Two patterns of beta-amyloid precursor protein (APP) immunoreactivity in cases of blunt head injury

Immunostaining for beta-amyloid precursor protein (APP) is widely recognized as an effective tool for detecting diffuse traumatic axonal injury (TAI). APP selectively labels injured axons, such as axonal bulbs and varicose axons. However, it has been reported that axonal bulbs are detected in cases of cerebral hypoxia without head injury. Therefore, we examined whether there are differences in the morphological pattern of axonal bulbs between trauma and hypoxia. Sections of the corpus callosum from 25 cases of head injury and 23 control cases were immunostained for APP. APP staining detected axonal bulbs in 14 cases of head injury, who survived more than several hours, although it failed to label axons in control cases. In addition, two patterns of immunoreactivity were identified in several cases of head injury. The first pattern showed that labeled axons were oriented along with white matter bundles; the second demonstrated that the axons were scattered irregularly. The first pattern alone was found in 5 of 14 cases, while cases of the second pattern alone were not observed. Both patterns were detected in 5 cases and in the remaining 4 cases, clear patterns were not found. From these findings, we speculated that the first pattern may represent TAI. Further examinations are required for determining whether these two patterns are identical with patterns of trauma and hypoxic brain damage as indicated by [Oehmichen M, Meissner C, Schmidt V, Pedal I, König HG, Saternus KS. Axonal injury--a diagnostic tool in forensic neuropathology? A review. Forensic Sci Int 1998;95:67-83] and [Graham DI, Smith C, Reichard R, Leclercq PD, Gentleman SM. Trials and tribulations of using beta-amyloid precursor protein immunohistochemistry to evaluate traumatic brain injury in adults. Forensic Sci Int 2004;146:89-96].