0:01

We are continuing our discussion about

0:04

traumatic injuries to the brain, and one of

0:06

the classic questions that residents will be

0:09

asked is, where is this extra-axial collection?

0:12

Is it an epidural hematoma?

0:15

Or is it a subdural hematoma?

0:18

The epidural hematomas usually are associated

0:20

with fractures of the squamosal portion of the

0:23

temporal bone, and that usually will injure the

0:26

middle meningeal artery, leading to arterial

0:29

bleeding into the epidural space outside the dura.

0:34

These are typically seen as biconvex collections,

0:39

and the patient generally has a lucid interval where

0:43

they are asymptomatic, followed by a deterioration.

0:47

Nonetheless, epidural hematomas actually have

0:50

a better prognosis than subdural hematomas,

0:54

and this is because subdural hematomas more

0:56

commonly are associated with parenchymal

0:59

abnormalities as well, and diffuse axonal injury.

1:02

Subdural hematomas are due to

1:07

injury to the bridging veins.

1:09

Remember that they occur more commonly

1:12

contracoup to the direct hit of the calvarium,

1:18

which is our coup injury.

1:20

And they are crescentic, and they also

1:25

are associated with non-accidental trauma.

1:31

With respect to extra-axial collections in

1:33

MRI scans, we usually do not see hemosiderin

1:36

staining of these extra-axial collections

1:38

unless they are recurrently re-bleeding.

1:42

They also do not evolve in a typical pattern

1:46

as intraparenchymal hematomas with respect

1:48

to the presence of adjacent edema, as well

1:52

as the evolution of blood products from

1:54

deoxyhemoglobin to methemoglobin to hemosiderin.

1:59

Diagrammatically, you can see here that the epidural

2:04

hematomas are due most commonly to middle meningeal

2:08

artery involvement, or they may occur due to

2:13

tears of the sinus, and they rip into that space

2:17

between the dura and the calvarium.

2:21

Contrast that with the tears of the bridging

2:24

veins, which lead to the subdural hematoma.

2:29

Diagrammatically here, what we're seeing is the

2:31

involvement of an artery, the middle meningeal artery,

2:35

and the elliptical shape of an epidural hematoma.

2:40

And contrasting that with something that is

2:43

deep to the dura here in a subdural location,

2:49

with ripping of the bridging veins and more

2:53

of a crescentic appearance to the collection.

Extra-Axial Collections

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