Acute Ischemic Stroke

Acute ischemic stroke (AIS) is responsible for almost 90% of all strokes. Acute ischemic stroke occurs when blood flow through a brain artery is blocked by a clot, a mass of thickened blood. Clots are either thrombotic or embolic, depending on where they develop within the body. A thrombotic stroke, the most common of the two, occurs when a clot forms within an artery in the brain. An embolic stroke occurs when a clot or small piece of plaque (fatty deposit) breaks off from elsewhere in the body, such as the heart, and travels through the bloodstream only to become stuck in a narrower vessel in the brain.

Almost half of all acute ischemic strokes are due to large vessel occlusion (LVO). An LVO is the most severe and debilitating type of stroke as the clot occludes major arteries and prevents blood flow to significant portions of the brain.

IMPORTANT NOTE: This overview is provided for informational purposes only and should not be used as a substitute for talking with your doctor. Be sure to talk with your doctor for a complete discussion of this condition as well as the benefits and risks of any treatment options.


The acronym F.A.S.T. (face, arm, speech, time) has been popularized in the United States and elsewhere in order to teach the telltale signs of stroke and the critical need to contact emergency services immediately. Face drooping, arm weakness, and speech difficulty are the outward signs that it’s time to call 911.

Symptoms depend on severity of the stroke and location in the brain. Some people do not experience any symptoms and others experience only one. Most people, however, experience a combination of symptoms.

Symptoms may include:

  • Paralysis on one side of the body
  • Change in alertness
  • Changes in hearing or taste
  • Problems swallowing
  • Dizziness or loss of balance
  • Problems with eyesight


Your doctor may:

  • Ask you or your family member about your risk factors, such as high blood pressure, smoking, heart disease, and a personal or family history of stroke.
  • Ask about your signs and symptoms and when they began.
  • Conduct a physical examination to assess your mental alertness and your coordination and balance. He or she may check for numbness or weakness in your face, arms, and legs; trouble speaking and seeing clearly; and confusion.
  • Look for signs of carotid artery disease, a common cause of ischemic stroke. A stethoscope can detect a whooshing sound called a bruit, which may suggest changed or reduced blood flow due to plaque buildup.

Your doctor may order one or more of the following tests:

  • Cerebral angiography , also called cerebral arteriography, uses an injection of a water-soluble dye, called a contrast agent, to highlight the affected area so that it can be seen on X-rays.
  • Computed tomography (CT scan) uses X-rays to take clear, detailed pictures of your brain.
  • Computed tomography angiography (CTA) uses a combination of CT scanning, special computer techniques, and dye injected into the blood to produce images of blood vessels.
  • Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to create detailed images that can show subtle changes in neurological tissues.
  • Magnetic resonance angiography (MRA) can record the pattern and velocity of blood flow through vascular lesions as well as the flow of cerebrospinal fluid throughout the brain.
  • Transcranial Doppler ultrasound evaluates blood flow through the brain by directing high-frequency sound waves through the skull at particular arteries. The resulting sound wave signals that bounce back from blood cells are interpreted by a computer to make an image of the speed of blood flow.

Additional tests may include: carotid ultrasound, carotid angiography, electrocardiography (EKG), echocardiography, and/or blood tests.


Treatment for this condition must always be discussed with your doctor
for a full discussion of options, risks, benefits, and other information.

Treatment consists of one or a combination of two basic approaches to restore proper blood flow: 1) an injection of a clot-busting drug and 2) mechanical thrombectomy, a minimally-invasive procedure that physically removes clot from blocked arteries. Physicians can choose to use mechanical thrombectomy and pharmaceuticals in combination or independent of one another. The treatment window for patients receiving mechanical thrombectomy is time critical.

Support for the broader use of endovascular treatment increased significantly beginning in 2014 with the release of results from several clinical trials that demonstrated the treatment’s effectiveness. These new studies prompted specialty societies, such as the Society of NeuroInterventional Surgery (SNIS), to update their treatment guidelines to reflect the new evidence.