Prompt medical diagnosis of a stroke is essential: the sooner stroke treatment begins, the better the chance of survival. This is especially true since the treatments for ischemic and hemorrhagic strokes are very different. Determining the type and severity of a stroke is the first step in minimizing damage from the event.

The diagnostic work-up begins as soon as stroke symptoms are reported. Symptoms such as a sudden and severe headache, weakness or paralysis on one side of the body, loss of speech, incontinence, or numbness suggest a stroke. Once a stroke is suspected, brain-imaging tools such as magnetic resonance imaging or computed tomography provide further clues about the nature of the stroke.

Stroke Symptoms: Report Them Immediately

The hallmark of a stroke is the sudden onset of neurologic symptoms. Stroke symptoms should be reported to medical professionals immediately. Many people wait up to 24 hours before reporting stroke symptoms, a delay which results in severe stroke damage and high fatality rates.

Magnetic Resonance Imaging

Magnetic resonance imaging, or MRI, is the most sensitive imaging tool for the medical diagnosis of ischemic stroke. Magnetic resonance imaging techniques generate images of the brain using magnetic fields. Areas of ischemia in the brain can be visualized with MRI.Magnetic resonance imaging can detect an ischemic stroke within six to twelve hours of onset of the stroke. While this is more sensitive than other tests, such as computed tomography, the time delay somewhat limits the effectiveness of MRI for stroke diagnosis. Nearly all current stroke treatments are most effective if started within three hours of stroke onset.

Stroke Symptom Checklist

All stroke symptoms occur suddenly and without warning.

• dizziness or loss of coordination
• hearing difficulties
• numbness, usually on one side
• weakness or paralysis, usually on one side
• severe, "thunderclap" headache
• speech problems
• urinary incontinence
• vision difficulties.

Computed Tomography and the Brain Stem "Blind Spot"

Although it is sometimes the second choice for medical imaging of a suspected ischemic stroke, computed tomography is more often available for diagnosis of a stroke than an MRI. Computed tomography, also known as a CT or CAT scan, uses multiple x-rays to take images of "slices" of the brain. The major limitation in using computed tomography to diagnose an ischemic stroke is that evidence of the stroke takes between 24 to 36 hours to appear on a CT scan. In addition, the brain stem and cerebellum cannot be viewed using computed tomography. These "blind spots" mean that ischemic strokes in the brain stem or cerebellum may be overlooked.Computed tomography is, however, the preferred imaging tool for diagnosis of hemorrhagic stroke. Hemorrhagic strokes can be detected quickly and definitively using CT scanning.

Additional Tools for Stroke Diagnosis

In addition to magnetic resonance imaging and computed tomography, other tests help make a medical diagnosis of stroke.

• Ultrasound: "Doppler" ultrasound detects blockages in the carotid arteries.
• Spinal tap: A spinal tap is a procedure in which cerebrospinal fluid is collected and analyzed. These results can help diagnose bleeding in the brain or brain stem.
• Neurological exam: The examining physician looks for stroke-related defects in movement, sensation, speech, and auditory or visual abilities.
• EKG: An electrocardiogram checks heart function for possible arrhythmia, in order to rule out this potential source of thrombus (blood clot) formation.
• Evoked response: Electrodes attached to the scalp measure the brain's response to hearing, sensation, and visual stimulation. Discrepancies in brain activity indicate a possible stroke.
• Angiography: Angiography occasionally aids a medical diagnosis of stroke. Dye is injected into the blood stream, focusing on the vessels in the heart and brain. The dye appears on x-rays, offering clues about blood flow and circulation obstructions.
• Health screening: Certain conditions indicate an increased risk of stroke, including:
  • diabetes
  • high cholesterol
  • high blood pressure
  • possibly the presence of high levels of homocysteine (an amino acid).

Resources

American Stroke Association. (nd). Diagnosis. Retrieved February 17, 2004, from www.strokeassociation.org/presenter.jhtml?identifier=2552.

Fauci, A., Braunwald, E., Isselbacher, K., Wilson, J., Martin, J., Kasper, D., Hauser, S. & Longo, D. (ed). Harrison's Principles of Internal Medicine, 14th Edition. McGraw-Hill, New York, 1998.

Mayo Foundation for Medical Education and Research. (2003). Stroke: Screening and diagnosis. Retrieved February 17, 2004, from www.mayoclinic.com/invoke.cfm?objectid=487C37FA-C927-45BF-84 821670F1635148&dsection=6.

National Institute of Neurological Disorders and Stroke. (updated 2002). NINDS transient ischemic attack (TIA) information page. Retrieved February 17, 2004, from www.ninds.nih.gov/health_and_medical/disorders/tia_doc.htm.