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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 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