Identifying latent subgroups of primary head injury: an explorative latent class analysis on neuropathologically examined medico-legal autopsy cases.

Traumatic brain injury (TBI) is a significant global health concern and frequently encountered in medico-legal autopsies. Previous studies suggest that certain TBI subtypes are more likely to co-occur than others. Therefore, we aimed to explore the potential of latent class analysis (LCA) to identify and characterize primary head injury combinations in neuropathologically examined medico-legal autopsy cases. The dataset comprised 78 cases from the Forensic Medicine Unit of the Finnish Institute for Health and Welfare over the period of 2016-2022. Data on background and circumstantial characteristics as well as primary and secondary head and brain injuries were collected from police documents, medical records, general autopsy reports and neuropathology reports. Latent class solutions with two to five classes were explored to identify clustering of primary head injuries among the sample. The dataset comprised 69.2% males and the median age was 49 years. In LCA, the solutions appeared reasonable, and each class appeared to represent a distinct TBI profile. The two-class solution was found to fit the present dataset best. Class 1 was characterized by older age, presence of an underlying CNS disease, and less diverse primary head injuries; these were interpreted as suggestive of lower traumatic forces. Class 2 was characterized by male sex and assaults as a prominent injury circumstance; subarachnoid and intracerebral/ventricular haemorrhages and contusions were classified exclusively into this class. In conclusion, this study identified two distinct subgroups of primary head injuries. Understanding typical injury combinations related to distinct circumstances could assist not only forensic pathologists but also clinicians treating TBI patients. However, the present latent class solution should not be interpreted as "ground truth", but instead further research is needed.