Penetrating (Open) Injuries
Penetrating injuries are caused by gunshots and severe blunt trauma. They are associated with severe brain damage and a high incidence of infection. The symptoms and sequelae depend on the extent and area of damage.
Nonpenetrating (Closed) Injuries
Nonpenetrating injuries, usually caused by blunt trauma, may produce several degrees of damage.
Cerebral Concussion (Commotio Cerebri)
Cerebral concussion is transient loss of cerebral function—in most definitions including loss of consciousness—that immediately follows head injury. It is probably the result of relative motion between the brain stem and the cerebral hemispheres, causing temporary neuronal dysfunction in the reticular formation. The brain shows no gross or histologic abnormality.
Concussion is frequently associated with loss of memory for events occurring shortly before the traumatic episode (retrograde amnesia) or immediately afterward (posttraumatic amnesia). Recovery from concussion may be followed by recurrent headache, impaired ability to concentrate, and other minor neurologic symptoms (postconcussion syndrome). These symptoms are usually transient but in some cases may persist for years.
Rupture of small blood vessels in the brain near its surface and extravasation of blood into the brain substance is most commonly caused by movement of the brain relative to the skull (acceleration–deceleration injuries), causing it to strike bony prominences within the skull, such as those in the floor of the anterior cranial fossa or the internal occipital protuberance (Figure 64-1). Contusions also occur in the brain subjacent to the point of impact, particularly if there is a depressed skull fracture. Contusions may also occur on the side opposite the point of impact (contrecoup injuries).
Direct effects of craniocerebral trauma.
Cerebral contusions appear initially as an area of subpial hemorrhage. Like an ordinary contusion (bruise) anywhere on the body, the lesion undergoes color change from red to brown as iron is deposited in the tissues. Cerebral contusions may serve as the focus for subsequent epileptic activity.
In rare patients who died of prolonged coma after a head injury, the only autopsy abnormality is surface contusion. In these patients, it is likely that widespread axonal disruption caused by shearing forces at the time of injury is responsible for the severe neurologic deficit. Such axonal shearing produces minimal microscopic changes and is difficult to demonstrate.
The most severe type of brain injury is tearing of cerebral tissue, resulting in acute hemorrhage in the subarachnoid or subdural space. Cerebral laceration is often associated with profound neurologic dysfunction and with a high mortality rate.
Spinal cord injuries result from forced movements (such ...