Figure 1.

Stages of chronic traumatic encephalopathy (CTE) [adapted from McKee et al 59]. In stage I CTE, p‐tau pathology is found in discrete foci in the cerebral cortex, most commonly in the superior or lateral frontal cortices, typically around small vessels at the depths of sulci. In stage II CTE, there are multiple foci of p‐tau at the depths of the cerebral sulci and there is localized spread of neurofibrillary pathology from these epicenters to the superficial layers of adjacent cortex. The medial temporal lobe is spared neurofibrillary p‐tau pathology. In stage III CTE, p‐tau pathology is widespread; the frontal, insular, temporal and parietal cortices show widespread neurofibrillary degeneration with greatest severity in the frontal and temporal lobes, concentrated at the depths of the sulci. Also in stage III CTE, the amygdala, hippocampus and entorhinal cortex show substantial neurofibrillary pathology that is found in earlier CTE stages. In stage IV CTE, there is widespread severe p‐tau pathology affecting most regions of the cerebral cortex and the medial temporal lobe, sparing calcarine cortex in all but the most severe cases. All images, CP‐13 immunostained 50 μ tissue sections.