0:00

Classic history. Fever, back pain, IV drug abuser.

0:06

Here we see on the T1-weighted scan,

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T2-weighted scan and STIR imaging,

0:11

the imaging features of discitis and osteomyelitis.

0:16

We see on the T1-weighted scan dark signal intensity

0:20

in the endplates, as well as the disc.

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On the T2-weighted scan, high signal intensity in the

0:27

disc, as well as the endplates.

0:29

This is not as well seen on the T2-weighted scan as the STIR

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image because with the STIR image, we suppress

0:37

the fat of the normal vertebral bodies.

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But the edematous vertebral bodies is not able

0:43

to be suppressed because of the fluid content.

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So you notice that the L4 vertebra and the

0:49

L5 vertebra are both high in signal intensity

0:52

on the STIR image. The disc is also bright in signal intensity.

0:57

You also see irregularity of the inferior endplate of

1:01

the L4 vertebra and the superior endplate.

1:05

So this irregularity and erosion is yet another finding that will

1:08

help us to distinguish between degenerative changes,

1:12

which may cause bone edema.

1:14

Remember,

1:14

we have the modic type changes which are bright on

1:17

T2 and dark on T1 in modic type 1 changes.

1:21

But this irregularity of the endplate is one

1:25

of the helpful findings. In addition,

1:28

we want to look at the post-gadolinium scans.

1:32

Let's look at the gadolinium-enhanced

1:34

image of the same patient.

1:36

You notice that on this gadolinium-enhanced image, you

1:40

see marked enhancement of the intervertebral disc.

1:43

This would not be occurring in the

1:45

typical degenerative category.

1:48

Once we've looked at the diagnosis and the endplates

1:52

in the disc, we have discitis/osteomyelitis complex,

1:56

or what some people will refer to as the

1:58

DOI, Disguised Osteomyelitis Infection.

2:01

We want to look at the epidural space and this

2:04

is best seen on the sagittal and the axial scans.

2:08

We're going to look at the axial post contrast scans.

2:12

Here we have the axial post contrast scans.

2:16

And as we scroll down to the level in which

2:18

there is the abnormal infection,

2:22

you will see that there is soft tissue anterior to the thecal sac,

2:27

which is demonstrated along the back of the vertebral

2:30

body of L4 representing epidural infection.

2:35

When we look at the scan along the paraspinal soft tissue,

2:43

you see that there is enhancement in the

2:45

medial aspect of the psoas muscle,

2:48

both on the left side as well as the right side,

2:52

as well as this inflammatory epidural collection that's

2:56

compressing the thecal sac, just at the L4-L5

3:00

level. So this is discitis/osteomyelitis with epidural phlegmon,

3:05

epidural abscess,

3:07

as well as paraspinal involvement

3:10

extending into the psoas muscles.

3:12

In order to confirm that this is enhancement

3:15

and not fat in the psoas muscle,

3:17

you might want to look at the T2-weighted scans.

3:20

On the T2-weighted scans,

3:22

one would expect the edema of the infection to be bright

3:25

in signal intensity as opposed to the muscle,

3:28

which is usually very dark in signal intensity.

3:31

So let's confirm that.

3:36

We're going to scroll through the axial T2

3:39

weighted scans, and as we get down to the L4-L5 level,

3:44

we can see some of the bright signal intensity in the medial

3:47

aspect of the psoas muscle representing the inflammation.

3:52

Now, this is not a psoas abscess.

3:54

We're not seeing necrosis within the psoas musculature,

3:58

but we are seeing the inflammation

4:00

in the paraspinal soft tissues.

4:02

So these are the findings that we're going

4:03

to rely on in a patient who has

4:07

suspected fever, back pain for discitis/osteomyelitis.

4:12

Sometimes, if I'm a little bit unsure about whether it

4:15

represents degenerative change and modic type endplate

4:18

changes versus an infection, I will specifically say

4:21

in the impression of the report, "Recommend correlation

4:25

with the patient sed rate, C-reactive protein,

4:28

and white blood count. Because discitis/osteomyelitis usually elicits a

4:34

pretty active elevation of the erythrocyte sedimentation

4:38

rate and the C-reactive protein levels,

4:41

as well as elicits an elevated white blood count.