Primary and secondary injury Primary injury

The events that occur at the moment of injury, although possibly preventable, are not reversible. However, brain contusions and hemorrhages are potentially avoidable causes of death and disability if evacuated promptly. Intracranial hemorrhage is classified based on location as being intracerebral (within the brain parenchyma), subdural (beneath the dura mater covering the brain surface), or epidural (outside the dura mater). Combinations of these hemorrhages are not uncommon. Epidural hematomas are classically associated with hemorrhage from a lacerated middle meningeal artery with formation of a lenticular hematoma in the temporal fossa (Fig, 1(a)). Other causes of epidural hemorrhage include diploic bleeding from a skull fracture or injury to a venous sinus. Clinically, epidural hematomas classically present with a lucid interval where the patient may be alert initially but deteriorates to coma because of the rapidly increasing epidural mass. Prompt evacuation of a rapidly enlarging epidural hematoma is not only lifesaving, but may allow good recovery. Patients with epidural hematomas have the greatest potential for good recovery from prompt hematoma evacuation because the underlying brain is usually normal.

Fig. 1 Axial CT scans of (a) a left temporal acute epidural hematoma with compressed cisterns and contralateral contusions, (b) a right hemispheric subdural hematoma with a shift in midline, and (c) a left frontal and temporal intracerebral contusion and hematoma with an associated right subdural hematoma.

Acute subdural hematomas (Fig 1(b)) are more common than epidural hematomas and are generally associated with a poorer prognosis. Hemorrhage in the subdural space frequently results from injury to bridging veins that drain blood from the cortical surface to the dural sinuses, or from lacerations of the brain surface. Prompt evacuation of an acute subdural hematoma may help to reduce the high mortality associated with these lesions.

Contusions or intracerebral hematomas (Fig 1(c)) are common after traumatic brain injury and are frequently seen in the frontal and temporal lobes. They often coexist with subdural hematomas and develop over time; hence it is important to perform a follow-up CT scan 4 to 8 h after the initial CT scan in patients with demonstrated brain injury.

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