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Diagnostic Tests for Stroke

Stroke Diagnosis at Medical City Las Colinas

Recent advances in technology provide for many methods of testing. These tests range from the traditional physical exam measurements of blood pressure to sophisticated imaging of the brain and blood vessels. Your physician will decide which tests will be most helpful in determining the cause of your stroke.

Blood Tests

Cholesterol 

High cholesterol levels may contribute to the narrowing of the arteries that supply blood to your head and neck. A simple blood test can measure your cholesterol level.

Clotting Studies

These tests are used to evaluate the ability of your blood to clot. After the stroke, these tests may be ordered to monitor the effectiveness of medication used to help prevent further strokes.

Blood Glucose (sugar) 

High blood sugar may contribute to the injury and narrowing of the arteries that supply blood to your head and neck. Simple blood tests can measure your current and recent glucose levels.

Imaging

With modern imaging technology, all the structures inside the skull can be imaged including the brain; the brain’s supporting structures, and the blood vessels. Imaging can help differentiate a stroke from other brain pathology such as a tumor. Brain imaging can also determine the exact size and location of brain injury due to the stroke, and this information can help determine the cause and chance of recovery. Vascular imaging can identify any problems within the blood supply to the brain such as blocked or narrowed vessels, aneurysms or other abnormal blood vessels.

Computerized Tomography (CT) Scan

What is CT scanning?

CT scanning, also called computed tomography or computerized axial tomography CAT scan), is an X-ray test used for diagnosis. X-rays are taken from a series of different angles and arranged by a computer to show a cross-sectional view of organs in the body.

When is it used?

CT scanning of the brain is often the first imaging test of the brain done in the Emergency Department. CT scan is best used to identify hemorrhage (bleeding) and large ischemic strokes. Damage from an ischemic stroke may not show up on a CT scan for several hours or days. CT is sometimes used to perform follow-up imaging after a hemorrhage or large stroke.

How do I prepare for a CT scan?

No preparation is necessary unless your healthcare provider gives you special instructions. For example, if you are allergic to CT dye then you may have to take certain pre-medications to prevent an allergic reaction.

What happens during the procedure?

CT scanning can be done in either the Emergency Department or Radiology Department. You will lie down on a moving table, which will slide you into the tunnel-like scanning machine. The scanner can move around you to change the angles of the X-rays.

Inside the scanner, multiple X-ray beams are passed very quickly through your body at different angles. The images are projected onto a TV screen and prepared for your healthcare provider to examine.

A solution of dye (also called contrast) may be injected into a vein. This allows the scanner to show any abnormal areas as the dye passes through your body.

Scans usually last about 5 to 15 minutes. They are painless, but your may get uncomfortable from lying in the scanner if the scan takes more than a few minutes. You can talk to the technologist at any time during the procedure. Because of the small, enclosed space, some people became anxious. If you start feeling panicky, the procedure may be stopped. 

What happens after the procedure? 

If you were given dye for the scan, drinking a lot of fluids after the procedure may help your body get rid of the dye. Rarely so people have an allergic reaction to the dye. Most reactions happen right away, but you could have a delayed reaction. After a CT scan that uses dye, watch for signs of a reaction. These signs include itching, rash, or sweating. If you start having these symptoms, call your nurse.

What are the benefits of this procedure?

A CT scan provides detailed pictures to help your healthcare provider diagnose your problem.

What are the risks associated with this procedure: 

In this procedure your body is exposed to a very small amount of radiation. Exposure to radiation can be dangerous if you are exposed to it often or in large amounts. However, the amount of radiation you receive in a CT scan is less than you might receive in many other X-ray tests.

If you are pregnant, you should not have a CT scan without first discussing the possible risks with your healthcare provider.

There is a small risk that you will have an allergic reaction to the dye. For example, there is a chance you will be allergic to the dye if you have a shellfish allergy. Even if you are not allergic to the dye, the dye may cause warm feelings, a flushed face, headache, or salty taste in the mouth. Rarely, it can cause nausea and vomiting.

CT Angiography (CTA)

Using the same technology as a plain CT scan, the blood vessels in the neck going to the brain and the larger blood vessels in the skull can be visualized. This test requires an injection of contrast dye into a vein. It is very useful for looking for blocked or narrowed arteries or abnormal arteries that may cause bleeding inside the head.

Magnetic Resonance Imaging (MRI)

What is magnetic resonance imaging (MRI?)

Magnetic resonance imaging (MRI) is a special test that produces very clear, detailed pictures of the organs and structures in your body. The test uses a powerful magnetic field, radio waves, and a computer to create images in cross-section. While an X-ray is very good at showing bones, an MRI lets your healthcare provider see much more detailed images of the brain.

When is it used?

MRI can diagnose both ischemic and hemorrhagic strokes, determine size and location of stroke, as well as rule out other problems such as tumors. A stroke will show up on an MRI within an hour on symptom onset.

How do I prepare for the procedure?

No special preparation is needed. You may eat normally and take any usual medicines. For the test, you will wear loose, comfortable clothing without metal fastenings such as zippers or clasps because metal will interfere with the test. Do not wear jewelry. If you have any metal in your body (such as plates or screws from a previous surgery) tell your healthcare provider. If you have a pacemaker you may or may not be able to have an MRI, depending on the type of pacemaker. If you have any metal fragments in or around your eyes you cannot have an MRI.. If you have anxiety or claustrophobia) difficulty with small or crowded spaces), let your provider know so that an appropriate sedative can be used.

What happens during the procedure?

You lie down on a cushioned bed that moves into a tunnel-shaped magnet that is open on one ends. If you get nervous when you are in a small closed space you should talk to your healthcare provider about this before you have your MRI. He or she may be able to give you a medicine that will help you feel less nervous or may refer you to a site that has an open MRI scanner. You will have to be very still during the procedure so the pictures will not be blurry.

Sometimes you are given a shot of a fluid called gadolinium during an MRI. This causes any abnormal areas to become very bright on the MRI. This makes them easier to see.

Most MRIs take between 25 and 50 minutes. You will hear loud knocking and whirring sound while the pictures are being taken. You may wear earplugs or music will be provided so that the noise doesn’t sound so loud. You will be able to speak with the person doing the test through a sound system so you can let him or her know if you are having any problems. When the test is over you will return to your room. Your healthcare provider will discuss the results with you.

What are the benefits and risks?

An MRI is painless. There is no radiation. If you were given a shot of gadolinium, there is a chance you will have an allergic reaction but this is very rare.

Although there is no evidence that an MRI will hurt a baby during the first trimester of pregnancy, the National Radiologic al Protection Board recommends not using it at this time of pregnancy. MRI may be used safely later in pregnancy.

Magnetic Resonance Angiography (MRA)

Using the same technology as MRI, this test can image the blood vessels of your head and neck. It can be done with or without contrast. It has the advantage of not using x-rays. The disadvantage is that it requires more time and therefore much more patient cooperation. 

Duplex Ultrasound (DUS)

Using ultrasound technology, blood vessels and flow in the carotid arteries can be assessed using a handheld wand-like device and gel creating sound waves to detect blocked or narrowed blood vessels. This test has the advantage of being risk-free and pain free. It has the disadvantage of only being useful in assessing a small part of the carotid artery in the neck.

Transcranial Doppler (TCD)

This test also uses ultrasound technology and is safe and pain free. It is used to assess blood flow in some of the larger arteries inside the head. It may also be used to look for small clots traveling through these vessels.

Cardiac Testing

Electrocardiogram (ECG) and Telemetry Monitor

The ECG assesses the electrical activity of the heart using sticky pads connected to a monitor with wires. It is useful for testing for evidence of injury to the heart muscle as well as testing for abnormalities n heart rhythm. It may detect rhythm abnormalities that are a risk for stroke such as atrial fibrillation. Because the ECG monitors the heart for a very brief time, it can miss intermittent irregular beats.

The telemetry monitor assesses the electrical activity of the heart for as long as the box is connected to you through small wires. It allows the hospital staff to assess for any intermittent irregularities in the heart rhythm.

Echocardiogram (Echo)

Echocardiogram uses ultrasound technology of a handheld wand and gel to take pictures of the heart. It allows assessment for any structural problems of the heart as well as blood clots within the heart which may be a source of stroke. It is simple, painless and without risk.

Transesophageal Echocardiogram (TEE)

TEE is a more invasive diagnostic test that is able to provide more detailed images of the heart. This test is typically done when the cause of the stroke has not been found by other imaging described above or in people who have a high risk of a cardiac source of stroke. The test is performed by using a flexible probe placed into the esophagus by a cardiologist. This allows imaging of the heart from the backside, where clots are likely to be found. You will be given a mild sedative for the procedure. A more detailed consent will be obtained from you prior to the test.

As you can tell from the list above, there are many tests to evaluate a stroke. Your physician will prescribe the tests that are most appropriate for your specific status.