An acute epidural hematoma (EDH) is a hyperdense (higher Hounsfield unit number), extra-axial (outside the brain parenchyma) blood collection that occurs after a coup injury. The “classical” EDH occurs from a laceration of the middle meningeal artery after blunt trauma and is biconvex (lens-shaped) in appearance.
Hypodense blood within an EDH represents acute unclotted hemorrhage, while hyperdense blood corresponds to acute clotted hemorrhage. The mixed-density pattern, termed the “swirl sign,” is caused by clotted and unclotted blood products.
EDH is confined by dural attachments to the cranium, which occur at cranial sutures. EDH will cross the sagittal suture at the midline but subdural hematomas (SDH) will not, because the dura does not invest the superior sagittal sinus.
EDH in the middle cranial fossa anterior to the temporal lobe tips is due to venous injury of the sphenoparietal sinus.
EDH comprise 1 to 4% of traumatic brain injury (TBI) and most often occur from falls less than 10 ft or from assault with an object (coup injury). The classical clinical scenario, which occurs in 10% of patients with EDH, presents with loss of consciousness, followed by a period of lucency. Patients then become progressively obtunded as the EDH enlarges. EDH may expand rapidly, causing mass effect that can lead to herniation. Decompressive craniectomy is required in most patients with rapidly expanding EDH. Despite the possibility for rapid expansion with EDH, patients with EDH generally have a better prognosis than patients with SDH. EDH of the anterior temporal lobes is venous rather than arterial, and typically has a benign course and frequently does not require surgical evacuation.
Figure 1.1 ▪ Epidural Hematoma.
NECT shows a lenticular (lens-shaped) hyperdense collection of blood along the high right parietal convexity with overlying scalp swelling.
Figure 1.2 ▪ Skull Fracture.
NECT in bone windows shows a nondisplaced right parietal skull fracture that involves the right coronal suture (allowing blood to extend past the suture).
Figure 1.3 ▪ Epidural Hematoma.
NECT shows a large collection of hyperdense blood along the right parietal surface. Note the swelling of the subjacent sulci and mass effect on the normally midline falx cerebri.
Figure 1.4 ▪ Epidural Hematoma.
NECT shows a collection of hyperdense blood along the right parietal convexity.
Figure 1.5 ▪ Skull Fracture.
NECT shows a faintly visible skull fracture extending to the right coronal suture (arrow). Although imaged in bone windows, underlying epidural hematoma and overlying scalp swelling is seen.