Dating of Traumatic Brain Injury in Forensic Cases Using Immunohistochemical Markers (I)

Neurofilaments and β-Amyloid Precursor Protein

Abstract

Studies about head trauma are experimental or have a clinical or prognosis purpose. In this study, we used samples from human autopsies to answer common medical-legal questions.

We studied 21 problem cases and 4 controls. Samples were obtained directly from the injured area, fixed in 10% formalin during 24 hours and then preserved in 70% ethanol. This procedure optimizes the immunohistochemical technique.

The neurofilament antibody shows beaded axons since the first moment; over time, they increase their density and diameter as survival time also increases. These changes begin in the gray matter, 2 hours after trauma can be seen around vessels and in hemorrhagic areas. At 24 hours, beaded axons appear in the white mater, which finally loses its structure and cellular density.

On the other hand, the β-amyloid precursor protein marker begins to be weakly seen 2 hours after injury. At 24 hours, a diffuse pattern can appear, suggesting primary traumatic injury. The marker reading keeps increasing until day 26, when a “Z” pattern appears in the white matter, suggesting secondary hypoxic injury.

All these chronologic changes could be useful to approach the date of trauma. They let us to distinguish between long surviving cases from those whose death was immediate (within the first 30 minutes).