0:00

If you recall my survey of the neurosurgeons

0:03

at Johns Hopkins,

0:05

in describing protrusions versus extrusions,

0:09

they made some distinction about whether or not a

0:12

disc herniation is still contained by the annulus

0:16

or the posterior longitudinal ligament.

0:18

This has nothing to do with

0:20

protrusion or extrusion,

0:21

which is a description of the shape

0:24

of the disc herniation. However,

0:26

it is something that the surgeons are interested in

0:29

and this relates to their approach to the disc,

0:32

as far as a discectomy.

0:34

If they are coming from anteriorly,

0:37

they would like, if you will,

0:39

that disc herniation to still be defined by the

0:43

annulus or the posterior longitudinal ligament

0:46

because it kind of escapes from their approach

0:49

if it is through the ligamentous complex.

0:54

So this distinction about contained or uncontained

0:59

disc herniation is something that was recently

1:03

evaluated by O and others in the American

1:07

Journal of Neuroradiology in 2013.

1:10

What they looked at was the margin of the disc

1:13

herniation and the signal intensity of the

1:16

posterior ligamentous complex along the

1:19

posterior longitudinal ligament.

1:22

And they then looked at their surgical cases to

1:27

define what are the best criteria for determining

1:31

contained or uncontained.

1:34

The criteria that they looked at was whether or

1:37

not the spinal canal was compromised for

1:39

more than half its dimension.

1:41

Again, just a size criteria. The signal intensity

1:44

difference in the herniated intervertebral disc

1:48

or HIVD, is basically a herniation,

1:51

an ill defined margin of that herniated

1:54

intervertebral disc,

1:56

disruption of the continuous low signal intensity

2:00

line covering the disc herniation and the presence

2:04

of an internal dark line in the disc herniation.

2:08

So, the latter two revolve around the low signal

2:13

intensity that you'd expect of the posterior

2:15

longitudinal ligament and the annulus.

2:19

The sensitivity and the specificity and

2:21

accuracy was actually intermediate.

2:24

You see that we're in the 75% range for sensitivity,

2:28

specificity and accuracy in this

2:31

large series that they did.

2:33

And therefore, there are many people who feel that

2:36

it's not something that we can really

2:38

predict very well with MRI.

2:41

Let me show some of the examples from O's article

2:45

with giving credit to them.

2:47

On the upper two's images,

2:49

you see what is depicted as a

2:52

low signal intensity around the disc material.

2:59

And on the lower image, you see low signal intensity,

3:03

which is incomplete in certain areas.

3:08

In this terminology that O used,

3:14

the disc herniation above is considered subligamentous ,

3:19

that is it is still contained by the ligament because you

3:23

see the continuous dark sigal intensity

3:25

around the disc herniation.

3:28

Supraligamentous means that it has gone through

3:31

the ligament and is no longer contained as defined

3:35

by the discontinuity in that dark signal

3:39

intensity on the bottom right image.

3:43

Let's see how we do with this next set of cases.

3:47

So here on the upper images, we have dark

3:50

signal intensity and a disc herniation.

3:54

In this case,

3:55

one would argue that that dark signal intensity is

4:00

continuous throughout the circumference

4:03

of the disc herniation.

4:06

If we compare that with the lower image,

4:09

we have the dark signal intensity

4:11

of the periphery of the disc.

4:14

But there is a component here where there

4:16

is loss of that dark signal intensity.

4:19

The terminology therefore would be subligamentous,

4:23

that is still under the ligament on the upper image,

4:27

whereas this one would be termed supraligamentous.

4:31

Here is another example of a series of cases.

4:36

In this case, we have,

4:37

on the upper example,

4:40

a disc herniation which on the sagittal appears to show

4:44

dark signal intensity around the periphery

4:46

of the disc as subligamentous.

4:49

But O shows this on the axial scan as

4:52

losing that dark signal intensity.

4:55

So let me use my pen.

4:58

That although it had dark signal intensity on the sagittal,

5:02

you were missing that dark signal intensity on the axial.

5:06

And therefore, this was

5:08

termed a supraligamentous one.

5:11

And on the bottom image, you have

5:13

the dark signal intensity here.

5:15

And he characterized this as showing dark signal

5:18

intensity around the entirety of this as

5:21

a subligamentous. In point of fact,

5:23

at surgery, these were reversed.

5:26

So this is a false positive, false negative,

5:30

if you will,

5:31

about the ability of the neuroradiologist to

5:34

identify whether or not the disc is still

5:36

contained by annulus posterior ligamentous complex.

5:43

Sub and sub.

5:45

Another example, again, I'll let you decide.

5:49

The upper images are one specific case,

5:51

the lower image is a different case.

5:53

I would characterize the one above as showing dark

5:56

signal intensity around the disc and

5:58

therefore subligamentous.

6:00

Whereas the one below as not showing a dark signal

6:03

intensity around the disc herniation.

6:05

In fact the one on the bottom left may end

6:08

up being a free fragment.

6:11

And indeed, sub and supraligamentous.

6:15

So again, the numbers pointed out were about 75%

6:19

accuracy in making that distinction.

6:21

If you want to add that to your radiology reports,

6:24

it's not something that I typically do because I

6:27

like to see accuracies at high 80% to 90%.

6:31

But it is something that would be of value if we

6:34

were able to tell the neurosurgeon about this.