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Well, let's have a look at this postoperative case.

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It's seven months out after surgery.

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It's a 28-year-old woman and the history they were given

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is low back pain, shooting pain down the right leg.

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Evaluate for infection versus history and physical.

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So that's an important differential diagnosis because

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the treatments are completely different.

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One is surgical, one is medical.

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We've got a Sagittal T2,

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one non-contrast and a Sagittal T2 fast spin echo,

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also non-contrast. So let's scroll a little bit.

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We can see where they entered the back, and we can

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see an area of disc prolapse posteriorly.

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Now, I'd like to make a couple of points.

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Let's see if my drawing tool works.

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It wasn't working earlier. And here's the disc.

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And typically, when you have a disc prolapse,

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if it's not a free fragment or an extrusion,

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you can almost merge or blend

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the prolapsed disc with the main disc so they almost

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appear as one. It's like one single tongue.

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And if you color it in,

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the color or the shade of the two is almost exactly

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identical, it's very hard to separate them apart.

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Now, occasionally what will happen is if you extrude a disc,

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it will accumulate a fair amount

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of water and edema and blood.

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And so now the disc has a completely different signal

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than the parent disc. And that's a bit unnerving.

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That's where contrast really is helpful because on the

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standard T2 weighted image when everything is the

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same signal intensity and it's a contiguous structure,

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it's easy.

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But when you have this disparity in signal

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between the two, it becomes tougher.

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Now, another helpful sign that I use in determining

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whether I have a disc prolapse versus, say,

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granulation tissue is what I call a cleft sign.

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Now, the cleft sign can occur in two circumstances.

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One, if you've got a free fragment, in other words,

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the disc breaks off.

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So now there's a cleft between the fragment and the

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parent disc or it's scar, and you see this cleft between

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the two. So that would be the differential diagnosis.

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Whereas if it's nuclear material that's squeezing out

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but still connected, you don't see the cleft.

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So now let's go back and drill into this differential

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diagnosis we were given because there is a polypoid

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appearance of the back of the disc and try

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and decide before we even give contrast.

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Is this an abscess? Yes, it's a little bright.

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We've already said that discs can swell.

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So the mere fact that this disc is brighter

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doesn't tell you that it's an abscess.

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But there is a sign here that is very helpful.

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People that get disc space abscesses have

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endplate inflammation. And destruction,

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and this patient doesn't have that.

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Yes, there is some high signal at the endplate,

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both at L5 and at S1, but on the T1 fat,

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so the fat shouldn't be preserved.

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Fat has been there since the Jurassic period.

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It's been there for a very, very long time.

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It implies chronicity, it implies stability,

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it implies benignity.

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The fact that you're seeing fat at the endplates is a

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very useful sign telling you that this is

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not likely at all to be an abscess.

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Plus, it looks connected to the disc space.

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There isn't really a clear cleft.

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Granted, the shade is different, it's brighter than that,

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but you don't see a clear line between the two.

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So now let's go to the axial.

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We've got an axial T1 and an axial T2,

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and it's kind of weird because the axial T2

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part of the extradural abnormality is pretty dark,

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and part of the extradural abnormality is a

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little bit brighter with a rim around it,

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which is a little bit reminiscent of an abscess, right?

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You got the capsule of the abscess with pus in the

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middle, so that makes it a little bit more difficult.

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But when you go back and look at this, once again,

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it's very hard to have an abscess and have complete

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preservation of the endplates on both sides of the

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disc space after an operation.

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Now, granted, we are seven months out.

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Let's go now to our contrast-enhanced MRI.

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And I generally don't use contrast-enhanced MRI

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to decide if I have an infection or not.

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In fact, I almost never do.

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And let's look at the pre-contrast T1,

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the post-contrast T1,

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and the sagittal post-contrast T1.

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Now, if you're going to have an abscess,

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you should see a heck of a lot more swelling and

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inflammation and enhancement than you do here.

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Granted, there's a little bit over here.

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There's hardly any over here,

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which is where you would be next to the alleged abscess.

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There's no enhancement whatsoever, so that doesn't fit.

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You kind of have a skip area right there.

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So what are we seeing?

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Enhancing granulation tissue. Now,

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let's look at the axial.

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We've got our masses.

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One was a little bit darker and one was a little

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bit lighter. But both sets of masses,

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the lighter one on T2 and the darker one on T2,

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are cold. Let's look at them.

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They don't enhance inside.

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They have peripheral serpiginous enhancement.

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So when you take those things together,

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cold in the middle,

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granulation tissue enhancing around the outside,

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relative preservation of the endplate,

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nothing in the front,

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no dramatic massive areas of enhancement.

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It fits very nicely for a large, large disc prolapse,

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some of which is edematous and some of which is.

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Lot. Any comments you have on this case?

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Yeah,

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contrast are instances where it can help you,

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but it can also complicate matters.

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The history. Recurrent disc the history is key.

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Meaning there is a big difference between somebody

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who had a back surgery never got better,

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and somebody who had a back surgery say, wow,

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I was great for three weeks, then I sneezed,

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and then pain shot down my leg going to my big toe.

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Okay. Because you're looking for that second,

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history has got to be a recurrence.

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And so the only thing that you're really looking for is,

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is there mass effect on the root.

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Because if there's no mass effect on the root,

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there's no operation,

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there's no purpose to an operation.

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So if you hear that history, that is, I was great,

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recurrent symptoms correlate with the nerve root,

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and you have mass effect on the root.

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I don't care what's on the contrast you're reoperating.

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So don't say something that's going

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to make it difficult to do that,

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because what are you going to do with that patient?

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The history is strong.

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There's something compressing the

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root or mass effect on the root,

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that patient's going to have another operation.

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So even if it does enhance,

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you don't want to be so categorical, say, oh, well,

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enhanced can't be disc. It could be.

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Let me assure you, I've been there.

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Discs do enhance, although more delayed than gradually.

7:18

Well, right.

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But just anything you got to sort of go on the weight of

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the evidence and the clinical evidence

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is always the most powerful thing.

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So you got to put these things together.

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So looking at the contrast one can be very helpful.

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But mass effect is one thing you

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definitely need to comment on,

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because if there is mass effect on the root

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and the patient has that kind of history,

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the surgeons are going to be forced to reoperate.

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And there is right here.

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Here's the root. Yeah. There's plenty of mass effect.

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Yeah.

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Getting slammed against the facet by this thing right

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here. And here's the root on the opposite side.

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So there's a lot of mass effects.

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So don't say anything that's going to complicate

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something that they have to do anyway.

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So it can be helpful.

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But really, if you get a decent history,

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which unfortunately we don't always do,

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but at least know what history you're looking for,

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then that will really help you sort these matters out.

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So what you're saying is the clinical

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in the right concrete setting trumps everything.

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And here is an axial T2,

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a C+ T1,

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a C- T1.

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And look at what's happened.

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You've got a mass here,

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and then when you look at the T2,

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you've got a mass here.

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And then you give contrast and everything cleans up,

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everything enhances, so much so that it looks like fat.

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You don't even recognize the granulation tissue.

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That's why I don't like to have just a C+ only

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because then you can't see the mass effect that's

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generated from all that so-called scar.

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And then here's your nerve root sitting cold all by

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itself. So at this level, you would call it all scar.

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If you go up here,

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you clearly call it a large non-enhancing mass.

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In this case, a disc prolapse or disc herniation.

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Fits with the clinical syndrome compresses

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the ipsilateral nerve root.