Introduction: Beta-amyloid precursor protein (betaAPP) expression has been found in traumatic brain injury, hypoxia, ischemia and infection which affect axonal transport. Although betaAPP is a sensitive marker for detecting axonal damage, it has become non-specific for a particular type of injury. The aim of this study was to identify a difference in the pattern, distribution and intensity of betaAPP expression in head injury compared to hypoxic/ischemic insults.
Materials and methods: Thirteen primary head injury and 12 primary hypoxic/ischemic cases were selected. The anterior and posterior parts of corpus callosum, internal capsule (basal ganglia), middle cerebellar peduncles (cerebellum) and pons were examined and stained immunohistochemically for betaAPP antibody. A computerized system of image analysis was used to examine the intensity (strength of staining) and density (area fraction) of betaAPP.
Results: Significant differences were observed in the overall intensity and density of betaAPP expression (p < 0.05) and in all 5 brain regions in cases of head injury compared to the hypoxic/ischemic group (p < 0.05). Positive staining for betaAPP was found in all regions in all cases of head injury, however, 4 out of 12 cases of hypoxia/ischemia were positive for betaAPP. One case expressed positivity in all 5 regions, 2 cases exhibited positivity in the pons alone, with only 1 case exhibiting immunoreactivity in the posterior corpus callosum and internal capsule. Differences in the pattern of betaAPP expression identified a predominantly granular pattern with a dirty background seen in hypoxia/ischemia, while fusiform swellings, beaded and thick filaments with clear background were observed in head injury.
Conclusion: There are differences in the pattern, distribution and intensity of betaAPP in head injury compared to hypoxia/ischemia. These could be due to pathophysiological differences. The results may be helpful in differentiating head injury from hypoxia in medicolegal cases.