arteries, blood clots, extremely low blood pressure as a result of heart attack, and congenital heart defects have a higher predisposition to brain ischemia in comparison to the average population.
Brain trauma or stroke can cause ischemia, in which blood flow is reduced to inadequate levels. Ischemia is followed by accumulation of glutamate and aspartate in the extracellular fluid, causing cell death, which is aggravated by lack of oxygen and glucose.
Damage to the Broca's area and the Wernicke's area of the brain (left side) typically causes problems with speech and language. Damage to the right side of the brain may interfere with the ability to express emotions or interpret what one sees. Damage on either side can cause paralysis of the opposite side of the body. [citation needed]
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]
In PRES secondary to other causes, the blood vessel damage has been attributed to other mechanisms. The "cytotoxic" theory suggests that it is direct cell damage by toxins (usually medications) that precipitates the edema. The "immunogenic" theory suggests a role for the immune system (specifically T cells).
Another factor in secondary injury is loss of cerebral autoregulation, the ability of the brain's blood vessels to regulate cerebral blood flow. [5] Other factors in secondary damage are breakdown of the blood–brain barrier, edema, ischemia and hypoxia. [15] Ischemia is one of the leading causes of secondary brain damage after head trauma. [9]
The blood–brain barrier consists of astrocytes and pericytes joined with adhesion proteins producing tight junctions. [1] Return of blood flow to these cells after an ischemic stroke can cause excitotoxicity and oxidative stress leading to dysfunction of the endothelial cells and disruption of the blood-brain barrier. [1]
Atrial fibrillation causes blood clots to form within the heart, which may travel to the arteries within the brain and cause an embolism. The embolism prevents blood flow to the brain, which leads to a stroke. [26] An aneurysm is an abnormal bulging of small sections of arteries, which increases the risk of artery rupture.