Axonal Injury in Stroke: A Forensic Neuropathology Perspective

The use of β-amyloid precursor protein (β-APP) immunocytochemistry is standard practice in forensic neuropathology to assess the presence and severity of traumatic axonal injury. However, axonal injury has many causes, in addition to trauma. The principal complicating factor in interpretation is where traumatic brain injury is associated with brain swelling or hemorrhage, resulting in ischemic axonal injury. Although it has been claimed that different patterns of β-APP immunoreactivity are seen in trauma, as opposed to hypoxia-ischemia, there have been few systematic studies of β-APP immunostaining patterns in ischemic or hemorrhagic stroke. This study investigated staining patterns in 96 cases of stroke with no history of head injury and found complex staining patterns, some of which were indistinguishable from those said to be specific for trauma. A questioning approach to the assessment of β-APP immunostaining patterns in cases of head injury is proposed to ensure that the possibility of some or much of the staining being due to ischemia has been excluded, before concluding that the axonal injury identified is traumatic in causation.