What is Acute Epidural Hematoma? A Clear Explanation of Key Points in CT Imaging Diagnosis
Among head injuries, a condition where rapid diagnosis and treatment are critical is "Acute Epidural Hematoma."
CT scans show characteristic imaging findings, and it is a condition that is relatively easy to diagnose if you correctly understand the images.
In this article, I will explain:
The mechanism of occurrence of acute epidural hematoma
Typical findings on CT images
Differences from acute subdural hematoma
Points to note during image interpretation
based on the content of the figures.
What is an acute epidural hematoma?
An acute epidural hematoma is traumatic bleeding where blood accumulates between the skull and the dura mater.
Normally, this space does not exist, but when blood vessels are ruptured due to trauma, blood collects between the bone and the dura mater.
Mechanism of occurrence
In many cases, the cause is a skull fracture due to a head impact.
The typical progression is as follows:
Head trauma (traffic accident, fall, etc.)
Skull fracture occurs at the site of injury
Middle meningeal artery rupture
Bleeding between the inner table of the skull and the dura mater
Rapid expansion of the hematoma
In other words,
Fracture → Arterial rupture → Epidural hemorrhage
This is the sequence of events.
Particularly common is injury to the middle meningeal artery.
Understanding the structure of the dura mater
The dura mater actually has a two-layer structure.
Structure of the dura mater
Periosteal dura
Meningeal dura
These are usually tightly adhered.
Therefore, the space known as the epidural space does not exist under normal conditions.
It is only when blood enters due to trauma that the "epidural space" is formed.
Typical findings on CT images
Acute epidural hematoma has very characteristic CT findings.
Biconvex shape
The most important finding is a biconvex high-density area.
Characteristics:
Both sides are rounded
Lens-like shape
Locally confined
This occurs because the dura mater is strongly attached to the bone, making it difficult for the hematoma to spread.
Does not cross the suture line
There is another important point.
That is the characteristic that the hematoma does not cross the suture line.
The reason is that the dura mater is strongly fixed at the suture.
Therefore, on CT, it appears as
a localized hematoma
stopping at the bone suture
.
Differences from acute subdural hematoma
A common issue in diagnostic imaging of head trauma is
acute epidural hematoma vs. acute subdural hematoma.
To summarize the differences simply:
Epidural hematoma Subdural hematoma Shape Convex lens shape Crescent shape Vessel Middle meningeal artery Bridging vein Suture line Does not cross Crosses Frequency Low High
In particular, the difference in shape is very important.
Lens shape → Epidural hematoma
Crescent shape → Subdural hematoma
It is easier to understand if you remember it this way.
Complication of fracture
Acute epidural hematoma is very frequently accompanied by skull fractures.
In adults, fractures are observed in approximately 90% of cases.
Therefore, when interpreting images, it is important to always check the bone window.
Epidemiology
The characteristics of acute epidural hematoma are as follows.
Frequency
1 to 4% of head injuries
Comparison with subdural hematoma
Subdural hematoma is about 5 times more common
.
Common age group
It is relatively common in young people.
Reasons:
Susceptible to severe trauma
Dura mater is easily detached from the bone
On the other hand, it is less common in the elderly, because the dura mater is strongly adhered to the bone.
In infants, the bones are soft and arterial damage is less frequent.
Clinically important "Lucid interval"
In acute epidural hematoma,
Lucid interval
It may follow a characteristic clinical course.
Flow:
Loss of consciousness immediately after trauma
Temporary recovery of consciousness
Deterioration again due to hematoma expansion
For this reason,
the possibility of a sudden change even if they appear fine
exists, making it extremely dangerous.
Checkpoints for CT Interpretation
In head trauma CT scans, checking in the following order makes it less likely to miss findings.
1. Skull fracture
2. Convex lens-shaped hematoma
3. Relationship with suture lines
4. Midline shift
5. Signs of brain herniation
In particular,
if you see a fracture + lens-shaped hematoma,
you should
strongly suspect acute epidural hematoma.
Summary
Here is a summary of the key points for acute epidural hematoma.
Key points for CT diagnosis
Convex lens-shaped hyperdense area
Does not cross suture lines
Often caused by rupture of the middle meningeal artery
Frequently associated with skull fractures
And clinically,
it is an emergency condition that can rapidly deteriorate
.
In CT scans for head trauma,
it is extremely important not to overlook these typical findings.
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