Stroke is an emergency involving the disruption of blood flow through a cerebral vessel within the brain. It may result in significant motor (movement), sensory or cognitive (thought or perception) dysfunction, or even death. It is also commonly referred to as a "brain attack," since immediate recognition and management can reduce the amount of disability or death associated with stroke.
Stroke is the third-leading cause of death in the United States. It is also a major cause of permanent disability and results in billions of dollars in medical costs and lost productivity. According to the American Stroke Association, 700,000 people in the United States suffer a stroke each year, which is approximately one case every 45 seconds. Every three minutes, a person will die from a stroke. African-Americans and Hispanic/Latinos have a higher risk of suffering a stroke. Women suffer about 40,000 more strokes per year than men.
Often, the signs and symptoms of stroke are subtle and go unrecognized for a period of time by the patient and family. Like a heart attack, immediate recognition of the stroke condition and initiation of treatment can reduce the amount of disability and death. This may mean the difference between a patient who suffers significant permanent disability and one who recovers completely or with only minor deficits. There is a narrow window of three hours in which fibrinolytic drugs can be used to dissolve a clot and restore circulation to the brain tissue. It is imperative that EMS personnel be completely aware of and able to recognize the signs and symptoms of stroke; gain information regarding the time of onset of the first signs and symptoms from family, relatives, friends or bystanders at the scene; initiate stroke treatment; begin rapid transport; and accurately report the stroke findings to the receiving medical facility.
Types of Stroke
A stroke is defined as acute impairment of neurologic function that results from an interruption of cerebral blood flow to a specific area in the brain. There are two broad categories of stroke: ischemic and hemorrhagic. Ischemic strokes result from the occlusion of a cerebral artery by a blockage or a clot. Hemorrhagic strokes occur from a cerebral vessel that ruptures, disrupts the blood flow and allows bleeding in and around the brain.
Approximately 80%-85% of all strokes are ischemic. The primary etiology of these strokes is from blockage of a cerebral artery that obstructs blood flow to an area of the brain. The most common underlying cause of ischemic strokes is atherosclerosis. This is the process where fatty deposits collect and line the walls of vessels. This fat will continue to build up inside the vessel wall and may eventually lead to a blockage at the site of the buildup, or a piece of the fatty plaque can break off and travel through the bloodstream and cause a blockage in a smaller vessel distal to the fatty buildup.
Ischemic strokes are further classified as thrombotic stroke, embolic stroke, transient ischemic attack (TIA), reversible ischemic neurologic deficit (RIND) and hypoperfusion stroke.
A thrombotic stroke results from an acute blockage of a cerebral artery at the site of the buildup of fatty deposits where the internal diameter (lumen) of the vessel is narrowed. This type of clot, a cerebral thrombosis, is often referred to as a "stationary clot," since the site of blockage is at the same site where the clot has formed. Approximately 60% of ischemic strokes are thrombotic.
The signs and symptoms of thrombotic stroke may be progressive. As clot formation progresses, blood flow is reduced to areas supplied by the affected cerebral artery, and ischemia to the brain cells worsens, producing signs and symptoms that may gradually develop and progress. During thrombus formation, as the artery narrows, the surrounding smaller cerebral arteries may begin to dilate in an attempt to deliver more blood to the brain tissue distal to the diseased artery. This collateral circulation, which is similar to that found in the coronary vessels in the heart, may reduce the extent of brain tissue ischemia and death following the stroke.