The neuropathology of CTE is well-characterized post-mortem and is defined by hyperphosphorylated tau (P-tau) accumulation in perivascular spaces and regional brain atrophy.7,9,11,12,14,16,19-22 The disease follows a staged progression (Stages I–IV), with increasing severity of neuropathology.23,24 Despite extensive post-mortem documentation,7,9,11,14-16,19-22,25-27 there remains a critical lack of in vivo biomarkers for diagnosing CTE, which is essential for developing interventions to slow or prevent disease progression. This evidence concerns the gene MAPT and Brain atrophy.