Table 1.

Grading system of CTE, based on a provisional four-stage classification scheme centered around the extent and severity of tau pathology.

Stage	Criteria
I	1 or 2 focal perivascular CTE lesions in cerebral cortex at the depths of the sulci.
II	>3 CTE lesions in multiple cortical regions and superficial NFTs along the sulcal wall and gyral crests.
III	Multiple CTE lesions, widespread cortical NFTs, and NFTs in the medial temporal lobes.
IV	Multiple CTE lesions, widespread cortical NFTs, NFTs in the medial temporal lobes, widespread astrocytic p-tau pathology, neuronal loss, and gliosis.

Note: Aß amyloid plaques are entirely age-dependent and have no relationship to staging. Adapted from (56) with permission.