Sickle shaped blood cells clot more easily than normal blood cells, impeding blood flow to the brain.Compression of blood vessels may also lead to brain ischemia, by blocking the arteries that carry oxygen to the brain. Tumors are one cause of blood vessel compression.Ventricular tachycardia represents a series of irregular heartbeats that may cause the heart to completely shut down resulting in cessation of oxygen flow. Further, irregular heartbeats may result in formation of blood clots, thus leading to oxygen deprivation to all organs.Blockage of arteries due to plaque buildup may also result in ischemia. Even a small amount of plaque build up can result in the narrowing of passageways, causing that area to become more prone to blood clots. Large blood clots can also cause ischemia by blocking blood flow.A heart attack can also cause brain ischemia due to the correlation that exists between heart attack and low blood pressure. Extremely low blood pressure usually represents the inadequate oxygenation of tissues. Untreated heart attacks may slow blood flow enough that blood may start to clot and prevent the flow of blood to the brain or other major organs. Extremely low blood pressure can also result from drug overdose and reactions to drugs. Therefore, brain ischemia can result from events other than heart attacks.Congenital heart defects may also cause brain ischemia due to the lack of appropriate artery formation and connection.
Evidence supporting the use of therapeutic hypothermia after brain ischemia, however, is limited.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. Symptoms of brain hypoxia are similar to ischemia and include inattentiveness, poor judgment, memory loss, and a decrease in motor coordination. Potential causes of brain hypoxia are suffocation, carbon monoxide poisoning, severe anemia, and use of drugs such as cocaine and other amphetamines. Other causes associated with brain hypoxia include drowning, strangling, choking, cardiac arrest, head trauma, and complications during general anesthesia. Treatment strategies for brain hypoxia vary depending on the original cause of injury, primary and/or secondary. See also
Mechanism of anoxic depolarization in the brain
Watershed stroke

References
Bibliography
Gusev, Eugene I.; Skvortsova, Veronica I. (2003). Brain ischemia. New York: Kluwer Academic/Plenum Publishers. ISBN 0-306-47694-0. Further reading
Chang, Steven; Doty, James; Skirboll, Stephen; Steinberg, Gary. Cerebral ischemia . cgi.stanford.edu. URL last accessed February 26, 2006. == External links ==