If you require emergency medical attention, please call 911 to access your local emergency services.


What Is Ischemic Stroke?

More common than hemorrhagic strokes or transient ischemic attacks (TIAs), ischemic strokes account for roughly 87% of all strokes. An ischemic stroke will occur when a blood clot keeps oxygen-rich blood from reaching your brain.

This obstruction is often due to what is known as the hardening of the arteries, or atherosclerosis, the buildup of fatty cholesterol plaque on the inner lining of blood vessels. When your arteries become too narrow as a result, blood cells may collect and form blood clots. If you’re familiar with heart attacks, then the phrase “brain attack” can be helpful in understanding how ischemic strokes work, because the concepts are very much the same and are often due to atherosclerosis.

Types of ischemic strokes

  • A thrombotic stroke (also known as cerebral thrombosis or cerebral infarction) occurs when the blood clot has formed in a blood vessel in your brain. Thrombotic strokes represent almost half of all strokes.
  • An embolic stroke occurs when the blood clot has formed in another part of your body (often the heart) and traveled through the bloodstream to become lodged and restrict blood flow to the brain. Embolic strokes may be a result of atrial fibrillation, a condition that causes irregular heartbeats.

It’s important to note that, unlike the temporary TIA, the blood clot that causes an ischemic stroke will not go away on its own and requires medical intervention and treatment.


During a stroke, blood stops flowing to part of the brain. In an ischemic stroke, usually a blood clot or piece of plaque (fat) blocks a blood vessel in the brain. This can damage areas in the brain that control the rest of the body. Stroke symptoms come on suddenly.

Symptoms of stroke include:

  • Weakness: You may feel a sudden weakness, tingling or a loss of feeling on one side of your face or body including your arm or leg.
  • Vision problems: You may have sudden double vision or trouble seeing in one or both eyes.
  • Speech problems: You may have sudden trouble talking, slurred speech or problems understanding others.
  • Headache: You may have a sudden, severe headache.
  • Movement problems: You may have sudden trouble walking, dizziness, a feeling of spinning, a loss of balance, a feeling of falling or blackouts.

Think FAST

The National Stroke Association’s acronym FAST can help you quickly determine whether someone is having a stroke:

  • F (Face): Ask the person to smile. Does one side of his or her face droop?
  • A (Arms): Ask the person to raise both arms. Does one arm drift downward?
  • S (Speech): Ask for a simple phrase (such as,“You can’t teach an old dog new tricks”) to be repeated. Is speech slurred or hard to understand?
  • T (Time): If you observe any of these signs, call 911 immediately.

If you or someone else has any of these symptoms, act fast and call 911. With stroke, time lost is brain lost.


Blocked brain arteries cause ischemic strokes and TIAs. Any condition that leads to increased fatty plaques in the blood vessels, or blood clots in the bloodstream, can increase the risk of ischemic stroke and TIAs. Conditions include:

  • Atherosclerosis (hardening of the arteries): Fatty buildup (plaque) on artery walls narrows the arteries (stenosis) and increases the risk of plaque breaking off. It may also cause platelets to form where the plaque damages arteries, increasing the risk of a blood clot or blockage.
  • Carotid artery disease: Plaques forming in the carotid arteries (major arteries in the neck that supply blood to the brain) are a main cause of ischemic stroke and TIAs.
  • Atrial fibrillation (rapid, irregular heartbeat): This and other heart conditions can create blood clots that may lead to an ischemic stroke or TIA. Atrial fibrillations are a common cause of embolic (blood clot) strokes.


Knowing the type of stroke will determine the best course of treatment and therapy to help you recover. Experienced neurologists at Northwestern Medicine will diagnose you based on signs and symptoms, a physical examination and diagnostic tests that may include:

  • Computed tomography (CT) scan: This test can show bleeding in the brain or damage to brain cells caused by a stroke, and may also reveal any brain conditions that may have caused the symptoms.
  • Magnetic resonance imaging (MRI): Images from this test can reveal changes in brain tissue from the stroke.
  • CT or MR arteriograms: These imaging tests can show the large blood vessels in the brain, as well as reveal the flow of blood through the brain or the size of a blood clot.
  • Carotid ultrasound: This test uses sound to create images of the insides of the carotid arteries to show whether plaques have narrowed or blocked the carotid arteries.
  • Doppler ultrasound: This special ultrasound shows the speed and direction of blood flow through the blood vessels.
  • Carotid angiography: This imaging test uses a contrast dye solution and X-rays to show the inside of the carotid arteries

There are also tests available at Northwestern Medicine to record the heart’s activity and blood tests to measure levels of glucose (sugar) in the bloodstream, the number of platelets in the blood and whether the blood is clotting normally.


In the spirit of keeping you well-informed, some of the physician(s) and/or individual(s) identified are neither agents nor employees of Northwestern Memorial HealthCare or any of its affiliate organizations. They have selected our facilities as places where they want to treat and care for their private patients.