Tau Pathology in Chronic Traumatic Encephalopathy: Mechanisms and Diagnostic Advances.

Chronic Traumatic Encephalopathy (CTE) is a progressive neurodegenerative tauopathy associated with repetitive head impacts (RHI), yet it remains diagnosable only at post-mortem. Tau, a microtubule-associated protein, normally stabilizes neuronal microtubules and regulates cytoskeletal dynamics. Mechanical strain from RHI is thought to disrupt calcium homeostasis and kinase-phosphatase balance, driving hyperphosphorylation and phosphorylated-tau (p-tau) formation. This results in detachment from microtubules and subsequent p-tau aggregation. These mechanically-induced biochemical changes produce CTE's characteristic lesion: perivascular p-tau deposition in the depths of cortical sulci, reflecting the non-uniform mechanical loading experienced by brain tissue following head impacts. Advances in molecular neuropathology have revealed that CTE tau filaments adopt a unique conformational fold, and that early tau species may contribute to neurotoxicity. Despite this growing understanding, antemortem diagnosis remains challenging. Structural MRI demonstrates frontotemporal atrophy and white-matter abnormalities in impact-exposed individuals, but these findings lack disease specificity. Tau-PET tracers developed for Alzheimer's disease (AD) show limited affinity for the distinct CTE tau fold, while fluid biomarkers variably reflect cumulative exposure but cannot yet discriminate CTE from other tauopathies. Future progress will depend on mechanistically informed diagnostic tools, including conformation-specific biomarkers and PET radiotracers tailored to CTE-specific tau. Multimodal approaches integrating neuroimaging, molecular profiling, exposure metrics, and computational modelling will be essential for early detection, disease monitoring, and informed public health policy around repetitive head impacts.