Overview of Ischemic Stroke

An ischemic stroke occurs when a blood clot blocks blood flow in a vessel that is carrying blood to the brain. The most common risk factor for this type of stroke is high blood pressure. Approximately 87% of all strokes are ischemic strokes.

Comparison of a normal artery with an artery narrowed by atherosclerotic plaque
Encyclopaedia Britannica / UIG / Getty Images


There are two types of ischemic stroke: embolic stroke and thrombotic stroke.

Embolic Stroke

An embolic stroke occurs when an embolus, or a clot that moves through the bloodstream, forms in either the heart or neck arteries. It is then carried in the bloodstream where it blocks a blood vessel leading to or in the brain.

Thrombotic Stroke

A thrombotic stroke occurs when a blood clot, or thrombus, forms in an artery supplying blood to the brain. The blood clot blocks the flow of oxygen-rich blood to a portion of the brain. A thrombotic stroke may be preceded by a series of one or more transient ischemic attacks (TIAs), also known as “mini-strokes.”


Ischemic strokes are most often caused by arteries becoming narrowed, a condition known as atherosclerosis. Other causes include the use of drugs (such as opioids, stimulants, cannabinoids, and steroids), trauma to blood vessels in the neck, and blood clotting disorders.


When a person shows symptoms of a stroke or has a TIA (transient ischemic attack), the doctor will examine the patient in order to make a diagnosis. After obtaining a medical history, the following diagnostic tests may be performed:

  • Neurological examination
  • Complete blood count
  • CT scan
  • MRI scan


A person who is having a stroke may not notice that they are experiencing symptoms. If you think you are having stroke symptoms, or if you believe someone else is, a simple test is to think “FAST” and do the following:

  • Face: Ask the person to smile. Does one side of their face droop?
  • Arms: Ask the person to raise both arms. Does one of the arms drift downward or are they unable to raise either one of their arms?
  • Speech: Ask the person to repeat a simple phrase. Is their speech slurred?
  • Time: Seek immediate medical attention if you observe any of these signs.

Other symptoms of an ischemic stroke include:

  • Trouble understanding or speaking
  • Numbness of the arm, face, or leg
  • Blurred or blackened vision in one or both eyes
  • Double vision
  • Sudden, severe headache
  • Vomiting
  • Dizziness
  • Difficulty walking
  • Loss of balance or coordination


Immediate treatment is required to limit the level of brain damage that results from the blockage in blood flow. Treatment with tissue plasminogen activator, or tPA, has been effective for patients with an ischemic stroke as long as the patient has received it intravenously within three hours of the onset of symptoms.

Reducing Risk Factors

While certain risk factors as age, gender, heredity, and ethnicity are uncontrollable, a patient can reduce their risk of stroke by beginning treatment that controls their risk factors and adjusts their lifestyle choices.

Ways to control risk factors for a stroke include:

  • Quitting smoking
  • Losing weight
  • Increasing physical activity
  • Reducing alcohol intake
  • Eliminating illegal drug use
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Tsao CW, Aday AW, Almarzooq ZI, et al. Heart disease and stroke statistics—2022 update: a report from the American Heart Association. Circulation. 2022;145(8):e153-e639. doi:10.1161/CIR.0000000000001052

  2. American Stroke Association. Ischemic stroke (clots).

  3. American Heart Association. What is a TIA.

  4. Tsatsakis A, Docea AO, Calina D, et al. A mechanistic and pathophysiological approach for stroke associated with drugs of abuse. J Clin Med. 2019;8(9):1295. doi:10.3390/jcm8091295

  5. Powers WJ, Rabinstein AA, Ackerson T, et al. Guidelines for the early management of patients with acute ischemic stroke: 2019 update to the 2018 guidelines for the early management of acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2019;50(12):e344-e418. doi:10.1161/STR.0000000000000211

  6. American Stroke Association. Stroke symptoms.

  7. Fonarow GC, Zhao X, Smith EE, et al. Door-to-needle times for tissue plasminogen activator administration and clinical outcomes in acute ischemic stroke before and after a quality improvement initiative. JAMA. 2014;311(16):1632-1640. doi:10.1001/jama.2014.3203

By Jose Vega MD, PhD
Jose Vega MD, PhD, is a board-certified neurologist and published researcher specializing in stroke.