Your doctor will diagnose a stroke based on your signs and symptoms, your medical history, a physical exam, and test results.
Your doctor will want to find out the type of stroke you’ve had, its cause, the part of the brain that's affected, and whether you have bleeding in the brain.
If your doctor thinks you’ve had a transient ischemic attack (TIA), he or she will look for its cause to help prevent a future stroke.
Medical History and Physical Exam
Your doctor will ask you or a family member about your risk factors for stroke. Examples of risk factors include high blood pressure, smoking, heart disease, and a personal or family history of stroke. Your doctor also will ask about your signs and symptoms and when they began.
During the physical exam, your doctor will check your mental alertness and your coordination and balance. He or she will check for numbness or weakness in your face, arms, and legs; confusion; and trouble speaking and seeing clearly.
Your doctor will look for signs of carotid artery disease, a common cause of ischemic stroke. He or she will listen to your carotid arteries with a stethoscope. A whooshing sound called a bruit (broo-E) may suggest changed or reduced blood flow due to plaque buildup in the carotid arteries.
Diagnostic Tests and Procedures
Your doctor may recommend one or more of the following tests to diagnose a stroke or TIA.
Head CT Scan
The most widely used imaging test for acute stroke is the computed tomography(CT) scan. CT creates a series of cross-sectional images of the head and brain. A Head CT will quickly rule out a hemorrhage (bleeding), can occasionally show a tumor that might mimic a stroke, and may even show evidence of early infarction. Infarctions generally show up on a CT scan about 6-8 hours after the start of stroke symptoms.
If a stroke is caused by hemorrhage, a CT can show evidence of bleeding into the brain almost immediately after stroke symptoms appear.
Hemorrhage is the primary reason for avoiding certain drug treatments for stroke, such as thrombolytic therapy, the only proven acute stroke therapy for ischemic stroke.
Thrombolytic therapy cannot be used until the doctor can can be reassured that there is no bleeding in the brain because this treatment can increase bleeding and could make a hemorrhagic stroke worse.
Magnetic resonance imaging (MRI) scan of the head is also frequently performed to diagnose and manage stroke.
MRI uses magnetic fields to detect subtle changes in brain tissue content. One effect of stroke is the slowing of water movement, called diffusion, through the damaged brain tissue. MRI can show this type of damage within the first hour after the stroke symptoms start. The benefit of MRI over a CT scan is more accurate and earlier diagnosis of infarction, especially for smaller strokes. It is also accurate in determining if hemorrhage (bleeding) is present. MRI is more sensitive than CT for other types of brain disease, such as brain tumor, that might mimic a stroke. MRI cannot be performed in patients with certain types of metallic or electronic implants, such as pacemakers for the heart.
Although increasingly used in the emergency diagnosis of stroke, MRI is not immediately available at all hours in most hospitals, where CT is used for acute stroke diagnosis. Also, MRI takes longer to perform than CT, and may not be performed if it would significantly delay treatment.
Magnetic Resonance Angiography(MRA) and Functional Magnetic Resonance Imaging (fMRI)
Magnetic Resonance Angiography(MRA) and Functional Magnetic Resonance Imaging (fMRI) are other forms of MRI tests that may be used to diagnose problems with blood flow to the brain that predict the risk of stroke.
Neurosurgeons use MRA to detect stenosis (blockage) of the brain arteries inside the skull by mapping flowing blood. Functional MRI uses a magnet to pick up signals from oxygenated blood and can show brain activity through increases in local blood flow.
Ultrasound and Arteriography
Duplex Doppler ultrasound and arteriography are two diagnostic imaging techniques used to decide if an individual would benefit from a surgical procedure called carotid endarterectomy. This surgery is used to remove fatty deposits from the carotid arteries and can help prevent stroke.
Ultrasound of the carotid is a painless, noninvasive test in which ultrasound waves are sent into the neck. Echoes bounce off the moving blood and the tissue in the artery and can be formed into an image. Ultrasound is fast, painless, risk-free, and relatively inexpensive compared to MRA and arteriography, but it is not considered to be as accurate as arteriography.
Arteriography is an X-ray of the carotid artery taken when a special dye is injected into the artery. The procedure carries its own small risk of causing a stroke and is costly to perform. The benefits of arteriography over MR techniques and ultrasound are that it is extremely reliable and still the best way to measure stenosis of the carotid arteries. Even so, significant advances are being made every day involving noninvasive imaging techniques such as fMRI.
An EKG is a simple, painless test that records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through each part of the heart.
An EKG can help detect heart problems that may have led to a stroke. For example, the test can help diagnose atrial fibrillation or a previous heart attack.
Echocardiography (EK-o-kar-de-OG-ra-fee), or echo, is a painless test that uses sound waves to create pictures of your heart.
The test gives information about the size and shape of your heart and how well your heart's chambers and valves are working.
Echo can detect possible blood clots inside the heart and problems with the aorta. The aorta is the main artery that carries oxygen-rich blood from your heart to all parts of your body.
Your doctor also may use blood tests to help diagnose a stroke.
A blood glucose test measures the amount of glucose (sugar) in your blood. Low blood glucose levels may cause symptoms similar to those of a stroke.
A platelet count measures the number of platelets in your blood. Blood platelets are cell fragments that help your blood clot. Abnormal platelet levels may be a sign of a bleeding disorder (not enough clotting) or a thrombotic disorder (too much clotting).
Your doctor also may recommend blood tests to measure how long it takes for your blood to clot. Two tests that may be used are called PT and PTT tests. These tests show whether your blood is clotting normally.
Reference: National Institute of Neurological Disorders and Stroke (NINDS)
Last updated: May 2, 2016.