Diagnosing Stroke: The Key Factors Doctors Must Know Before Treatment
“As a stroke neurologist, I think of myself as a detective.”

If you think you’re having symptoms of a stroke, getting to the emergency room promptly is critical. Don’t “wait and see” if it’s a false alarm, and don’t take an aspirin at home. Call an ambulance and get professional care ASAP.
Once you’re in professional care, doctors will evaluate your symptoms and medical history to see if you’re actually having a stroke, and what kind of stroke you’re having, before moving forward with treatment.
What Doctors Look for When Diagnosing Stroke
Doctors look at three key factors before beginning treatment for stroke, according to Carolyn Brockington, MD, neurologist at Mount Sinai Hospital:
Patient history, such as high blood pressure or atrial fibrillation
A physical examination, including blood tests
Imaging of the brain with CT or MRI scans
Imaging of the brain can show if and where a stroke has occurred, as well as help doctors see which type of stroke may have occurred. “You have two main categories: a bleeding stroke, which is called hemorrhagic,” says Dr. Brockington, “versus an ischemic stroke, which means reduction in blood flow.” (Learn more about the two types of stroke here.)
How Calling 911 Can Speed Up Stroke Diagnosis
One of the major benefits of calling an ambulance when you are having a stroke is that it can shorten the amount of time before your diagnosis—so you can begin potentially life-saving treatment sooner.
“When EMS is bringing in a stroke patient, many times they pre-notify the emergency room,” says Dr. Brockington.
By calling ahead to alert the hospital of an incoming stroke patient, the hospital can call a “stroke code,” bringing together the team of stroke responders in the hospital. By the time you arrive at the ER, a crew of doctors and nurses may be ready to respond.
“We rapidly look at the patient but then take them right away to have imagining,” says Dr. Brockington. “We’re trying to shorten the time period … to begin treatment.” Here are more reasons to call 911 if you’re having a stroke.
Other Tests that Impact Stroke Treatment
Even once doctors are confident you are having a stroke, they must consider important factors before beginning treatment. The goal is to detect or rule out underlying conditions that may cause a misdiagnosis, complications, efficacy of treatment, or other risks.
Blood tests can check that glucose levels are within a safe range. Low blood sugar (hypoglycemia) can produce similar symptoms as a stroke, according to the National Heart, Lung, and Blood Institute. On the other hand, high blood sugar at the time of stroke may make tPA (the most effective treatment for ischemic stroke) less effective or even dangerous.
“We also have to do an EKG because we know the brain and the heart are obviously connected,” says Dr. Brockington. “Sometimes if people are having a stroke, they might also have some heart problems.” People with heart disease, angina, or a history of heart attack have double the risk of having a stroke, according to the American Stroke Association.
Since certain conditions, surgeries, and medications can impact the risk of stroke, learning your personal medical history is important to your doctor’s evaluation.
Learning your possible health conditions and current medications helps doctors decide if you can be given blood thinners, a common treatment for ischemic strokes to restore blood flow to the brain.
Better Late Than Never: Seeing a Doctor After Stroke
The most effective treatment for stroke is only useful within three to four hours after the onset of stroke symptoms. However, if those hours have passed, you should still visit the hospital immediately.
“When someone has a stroke, the first 24 hours is the greatest risk of having another stroke,” says Dr. Brockington. “Whatever caused the stroke can happen again.” Doctors can figure out what caused the stroke and possibly prevent another from occuring.
For more information, here are ways a stroke affects the brain, and check out how doctors use the acronym F-A-S-T for quick stroke recognition and treatment.
Dr. Brockington is a neurologist and director of the Stroke Center at Mount Sinai St. Luke’s and Mount Sinai West Hospital in New York City.
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When someone comes into the emergency
room with stroke-like symptoms,
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the first thing to determine is,
number one, do we think it's a stroke?
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We diagnose a stroke first by history and
physical examination, and
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then we take a picture of the brain.
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And the reason is is because there
are many different types of strokes.
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Sort of two main categories, a bleeding
stroke, which is called hemorrhagic,
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versus an ischemic stroke,
which means reduction in blood flow.
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We may take a CAT scan or a CT scan,
which is an x-ray of the brain,
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in order to look to see
what type of stroke.
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When EMS is bringing in a stroke patient,
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many times they pre-notify
the emergency room,
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which means they call ahead to say that
they're having a patient with a stroke.
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So we call a stroke code, and
what that means is the whole stroke team,
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all the doctors that care for
stroke, come to the emergency room.
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And we rapidly look at the patient, but
then take them right away to have imaging.
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Because we're trying to shorten the time
period that we need to do certain things
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to decide they're having a stroke,
so that they get treatment rapidly.
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The next thing is that
we have to do lab tests.
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We have to make sure that their sugar and
certain other levels are appropriate.
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We also have to do an EKG,
because we know that the brain and
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the heart are obviously connected.
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And sometimes the people having a stroke,
they might also have some heart problems,
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so we need to know that
their heart is okay.
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Then we need to go through history,
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in terms of the medication they're on,
that they haven't had surgery recently.
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So there's a whole checklist in order to
give them a very strong blood thinner.
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So we need to know that we're not risking
further injury, but we're trying to help.
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As a stroke neurologist,
vascular neurologist,
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i think of myself as a detective.
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Not everybody comes in with their
medication list and what happened, etc.,
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so sometimes you need bystanders,
or coworkers, or
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family, that can really
fill in the details.
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What time did this start?
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What did you notice about the patient?
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In order to try to fill
in the missing pieces,
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if the patient can't tell
us all the information.
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When someone has a stroke,
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the first 24 hours is the greatest
risk of having another stroke,
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because whatever happened, or whatever
caused the stroke, can happen again.
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So it's very important to come in, even
if you're not in that early time window,
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to try to figure out
why you had the stroke,
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to reduce the chance
of it happening again.
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Diagnosis. Bethesda, MD: National Heart, Lung, and Blood Institute. (Accessed on June 4, 2018 at https://www.nhlbi.nih.gov/node/3849.)
Hafez S, Coucha M, Bruno A, Fagan SC, Ergul A. Hyperglycemia, acute ischemic stroke and thrombolytic therapy. Trans Stroke Res. 2014 Aug;5(4):442-453.
How cardiovascular & stroke risks relate. Dallas, TX: American Stroke Association, 2016. (Accessed on June 4, 2018 at http://www.strokeassociation.org/STROKEORG/LifeAfterStroke/HealthyLivingAfterStroke/UnderstandingRiskyConditions/How-Cardiovascular-Stroke-Risks-Relate_UCM_310369_Article.jsp#.WxVhmZM-fVo.)
Stroke diagnosis. Dallas, TX: American Stroke Association, 2017. (Accessed on June 4, 2018 at http://www.strokeassociation.org/STROKEORG/AboutStroke/Treatment/Diagnosis/Stroke-Diagnosis_UCM_310890_Article.jsp#.WxVW2pM-fOQ.)