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Causes and Diagnoses

Causes and Diagnoses of Ischemic Stroke

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.

Diagnostic Tests