Objective: Hypodensities on computed tomographic (CT) brain scans are thought to take at least 6 hours to become apparent after blunt head trauma. This finding, in conjunction with the later evolution of the hypodensities, is used in timing the injury in children with suspected non-accidental brain injury, in whom the history may be inaccurate. The purpose of this study is to report the occurrence of diffuse cerebral parenchymal hypodensities on CT scans performed within 5 hours of a well-defined accidental head injury.
Methods: A retrospective review was performed of five patients admitted to British Columbia Children's Hospital who had accidental head injury and who were identified as having diffuse cerebral hemispheric hypodensities on early CT scans.
Results: We present five patients (age range, 4 mo-14 yr) with well-documented accidental head injuries who demonstrated obvious and extensive CT brain scan cerebral hemispheric hypodensity from 60 minutes to 4.5 hours after trauma. All five patients presented with severe head injuries and immediate, unremitting coma, and all five progressed rapidly to brain death within 48 hours.
Conclusion: It is unusual, but possible, to develop CT hypodensities as early as 1 hour after accidental head injury. In our small series of cerebral hemispheric hypodensity occurring less than 5 hours after trauma, all five patients had a uniformly fatal outcome. These observations may be important medicolegally in the assessment of the timing of head injury when the history of the trauma is not clear, as in children with suspected non-accidentally inflicted injury. It is inappropriate to generalize these findings to patients who are not unconscious immediately after a head injury, who regain consciousness after an injury before deteriorating, or who do not progress rapidly to brain death.