Neuroradiologic timing of intracranial hemorrhage in abusive head trauma

Determining the timing of intracranial injuries in general, and abusive head trauma (AHT) in particular, is important to the care of children with traumatic brain injury. Additionally, identifying the time of the injury provides important information as to who might have, and who did not, inflict the trauma. Understanding the appearance and evolution of intracranial findings on neuroimaging has been an important factor in assessing the time of the injury. However, a number of studies in the last two decades have both suggested greater uncertainty about the reliability of this process and advanced our knowledge in this area. In this review, the authors consider the biophysical factors that contribute to the appearance and evolution of intracranial hemorrhage and, in particular, subdural hemorrhage (SDH). The traditional view of SDH is predicated largely on prior studies of intracerebral hemorrhage, although a number of variables make this comparison untenable. Moreover, more recent studies have suggested a number of factors that could alter the density (CT) or signal intensity (MRI) and produce mixed density/intensity SDH. These factors need to be considered in interpreting neuroimaging studies. A number of these recent studies evaluating serial neuroimaging in children with AHT have modified our understanding of intracranial hemorrhage and its evolution in this context. Taken together, the studies to date, having important limitations, provide only broad ranges over which to time injuries. The authors conclude that neuroimaging studies at this time are not likely, in isolation, to be able to accurately pinpoint a specific time of injury; rather, neuroimaging can only provide a range of possible times and should instead be used as a means to supplement or corroborate timing based on clinical presentation and other imaging findings.