Comparison of background characteristics and neuropathology findings between medico-legal autopsy cases with traumatic axonal injury, vascular axonal injury, or absence of axonal injury in β-amyloid precursor protein stain.

In forensic neuropathology, the β-amyloid precursor protein (β-APP) immunostain is used to diagnose axonal injury (AI). The two most common aetiologies are traumatic (TAI) and ischaemic (vascular; VAI). We aimed to identify background characteristics and neuropathology findings that are suggestive of TAI, VAI, or no AI in neuropathologically examined medico-legal autopsy cases. The dataset comprised 166 cases from Finland over the period 2016-2023. The diagnosis of AI was based on β-APP stain (TAI, VAI, or no AI). Data on background characteristics and neuropathology findings were collected from cause-of-death investigation documents. Prevalence ratios were calculated for each variable to enable comparisons between the AI categories. The sample were 71.7% males; median age was 41 years (range 0-96). There were 26 cases with TAI, 44 with VAI, and 96 with no AI. The variables that showed statistical significance and had at least two-fold prevalence among TAI cases compared to VAI cases were: a documented recent injury; and presence of any extracranial/cranial/intracranial injury (including subdural haemorrhage [SDH], subarachnoid haemorrhage [SAH], intracerebral/ventricular haemorrhage [ICVH], or contusion) in autopsy or neuropathology. Correspondingly, variables indicating TAI over no AI were: a documented recent injury; postinjury survival ≥ 24 h; and presence of any extracranial/cranial/intracranial injury (including SDH, SAH, ICVH, contusion), herniation, or infarction in autopsy or neuropathology. Postinjury survival < 30 min was identified as an indicator of no AI over TAI. Finally, variables indicating VAI over no AI were: postinjury survival ≥ 24 h; lack of external injury to the head; and presence of SDH, brain oedema, herniation, or infarction in autopsy or neuropathology. In conclusion, we report several differences in characteristics and findings between cases diagnosed with TAI, VAI, and no AI. Our findings may help estimate the likelihood and potential aetiology of AI based on background characteristics and other neuropathology findings.