A panel of clinician-scientists has published the first consensus criteria to diagnose—for research purposes—a disorder associated with chronic traumatic encephalopathy (CTE) among living people, offering a framework for future studies on the rare and little understood brain disease.

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What we know about CTE

CTE, which has no known treatments, is believed to cause deterioration of brain matter and the abnormal accumulation of tau, a protein found in brain cells, in the brain.

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While the exact cause of CTE remains unclear, many scientists theorize that it stems from repeated head trauma. As a result, much of the research done into CTE has focused on contact sports players, such as football and hockey athletes, as well as military servicemembers who've served in war zones.

Currently, CTE can be diagnosed only post-mortem by examining the brain tissue of deceased subjects, which makes it difficult to know CTE's prevalence. However, scientists believe people who are diagnosed with the disease post-mortem can present with symptoms while alive—such as aggression, anxiety, confusion, dementia, depression, memory loss, and substance misuse—that could serve as indicators of the disease.

Clinicians publish first consensus criteria to diagnose disorder linked to CTE

In a peer-reviewed study published in Neurology and funded by the National Institute of Neurological Disorders and Stroke (NINDS), a panel of clinicians from 11 academic institutions provided the first consensus criteria for researchers to diagnose in living people a clinical disorder called traumatic encephalopathy syndrome (TES), which is linked to CTE.

The panel developed the criteria for diagnosing TES based on a review and analysis of evidence from "all published cases of CTE with neuropathological confirmation," as well as predictive data on the clinical features connected to CTE's pathology from a study involving 298 participants.

Under the panel's criteria, people diagnosed with TES for research purposes must:

• Have experienced "substantial" repetitive head impacts
• Show cognitive impairment, such as memory loss or irregular behavior
• Show a pattern of deterioration
• Not have their clinical signs of TES explained by "other neurologic, psychiatric, or medical condition"

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People who meet the criteria will receive a grade on a scale from 1 to 5, with 1 indicating the patient is independent and 5 indicating the patient has severe dementia.

The authors cautioned that these criteria are meant for research purposes and are not to be used by providers to diagnose patients. Specifically, according to MedPage Today, the authors "aimed to provide researchers with detailed criteria for diagnosing study participants with TES with a 'provisional level of certainty' that an individual would have CTE brain pathology."

However, the paper's authors believe their criteria, despite being intended solely for research purposes, represent a critical step toward the discovery of a biomarker for CTE among living people, which could allow providers to reliably diagnose the brain disease in the future.

A 'game-changer for the future'

Robert Stern, director of clinical research at Boston University's CTE Center and one of the paper's authors, said, "Although I wish I could say it's a game-changer right now, it's a game-changer for the future. We're really not at the point of being able to diagnose CTE during life yet. We're getting much closer, and this new paper is an important step forward."

NINDS Director Walter Koroshetz said, "The publication of these criteria is another important step that will enable scientists to fill knowledge gaps, including a better understanding of CTE's clinical features and natural history, incidence and prevalence, as well as the causes and risk factors for developing this neurodegenerative disease."

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Stern, for example, said the new criteria will bring researchers closer to formalizing the symptoms of CTE, which would ultimately help researchers determine CTE's causes, prevalence, and risk factors—and differentiate the disease from other neurodegenerative diseases, including Alzheimer's disease.

According to Stern, Alzheimer's research also serves as a possible precedent for scientists searching for ways to diagnose CTE. Although scientists haven't identified a "single telltale" biomarker for Alzheimer's, they've discovered a combination of symptoms and tests can help providers reliably diagnose the disease, the Washington Post reports.

Stern also said that recent advances in blood tests provide more reason to believe researchers are close to finding a definitive way to diagnose CTE among living people. "We're talking within several years," Stern said. "There's this unbelievably exponential advance in the development of biomarkers for all neurodegenerative diseases."

Still, Stern said, "It's not today. But we are indeed one step further, and we're getting much closer with our biomarker development as well" (Kilgore, Washington Post, 3/15; Baker, Axios, 3/23; George, MedPage Today, 3/15; Katz et al., Neurology, 3/15).