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Before I move to a discussion about diffuse axonal injury,

0:06

I wanted to review the appearance of extra-axial

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collections over the course of time.

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The density of the extra-axial collection will become less

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and less dense over the course of time as the blood

0:19

products are removed and / or they resolve.

0:23

However, one can have recurrent hemorrhages

0:26

into an extra-axial collection,

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in which case you may have different aged densities

0:31

of acute-on-chronic subdural hematomas,

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for example.

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As the collections age,

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the typical shape of the collection may change.

0:44

I've spoken on numerous occasions

0:46

about how epidural hematomas

0:49

are usually biconvex lenticular-shaped collections.

0:53

However, over the course of time,

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and by this, I mean weeks to months,

0:57

that epidural collection may become crescentic in shape.

1:02

And curiously, subdural hematomas,

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which acutely are crescentic in shape, may,

1:09

over the course of time, weeks to months,

1:11

assume a more lenticular shape.

1:15

However,

1:17

one may occasionally see a strange phenomenon of

1:23

calcification of the extra-axial collection,

1:27

and this is an example thereof.

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This patient came in and was being

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evaluated for sinusitis.

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And as we scrolled into the intracranial

1:35

portion of the paranasal sinuses,

1:37

we start to come upon this area that looks

1:42

almost like bone and bone marrow.

1:45

And as you can see,

1:46

has a component which is lenticular in shape,

1:51

but also a component that becomes crescentic in shape.

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And this is bilaterally present.

2:03

So these are extra-axial collections.

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Initially, probably epidural,

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but could be subdural collections that have

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calcified over the course of time.

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You'll notice that there isn't that much in the way of brain

2:19

atrophy, so the brain is responding to these collections.

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What's also interesting is the appearance on the MRI scan.

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So here is a patient who has a T1-weighted post

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gadolinium MRI scan, and as you can see,

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this collection has some areas that are bright in signal

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intensity on the T1-weighted scan before contrast,

2:41

and therefore, likely represents the bone marrow fat,

2:44

if you will, of an ossified subdural collection.

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Let's see on the T1-weighted sagittal scan.

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You'll see that it is bright on a T1-weighted scan

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and bright on T1-weighted scan,

2:59

what it could represent,

3:01

subacute blood products of methemoglobin.

3:04

In this case,

3:05

it represents ossification of the extra-axial collections.

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Here on the T2-weighted scan,

3:12

you'll see, again, these collections.

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In this case,

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sort of assuming a more lenticular shape.

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And on the right,

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a more crescentic shape.

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So chronic subdural hematomas,

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chronic epidural hematomas have unusual shape

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characteristics and in rare cases may ossify,

3:37

as you see here.