Neurodegenerative disease findings in Finnish neuropathologically examined medico-legal autopsy cases with acute head injuries.

Neurodegenerative diseases present diagnostic challenges due to their diverse clinical presentations, which emphasizes the importance of postmortem neuropathological examination. As neurodegenerative diseases become more common with age, they contribute to a higher risk of falls, accidents and head injuries. Our aims were to, first, report the prevalence of neurodegenerative disease findings in Finnish neuropathologically examined medico-legal autopsy cases with acute head injuries and, second, report the prevalence, injury circumstances, and types of specific brain injuries in the most common disease entities. We analyzed cases from the Helsinki office of the Forensic Medicine Unit, Finnish Institute for Health and Welfare, over the period 2016-2022. Cases were included if they had a suspected or confirmed head injury, and underwent a full neuropathological examination with neurodegenerative immunohistochemistry. Data on background characteristics, neurodegenerative immunostains and diagnoses, and head injuries were collected from cause-of-death investigation documents and neuropathology reports. Prevalences of neurodegenerative diagnoses were calculated, and head injury findings were presented for the most common disease entities. During the study period, there were a total of 128 neuropathologically examined cases with suspected or confirmed acute head injuries. Neurodegenerative immunohistochemistry was performed in 57 of them, and a neurodegenerative diagnosis was established in 47 cases. The most prevalent diagnoses were Alzheimer's disease neuropathologic change (ADNPC) (n = 34), cerebrovascular disease (CVD) (n = 34) and Lewy body disease (LBD) (n = 9). Old head injuries were common among cases with any neurodegenerative diagnosis (36.2 %). Of specific findings, subdural haemorrhage and hypoxic-ischaemic neuronal injury had the highest absolute prevalence in cases with ADNPC, although there were no major differences between ADNPC, CVD and LBD. In conclusion, the most prevalent neurodegenerative disease entities in this dataset were ADNPC, CVD and LBD. A history of head injuries was common regardless of the neurodegenerative entity.