Cerebral ischaemia is tissue damage and localized death due to lack of oxygen. Without enough blood, the brain does not get the necessary amounts of oxygen and glucose, and eventually that part of the brain dies. This generally happens within three hours of onset of symptoms. The cause of cerebral ischaemia may be a deficiency in oxygen delivery capacity of the blood, brain damage or other causes, the most common being vascular restrictions (eg stroke).
Ischaemic stroke is a type of stroke caused by a blood clot that blocks an artery serving the brain. If the block is temporary (transient ischemic attack, TIA) no obvious symptoms may be discerned and no permanent damage done. Once symptoms appear, brain death follows within hours. The result of brain tissue death depends on which portion of the brain is affected, because certain areas of the brain control specific actions. If the speech center on the left side of the brain is affected, the result may be that the patient slurs words, speaks in nonsense words or is unable to speak at all. If stroke destroys one of the motor areas on either side of the brain, movement on the opposite side of the body will be affected, so that a blocked artery on the right side of the brain can result in partial or total paralysis of the left side of the body. Stroke can also result in breathing and heart function deficits, memory or reasoning deficits, coma or death.
Ischemic stroke is among the leading causes of death and disability in many industrialized nations. For acute serious stroke, approximately 25 percent of patients recover fully, another 20 percent die and the remaining 55 percent are left with some degree of deficit. People who have had a transient ischemic attack (TIA) have a much higher risk of stroke than does the general population. Overall, the risk of stroke after a TIA is 24% to 29% during the next 5 years. The risk is 4% to 8% in the first month and 12% to 13% during the first year. The stroke risk of patients with TIAs is increased 13- to 16-fold during the first year and approximately sevenfold during the subsequent 5 years.
Approximately 500,000 people in the USA have a new or recurrent stroke each year, and approximately 150,000 will die as a result. There are more than 3 million survivors of stroke in the USA. The annual economic costs of stroke in the USA due to health care expenses and lost productivity are estimated to be more than $18 billion. Every year 50,000 Americans suffer transient ischemic attacks (TIAs), and about one third of these people will develop a stroke.
In a study of the effect of stroke on dementia, British researchers examined 48 studies that included 3.2 million people worldwide. A history of stroke increases dementia risk by around 70 per cent, and recent strokes more than doubled the risk.