- [Voiceover] You can develop all sorts of symptoms
after having a stroke
because if something's happened
to your master control center, your brain,
then all sorts of stuff,
all sorts of functions can be compromised
and that will manifest as you having symptoms, right?
That makes sense.
But there are certain groups of symptoms
that happen the most frequently
and I want to take a look at these.
These happen the most because,
well, remember strokes happen
when blood flow is compromised, right?
These groups of symptoms are the result of
common blockages in certain arteries.
And we'll explore this.
The first one we'll look at is sudden numbness
or weakness of the face,
the arm or the leg.
Immediately, a few questions pop into your mind, right?
Why would you develop numbness or weakness?
Why commonly the face, the arm and the leg?
Also, does this happen on both sides of the body
or is it just one side of the body?
These are all great questions.
Oh, thank you.
Let's look at each one in turn for some possible reasons.
Why would you develop numbness or weakness?
The numbness might happen
if you developed a stroke in this area here
called the Primary Somatosensory cortex, right?
As its name implies,
it's the key part of your brain
that allows you to feel stuff
so if it gets damaged,
you might end up with a change in your sensation.
For example, numbness.
The weakness could happen
if you developed a stroke next door,
in this Motor cortex area here, right?
Again, the name, kind of, lets you know
it's a major player in controlling your movements.
Damage could result in weakness of your movements.
Let me just clarify that it's a little bit more complicated
than just the Sensory cortex is in charge of your sensation
and your Motor cortex is in charge of your movements,
there's a lot more bits of your brain
that have inputs to all these things
but we won't worry about those for now
because I just want to focus on some of the concepts here.
Now, why the face, the arm, the leg, why?
Why different parts of the body?
The short answer is that it depends on which part
of the Motor or the Sensory cortex gets damaged.
Let me put it to you this way,
the different parts of the body are, sort of,
represented on the Motor and Sensory cortices
in different places.
This isn't perfect but conceptually
a common way to think of it
is as this guy, sort of, draped over, right?
through a line down on the brain
with his legs dangling in the longitudinal fissure
and his arms, sort of, about here
and his face down here.
It turns out that the neurons in roughly this area
supply the Motor and Sensory for the legs
and neurons in roughly this area
supply Motor and Sensory for your body.
The ones in this area here
control the bulk of your upper limbs
and then these ones here, for your face.
You might, actually, notice that
the lips and the face and the hands
aren't proportional to the rest of the body here.
That's because more sensitive parts of the body,
like your lips and your face and your hands,
they get dibs on more neurons to supply them
so this is usually drawn to reflect that.
You can probably see where I'm going with this
but if you get some compromise of your end
to your cerebral artery, your ACA,
which supplies this part of your brain here,
you'd get possible Motor or Sensory symptoms in your legs.
If you get some compromise of your Middle Cerebral Artery,
your MCA,
which supplies all of this area here,
you'd end up with symptoms affecting your face
and your upper limbs, right?
Finally, one or both sides of the body.
Most of the brain is setup in this interesting way where,
and actually we'll go into details,
but it's setup so that this Motor and Sensory cortex
on say the left side,
are controlling and interpreting
sensations for the opposite,
the right side of the body and vice versa.
That just has to do with the way
that their neurons are connected up
to send and receive signals.
The neurons, actually, cross
from one side of the body to the other.
That happens either in the spinal cord,
in the brainstem
or in the brain itself.
You get this crossing over.
But I digress.
If you have damage to one side,
you'd end up with symptoms on the opposite side.
If you have damage to both sides,
then you get symptoms on both sides of the body, savvy?
I just watched 11 hours of Pirates of the Caribbean
so I might use pirate speak a lot, savvy?
All right, so that's one major set of symptoms,
sensory changes or weakness.
What's next?
Sudden trouble speaking or understanding others.
Why would this happen?
The most common reason you might have
trouble with your speech
is that the stroke has affected
some of the key parts of your brain
that deal with your speech
which are served by the Middle Cerebral Artery.
Actually, almost 40% of people who have a stroke
end up with some problems with expression of their language.
Let me give you an example here of two important areas.
You got his area of the brain here in your frontal lobe
called your Broca's area
which is involved in nice, fluid speech productions.
If this gets damaged, you might end up with,
sort of, slow and poorly articulated speech.
You've got this area right here
near the junction of your temporal and parietal lobes
called your Wernicke's area
which is important in your ability
to understand what people say to you.
It's, actually, also really important in producing
nice, meaningful, specific speech
so if you damaged this area,
you'd end up with poor comprehension
of what people are saying to you
and when you speak,
you wouldn't really be able to pick the right words
to express what you want to say.
You, kind of, just end up rambling a bit, unfortunately.
Next up, we have sudden trouble seeing in one or both eyes.
Here's a top-down view of the brain
to help us understand this.
Up here is the front
and back here is the back.
This is the left eye
and this is the right eye.
There's really two, sort of,
overarching parts to proper vision.
You need a healthy set of eyes,
to bring in the visual information,
and you need a healthy brain
to process and interpret that information, right?
If you had some stroke-related damage
to one of the parts of the brain
that manage your vision, right?
let's say you had a blockage in your
Posterior Cerebral Artery, your PCA,
which supplies your occipital lobe,
that's the major lobe that allows you to have vision,
you could, actually, end up with some vision loss.
The occipital lobe is also wired up
in an interesting way where...
Actually, let me just draw out the two fields of vision
to make this really clear.
Here's your left field of vision from your left eye
and here's your right field of vision from your right eye.
If you sustain some damage to this
left side of the occipital lobe,
you, actually, end up with loss of vision
in the right halves
of both
your left and your right visual fields.
That's weird, right?
That just has to do with the way your
neurons are connected up from your
eyes to your occipital lobe.
Similarly, if you have a stroke affecting your
right side of your occipital lobe
then you'd lose vision in both your left
visual fields, right?
Very interesting.
All right, what's next?
Another common set of symptoms are ones to do with balance.
You get this sudden feeling of dizziness
or loss of balance or coordination.
You might have trouble, say walking.
This can happen if you have a stroke in your Cerebellum.
A substantial enough blockage
in at least one of the three main arteries
that supply it with blood.
Why would this result in dizziness or loss of balance?
Well, because the Cerebellum
is the major coordinator of our movements,
if something happens to it,
we start to get imprecise and uncoordinated
and we end up having poor timing to out movements.
Okay, so the last symptom I'll cover
is just a sudden severe headache with no known cause,
no cause that you can, sort of, think of.
You might remember that there's a subtype of stroke
called the Hemorrhagic stroke
which is where a blood vessel in the brain,
actually, bursts and causes a stroke
by loss of blood from the cerebral circulation.
This is probably not so surprising
but when a blood vessel bursts in your head,
it hurts a lot.
You get a sudden severe headache with no explanation.
There you go, those were five of the most common
stroke signs and symptoms.