Epidural hematoma (EDH) is a traumatic accumulation of blood between the inner table of the skull and the stripped-off dural membrane. The inciting event often is a focused blow to the head, such as that produced by a hammer or baseball bat. In 85-95% of patients, this type of trauma results in an overlying fracture of the skull. Blood vessels in close proximity to the fracture are the sources of the hemorrhage in the formation of an EDH. Because the underlying brain has usually been minimally injured, prognosis is excellent if treated aggressively. Outcome from surgical decompression and repair is related directly to patient's preoperative neurologic condition.

Pathophysiology

Approximately 70-80% of EDHs are located in the temporoparietal region where skull fractures cross the path of the middle meningeal artery or its dural branches. Frontal and occipital EDHs each constitute about 10%, with the latter occasionally extending above and below the tentorium. Association of hematoma and skull fracture is less common in young children because of calvarial plasticity.

EDHs are usually arterial in origin but result from venous bleeding in one third of patients. Occasionally, torn venous sinuses cause EDH, particularly in the parietal-occipital region or posterior fossa. These injuries tend to be smaller and associated with a more benign course. Usually, venous EDHs only form with a depressed skull fracture, which strips the dura from the bone and, thus, creates a space for blood to accumulate. In certain patients, especially those with delayed presentations, venous EDHs are treated nonsurgically.

Expanding high-volume EDHs can produce a midline shift and subfalcine herniation of the brain. Compressed cerebral tissue can impinge on the third cranial nerve, resulting in ipsilateral pupillary dilation and contralateral hemiparesis or extensor motor response.

EDHs are usually stable, attaining maximum size within minutes of injury; however, Borovich demonstrated progression of EDH in 9% of patients during the first 24 hours1. Rebleeding or continuous oozing presumably causes this progression. An EDH can occasionally run a more chronic course and is detected only days after injury.

Frequency

United States

EDH occurs in 1-2% of all head trauma cases and in about 10% of patients who present with traumatic coma.

Mortality/Morbidity

  • Reported mortality rates range from 5-43%.
  • Higher rates are associated with the following:
    • Advanced age
    • Intradural lesions
    • Temporal location
    • Increased hematoma volume
    • Rapid clinical progression
    • Pupillary abnormalities
    • Increased intracranial pressure (ICP)
    • Lower Glasgow coma scale (GCS)
  • Mortality rates are essentially nil for patients not in coma preoperatively and approximately 10% for obtunded patients and 20% for patients in deep coma.

Age

  • Patients younger than 5 years and older than 55 years have an increased mortality rate.
  • Patients younger than 20 years account for 60% of EDHs.
  • EDH is uncommon in elderly patients because the dura is strongly adhered to the inner table of the skull. In case series of EDH, fewer than 10% of patients are older than 50 years.

Clinical

History

  • Fewer than 20% of patients demonstrate the classic presentation of a lucid interval between the initial trauma and subsequent neurological deterioration.
  • Following injury, the patient may or may not lose consciousness. If he or she becomes unconscious, the patient may awaken or remain unconscious.
  • Severe headache
  • Vomiting
  • Seizure
  • Patients with posterior fossa EDH may have a dramatic delayed deterioration. The patient can be conscious and talking and a minute later apneic, comatose, and minutes from death.

Physical

  • Cushing response, consisting of the following, can indicate increased ICP:
    • Hypertension
    • Bradycardia
    • Bradypnea
  • Level of consciousness may be decreased, with decreased or fluctuating GCS.
  • Contusion, laceration, or bony step-off may be observed in the area of injury.
  • Dilated, sluggish, or fixed pupil(s), bilateral or ipsilateral to injury, suggest increased ICP or herniation.
  • Classic triad indicating transtentorial herniation consists of the following:
    • Coma
    • Fixed and dilated pupil(s)
    • Decerebrate posturing
  • Hemiplegia contralateral to injury with herniation may be observed.

Causes

  • EDH results from traumatic head injury, usually with an associated skull fracture and arterial laceration.