PET scans show high tau levels in former NFL players with potential chronic traumatic encephalopathy

1. Former National Football League (NFL) players with cognitive and neurological symptoms showed higher tau amyloid levels as detected on positron emission tomography (PET) scans than control patients.

2. No association between tau deposition found on PET scans and scores on cognitive and neuropsychiatric tests was observed.

Evidence Rating Level: 4 (Below Average)      

Study Rundown: Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease often associated with repeated head impact occurring in collision sports. Pathological diagnosis is defined by tau aggregates in irregular patterns in regions of affected brains and is distinguishable from other neurodegenerative conditions such as Alzheimer’s disease. Detection and diagnosis of CTE during life would greatly aid study and potential treatment of the disease. PET with ¹⁸F-flortauciper had been studied for its ability to detect tau deposition in Alzheimer’s disease but not CTE. This study evaluated PET images from neurologically affected former NFL players with control subjects. Average flortauciper signals were higher in superior frontal, medial temporal, and left parietal regions of affected former players compared to controls. No association was found between tau levels and scores on neuropsychiatric exams.

This exploratory study provides an initial baseline for evaluating how tau levels compare in suspected CTE patients versus healthy controls. Strengths of the study include localization of tau signals and robust quantitative description of PET signals. The main limitations are the limited numbers of patients and participants with suspected CTE limited to only former NFL players, leaving uncertainty as to how these results may generalize to former amateur players or participants in other contact sports.

Click to read the study in NEJM

Relevant Reading: Relationships between flortaucipir PET tau binding and amyloid burden, clinical diagnosis, age and cognition

In-Depth [case-control study]: This case-control study imaged patients with suspected CTE and healthy controls. Eligible suspected CTE participants (n=26) had neuropsychiatric symptoms, were 40 to 69 years old, had a minimum of 2 years NFL experience and 12 years tackle football experience, and had no recent traumatic brain injury. Control patients (n=31) were of the same age and had no neuropsychiatric symptoms or history of brain injury. All participants underwent a Mini–Mental State Examination as well as additional neuropsychiatric tests. Imaging on all participants included flortauciper to evaluate tau levels, florbetapir to evaluate amyloid-beta, and T1-weighted MRI of the head. Significantly higher tau levels (P<0.005) were found in former-players for the bilateral superior frontal, bilateral medial temporal, and left parietal regions. No association was found between neuropsychological tests and tau levels in the three listed brain regions. The former-player and control groups did not significantly differ in their beta-amyloid levels.

Image: PD

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