Chronic traumatic encephalopathy: brain scan shows tau deposits in NFL players

  • Stern RA & al.
  • N Engl J Med
  • 10 Apr 2019

  • International Clinical Digest
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  • Brain levels of τ (but not amyloid β) on positron-emission tomography (PET) were higher among former NFL players with cognitive and neuropsychiatric symptoms than among asymptomatic male controls.

Why this matters

  • Repetitive head impacts are linked to development of chronic traumatic encephalopathy, but pathophysiologic mechanism and potential therapeutic targets are still unclear.

Key results

  • τ deposition (mean flortaucipir standardized uptake value ratio [SUVR]) was higher among former players vs controls in 3 brain regions; adjusted mean difference:
    • 0.13 (P<.001 for bilateral superior frontal>
    • 0.13 (P<.001 for bilateral medial temporal and>
    • 0.12 (P=.002) for left parietal.
  • SUVR correlated with years of play; correlation coefficient:
    • 0.58 for bilateral superior frontal,
    • 0.45 for bilateral medial temporal, and
    • 0.50 for left parietal.
  • However, τ deposition did not correlate with cognitive and neuropsychiatric test scores.
  • Amyloid β deposition (mean florbetapir SUVR) was not significantly different.
  • Only 1 former player had amyloid β deposition level similar to those seen in Alzheimer’s disease.

Expert comment

  • In an editorial, Allan H. Ropper, MD, writes, “The report … certainly does strengthen the case that tau is the offender early in CTE, but other links remain to be clarified. The techniques for studying living biology, such as this use of tau-ligand PET, are making a difference.”

Study design

  • Cross-sectional cohort study of 26 former NFL players with cognitive, neuropsychiatric symptoms, 31 asymptomatic men with no history of traumatic brain injury.
  • Main outcome: differences in SUVR.
  • Funding: Avid Radiopharmaceuticals; others.


  • Small sample size.
  • Some analyses post hoc.
  • Uncertain generalizability.
  • Temporal changes unknown.