How is a stroke diagnosed?

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How is a stroke diagnosed?
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
MedicineNet.com

A stroke is a medical emergency. Anyone suspected of having a stroke should be taken to a medical facility immediately for evaluation and treatment. Initially, the doctor takes a medical history from the patient if he/she is alert or others familiar with the patient if they are available, and performs a physical examination. If a person has been seeing a particular doctor, it would be ideal for that doctor to participate in the assessment. Previous knowledge of the patient can improve the accuracy of the evaluation. A neurologist, a doctor specializing in disorders of the nervous system and diseases of the brain, will often assist in the diagnosis and management of stroke patients.

Just because a person has slurred speech or weakness on one side of the body does not necessarily signal the occurrence of a stroke. There are many other possibilities that can be responsible for these symptoms. Other conditions that can mimic a stroke include:

* brain tumors,

* a brain abscess (a collection of pus in the brain caused by bacteria or a fungus),

* migraine headache,

* bleeding in the brain either spontaneously or from trauma,

* meningitis or encephalitis,

* an overdose of certain medications, or

* an imbalance of sodium, calcium, or glucose in the body can also cause changes in the nervous system that can mimic a stroke.

In the acute stroke evaluation, many things will occur at the same time. As the physician is taking the history and performing the physical examination, nursing staff will begin monitoring the patient's vital signs, getting blood tests, and performing an electrocardiogram (EKG or ECG).

Part of the physical examination that is becoming standardized is the use of a stroke scale. The American Heart Association has published a guide to the examination of the nervous system to help care providers determine the severity of a stroke and whether aggressive intervention may be warranted.

There is a narrow time frame to intervene in an acute stroke with medications to reverse the loss of blood supply to part of the brain (please see TPA below). The patient needs to be appropriately evaluated and stabilized before any clot-busting drugs can be potentially utilized.

Computerized tomography: In order to help determine the cause of a suspected stroke, a special x-ray test called a CT scan of the brain is often performed. A CT scan is used to look for bleeding or masses within the brain, a much different situation than stroke that is also treated differently.

MRI scan: Magnetic resonance imaging (MRI) uses magnetic waves rather than x-rays to image the brain. The MRI images are much more detailed than those from CT, but this is not a first line test in stroke. While a CT scan may be completed within a few minutes, an MRI may take more than an hour to complete. An MRI may be performed later in the course of patient care if finer details are required for further medical decision making. People with certain medical devices (for example, pacemakers) or other metals within their body, cannot be subjected to the powerful magnetic field of an MRI.

Other methods of MRI technology: An MRI scan can also be used to specifically view the blood vessels non-invasively (without using tubes or injections), a procedure called an MRA (magnetic resonance angiogram). Another MRI method called diffusion weighted imaging (DWI) is being offered in some medical centers. This technique can detect the area of abnormality minutes after the blood flow to a part of the brain has ceased, whereas a conventional MRI may not detect a stroke until up to six hours after it has started, and a CT scan sometimes cannot detect it until it is 12 to 24 hours old. Again, this is not a first line test in the evaluation of a stroke patient, when time is of the essence.

Computerized tomography with angiography: Using dye that is injected into a vein in the arm, images of the blood vessels in the brain can give information regarding aneurysms or arteriovenous malformations. As well, other abnormalities of brain blood flow may be evaluated. With increasingly sophisticated technology, CT angiography has supplanted conventional angiograms.

Conventional angiogram: An angiogram is another test that is sometimes used to view the blood vessels. A long catheter tube is inserted into an artery (usually in the groin area) and dye is injected while x-rays are simultaneously taken. While an angiogram delivers some of the most detailed images of the blood vessel anatomy, it is also an invasive procedure and is used only when absolutely necessary. For example, an angiogram is done after a hemorrhage when the precise source of bleeding needs to be identified. It also is sometimes performed to accurately evaluate the condition of a carotid artery when surgery to unblock that blood vessel is contemplated.

Carotid Doppler ultrasound: A carotid Doppler ultrasound is a non-invasive (without injections or placing tubes) method that uses sound waves to screen for narrowings and decreased blood flow in the carotid artery (the major artery in the neck that supplies blood to the brain).

Heart tests: Certain tests to evaluate heart function are often performed in stroke patients to search for the source of an embolism. An echocardiogram is a sound wave test that is done by placing a microphone device on the chest or down the esophagus (transesophageal echocardiogram) in order to view the heart chambers. A Holter monitor is similar to a regular electrocardiogram (EKG), but the electrode stickers remain on the chest for 24 hours or longer in order to identify a faulty heart rhythm.

Blood tests: Blood tests such as a sedimentation rate and C-reactive protein are done to look for signs of inflammation that can suggest inflamed arteries. Certain blood proteins that can increase the chance of stroke by thickening the blood are measured. These tests are performed to identify treatable causes of a stroke or to help prevent further injury. Screening blood tests looking for potential infection, anemia, kidney function, and electrolyte abnormalities may also be considered.

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