What Is a Stroke?


A stroke occurs when blood flow to the brain is reduced or cut off.  Without enough blood flow, brain cells are deprived of essential nutrients and oxygen and begin to die within minutes. The stroke’s impact depends on where the affected brain cells are located and how long blood flow is blocked. A stroke can happen to anyone, at any age. Some people recover fully, while many will have some type of disability.

Symptoms of a stroke

A stroke is always a medical emergency, and the long-term effects can depend in part on how quickly it is treated. That’s why it’s important to know the symptoms of a stroke—and act swiftly. The most common signs of a stroke are:

  • Sudden weakness or numbness in the arms, legs, or face on one or both sides of the body
  • Difficulty speaking
  • Dizziness
  • Confusion
  • Loss of balance
  • Sudden blurring or loss of vision
  • Headache with no known cause

The acronym FAST can be an effective way to remember what to look for:

  • Face: Watch the person’s face. Can he or she smile? Does one side look lopsided?
  • Arms: Ask if the person can lift both arms. Do they rise at the same height or does one arm drift downward?
  • Speech: Ask the person to repeat a simple phrase, like “the sky is blue.” Is his or her speech slurred or difficult to understand?
  • Time: If you notice any of these symptoms, even if they fluctuate or disappear, call 911. If you suspect a stroke, every minute matters.

Types of stroke

Ischemic stroke

Ischemic strokes occur when arteries to the brain are narrowed or blocked completely by a blood clot, drastically reducing blood flow. If the clot forms directly in the arteries that supply blood to the brain, the resulting stroke is called a thrombotic ischemic stroke. If the clot originates elsewhere in the body, like the heart, and becomes lodged in the narrow arteries that lead to the brain, it’s called an embolic ischemic stroke. Ischemic strokes are the most common type of stroke, accounting for over 80 percent of all cases.

Hemorrhagic stroke

This type of stroke is far less common, accounting for about 13 percent of stoke cases. While ischemic strokes are caused by a blockage in the arteries to the brain, hemorrhagic strokes occur when those arteries are ruptured. The rupture is generally caused by a burst aneurysm (a weak part of the artery wall that can balloon outwards)  or leakage from weakened blood vessels. Blood then leaks into the brain, causing swelling and pressure which damages brain cells and tissue.

There are two types of hemorrhagic strokes:

  • An intracerebral hemorrhage is when the ruptured blood vessel is located within the brain. It’s typically the result of trauma or high blood pressure.
  • A subarachnoid hemorrhage occurs when a blood vessel on or near the surface of the brain ruptures and blood flows into the space between the brain and the skull. This type of hemorrhagic stroke is often is accompanied by a sudden, severe headache—people will often call it the worst headache of their lives, or compare the feeling to being hit with a baseball bat in the head.

Transient ischemic attack (TIA)

Also known as “mini strokes,” TIAs are caused by a temporary decrease in blood supply to your brain. A TIA has the same symptoms as other types of stroke but usually lasts less than five minutes and causes little or no  permanent damage to the brain. Though a TIA is generally less serious than a full stroke, it should be treated like a warning sign for a potentially more serious strokes in the future. About one third of people who experience a TIA have a full-blown stroke within the year.

How a stroke is diagnosed

Speed and accuracy both matter when treating a stroke. Your doctor needs to know the type of stroke, its cause, and what part of the brain is being affected in order to provide effective treatment. To gather that info, the doctor will typically do a physical exam, assess symptoms, and run a series of tests.

The doctor will ask about symptoms, what medications you are taking, and family history. The care team may also ask about risk factors, such as smoking or a history of heart disease. During the physical exam, the team will test balance, alertness, and any numbness in the arms or legs. They will also check for carotid artery disease—a common cause of ischemic strokes—by listening for a whooshing sound, known as a bruit, in your carotid arteries (vessels carrying oxygen-rich blood to your brain).

The clinical tests for stroke include both imaging tests and blood tests. Blood tests help determine the condition of your arteries, if your blood sugar (glucose) is high, and how quickly your blood clots. Any abnormalities in the test results help doctors understand if a stroke is occuring—for example, glucose levels are often elevated during a stroke.

Imaging tests can help determine the type and location of the stroke, and whether there’s been a blockage or blood vessel rupture.  Common tests include:

Brain computed tomography (CT scan): A CT scan is usually one of the first tests a doctor will perform after a suspected stroke. This painless procedure uses a series of X-rays to create a detailed image of the brain.  A CT scan can show bleeding, a tumor, or other abnormalities. If there has been a stroke, the CT scan can also pinpoint the location and severity of the damage. Your doctor may use a dye to view veins in better detail and identify any abnormalities in a type of scan known as computed tomographic angiography, or CTA.

Magnetic resonance imaging (MRI): An MRI uses radio waves and magnets to create a sharp and detailed image of the brain. Like a CT scan, an MRI may be used to locate damaged tissues and brain cells after a brain hemorrhage or ischemic stroke. However, it often takes longer than a CT scan and may not be available under emergency conditions. Your doctor might suggest an MRI scan if the part of the brain affected by the stroke is too small to be seen in a CT scan, or in a part of the brain the CT can’t image well. Your doctor may inject dye into your blood to better view arteries and veins and monitor blood flow (known as magnetic resonance angiography). This can help detect aneurysms.

Carotid ultrasound: The carotid arteries supply your brain with oxygen and blood. This test uses sound waves to show whether fatty deposits, known as plaque, have built up inside your carotid arteries, potentially blocking blood from reaching the brain.

Echocardiogram: Similar to a carotid ultrasound, the echocardiogram uses sound waves to build an image of the heart. This image provides information about the size and shape of your heart and how well its chambers and valves are working. It can also be used to detect blood clots inside the heart, pieces of which may have broken off and traveled through the arteries up to the brain.

Emergency treatment for strokes

How a stroke is treated depends on the type of stroke. The priority for an ischemic stroke is breaking up the clot that’s blocking blood flow to the brain. For a hemorrhagic stroke, the top priority is to stop the bleeding.

If a patient is having an ischemic stroke, clot-busting drugs may dissolve the blockage in the arteries. The most common drug is tPA, which is delivered directly into the bloodstream with an IV. To be effective, tPA must be administered within three hours from the beginning of the stroke, or within 4.5 hours for certain patients.

Another treatment option for ischemic strokes is to physically remove the blood-blocking clot. Doctors may insert a catheter through an artery in the groin and guide it to the brain, using a stent retriever to remove the clot or to administer tPA closer to the site of the blockage.

After a hemorrhagic stroke, doctors are focused on locating and controlling any bleeding in the brain. If someone is on blood thinners or antiplatelet medications, both of which may make bleeding worse, he or she may be given medication or a blood transfusion to counteract that increased bleeding. The person may also be given medication to lower blood pressure. Once the bleeding stops, surgery may be necessary to relieve pressure in the brain.

If the stroke is due to ruptured blood vessels, surgery may be necessary to make repairs. Doctors may insert a clamp or a coil to keep an aneurysm from bursting, or to help the blood around it  clot.

Though causes and treatments vary, the one constant with strokes is taking swift action. If you suspect you or a loved one is having a stroke (even if the symptoms lessen over time), seek emergency care right away.

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