An intracranial epidural hematoma (EDH) occurs when blood accumulates between the dura and inner table of the calvarium. The classic etiology of the bleed is traumatic injury to the middle meningeal artery following a skull fracture. The source of bleeding is arterial in 85% of cases; in 15% of cases, the etiology is venous from a meningeal vein or dural venous sinus injury. As blood accumulates in the space between the outer layer of dura and skull, it strips the dura and forms a biconvex (lenticular or football-shaped) hematoma. The dura is very adherent to the overlying cranial sutures, so the hematoma is often limited. It is more commonly seen in children and adults, whose dura is less adherent to the inner table of the skull, as opposed to infants < 2 years of age or the elderly.

The classic presentation involves a brief post-traumatic loss of consciousness, then several minutes to hours of a lucid interval, followed by obtundation and focal neurologic deficits. While this classic clinical description is widely taught, it is seen in < 20% of cases. Other less specific signs and symptoms include headache, nausea and emesis, seizures, neurologic deficits (contralateral weakness, hyperreflexia), papilledema, pupil-involving third-nerve palsy, somnolence, or coma.