Pathological study of diffuse axonal injury patients who died shortly after impact

It is generally considered that axonal injury is apparent only on electron microscopy in the very early stage after a closed head injury. To clarify the pathological findings in head injury patients dying very shortly after the impact, we analyzed 8 fatal cases of diffuse axonal injury (DAI) who underwent medicolegal autopsy at the Department of Forensic Medicine of Kyoto Prefectural University of Medicine. Seven cases died within one hour after injury and another one case died 3 days after injury. We studied these cases macroscopically, microscopically, and electron microscopically. Macroscopically all cases showed the typical findings of diffuse axonal injury. Microscopical study of the cases who died within one hour revealed no characteristic findings of DAI such as appearance of retraction balls or microglia. On the other hand, in the case who died only 3 days after injury it showed the typical retraction balls. Electron microscopic study showed the remarkable destruction of cytoskeletal structure of axons in all cases. From our results, it is reasonable to speculate that DAI may be common among head injury patients who die very soon after the impact.