Acute hemorrhage appears hyperdense on computed tomography (CT) scans, with the shape and location of hemorrhage suggesting the underlying pathology. Epidural hematomas are classically lentiform (lens shaped) because of their relationship to arterial injury, with the higher pressure compressing the brain parenchyma (Fig. 73.2). Subdural hematomas are more commonly crescent shaped, with blood from torn veins tracking along the surface of the brain beneath the dura mater (Fig. 73.3). Intraparenchymal hemorrhage can exist as a discrete hematoma or as multiple smaller foci throughout a contused area of brain (Fig. 73.4). In addition to focal areas of hemorrhage, cerebral contusions typically involve cerebral edema, which may progress markedly over a period of several days. Skull fractures may be seen on plain radiographs, but more important is the potential for injury to the underlying brain parenchyma or the existence of intracranial hemorrhage (Fig. 73.5). Subarachnoid hemorrhage appears as hyperdensities within the ventricles, along the falx and tentorium, and around the circle of Willis (Fig. 73.6). One of the most elusive diagnoses is diffuse axonal injury, in which the findings on CT are often much less impressive than the degree of obtundation. Small, punctate hemorrhages along the gray-white interface at the cortical periphery suggest this diagnosis, although the initial scan may be completely normal.