Epidural hematomas are the result of blood collecting in the potential space between the skull and the dura mater. They occur in only 0.5 to 1 percent of all head-injured patients and in less than 10 percent of those with head injuries who are comatose. Most (80 to 90 percent) result from blunt trauma to the temporal or temporoparietal area with an associated skull fracture and middle meningeal arterial disruption ( Fig 24.7-7). Occasionally, trauma to the parietooccipital region or the posterior fossa causes tears of the venous sinuses with epidural hematomas. Almost all epidural hematomas are associated with skull fractures, and 80 percent will progress to uncal herniation. Additional cerebral lesions occur in 24 percent of patients, but they are usually not life-threatening. Epidural hematomas are rare in the elderly and children less than age two. In the elderly, the dura mater is firmly attached to the skull, which decreases the likelihood of dissection into the potential space. The less rigid skull of younger children protects against skull fractures and the resultant disruption of the middle meningeal artery.
The classic history of an epidural hematoma is for the patient to experience immediate loss of consciousness after significant blunt head trauma. The patient then awakens and has a lucent period prior to again falling unconscious as the hematoma expands. Unfortunately, this "classic" syndrome occurs in only about 20 percent of cases. The majority of patients either never loose consciousness or never regain consciousness after the injury.
The diagnosis of an epidural hematoma is based on CT scan and physical findings. On CT scans, epidural hematomas appear biconvex (football shaped), typically in the temporal region.
The high-pressure arterial bleeding of an epidural hematoma can lead to herniation. The sequence of epidural bleeding and herniation usually occurs within hours. Therefore, early recognition and intervention is key to reduce morbidity and mortality. More than 90 percent of patients with recognized epidurals will have the hematoma operatively evacuated within 48 h. One-third of these will be evacuated within the first 12 h. Bilateral emergency department trephination (burr holes) are only indicated if definitive neurosurgical care is not available. Full recovery can be expected if the hematoma is evacuated prior to herniation or to the presence of neurologic deficits. Otherwise, irreversible brain injuries from increased ICP may insue, resulting in a less favorable outcome.
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