An epidural hematoma is a pocket of blood that forms immediately outside the dura mater. The dura mater is the fibrous outermost sheath or membrane that encloses the brain and spinal cord. Epidural means outside the dura, and hematoma means mass of blood.
Epidural hematomas usually form when a violent blow breaks a blood vessel in the space outside the dura mater, whether in the skull or in the spinal column. In the skull, the vessel most often responsible for epidural hematoma is the middle meningeal artery.
Blood from the broken vessel forms a pressurized pocket of blood, like a large, internal blood blister. The growing hematoma pushes against the rigid bone of the skull or spinal column and thus exerts pressure on the dura mater, which in turn pushes on the brain or spinal cord. This pressure may stretch and tear blood vessels or even force the brain to herniate (i.e., partially squeeze out) through the foramen magnum, the hole in the bottom of the skull through which the spinal cord enters, or through the tentorium cerebelli, the part of the dura mater that covers the cerebellum and supports the occipital lobes from below. Herniation of the brain is likely to be fatal.
Epidural hematomas are less common than subdural hematomas, which are the most common mechanism of fatal brain damage in head trauma. They are also distinguished from intracranial hematomas, volumes of blood that collect inside the brain rather than at its surface.
Traumatic brain injuries such as those that can result in cranial epidural hematoma are common. About 500,000 patients are admitted to hospitals in the United States annually with head injuries that cause brain damage, and some 75,000–90,000 of these patients die. Motor vehicle accidents are the most common cause of closed-head injuries, accounting for 50–70% of such injuries. Falls are the second most common cause of closed head trauma. Alcohol is a contributing factor in about 40% of severe head injuries. Sports such as football can result in traumatic head injury, but do so relatively rarely. Three-quarters of patients with traumatic brain injury are male, and the risk of traumatic brain injury declines steadily with age.
Epidural hematoma occurs in about 1% of all patients with severe head injuries. The fraction of comatose head-injury patients with subdural hematoma is greater, but still only about 10%.
Intracranial subdural hematoma
The most common cause of cranial epidural hematoma is head trauma, which is some kind of blow to the head. Epidural hematomas are most commonly found in the temporal or temporoparietal region, i.e., along the sides of the brain. Patients often lose consciousness due to the original head trauma, regain consciousness and undergo a period of clear-mindedness, then deteriorate neurologically.
Spinal epidural hematoma
Trauma is a common cause of spinal epidural hematoma. Non-trauma causes include anticoagulant therapy, hemophilia, liver disease, aspirin use, systemic lupus erythematosus, and, rarely, lumbar puncture. In 40–50% of cases of spinal epidural hematoma, no precipitating trauma or other cause is observed; these cases are considered spontaneous.
Spinal epidural hematoma causes compression of the spinal cord. Symptoms vary with the amount and location of this pressure. Back pain may be slight or absent. The patient may have loss of feeling (anesthesia) or less-than-normal feeling (hypoesthesia) in the legs, arm, or trunk. There may be weakening of the legs and loss of deep tendon reflexes. There may be bowel and bladder dysfunction
Neurologic assessment is the first step in determining the severity of a head injury. The patient's speech, eyeopening, and muscular responses are evaluated, along with the orientation (if conscious) to place, time, and commands to open eyes or the like. If the patient is unconscious, examination of the pupillary light reflex is important. An epidural or other hematoma increases intracranial pressure, which quickly has an effect on the third cranial nerve, which contains, among other nerve fibers, those that control constriction of the pupil. Pressure that blocks this nerve leads to fixed dilation of the pupil. Fixed pupil dilation in one or both eyes is a strong indicator that the patient may have an intracranial hematoma. To distinguish between epidural, subdural, and intracranial hematoma, computerized tomography (CT) or magnetic resonance imaging (MRI) is probably necessary. Surgeons determine if swelling on one side of the brain has shifted the midline of the brain. If a shift of more than 0.2 in (5 mm) is found, an emergency craniotomy (opening of the skull) may be performed.
Patients with spinal epidural hematoma may experience sudden onset of back or neck pain at the site of the bleed. Coughing or any other maneuver that increases pressure inside the torso may worsen the pain transiently. In children, the bleeding is more likely to be in the cervical (neck) region than in the thoracic (middle back) region.
When making the diagnosis of spinal epidural hematoma, physicians must decide whether the symptoms of spinal compression are being caused by a hematoma or by a tumor. CT or MRI are definitive in distinguishing between compression of the spinal cord caused by tumor or hematoma.
Treatment for hematoma is primarily surgical. A neurologist and a neurosurgeon will be essential members of the treatment team, as will nursing staff, in the operating room and out of it, who are specially trained in head trauma care.
Emergency care for spinal trauma consists of immobilizing the patient and administering high-dose corticosteroids. However, the highest priority for any intracranial or spinal hematoma is relief of the pressure by surgical drainage of the hematoma.
Recovery and rehabilitation
Epidural hematoma can result in permanent paralysis or other neurological deficits. If spinal cord compression due to hematoma is alleviated within 6–12 hours, permanent symptoms may be avoided. Prevention of brain damage depends more on preventing the brain from being deformed by the pressure of the hematoma than on relieving that pressure. Rehabilitation needs will depend on how much permanent damage, if any, has been caused.
As of 2004, no clinical trials were being conducted for epidural hematoma patients in the United States.
Marsh, Cherly. "Surgical Management of Patients with Severe Head Injuries." AORN Journal May 1, 1996.
Sung, Helen Minjung. "How to Diagnose and Treat Acute, Nontraumatic Spinal Cord Lesions." The Journal of Critical Illness April 1, 2000.
Trask, Todd. "Management of Head Trauma (Critical Care Review)." Chest August 1, 2002.
Epidural Hematoma Patient/Family Resources. April 26, 2004 (May 30, 2004). <http://cchs-dl.slis.ua.edu/patientinfo/orthopedics/head/epidural-hematoma.htm>.
NINDS Traumatic Brain Injury Information Page. National Institute of Neurological Disorders and Stroke. April 26, 2004 (May 30, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/tbi_doc.htm>.