Classic CT presentation of epidural hematoma
On non-contrast brain CT scans (in axial, coronal, and sagittal projections), epidural hematoma appears as an extra-axial blood collection. The typical location of such hemorrhage is the parietal region.
The primary visual characteristic on scans is a well-circumscribed biconvex (lens-shaped) hyperdense area. Anatomically, the hematoma is located between the skull and the dura mater (dura mater). On CT slices, the medial border of the hemorrhage represents the displaced dura mater.
Key diagnostic sign: the classic variant of the hematoma does not cross the cranial sutures. This occurs because the dura mater is extremely tightly fused to the bones at the suture sites, creating a natural barrier.
Rupture of meningeal arteries is most commonly triggered by an underlying bone fracture (e.g., of the left parietal bone). Interestingly, the fracture line itself is not always visible on standard CT slices; however, the overlying subgaleal hematoma (subgaleal haematoma) — pronounced edema and blood collection — is clearly visualized in the soft tissues of the cranial vault above the affected area.
Venous epidural hematoma
A distinct variant of trauma is venous epidural hematoma. Non-contrast CT, CT venography, and 3D skull reconstruction are used for its detailed diagnosis.
In severe injuries of the cranial vault (calvarium), 3D models may reveal suture diastasis (diastasis). For example, with diastasis of the lambdoid (sutura lambdoidea) and occipitomastoid (sutura occipitomastoidea) sutures, the fracture line may cross the projection of major venous collectors—the transverse (sinus transversus) and sigmoid (sinus sigmoideus) sinuses. Sometimes the fracture extends caudally into the mastoid part of the temporal bone (pars mastoidea ossis temporalis).
Unlike the arterial type, a venous hematoma behaves differently: it is capable of crossing sutures and spreading across the tentorium cerebelli (tentorium cerebelli). On sagittal CT venography, one can see how the hematoma deforms and compresses the adjacent transverse sinus.
If gas bubbles (pneumocephalus) are visible within the blood collection, this is considered a secondary sign of compromised integrity of the cranial base bones.
Differential diagnosis with subdural hematoma
It is important for the radiologist not to confuse an epidural blood collection with an acute subdural hematoma, which has different characteristics:
- A subdural hematoma over the convexity of the hemisphere acquires a classic crescent shape.
- It spreads freely over the cerebrum because it is not limited by sutures.
- Its medial spread is strictly limited by the falx cerebri (falx cerebri).
Subdural hemorrhages frequently cause severe complications in the form of midline shift, for example, subfalcine herniation.
Of particular difficulty for visualization are flat (thin) subdural hematomas of the tentorium cerebelli. On axial slices, their only manifestation may be merely asymmetric hyperdensity of the tentorium. Therefore, for accurate evaluation, coronal and sagittal reconstructions must be reviewed.
Briefly: answers to topical questions
Which specific artery is the most frequent source of bleeding in a classic epidural hematoma?
The most frequent source of bleeding in a classic epidural hematoma is the middle meningeal artery (a. meningea media). It runs within the bony canal of the squamous part of the temporal bone; a fracture in this area can injure the artery and lead to the formation of an epidural hematoma.
In the region of which anatomical landmark of the skull does a fracture most commonly occur that leads to arterial rupture and an epidural hematoma?
A fracture leading to arterial rupture and the formation of an epidural hematoma most commonly occurs in the region of the squamous part of the temporal bone or the parietal bone.
- Squamous part of the temporal bone — its bone canal contains the middle meningeal artery, damage to which causes a classic complication of temporal trauma.
- Parietal bone — a fracture of the underlying bone in this area is also a typical cause of meningeal artery rupture.
What is the classic clinical period characteristic of the course of an epidural hematoma prior to a sharp deterioration in condition?
The classic clinical period preceding a sharp deterioration in condition is the «lucid interval» (lucid interval). This is a period of complete or partial recovery of consciousness between the initial loss of consciousness at the time of trauma and its secondary loss.
At this stage, the following clinical picture is observed:
- Consciousness recovers to alert or moderate obtundation.
- The headache temporarily decreases or disappears completely.
This is followed by secondary deterioration with increasing headache, vomiting, and depression of consciousness up to coma.
Lemon and banana. An epidural hematoma on CT looks like a lemon (biconvex, limited by cranial sutures). A subdural hematoma looks like a banana (crescent-shaped, spreading freely along the hemisphere).
Class and exam questions
Why doesn't a classic epidural hematoma cross cranial sutures?
In the area of the sutures, the dura mater (dura mater) is tightly fused with the cranial bones. This creates a mechanical barrier that blood cannot cross.
Can an epidural hematoma extend beyond a suture?
Yes, this is typical for a venous epidural hematoma. Unlike the arterial one, it is capable of crossing cranial sutures and the tentorium cerebelli.
What does gas inside an epidural hematoma indicate?
The accumulation of gas bubbles (pneumocephaly) within the hematoma structure is a secondary radiological sign of a basilar skull fracture.
What else to study on this topic
- Evaluation of 3D CT reconstructions in cranial suture diastasis
- CT venography technique for diagnosing dural venous sinus compression
- Subfalcine herniation of the brain in convexity hematomas
- Imaging features of thin subdural hematomas in different CT projections
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