SAL KHAN: I'm here with Dr. Mahadevan,
who's an ER physician at Stanford.
And what are we looking at here?
DR. MAHADEVAN: Well, what we're going
to do is look at some radiographs
of the cervical spine or of your neck
and try to determine whether they're adequate or not.
SAL KHAN: And what does it mean to be adequate?
DR. MAHADEVAN: When you have an adequate view,
you can see from the first vertebra
all way down to the junction of the seventh cervical vertebra
and the first thoracic vertebra.
SAL KHAN: I see.
And we call it adequate because it
means it's adequate to make a diagnosis.
DR. MAHADEVAN: Exactly.
You want to be able to see the entire cervical spine,
so you can make sure that there's not an injury there.
SAL KHAN: Cool, cool.
And so what are we looking at over here?
What are we directly staring at?
DR. MAHADEVAN: So what we're looking at is the lateral,
which shows essentially part of the cervical spine,
shows cervical vertebra one through five.
SAL KHAN: I see.
So just to make myself clear.
So these are both lateral x-rays.
And we say, lateral.
It is actually from the side of the person.
And this shows how well I know my anatomy.
This person, on this x-ray, they're facing this way?
DR. MAHADEVAN: They're actually facing the other way.
SAL KHAN: See, look at that.
I can see, there's a little jaw.
OK.
No, I was just testing you.
Good job.
All right.
So the person is facing that way.
This way is the front.
And you were just showing-- you were
kind of counting the different bones.
DR. MAHADEVAN: Exactly.
SAL KHAN: And you were saying, this is one.
DR. MAHADEVAN: That's one.
SAL KHAN: Two.
DR. MAHADEVAN: Two.
SAL KHAN: Three, four, five, and that's
why you hear people, sometimes, with back injuries saying,
I have a problem in-- what do they call it?
DR. MAHADEVAN: L5 is one.
SAL KHAN: Right.
That's what they're talking about, like that.
OK, so sorry.
DR. MAHADEVAN: And actually, we count even further forward
from there.
And we look exactly at those things that kind of look
like squares.
Those are the actual vertebra, exactly, right there.
SAL KHAN: This.
DR. MAHADEVAN: Exactly.
And although we're interested in the entire the spine, when
we count.
We kind of go down.
And as you can see, if you look at the fifth square
there, below that it's really hard to see
the squares of six and seven.
SAL KHAN: Right, we can't see anything below that.
And looks like what is this person's shoulder
is blocking it.
DR. MAHADEVAN: Exactly.
You can see that that big white thing there
is the shoulder that's gotten in the way.
And it's making it hard to see.
SAL KHAN: They shouldn't have worn those lead shoulder pads.
DR. MAHADEVAN: [LAUGHING] And it's making it
hard to see whether there's something going on down there
right now.
So it's really a mystery, as you've shown.
SAL KHAN: So how do you solve this problem?
DR. MAHADEVAN: If you look over at the other film,
it's what we call a swimmer's view.
And what we've asked the patient to do
is raise one arm up and lower the other.
And in doing so, you kind of clear that lower cervical spine
and allow better visualization of the entire spine.
SAL KHAN: I see.
And you're taking it from the direction of the raised arm,
on the side of raised arm.
DR. MAHADEVAN: You take it from the side.
And you can see.
SAL KHAN: This is the raised arm right over here.
DR. MAHADEVAN: Exactly, that's the raised arm.
SAL KHAN: I see.
And the other arm on the further side of the patient is down.
And that's what allows us to get to the shoulder in a position,
so it doesn't block like it does in this left view.
DR. MAHADEVAN: Exactly, exactly.
SAL KHAN: I see.
And over here, it is much clearer
that this person is also facing in this direction.
And OK.
So let me see.
So we can count.
This is number one right up here.
DR. MAHADEVAN: That's one.
SAL KHAN: One, two, three, four, five, six-- yeah,
we already got to six.
We didn't see six over here.
And then we got seven.
DR. MAHADEVAN: Exactly.
SAL KHAN: OK.
And so you would call this is an adequate view for what we're
trying-- of the neck, because now we can look at all the way
through seven.
DR. MAHADEVAN: Absolutely.
We can get all the way down to seven.
And ideally, you want to see the top of one, which
comes-- actually, in this counting system,
we go one through seven.
And then we start back at one again,
because we're starting with the thoracic vertebrae.
SAL KHAN: Oh, look at that.
It's like with those streets, where they restart numbering.
And you can't find it.
All right.
So it becomes one again.
DR. MAHADEVAN: Exactly.
SAL KHAN: Did I number that right?
DR. MAHADEVAN: You did.
And again, we're looking more to the front.
You've got your numbers perfectly
on every spinous process, the little bump that you can feel,
if you press on the back of your neck.
But what we're really interested is the alignment
of the front of the vertebral bodies.
SAL KHAN: So this is one.
This is two, three, four, five, six, seven.
You want to look at the top of one.
Where's the top of one?
DR. MAHADEVAN: If you just continue down right there.
And it sometimes is difficult to see.
But exactly, you want to see that there's alignment
right in front of--
SAL KHAN: OK.
I'll assume that there's something here
that I can't really see.
But you're an expert.
So maybe you see things that I don't.
All right.
OK, so now what do we do with this?
DR. MAHADEVAN: Now, we've shown you
that you can get a swimmer's view.
And it can show you all the way down to C7, T1.
But on the original view, as you've shown,
we can't see that.
So what we did for this patient was get a swimmer's view.
SAL KHAN: I see.
So this is adequate.
And we have this other slide right over here.
We have this other one right over here.
And why is this one interesting?
DR. MAHADEVAN: This is the same patient.
And now we've taken that same view
that we talked about before, the swimmer's view,
where you've got--
SAL KHAN: This is the same patient
as this patient right over here, not this patient over here
on the right.
DR. MAHADEVAN: Exactly.
SAL KHAN: Because that one looked overall pretty healthy.
DR. MAHADEVAN: That was a normal swimmer's view.
But here is an abnormal swimmer's view.
SAL KHAN: It's the same person?
DR. MAHADEVAN: Same person--
SAL KHAN: As this one, not the other swimmer's view.
DR. MAHADEVAN: Facing in the same direction,
in case you want to test me again.
SAL KHAN: OK, good.
DR. MAHADEVAN: And if you count again,
starting with the first vertebra.
So we go one--
SAL KHAN: Two-- this is three right here?
DR. MAHADEVAN: Three is this one right here.
SAL KHAN: Three, oh, it's a kind of a-- oh, I see.
This whole thing is three?
DR. MAHADEVAN: That whole thing is three right there, exactly.
SAL KHAN: Four, five, six, and then seven,
it looks like right around there,
if I'm reading that, if I see that properly.
It's a little darker there.
DR. MAHADEVAN: And the key important finding there
is, that as you draw a line along the anterior
or the front of all those vertebral bodies,
if you were to connect them just like that.
SAL KHAN: I'll draw a dotted line.
DR. MAHADEVAN: Fantastic.
SAL KHAN: It looks pretty all right.
DR. MAHADEVAN: And as you go down--
SAL KHAN: Oh, look at that, at seven,
looks like a little disruption there.
DR. MAHADEVAN: Exactly, and it's pushed back.
And the problem is, right behind those bones
is your spinal cord.
And so in any kind of an injury like this, potentially,
could injure your spinal cord and lead to permanent paralysis
or weakness.
SAL KHAN: I see.
So this is the main thing.
I guess, there's two big takeaways,
at least from this little short segment, that we've set.
One is, you've got to make sure that you have the information
to make a diagnosis on.
So for example, this right over here,
you couldn't even do something useful,
because you're not able to see the number six and number
seven.
DR. MAHADEVAN: Exactly, we would call it inadequate.
And we would say, we can't draw any firm conclusions from that
actually.
SAL KHAN: And that's why you want
them to get in that swimmer's position,
raise the arm from the direction that you're looking at.
DR. MAHADEVAN: Correct.
SAL KHAN: And they'll lower the other arm.
And then you can see something like this.
And this right over here is cause for trouble,
because now you can go all the way down to seven.
And you can actually see that they're not aligned.
DR. MAHADEVAN: Absolutely.
And so this is someone you wouldn't
let get out of your emergency department
without seeing a specialist, a spine specialist.
Whereas if you didn't have that view,
you might be falsely reassured that everything was OK,
when in fact, there's a serious problem there.
SAL KHAN: Very cool, very cool.
Thanks a bunch.
DR. MAHADEVAN: Thank you.