An epidural hematoma is a collection of blood between the dura and .
USMLE® Step 1 style questions USMLE
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A 45-year-old man is wheeled into the operating room for a surgical evacuation of an epidural hematoma. Which of the following hemodynamic changes would be indicators concerning for an increase in intracranial pressure (ICP)?
Epidural hemorrhage can be broken down. "Epi" means above, "dural" refers to the outermost protective layer of the brain, which is called dura mater and and “hemorrhage” refers to bleeding.
So, an epidural hemorrhage is when there’s bleeding above the dura mater.
OK - let’s start with some basic brain anatomy. The brain is protected by the meninges, which are 3 thin layers of tissue which cover the brain and spinal cord.
The inner layer of the meninges is the pia mater, the middle layer is the arachnoid mater, and the outer layer is the dura mater.
The pia and arachnoid maters, are also called leptomeninges.
Between the leptomeninges, there’s the subarachnoid space, which houses cerebrospinal fluid, or CSF.
CSF is a clear, watery liquid which is pumped around the spinal cord and brain, cushioning them from impact and bathing them in nutrients.
The outer membrane, the dura mater consists of two layers.
The internal layer of the dura mater lies above the arachnoid mater - the two are separated by the subdural space.
The external layer of the dura mater adheres to the inner surface of the skull.
These two layers of the dura mater travel together, but at certain spots, the internal layer of the dura mater separates from the external one to form the meningeal folds.
The meningeal folds help divide the sections of the brain like the falx cerebri which separates the two hemispheres of the cerebrum, and the tentorium, which covers the cerebellum and separates it from the cerebrum.
Between the external layer of the dura mater and the inner surface of the skull, there are arteries that supply meninges.
The most common cause of epidural hemorrhage is a head trauma which might happen after tripping and falling in a bathtub.
The meningeal arteries are protected by the skull but can be damaged by a serious head trauma.
The most common site is at the pterion which is the spot where the frontal, parietal, temporal and sphenoid bones join together.
This section of the skull is relatively thin and it’s located right above the middle meningeal artery.
When a blood vessel is damaged and there’s active bleeding, it’s called a hemorrhage, and the collection of blood that results is called a hematoma.
In the case of an epidural hemorrhage, once a meningeal artery is torn, blood will pool between the skull and the external layer of the dura mater, separating it from the inner surface of the skull.
The blood builds up between the skull and the outer layer of the dura mater but cannot cross the suture lines where the dura mater adheres more tightly.