0:01

In our mnemonic of vitamin C and D,

0:03

we've now covered the acquired

0:05

disorders, that is degenerative change in the spine

0:09

that can lead to extradural compression of the thecal sac.

0:14

And we also dealt with T for trauma. Let's move on to I for

0:19

infectious etiologies.

0:21

Discitis and osteomyelitis are

0:23

the infections that we worry about most with regard to

0:26

the vertebral column,

0:27

and usually they occur together.

0:29

The imaging findings for discitis

0:31

and osteomyelitis are increased signal intensity within the

0:36

disk and the endplates

0:37

on T2-weighted scanning, with

0:40

contrast enhancement of both the disk and the endplates.

0:44

You may see erosion or irregularity of the inferior or

0:48

superior endplate on either

0:49

side of the discitis. And occasionally, we do see

0:53

paravertebral masses and abscesses that can occur on the

0:57

side of the canal or in the epidural space.

1:00

When we see particularly anterior spread of disease under

1:04

the anterior longitudinal ligament,

1:06

it is a marker for tuberculous spondyloarthropathy. In general,

1:12

children are more commonly affected in the lumbar region,

1:15

whereas in the adults, we typically see thoracic discitis

1:20

and osteomyelitis.

1:22

One thing that is in the differential diagnosis for

1:25

infectious discitis and osteomyelitis is dialysis

1:29

arthropathy or amyloid arthropathy, associated with

1:33

chronic renal failure in patients on dialysis,

1:36

which can simulate discitis and osteomyelitis.

1:40

Although the signal intensity of

1:42

the disk and the endplate will be bright with dialysis arthropathy.

1:46

Enhancement within the disk is more common in infectious

1:50

discitis than it is in dialysis arthritis.

1:53

Here we have a patient in which

1:55

we are seeing T1-weighted, T2-weighted, STIR,

1:58

post-gadolinium and axial scans.

2:01

We note that on the T1-weighted scan, we see low signal

2:04

intensity in the endplates of the second and first

2:08

lumbar vertebrae.

2:10

On the T2-weighted and STIR images,

2:12

we see bright signal intensity in the inferior endplate of T1,

2:17

and the superior endplate of T2. In addition,

2:20

there is high signal intensity within the disk.

2:23

This is worrisome for discitis osteomyelitis with infection that

2:27

typically spreads from the disk to the endplates in the

2:31

adult population.

2:32

Why are we not worried about the level below?

2:35

This also appears to have high signal intensity within

2:38

the disk. Well, in the absence of edema in

2:41

the adjacent endplates, we usually say that this could

2:45

be secondary to degenerative

2:46

disease. And in point of fact, we see a little bit of that also

2:49

at the L3-L4 disk level.

2:51

And if you want to see brighter disk,

2:53

you also see that on the L5-S1 level. However,

2:56

if there's any confusion, we would go with the

2:59

post-gadolinium enhanced scans.

3:00

On the post-gadolinium

3:02

enhanced scans, we see that there is enhancement

3:05

of portions of the disk, as well as a more necrotic area

3:10

centrally within the disk, and this would imply infection.

3:14

In addition,

3:14

when we compare the post-gad scan to the pre-gad scan,

3:20

we see that indeed the endplates

3:22

are showing contrast enhancement. Initially,

3:25

this would look like, oh, it looks the same as the level

3:27

above. Here and here and here.

3:29

So, it's normal. No, this was a low signal intensity

3:33

endplate that has now shown contrast enhancement.

3:36

So this is a classic example of

3:38

discitis osteomyelitis complex,

3:40

or some people would call it DOC.

3:42

And it is showing enhancement of the endplates,

3:45

enhancement of the disk,

3:47

high signal intensity endplates and high signal intensity

3:49

in the disk, and to gild the lily one

3:53

more step further, on the T2-weighted

3:55

axial scan, we see adjacent high signal

3:59

intensity in the psoas muscle.

4:01

So this is bright psoas muscle.

4:03

The muscles should be this color. Dark.

4:07

And on either side, here, we see

4:09

psoas muscle bright signal intensity, showing the infection

4:13

has escaped the vertebral body

4:14

and is now, in the paravertebral musculature.

4:17

On the post-gadolinium enhanced scan,

4:20

we see that the psoas muscle also is showing enhancement.

4:24

So, a nice example of discitis osteomyelitis at the L1-L2 level.