Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain (dura mater) and the skull. Often there is loss of consciousness following a head injury, a brief regaining of consciousness, and then loss of consciousness again. Other symptoms may include headache, confusion, vomiting, and an inability to move parts of the body. Complications may include seizures.
The cause is typically head injury that results in a break of the temporal bone and bleeding from the middle meningeal artery. Occasionally it can occur as a result of a bleeding disorder or blood vessel malformation. Diagnosis is typically by a CT scan or MRI. When this condition occurs in the spine it is known as a spinal epidural hematoma.
Treatment is generally by urgent surgery in the form of a craniotomy or burr hole. Without treatment, death typically results. The condition occurs in one to four percent of head injuries. Typically it occurs in young adults. Males are more often affected than females.
Signs and symptoms
Many people with epidural hematomas experience a lucid period immediately following the injury, with a delay before symptoms become evident. Because of this initial period of lucidity, it has been called "Talk and Die" syndrome. As blood accumulates, it starts to compress intracranial structures, which may impinge on the third cranial nerve, causing a fixed and dilated pupil on the side of the injury. The eye will be positioned down and out due to unopposed innervation of the fourth and sixth cranial nerves.
Other symptoms include severe headache; weakness of the extremities on the opposite side from the lesion due to compression of the crossed pyramid pathways; and vision loss, also on the opposite side, due to compression of the posterior cerebral artery. In rare cases, small hematomas may be asymptomatic.
If not treated promptly, epidural hematomas can cause tonsillar herniation, resulting in respiratory arrest. The trigeminal nerve may be involved late in the process as the pons is compressed, but this is not an important presentation, because the person may already be dead by the time it occurs. In the case of epidural hematoma in the posterior cranial fossa, tonsillar herniation causes Cushing's triad: hypertension, bradycardia, and irregular breathing.
Causes
The most common cause of intracranial epidural hematoma is head injury, although spontaneous hemorrhages have been known to occur. Epidural hematomas occur in about 10% of traumatic brain injuries, mostly due to car accidents, assaults, or falls. They are often caused by acceleration-deceleration trauma and transverse forces.
Epidural hematoma commonly results from a blow to the side (temporal bone) of the head. The pterion region, which overlies the middle meningeal artery, is relatively weak and prone to injury. 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. Epidural hematoma is usually found on the same side of the brain which was impacted by the blow, but on very rare occasions it can be due to a contrecoup injury.
A "heat hematoma" is an epidural hematoma caused by severe thermal burn, causing contraction and exfoliation of the dura mater and exfoliate from the skull, in turn causing exudation of blood from the venous sinuses. The hematoma can be seen on autopsy as brick red, or as radiolucent on CT scan, because of heat-induced coagulation of the hematoma.
Pathophysiology
The break of the temporal bone causes bleeding from the middle meningeal artery, hence epidural bleeding is often rapid as arteries are high-pressure flow. In 10% of cases, however, it comes from veins and can progress more slowly. A venous hematoma may be acute (occurring within a day of the injury and appearing as a swirling mass of blood without a clot), subacute (occurring in 2–4 days and appearing solid), or chronic (occurring in 7–20 days and appearing mixed or lucent).