Let’s begin now and focus on the epidural hemorrhage. We need to understand what
the vascular source of this type of hemorrhage comes from. The vascular source
of an epidural hemorrhage or a bleed would be from the branches of the middle meningeal artery.
The middle meningeal artery is a branch of the maxillary artery that enters the skull through the
foramen spinosum. As we take a look here, we can see the middle meningeal artery
and we see its branching pattern. This is an anterior branch. This area here, the middle
meningeal artery is coursing deep to the skull within the cranial cavity. It will groove the skull
at this particular point internally. This area of the skull is referred to as the pterion. This is
one of the thinnest portions of the skull on this side. So a blow here can fracture the skull.
Then this is the posterior division that has a more posterior course as we see here.
So, the most common cause of an epidural hemorrhage is indeed a traumatic cause.
So there is a severe blow to the side of the skull usually in the area of the pterion that’s
sufficient to fracture this region of the skull. Then the fractured bone gets pushed in internally
and then can sever one of the branches of the middle meningeal artery. In the case of the
pterion in this area here, that would be the anterior division of your middle meningeal artery.
Here, we see a section through the skull demonstrating an epidural hematoma.
Here, we can see the fracture of the skull right in through here on the lateral side.
As a result of that fracture, the middle meningeal artery has been severed. Because this is
under high pressure, you’ll get a separation of the dura away from the skull. You see the
fairly large substantial bleed here within the cranial cavity. The layer of the dura that is
separating from the skull will be the periosteal layer. As a result of this separation of the
periosteal layer of the dura mater from the skull, the hematoma creates a pathologic space
which is a bleed into the epidural space. This is normally not present except in this form
of pathology. A characteristic of an epidural hematoma is its shape. As we can appreciate
in this view, the epidural hematoma will produce a lens-shaped appearance.
A very important consideration of an epidural hematoma because of the rapid bleed
because this artery is under high arterial pressure, the hematoma can and usually does
cause a shift of brain structures that will then deviate to the opposite side. So you can see
a shift here of this side of the image being shifted over to the right side of the image
because of this high pressure of this space-occupying lesion. In addition, the increase
in intracranial pressure can cause a herniation of a couple of brain structures. Here, we see
herniation of the uncus in through here, through an opening in the tentorium cerebelli.
Then down inferiorly here where we have the medulla and the spinal cord transition occurring,
you can see herniation of the cerebellum through the foramen magnum. These are very,
very serious herniations and can result in the death of a patient.