What does herniation mean?
Displacement of tissue into a different area
What is a subfalcine herniation?
When part of one side of the brain gets pushed under to the other side
What is an uncal transtentorial hernation?
Whn the inferior temporal lobe gets pushed into the space that the cerebellum typically occupies
What are arachnoid granulations?
When parts of the arachnoid mater bulge through the dura
What is the function of arachnoid granulations?
Creates a space for CSF to be reabsorbed into venous blood
smaller granulations are called arachnoid villi
What does the arachnoid mater adhere to?
The meningeal layer of the dura
Where does the pia mater adhere?
To the outer surface of the cortex, following the gyri and sulci
like shrink wrap
Name the two potential spaces in the brain
- epidural space
- subdural space
Where is the epidural space?
Between the skull and the periosteal layer of the dura
Where is the subdural space?
Between the meningeal layer of the dura and the arachnoid mater
Where is the sub-arachnoid space?
Between the arachnoid and pia mater
What is found within the sub-arachnoid space?
CSF, arteries
What forms the sagittal sinus?
divergence of the dural layers at the falx cerebri
Where does the middle meningeal artery run?
Between the dura and the skull
What is a common cause of injury to the middle meningeal artery?
Fracture of the temporal bone
Why are the temporal bones prone to fracture?
- Bone is thinner at the temples
- Several bone sutures in that area
What are the three characteristics of an epi-dural hematoma?
- Fast-spreading arterial bleeding
- Lens-shaped
- Can cross the midline
What is a common cause of sub-dural hematomas?
Shearing of the bridging veins when the head experiences an abrupt change in acceleration
Where are the bridging veins located?
They pass through the arachnoid and meningeal layer of dura to drain into the dural sinuses
What are four characteristics of a sub-dural hematoma?
- Slow-spreading venous bleed
- Crescent-shaped
- Develops over time
- Cannot cross the midline due to the falx cerebri
How does acute blood appear on a CT scan?
Very bright, because it is hyper-dense
How does chronic blood appear on a CT scan?
Less bright, as it begins to liquefy
Why are older adults more prone to subdural hematomas?
Aging causes the brain to shrink over time, making the bridging veins more susceptible to shearing with smaller amounts of acceleration
What are the causes of sub-arachnoid hematomas?
- Non-traumatic: rupture of an arterial aneurysm
- Traumatic: contusions or other brain injury that results in bleeding
