Hi. We’re gonna be talking about acute ischemic stroke
which is essentially a stroke that’s caused by a blood clot.
Thinking about the epidemiology of acute ischemic stroke,
it’s the 5th leading cause of death and the big thing with ischemic strokes
are that they lead to significant disability.
So after a patient has a stroke,
they may not be able to walk or talk or see.
So this is a really big public health concern and a concern for the patient as well,
but after they have a stroke
they may not be able to go back to doing their activities of daily living
or to be able to live independently.
Now, when we’re thinking about strokes they’re actually divided into two categories:
Ischemic strokes are strokes that are caused by blood clots
and these are by far more common than hemorrhagic strokes.
Hemorrhagic strokes are strokes that are caused by bleeding,
generally into the parenchyma or the tissue of the brain
but can also be related to a subarachnoid hemorrhage.
We’ll be talking about those in another lecture.
But for the purpose of this lecture,
we’re strictly gonna be talking about ischemic stroke
and the treatment of ischemic stroke and how to work it up.
And it’s important to know,
like I said, that this is far more common than hemorrhagic stroke.
Ischemic stroke is more common in African-American and Hispanic patients.
So when patients come in and they have those risk factors it’s something important to keep in mind.
We’re gonna take just a moment to think about the anatomy
and how that affects what’s going on here.
So the anterior circulation supplies 80% of the brain.
The anterior circulation is what comes off of the Circle of Willis
which is the circular structure
and goes to the basically the front portions of the brain and most of the brain tissue.
The posterior circulation comes off of the back portion of the Circle of Willis
and that supplies about 20% of the brain.
So that supplies a smaller portion of the brain and we’ll go through
and we’ll talk about what different areas they supply.
So the anterior circulation supplies the optic nerve in the retina.
The fronto and parietal lobes and the anterior temporal lobe.
It’s important that we remember that and think about that
because when we’re thinking about the symptoms that patient present with
and helping to identify the vessel or where that blood clot is located
knowing what areas of the brain are supplied by that vessel are important.
The posterior circulation supplies the brain stem, the cerebellum,
the medial temporal lobe and the auditory and vestibular sensors of the ear.
There is something called a transient ischemic attack also known as a TIA.
What a TIA is it’s a transient episode of neurologic dysfunction.
The key thing here is that there is no evidence of infarction on neural imaging.
Historically, TIA was thought of to be stroke symptoms
that lasted for less than 24 hours.
But most recently, the definition has changed and the defining factor is that
there is no evidence of infarction on neural imaging.
Now why do we care, right?
Because essentially what’s gonna happen is these patients
are gonna come to the Emergency Department.
They’re gonna describe some kind of stroke symptoms either they have some weakness
or some sensory issues, difficulty with their speech potentially or their gait.
And by the time, generally, that they get to the Emergency Department
their symptoms may be totally improved, if not, somewhat better.
The reason that we care about this and that we wanna make sure
we’re thinking critically when patients present with these symptoms
is that they are warning sign for development of future stroke.
So what that basically means is when patients have a TIA,
10% of those patients will experience a stroke in the next 3 months
and half of those take place in the first 2 days.
So basically, by identifying who’s had a TIA
even though they can’t come in and can be relatively asymptomatic,
we’re identifying those people who are at greatest risk of stroke.
So when someone comes in to the hospital with a TIA
or with symptoms concerning for TIA,
our goal is to think critically about those patients
depending on where you’re practicing emergency medicine.
Some of those patients may actually get admitted to the hospital
to get an expedited workup for stroke symptoms.
So what that might mean is they might get an echocardiogram of their heart
to take a look and see if the heart is beating regularly,
to see if there is any hole in the heart that could predispose those patients
to getting a blood clot to their brain or the other thing that may take place
is they may get a Doppler of their carotid vessels
because we know that if patients have a significant amount
of atherosclerosis in their carotid vessels
then those patients may benefit from getting procedures done
to their carotid vessels
to decrease stroke risk.
So some of these patients may need to be admitted to the hospital to get it
or depending on what hospital system you’re working in
and what resources your patients may have access to.
Those patients may actually be able to be discharged
and get that expedited workup as an outpatient.
Moving along to acute ischemic stroke,
older age is generally a risk factor but 3-4% of strokes occur in younger patients.
Those are patients who are between the ages of 15 to 45 years of age.
Now, the reason that we—I wanna make sure that we bring this up
and that we talk about that
is you wanna make sure you’re not overlooking stroke symptoms in patient
who are in those younger age groups because often times these stroke symptoms are clear cut
but sometimes stroke symptoms may be a little bit more vague and not as clear cut as others.
So for those younger patients,
we wanna think about the risk factors that can predispose them to having strokes at a younger age.
So the risk factors are: Pregnancy
Pregnancy is a risk factor because it has an increased tendency to clotting in the setting of pregnancy.
One of the classic things that you wanna think about in pregnancy is the central venous thrombosis.
Protein C and S deficiency or disorders which predispose patients to clotting.
So someone has a known history of that,
that’s something that you wanna make sure you think about
and if someone presents with stroke symptoms and they get admitted to the hospital,
testing might be done to evaluate for protein C and S deficiency.
Sickle cell anemia predisposes patients to strokes because the blood cells are stickier
and when the blood cells sticks together they could potentially form a clot.
And then drug use is the last thing and drug use can sometimes cause stroke
due to the fact that if the patient uses dirty needles and they can get septic emboli
which are basically blood clots that are related to infection.