0:01

This is a case that sometimes becomes the

0:03

bane of the resident's existence, and that

0:06

is a patient who has a collection which

0:09

is isodense to the adjacent gray matter.

0:14

When it's small, it can be missed relatively easily.

0:17

In this case, as you see, the density of this subdural

0:22

collection is the same as that of gray matter,

0:24

defining it as an isodense subdural hematoma.

0:29

But this one's easy to diagnose because of the

0:31

degree of mass effect that it has with midline shift.

0:35

Remember, when you have subdural collections, you

0:38

wanna measure that midline shift by drawing a line

0:43

generally at the level of the septum pellucidum, from the

0:47

anterior midline falx to the posterior midline falx.

0:52

And then from that line, we measure

0:55

across to the septum pellucidum

0:57

for the degree of midline shift.

0:58

In this case, it's, uh, measuring 10.8 millimeters.

1:04

How do we know that this is a subdural collection?

1:07

Again, crescentic in its

1:10

appearance and crossing sutures.

1:14

Now, there are occasions when an acute

1:18

subdural hematoma may be isodense.

1:21

That occurs when patients are

1:24

anemic.

1:25

So if the hematocrit of the blood that is being

1:30

leaked into the subdural space is low—not the

1:34

normal, you know, 42 to 50 level—if it's low, in the

1:39

twenties, then the density of that blood is less.

1:43

It's low, lower globin content.

1:46

And in that situation, you may have an

1:49

acute isodense subdural hematoma.

1:53

In general, in a person who has a normal hematocrit, the

1:57

isodense subdural hematoma is not an acute collection.

2:00

It's usually a subacute collection.

2:02

We usually say maybe seven to 14 days in age.

2:08

So over the course of time, the density of an extra-

2:12

axial collection decreases as the blood products

2:16

are cleared away by macrophages, for example.

2:20

And therefore, it loses its density.

2:22

You will note that in this individual, there is

2:25

an additional extra-axial collection on the left

2:29

side superiorly, and we can tell that because the

2:34

gray matter edge here is lifted from the surface

2:40

of the brain and adjacent to the calvarium.

2:44

So this patient actually has bilateral

2:47

subdural hematomas, much easier to see on the

2:50

right side because of its size, but there is the

2:53

same phenomenon on the left side, posteriorly,

2:57

in the parietal region, and you can see that

2:59

there's a lower density area right back here.

3:02

So bilateral isodense subdural hematomas.

3:07

This entity, again, the isodense subdural

3:10

hematoma, may be seen in the elderly population

3:15

who present later with their collection.

3:19

Why do they present later with their collection?

3:22

Because the elderly have a greater

3:25

subarachnoid space by virtue of brain

3:28

evolution—I'll call it what it is—atrophy.

3:31

Uh, they don't shift from right to left,

3:34

and they don't show the mass effect until

3:36

later in the course of the collection, and

3:39

therefore, you may have them present later.

3:43

Because of that capacity for absorbing

3:46

or taking in a subdural hematoma that's

3:50

not seen in, uh, younger patients. 33 00:01:53,190 --> 00:01:57,330 In general, in a person who has a normal hematocrit, the

1:57

isodense subdural hematoma is not an acute collection.

2:00

It's usually a subacute collection.

2:02

We usually say maybe seven to 14 days in age.

2:08

So over the course of time, the density of an extra-

2:12

axial collection decreases as the blood products

2:16

are cleared away by macrophages, for example.

2:20

And therefore, it loses its density.

2:22

You will note that in this individual, there is

2:25

an additional extra-axial collection on the left

2:29

side superiorly, and we can tell that because the

2:34

gray matter edge here is lifted from the surface

2:40

of the brain and adjacent to the calvarium.

2:44

So this patient actually has bilateral

2:47

subdural hematomas, much easier to see on the

2:50

right side because of its size, but there is the

2:53

same phenomenon on the left side, posteriorly,

2:57

in the parietal region, and you can see that

2:59

there's a lower density area right back here.

3:02

So bilateral isodense subdural hematomas.

3:07

This entity, again, the isodense subdural

3:10

hematoma, may be seen in the elderly population

3:15

who present later with their collection.

3:19

Why do they present later with their collection?

3:22

Because the elderly have a greater

3:25

subarachnoid space by virtue of brain

3:28

evolution—I'll call it what it is—atrophy.

3:31

Uh, they don't shift from right to left,

3:34

and they don't show the mass effect until

3:36

later in the course of the collection, and

3:39

therefore, you may have them present later.

3:43

Because of that capacity for absorbing

3:46

or taking in a subdural hematoma that's

3:50

not seen in, uh, younger patients.