Health Library

Health library

Back to health library

Diagnosing stroke

An accurate diagnosis is essential for proper, and often lifesaving, treatment.

It used to be that doctors could do nothing about a stroke except wait for it to pass and hope for the best. Now, treatments can stop a stroke in its tracks and prevent serious, permanent or deadly damage to brain tissue.

To work properly, these treatments have to be started as soon as possible. And that requires fast, accurate diagnosis. A doctor has to know what type of stroke is happening to know which treatment to use.

An ischemic stroke, for instance, is caused by blocked blood flow to the brain. Medicines that thin the blood can help increase the brain's blood supply.

A hemorrhagic stroke, though, is caused by a blood vessel that has burst open. This type of stroke can be made worse with blood-thinning medicines, and the doctor has to find the location of the leak to stop the bleeding.

According to the American Stroke Association, a stroke is generally diagnosed, pinpointed or ruled out using some combination of the following tests:

A medical history. This can include questions about symptoms, overall health and past medical problems.

A neurological exam. The exam may include questions about the person's mental state, such as whether he or she has confusion or memory loss. Doctors may also check the size of the person's pupils and how they react to light, monitor the person's breathing rate and rhythm, check strength and reflexes, and look for problems with speech or balance.

Imaging tests. Imaging tests are used to create pictures of all or parts of the brain. These pictures can reveal damage to brain tissue or problems with blood flow. Some common imaging tests include:

  • A computerized tomography (CT) scan. This is one of the most commonly used tests for diagnosing strokes. A CT scan produces an image of the brain that can show areas of excessive bleeding or blocked blood flow. The test is very quick, which allows for rapid treatment if a problem is found.
  • Magnetic resonance imaging (MRI). MRI creates a sharper, more detailed image of the brain than a CT scan, so it's often used to diagnose small, deep injuries.

Tests that show electrical activity. Tests of electrical activity can help uncover abnormal function in specific areas of the brain, pointing to damaged brain tissue.

  • An EEG, or electroencephalogram, involves small metal disks—or electrodes—placed on the scalp, which send information to a machine that creates graphs of electric activity in the brain. Unusual patterns, such as reduced activity, can point to damage from a stroke.
  • Evoked-response tests measure how the brain handles different sensory stimuli. Noises, images or physical stimulation are given as brain activity is measured. This test can also uncover damage to brain tissue.

Tests that measure blood flow. Blood flow tests give doctors information about the brain's blood supply. These tests can reveal narrowed blood vessels, blockages and other interruptions in blood flow. Examples include:

  • Doppler ultrasound, which shows how well blood is flowing by bouncing sound waves off of moving blood cells. The returning sound waves provide information on how quickly blood is moving.
  • Arteriography (also called angiography), a specialized x-ray done after injecting a special dye into the artery. The x-ray image shows the width of the main artery that leads to the brain, so the doctor can check for unusual narrowing.

Reviewed 8/18/2020

Related stories