How is stroke diagnosed?

Stroke is a medical emergency. Tests for stroke usually start when you're in the ambulance, before you get to the hospital. This is one reason why it's important to call 911 for a stroke, rather than have someone drive you to the hospital. The goals of the tests are to figure out whether you've had a stroke, what type of stroke you've had, and what caused the stroke. This will help your doctors plan your treatment.

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Physical and neurological exam

After you call 911 and the ambulance arrives, an ambulance worker will start the stroke exam. A doctor will continue the exam at the hospital. The ambulance worker or doctor will:

  • Ask you or a family member about your symptoms and medical history.
  • Do a physical exam. This includes taking your blood pressure and checking for mental alertness, numbness or weakness, or trouble speaking, seeing, or walking.
  • Do a neurological exam. This test checks how well your nervous system is working to show whether you have had a stroke. In this exam, the doctor will ask you questions, test your reflexes, and ask you to do simple actions. Each part of the exam tests a different part of your brain. This test can show how serious your stroke was and where in your brain the stroke might have happened.

Imaging tests for stroke

At the hospital, you will probably get at least one imaging test that allows your doctor to see inside your brain, see how much damage was done and where the stroke happened. Some imaging tests you may get include:

  • Computed tomography (CT) scan. A CT scan uses X-rays to take pictures of the brain. A CT scan of the head is usually one of the first tests used for a stroke. A CT scan can show bleeding in the brain or damage to brain cells. The CT scan also can find other problems that can cause stroke symptoms.
  • Magnetic resonance imaging (MRI). MRI uses a strong magnet and radio waves to make pictures of the brain. MRI shows brain changes caused by stroke sooner than a CT scan. MRI also can show any bleeding or blood flow problems. It can rule out other problems such as tumors that can cause symptoms similar to a stroke.
  • CT or MR angiogram. An angiogram is an X-ray movie of the blood vessels and blood flow through them. A dye is injected into the veins to show a detailed picture of the blood vessels after a stroke. A CT angiogram is used with a CT scanner, and a MR angiogram is used with an MRI.
  • Carotid ultrasound. Carotid ultrasound is a test that uses sound waves to create pictures of your carotid arteries, which supply blood to your brain. Often used with a CT or MR angiogram, the carotid ultrasound shows whether plaque has built up in your arteries and is blocking blood flow to your brain.
  • Trans-cranial Doppler (TCD) ultrasound. Doppler ultrasound is a test that uses sound waves to measure blood flow. Also used with a CT or MR angiogram, the TCD helps your doctor find out which artery in your brain is blocked.
  • Electroencephalogram (EEG). An EEG is done less often. This test records electrical activity in the brain to be sure your stroke symptoms are not caused by a seizure. Seizures can cause symptoms like movement problems and confusion. These can be mistaken for the symptoms of stroke or transient ischemic attack (TIA). During this test, you'll have sticky electrodes placed on your head, with wires attached to a machine. The machine records the electrical signals picked up by the electrodes.
  • Electrocardiogram (ECG or EKG). This test detects and records your heart's electrical activity. It can help your doctor find out if atrial fibrillation caused the stroke. An ECG can be done during physical activity to monitor your heart when it is working hard.

Blood tests for stroke

There is no blood test that can diagnose a stroke. However, in the hospital, your doctor or nurse may do a series of blood tests to learn the cause of your stroke symptoms:

  • Complete blood count (CBC). A CBC measures the overall health of your blood and helps diagnose infection, anemia, clotting problems, or other blood problems.
  • Serum electrolytes. This test looks at substances in your blood that carry an electric charge, called electrolytes. An electrolyte problem can cause stroke-like symptoms such as confusion or muscle weakness. Electrolytes also show whether you are dehydrated, which can cause confusion or tiredness. This test can also show whether you have kidney problems, which can change the stroke tests and treatments your doctor does.
  • Blood clotting tests. These tests measure how quickly your blood clots. It is also called a coagulation panel. If your blood clots too quickly, your stroke may have been caused by a clot (ischemic stroke). If your blood clots too slowly, your stroke may have been caused by bleeding (hemorrhagic stroke).
  • Heart attack tests. Your doctor may also order tests to see whether you have had a heart attack. Some women with stroke symptoms also have heart attack symptoms. Some heart problems can lead to a stroke.
  • Thyroid tests. Your doctor may measure your thyroid hormone levels with a blood test. Having hyperthyroidism raises your risk of atrial fibrillation, which can lead to stroke.
  • Blood glucose. This test measures the glucose (sugar) in your blood. Low blood sugar is a common complication of diabetes treatments. Low blood sugar can cause symptoms of a stroke, even when it's not a stroke.
  • Cholesterol tests. This test examines whether high blood cholesterol might have led to your stroke.
  • C-reactive protein test and blood protein test. These tests look for substances in your blood that your body releases in response to swelling or inflammation. Damage to arteries is one cause of inflammation. Your doctor might order these tests to understand your stroke risk better and to determine how to treat your stroke.