So in this lecture we?ll be discussing intracranial hemorrhage
and traumatic injury to the brain.
Let?s start off by reviewing some normal brain anatomy.
Here we have an axial CT scan through the head
and you can see the 2 temporal lobes here.
We have the pons, which is a portion of the brain stem back here
and then we have the cerebellum seen most posteriorly
and inferiorly within the brain.
We have the frontal lobes anteriorly and then we have the 2 sylvian fissures.
Posteriorly, we see a portion of the fourth ventricle
and then the center we see the suprasellar cistern.
These are the frontal horns of the lateral ventricles
and then adjacent to them we see the caudate nucleus.
This is the sagittal MRI scan which shows us the corpus callosum,
the pons which is part of the brain stem,
the cerebellum seen posteriorly and inferiorly,
and the medulla, again, part of the brain stem.
So this is an axial T2 image of the brain.
You can see here anteriorly are the frontal lobes and we have the sylvian fissures.
Just behind the sylvian fissures are the temporal lobes
and then posteriorly are the 2 occipital lobes.
Here we have the occipital horns of the lateral ventricles.
On this axial T2 weighted image, we have the frontal horns of the lateral ventricles
and then again the occipital lobes posteriorly.
So MRI is usually the most sensitive examination at detecting brain abnormalities.
However, because MRI does take a long time being required,
CT is usually used as the first line of diagnosis.
It?s very easy to obtain and it?s quick and it does have a relatively high sensitivity
in detecting hemorrhage and mass effect.
We always start off with a non-contrast CT of the head.
If we administer contrast, contrast can be mistaken for hemorrhage
so a non-contrast CT of the head is really the first line of imaging
to look for hemorrhage.
There are 4 major types of hemorrhage.
There?s epidural, subdural, subarachnoid, and intracerebral.
So let?s take a look at each of these a little bit further.
This is the diagram that helps you differentiate how each one should look.
So we have an epidural hematoma here, which is located outside of the dura.
We have a subdural hematoma which is located just beneath the dura,
so you see a dural line right here, and we have an intracerebral hematoma here
which is within the brain parenchyma.
This is an example of a cause of a subarachnoid hemorrhage.
You can have a small aneurysm here
that can cause a subarachnoid hemorrhage which can fill the sulci.
So an epidural hematoma is a hemorrhage that?s located between the dura
and the skull. It?s usually caused by an injury to the middle meningeal artery,
it can be caused by trauma, and it can be caused by skull fractures
that often result in an injury to the middle meningeal artery.
Much less commonly so less than about 10% of the cases
are caused by an injury to the middle meningeal vein.
So epidural hematomas present as a high density,
extra axial lens-shaped collection.
It cannot cross suture line because the dura is connected to the skull
at the sutures, however, it can cross the midline.
So subdural hematoma is hemorrhage that is located between the dura
and to the brain. This is commonly caused by an injury to the bridging veins
that go from the cerebral cortex to the venous sinuses
and it is often related to trauma but it?s not often associated with skull fractures.
This is an example of a subdural hematoma, it?s a high density,
crescent shaped collection and this can actually cross suture lines
but this cannot cross the midline which different from an epidural hematoma
which is able to cross midline but is not able to cross the suture lines.
So as subdural hematomas become subacute,
they may develop a fluid-fluid level and they become hypodense overtime.
So this is a comparison of a subdural and an epidural hematoma.
In a subdural hematoma, the dura is attached to the skull
and the blood is underneath the dura, so between the dura and the brain.
In an epidural hematoma, the dura is peeled off of the skull
and the hemorrhage is between the skull and the dura
and it?s usually caused by a fracture.
Subdural hematomas predominantly consist of venous blood
while epidural hematomas consist of arterial blood
and a subdural hematoma is usually caused by a rupture of the bridging vein
while an epidural hematoma is usually caused by rupture
of a middle meningeal artery.
Let?s take a look at this case here.
Which type of hemorrhage do you think this is?
So this is a high density, biconvex collection
in the temporal-parietal region right here.
You have adjacent soft tissue swelling
and there?s an adjacent skull fracture which was later found,
it?s not visible on this images, so this is an example of an epidural hematoma.
This is an example of a subdural hematoma.
We have an acute subdural hematoma along the right convexity.
It presents as a high density, crescentic collection.
This is an example of a chronic subdural hematoma
that presents as a low density crescentic collection along the right hemisphere.
In this case, you can see that there?s persistent mass effect.
So if you take a look at the midline, the midline is still shifted to the left,
slowly this will resolve.
So subarachnoid hemorrhage is a high density fluid between the pia
and the arachnoid space. You can see blood within the sulci
and within the basal cisterns and common causes include trauma,
ruptured aneurysm, or an AV malformation.
Usually patients present with what?s called a thunderclap headache,
it's kind of like getting hit on the head with a hammer
and then patients often complain of it being the worst headache of their life.
So let?s take a look at these 3 CT axial images.
So can you see the abnormality here?
You can actually see blood within the basal cisterns and within the sylvian fissures.
Here we have an example of blood within the fissures.
You can see blood within the sulci and you can also see blood within the falx.
This subarachnoid hemorrhage was caused by ruptured aneurysm.
Let?s take a look at this image.
So what kind of hemorrhage is this?
How would you characterize this?
So this is an example of an intracerebral hematoma.
You have hemorrhage within the brain parenchyma here
and the hemorrhage is extended into the ventricular system
which can often happen with an intracerebral hematoma.
This is commonly caused by trauma, aneurysm rupture,
amyloidosis, or hypertension. There are many, many, other causes
but these are some of the more common ones.
Intracerebral hematomas present as small areas of high density
with surrounding edema. The edema, as we?ve talked about, appears hypodense.
It can also cause blood to enter the ventricular system
and it may displace or compress the surrounding structures
because of mass effect from the collection.
These can also result in herniation.
This is another example an intracerebral hematoma.
As you can see here, there are areas of high density
within the brain parenchyma with a surrounding area
of low density representing edema.