- [Voiceover] There's three main steps
in diagnosing strokes.
Step one is to get a good history from the patient
and to do a physical exam on them
to check for neurological symptoms
that the stroke might have caused.
Step two is to do some imaging, like CT scanning or MRI
to directly look at the brain to see
what's going on with it's blood supply.
And this is actually probably
the most useful step in diagnosing stroke.
Now, step three, the focus of this little chat
that we're gonna here, is lab testing.
So things like blood work.
And you might be thinking,
"Well, how can blood work diagnose a stroke?"
And you'd be on to something
because blood tests alone can't diagnose strokes,
but what they can do is look for conditions
that might be the cause of the stroke.
And they're also really helpful in excluding things
that may be mimicking a stroke,
like, say, abnormally low blood sugar levels,
which can sometimes cause symptoms
that look like stroke symptoms.
So what sorts of blood tests are usually ordered?
Well, a complete blood count, or a CBC, is one of them.
So this is a test to check that you have
a normal amount of red blood cells,
white blood cells, and platelets in your blood.
Because sometimes strokes can happen
as a result of certain blood conditions.
So, for example, say you had too many red blood cells
in your blood, and that's a condition called polycythemia.
Or say you had too few platelets in your blood
which is a condition called thrombocytopenia.
You'd be at a higher risk of stroke
and that's because these conditions,
and ones like them, they alter the rate
at which your blood clots.
So you can imagine that if your blood clotted too much
for whatever reason, you'd be at a higher risk
for getting a clot stuck in a cerebral blood vessel
and having an ischemic stroke.
And if your blood clotted too little
then you'd be at a higher risk
of having a hemorrhagic stroke, right?
So maybe if a blood vessel had some trauma to it
and the hole wasn't able to seal up
and stop blood from leaking out,
then you'd be at a high risk for hemorrhagic stroke.
You might also get your electrolytes
and your blood sugar checked
because this might reveal some conditions
that look like a stroke, but aren't.
So, for example, hyponatremia,
or sodium that's just too low in the blood,
can cause impaired electrical activity in the brain
and this can cause seizures and stroke-like symptoms
that might look like a true stroke.
So it's important to rule that out.
Oh, and the electrolyte check can also
give you an idea of whether there's some
underlying kidney disease in the patient as well.
Because the kidneys are responsible for maintaining
our electrolyte concentrations in our blood
at the proper levels.
So if our electrolytes are out of whack
then we check to see if the kidneys are out of whack.
And kidneys that are not functioning very well
can predispose you to stroke.
And now this hypoglycemia,
or blood sugar that's way too low, right?
Glycemia refers to glucose, which is blood sugar.
This can also look like a stroke
and it can even result in symptoms like weakness
or numbness on one side of the body
or trouble speaking and vision problems.
Sounds familiar, right?
It sounds a lot like a stroke
so it's important to get the blood sugar checked
so that if it is just a hypoglycemic event
that can be corrected and stroke can be somewhat ruled out.
And one more thing, the glucose check can give you an idea
of whether or not the patient has diabetes,
which increases your risk of stroke.
Now, what other blood tests?
Well, you could do coagulation studies to check
if the patient has an underlying blood clotting problem.
And this is slightly different
to what we talked about earlier.
Here we're talking about testing for problems
with your actual blood clotting proteins
that are made in your liver.
The proteins that are primarily responsible
for forming blood clots.
Whereas earlier we were talking
about conditions of your blood cells
that can predispose you to clots.
So before we were talking about blood cells
and now we're talking about the blood clotting proteins.
So this one's interesting.
I mean, these proteins are responsible for making
your blood clot, so if there's a problem with them,
for example if they cause clots too easily,
you can imagine that increases the risk
of a clot traveling up to the brain and causing a stroke.
Or maybe when they form clots
they don't break up when they're supposed to.
We have a nice mechanism in our bodies
to break up clots in certain situations,
so if that system malfunctions for some reason
that would increase your risk even higher, right?
And on the flip side, let's say,
actually, they don't even form clots properly
then could predispose you to likely a hemorrhagic stroke.
Another important blood test to do
is one for certain proteins that may have come
from your heart muscle, like troponin T
or troponin I or CKMB.
These are proteins that might sort of leak out
of your heart muscle cells when they get injured.
So, you might be thinking,
"Well, what does heart muscle injury
"have to do with a stroke?"
Well, for one, problems with your heart
might give you symptoms that look like a stroke,
so it's important to check if there is
underlying heart muscle injury
that's actually causing your symptoms.
And for two, it turns out that there's
an association between cerebral blood vessel disease
of the brain and coronary artery disease of the heart.
And that's because the same underlying process,
atherosclerosis, may have caused them both.
So it's important to test
for these little heart muscle proteins
because they could point to existing heart disease
in addition to the possible stroke
that we're trying to diagnose.
And the last blood test I'll mention
is a toxicology screen, or a tox screen.
That's probably how you heard it on Law & Order or CSI.
And this is mainly to identify patients that might be
a little intoxicated with any drug or alcohol
and who might be having symptoms
or behavior mimicking stroke syndromes.
So it's really a test to rule out intoxication
or look for any drugs in the blood
that might be associated with a risk of stroke.
So those are some of the more common blood tests
that are done in diagnosing a stroke.