0:00

Within the discussion of osmotic demyelination,

0:04

we should mention a rather unusual entity

0:07

known as Marchiafava-Bignami syndrome.

0:10

This is osmotic demyelination affecting

0:13

the splenium of the corpus callosum.

0:15

This was initially described in red wine

0:17

drinkers and initially was thought to

0:19

potentially be due to a toxic effect of

0:22

something within the red wine

0:24

and/or the alcohol.

0:26

However,

0:27

most recently is thought to represent either a

0:30

vitamin deficiency or an osmotic demyelination

0:34

manifestation of low sodium or low potassium

0:37

or other electrolytes.

0:38

Classically involves the splenium of the corpus callosum.

0:41

And therefore,

0:42

in our differential diagnosis

0:44

of splenium demyelination,

0:46

we would look for the potential for

0:48

this specific diagnosis.

0:50

Now, splenium demyelination has been described

0:53

in many, many entities.

0:56

This is a list of the various entities that have

1:01

been described that can cause a focal area

1:04

of splenium demyelination.

1:06

In fact, it can extend to other portions

1:09

of the corpus callosum.

1:10

So, it is quite an extensive differential diagnosis.

1:14

But the main ones that we see most commonly

1:17

relate to seizures and the administration or

1:20

withdrawal of antiepileptic drugs.

1:23

However, one might see it in regards to the osmotic

1:27

demyelination electrolyte imbalance.

1:29

Certainly, there are various infections,

1:31

usually viral or tick-borne infections

1:34

that can affect the splenium

1:35

of the corpus callosum.

1:37

There are drugs related to chemotherapy and/or

1:41

seizures associated with central

1:43

nervous system malignancy,

1:45

which can also lead to splenium demyelination.

1:47

And there's a wide variety of drugs.

1:50

We also think of Metronidazole encephalopathy.

1:54

That's another example of a drug,

1:56

Flagyl or Metronidazole,

1:58

which can lead to both involvement of the

2:01

dentate nucleus of the cerebellum,

2:03

as well as the splenium of the corpus callosum

2:06

in an area of demyelination.

2:09

And finally,

2:10

with subarachnoid hemorrhage

2:12

around these splenium,

2:13

or in the cisterns around the splenium

2:15

of the corpus callosum,

2:17

one can get an ischemic injury to the splenium

2:21

of the corpus callosum associated with vasospasm

2:24

from the subarachnoid hemorrhage,

2:26

or due to a direct injury of the

2:29

posterior cerebral artery.

2:31

What's not listed here is the traumatic

2:34

involvement with diffuse axonal injury,

2:36

in which the splenium is torn and then leads

2:39

to cytotoxic edema of the splenium.

2:42

I want to move to additional areas of either

2:47

toxic or metabolic demyelination.

2:49

In this case,

2:50

we are looking at the one that affects the

2:52

posterior columns of the spinal cord.

2:56

So, on the sagittal scan,

2:58

we see the bright signal intensity

2:59

in the posterior aspect of the spinal cord

3:02

on this T2-weighted scan.

3:03

On the axial scan,

3:05

we note that it does seem to spare the midline

3:07

and affect the posterior columns.

3:10

And these are two different patients,

3:12

one up top and one below, with the same entity.

3:15

When we see posterior column selective

3:18

involvement of the spinal cord,

3:19

we think about subacute combined degeneration

3:22

associated with B12 deficiency.

3:25

That said,

3:26

there are other toxic metabolic abnormalities

3:29

and vitamin deficiencies which can lead to

3:33

the same posterior column predilection.

3:35

Those include folate deficiency

3:38

and copper deficiency.

3:40

With regard to nitrous oxide toxicity,

3:44

one can also have focal demyelination in the

3:47

posterior aspect of the spinal cord.

3:49

Nitrous oxide toxicity is due to recreational

3:54

use of nitrous oxide as a way of getting high

3:57

with laughing gas.

3:58

When I was in college,

4:00

we used to call it whippets,

4:01

which were little canisters of nitrous oxide

4:04

that were used to get high on

4:06

so-called laughing gas.

4:08

The other entities that have a predilection for

4:11

the posterior aspect of the spinal cord,

4:13

particularly the thoracic spinal cord,

4:15

include multiple sclerosis affecting the

4:17

posterior columns and then tabes dorsalis.

4:21

The dorsalis, or dorsal portion,

4:24

referred to in tabes dorsalis,

4:26

refers to the dorsal portion of the spinal cord,

4:28

the posterior columns,

4:29

which may be affected with syphilis.

4:32

So there is a broad differential diagnosis

4:35

of numerous vitamins and toxins,

4:38

as well as some entities that affect the

4:41

posterior columns selectively.

4:44

Vacuolar myelopathy,

4:45

which is often associated with HIV or AIDS,

4:49

may also be an entity that leads to selective

4:53

demyelination of the posterior

4:55

aspect of the spinal cord.