Stroke
March 07, 2021A stroke occurs when the blood supply to part of the brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients. Within minutes, brain cells begin to die.
A stroke is a medical emergency. Early treatment is important. Early action can minimize brain damage and potential complications.
Strokes can be treated and prevented. Better control of stroke risk factors - high blood pressure, smoking and high cholesterol.
Symptoms
Look for signs and symptoms if you think you may be having a stroke. Note when signs and symptoms begin, as timing can guide treatment decisions.
Difficulty walking. You may stumble or suddenly become dizzy, lose your balance, or lose coordination.
Problems speaking and understanding may include confusion. You may have difficulty speaking or be unable to explain what is happening (aphasia). Try to repeat a simple sentence. If you cannot, you may be having a stroke.
Paralysis or numbness on one side of the body or face. You may develop sudden paralysis, weakness, or numbness on one side of the body. Try raising both arms above your head at the same time. If one arm begins to weaken, you may be having a stroke. Similarly, one side of the mouth may droop when trying to smile.
Problems with vision in one or both eyes. Vision may suddenly become blurred or dark, or double vision may occur.
Headache. A sudden severe headache, which may be accompanied by vomiting, dizziness or altered consciousness, may indicate a stroke.
Seek immediate medical attention if you notice any signs or symptoms of a stroke, even if they seem to fluctuate or go away every minute. Don't wait to see if symptoms go away. A stroke left untreated has the potential to cause brain damage and disability. To maximize the effectiveness of evaluation and treatment, it is best to get to the emergency room within 60 minutes of the first symptoms.
If a stroke is suspected, take precautions while waiting for emergency help. It may be necessary to:
Start mouth-to-mouth resuscitation if breathing stops.
Turn the head to the side if vomiting occurs, which can prevent choking.
Do not give food or drink.
Causes
A stroke disrupts the flow of blood through the brain and damages brain tissue. There are two main types of stroke. The most common type of stroke is ischemic - caused by a blocked artery. Other types of strokes are hemorrhagic, which occurs when a blood vessel leaks or ruptures. Transient ischemic attacks (TIA) — sometimes called ministrokes — temporarily interrupt blood flow through the brain.
Nearly 90% of strokes are ischemic strokes. They occur when an artery in the brain is narrowed or blocked, causing reduced blood flow (ischemia). The lack of blood flow deprives brain cells of oxygen and nutrients, and the cells can begin to die within minutes. The most common ischemic strokes are:
Thrombotic stroke. This type of stroke occurs when a blood clot (thrombus) forms in an artery that supplies blood to the brain. The clot usually forms in an area damaged by atherosclerosis — where the artery is blocked by plaque. This can happen in either the carotid arteries — the arteries in the neck that carry blood to the brain — or in other arteries in the neck or brain.
Embolic stroke. An embolic stroke occurs when a blood clot or other debris in a blood vessel — usually in the heart — blocks blood flow to the brain. The clot is called an embolus. It is often caused by an irregular heartbeat (atrial fibrillation). The irregular heartbeat can lead to clotting in the heart and the formation of clots that travel to other parts of the body.
Hemorrhagic stroke. Hemorrhage is the medical term for bleeding. Hemorrhagic stroke occurs when a blood vessel in the brain leaks or bursts. Brain hemorrhages can result from a number of problems that affect the blood vessels, including uncontrolled high blood pressure (hypertension) and weakness in the blood vessel wall (aneurysm). A less common cause of hemorrhage is the rupture of an arteriovenous malformation (AVM) — a blood vessel abnormality present at birth. There are two types of hemorrhagic strokes:
Intracerebral hemorrhage. In this type of stroke, a blood vessel in the brain bursts and spills into the surrounding brain tissue, damaging cells. Brain cells in the area of the leak are deprived of blood and also damaged. High blood pressure is the most common cause of this type of hemorrhagic stroke. Over time, high blood pressure can make the small arteries inside the brain brittle and more likely to crack and rupture.
Subarachnoid hemorrhage. In this type of stroke, bleeding begins in an artery on or near the surface of the brain and spills into the space between the surface of the brain and the skull. This bleeding is often signaled by a sudden, severe headache. This type of stroke is usually caused by a ruptured aneurysm, which can develop with age or be present from birth. After the hemorrhage, blood vessels in the brain can widen and narrow erratically (vasospasm), damaging brain cells by further restricting blood flow to parts of the brain.
Transient ischemic attack (TIA)
A transient ischemic attack (TIA) — sometimes called a ministroke — has symptoms similar to those of a stroke. The cause of a transient ischemic attack is a temporary reduction in the blood supply to part of the brain. TIA lasts less than five minutes.
Like an ischemic stroke, a TIA occurs when a blood clot or debris blocks the blood flow to part of the brain. But unlike a stroke, which involves a prolonged lack of blood supply and causes permanent tissue damage, a TIA leaves no lasting effects because the blockage is temporary.
Seek emergency care even if symptoms seem obvious. If you've had a TIA, it means there's likely a partially blocked or narrowed artery leading to the brain, putting you at risk of a full-blown stroke that could cause permanent damage later. And it's impossible to know if you're having a stroke or a TIA based on symptoms alone. Up to half of people who have symptoms actually have a stroke that causes brain damage.
Risk factors
Many factors can increase your risk of stroke. Some of these factors can also increase your chance of having a heart attack. Stroke risk factors include:
A family or personal history of stroke, heart attack, or TIA.
Being 55 or older.
High blood pressure - the risk of stroke begins to increase when blood pressure is higher than 115/75 millimeters of mercury (mm Hg). Your doctor will help decide on a target blood pressure based on your age, whether you have diabetes, and other factors.
High cholesterol - a total cholesterol level above 200 milligrams per deciliter (mg/dL), or 5.2 millimoles per liter (mmol/L).
Smoking or exposure to cigarette smoke.
Diabetes.
Being overweight (body mass index 25 - 29) or obese (body mass index 30 or higher).
Physical inactivity.
Cardiovascular disease, including heart failure, heart defects, heart infections, or abnormal heart rhythms.