Epidural or extradural hematoma is a type of traumatic brain injury (TBI) in which a buildup of blood occurs between the dura mater (the tough outer membrane of the central nervous system) and the skull. The dura mater also covers the spine, so epidural bleeds may also occur in the spinal column. Often due to trauma, the condition is potentially deadly because the buildup of blood may increase pressure in the intracranial space and compress delicate brain tissue. The condition is present in one to three percent of head injuries. Between 15 and 20% of patients with epidural hematomas die of the injury.
The cause of epidural hematoma is usually traumatic, although spontaneous hemorrhage is known to occur. Hemorrhages commonly result from acceleration-deceleration trauma and transverse forces. 10% of epidural bleeds may be venous. Venous epidural bleeds are usually due to shearing injury from rotational or linear forces, caused when tissues of different densities slide over one another.
Epidural hematoma commonly results from a blow to the side of the head. The pterion region which overlies the middle meningeal artery is exceptionally weak and prone to injury. Thus only 20 to 30% of epidural hematomas occur outside the region of the temporal bone. The brain may be injured by prominences on the inside of the skull as it scrapes past them. EDH is usually found on the same side of the brain that was impacted by the blow, but on very rare occasions it can be due to a contrecoup injury.