Traumatic Brain Injury and Risk of Incident Dementia: Forensic Applications of Current Research

Abstract Objective Traumatic Brain Injury (TBI) has been purported to increase risk for later developing neurodegenerative disorders (ND). Forensic neuropsychologists are frequently asked to opine on risk for ND after an alleged TBI. We provide an evidence-based foundation to aid forensic practice by summarizing the: role of the neuropsychologist in TBI-related litigation, complexities associated with identifying TBIs in forensic cases, science of TBI in relation to incident dementia, and current scientific evidence for chronic traumatic encephalopathy. Data Selection The most applicable studies to forensic settings are large prospective cohort and population-based cohort studies given their wider generalizability and long periods of follow-up/tracking for outcomes. Data Synthesis Developing ND after TBI is the exception rather than the rule. Only a small subset (< 5%) of individuals with moderate-to-severe TBI, and even fewer (< 1%) with mild TBI, appear to develop ND, and the characteristics that place some at risk remain unclear. Positive evidence for risk of ND after mild TBI is weak and mostly consists of observational studies characterized by methodological limitations. Conclusions Forensic methods used to establish the likely occurrence of TBI are typically more extensive than those used in clinical evaluations, while TBI definitions used in current research are even more rudimentary and inconsistent. Applying clinical research findings regarding TBI and dementia outcomes to forensic cases at an individual level carries significant limitations. Estimating the contribution of remote TBI/concussion in a causal manner to ND risk is a challenge forensic experts sometimes face, yet at present, the task is impossible beyond correlations and speculation.