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.
Epidural bleeds, like subdural and subarachnoid hemorrhages, are extra-axial bleeds, occurring outside of the brain tissue, while intra-axial hemorrhages, including intraparenchymal and intraventricular hemorrhages, occur within it.
Epidural bleeding is rapid because it is usually from arteries, which are high pressure. Epidural bleeds from arteries can grow until they reach their peak size at six to eight hours post injury, spilling from 25 to 75 cubic centimeters of blood into the intracranial space. As the hematoma expands, it strips the dura from the inside of the skull, causing an intense headache.
Epidural bleeds can become large and raise intracranial pressure, causing the brain to shift, lose blood supply, or be crushed against the skull. Larger hematomas cause more damage. Epidural bleeds can quickly expand and compress the brain stem, causing unconsciousness, abnormal posturing, and abnormal pupil responses to light.
On images produced by CT scans and MRIs, epidural hematomas usually appear convex in shape because their expansion stops at skull's sutures, where the dura mater is tightly attached to the skull. Thus they expand inward toward the brain rather than along the inside of the skull, as occurs in subdural hematoma. The lens like shape of the hematoma leads the appearance of these bleeds to be called "lentiform".
Epidural hematomas may occur in combination with subdural hematomas, or either may occur alone. CT scans reveal subdural or epidural hematomas in 20% of unconscious patients.
In the hallmark of epidural hematoma, patients may regain consciousness during what is called a lucid interval, only to descend suddenly and rapidly into unconsciousness later. The lucid interval, which depends on the extent of the injury, is a key to diagnosing epidural hemorrhage. If the patient is not treated with prompt surgical intervention, death is likely to follow.
The anatomy of the epidural space means that spinal epidural hematoma has a different profile from cranial epidural hematoma. In the spine, the epidural space contains loose fatty tissue, and the epidural venous plexus, a network of large, thin-walled veins. This means that bleeding is likely to be venous. Anatomical abnormalities and bleeding disorders make these lesions more likely.
They may cause pressure on the spinal cord or cauda equina, which may present as pain, muscle weakness, or bladder and bowel dysfunction.
The diagnosis may be made on clinical appearance and time course of symptoms. It usually requires MRI scanning to confirm.
The treatment is surgical decompression.
The incidence of epidural hematoma following epidural anaesthesia is extremely difficult to quantify; estimates vary from 1 per 10,000 to 1 per 100,000 epidural anaesthetics. This means that a typical anaesthetist or anesthesiologist is statistically unlikely to cause one in a whole career.
Delayed spinal extradural hematoma following thoracic spine surgery and resulting in paraplegia: a case report.(Case report)(Case study)
May 02, 2008; Authors: Chandra JKB Parthiban ; Shiju A Majeed (corresponding author) IntroductionSymptomatic spinal epidural (extradural)...