Sudden. If there is a defining feature of stroke it may be the sudden change in status and function. The sudden loss of strength in a limb. The sudden inability to speak, to swallow, to call out that something is terribly wrong. Is there a more dreaded affliction than the conscious awareness of something wrong and not being able to articulate it? This condition, well known in ancient times by many names, is what happened in the Bible to someone whom “the Lord smote.” Apoplexy is another term from the past. Despite the suddenness of the initial event, stroke does evolve. It is this evolution which determines the long term residual weakness or loss of function.
A stroke occurs when a significant alteration of blood flow through the brain deprives brain cells of necessary nourishment for them to perform their normal function. This alteration may result from a blockage, or from the sudden loss of integrity of a vessel causing bleeding, swelling, and destruction of neurons (brain cells) downstream from the injury. The events that precede a stroke are similar for the most part to those things which damage cardiac vessels. Therefore being “heart healthy” is probably the single best preventive measure to avoid stroke: Controlling high blood pressure, avoiding a high cholesterol diet, and regular exercise.
Once a thrombus (a clot) forms and travels through ever smaller diameter blood vessels it is inevitable that it will become lodged. Further blood flow is stopped and there is a build up of pressure behind the clot. The resulting pressure may be great enough to rupture the blood vessel causing significant hemorrhage. Or as the pressure builds it may cause the clot to break apart. In this case now many smaller clots are free to disperse throughout the arterial system of the brain causing multiple smaller strokes, each with its own consequence.
Just what is lost in the event of a stroke depends on the vessel involved which determines the area of nourishment and oxygen deprived brain cells. Some cells are heartier than others and can withstand some degree of deprivation. But others are extremely sensitive to even slight interruptions in homeostasis (the normal interactions between the elements that make up a physiologic system). The motor neurons are a prime example of this. For this reason even a relatively mild stroke will cause limb weakness which may be permanent.
Stroke can occur as a result of other derangements in the body. For example metabolic disorders like diabetes, if poorly controlled, may result in easy friability of blood vessels in the brain, making stroke likely and significant. A hypercoagulable state that results in easy formation of clots, or the development of deep vein thromboses, may be seen in certain cancers, or resulting from a hereditary predisposition. Also atrial fibrillation can result in clot formation which invariably travels through the carotid system causing thrombotic stroke.
Once a stroke occurs, time is critical. If there is a thrombus it can be dissolved by the judicious administration of tPA or other thrombolytic (“clot cutting”) medicine. But it won’t matter if arrival to hospital is delayed beyond a window of a few hours. The difference between a so called “mini” stroke and completed stroke may be a matter of degree. For example a small enough clot which dissolves spontaneously in a matter of minutes may cause sudden loss of vision and brief weakness with apparent full resolution. But it is a harbinger of a more destructive stroke which would likely soon present itself. Obtaining medical attention immediately is paramount.
Once a stroke has appeared what are the risks for recurrence? High in the immediate period which diminishes rapidly in time if proper preventative measures are taken. For example if there is a cardiac abnormality, like atrial fibrillation, instituting therapy with anti thrombotic is done immediately and treatment to prevent the cardiac conduction abnormality is undertaken. If there is blockage in the carotid artery, it is repaired. Anyone on a “baby” aspirin experiencing stroke will likely be placed on a thrombolytic medicine. A period of rehabilitation and therapy will most likely need to be undertaken to restore functionality where it is recoverable and accommodations made where recovery is not likely.
Much is made of whether alcohol is protective. Well certainly binge drinking is not. There is an increased risk in young people (for example, in college) who binge drink. Smoking also is a significant risk factor. It bears repeating, exercise, a healthy diet, and maintaining a healthy lifestyle by managing known conditions like high blood pressure, stress, and diabetes that increase stroke risk, all go a long way to preventing stroke.