Although it is unclear whether closed-head traumatic brain injuries directly correlate with likelihood of developing Alzheimer’s disease,24,48 there is growing evidence for a causal relationship between repetitive clinical and subclinical traumatic brain injuries and chronic traumatic encephalopathy.9,24,26 Regardless, the clinical outcomes of a mechanically induced dementia, chronic traumatic encephalopathy, and arguably more biological ones, stroke and Alzheimer’s disease, are very similar; in fact, both result in tau protein aggregation, brain atrophy, and deterioration of memory.4 Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.