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based upon mechanism; however, neurologic outcome is related to degree
of neurologic impairment at time of presentation.
Diffuse Injury. These injury patterns include DAI, cerebral edema, hypoxic
ischemia, and diffuse vascular injuries. DAI is due to shear injuries of axons
and blood vessels involving the white matter of the brain. The shear occurs
with acceleration and deceleration or rotational forces involving the brain
matter. The degree of tissue disruption is indicative of the amount of energy
dissipation. DAI may not be seen on CT scan, as the severity of injury
typically has DAI with associated intracerebral hemorrhages, especially
multiple petechial hemorrhages in the deep white matter. MRI is more
sensitive in delineating transient signal changes along white matter tracts.
Cerebral edema may be caused by a multitude of factors. Not only is
edema due to direct insult to the neurons with local release of inflammatory
mediators and vascular leakage, but may progress as secondary injury due
to hypoxemia and changes in cerebral blood flow. On CT scan, brain edema
appears as an area of decreased density associated with brain shift,
especially pronounced with loss of gray–white matter interface
differentiation. Both DAI and cerebral edema are commonly associated
with intracerebral hemorrhage and/or contusion and may lead to herniation.
The component of hemorrhage or significant mass effect resulting from
edema becomes a neurosurgical emergency.
Focal Injury. These injury patterns include contusions, lacerations,
hemorrhage, and midline shifts. Cerebral contusions are typically due to
direct impact of the brain along dural edges or intracranial bony surfaces.
The presentation may be benign or symptomatic with a focal neurologic
deficit or seizure. Isolated contusions with minimal localized swelling
without midline shift are injuries that may be managed nonsurgically.
Subdural hemorrhage occurs when bridging vessels rupture into the
potential space between the dura and the arachnoid. This anatomic location
allows the blood to transverse cranial sutures and accounts for the typical
crescent-shaped or convex appearance ( Fig. 113.1 ). Subdural hematomas

in children under the age of 2 years are more likely to be associated with
child abuse than other injury patterns. Please refer to Chapter 87 Child
Abuse/Assault for further discussion.