CTE: what we don’t know

Sunday, May 24, 2015

There is danger in learning medicine by assertions published by the press, and there is risk in relying upon isolated extracted quotes that may or may not reflect an expert’s view. It is especially difficult when the science behind a theory is very new. Changes in medical knowledge happen slowly and early adopters of new theories are often proven wrong…or are driven to develop compelling research that makes a difference in how medical care is provided.

All this to talk about chronic traumatic encephalopathy (CTE) and the criticism of Gary Bettman, NHL commissioner, when he was suggested in a press conference, that the correlation between head trauma and CTE has yet to be proven.

From a medical science standpoint, there is no evidence yet that one (concussion) necessarily leads to the other (CTE),” said Bettman to reporters on hand. “I know there are a lot of theories, but if you ask people who study it, they tell you there is no statistical correlation that can definitively make that conclusion.

Mr. Bettman was taken to task by researchers, broadcasters and others who want to be able to explain the consequences of repetitive head injuries, and how to prevent concussions in sports, the military and other workplaces, from causing significant brain deterioration, and loss of mental function and early death.

Chris Nowinski, the executive director and co-founder of the Sports Legacy Institute an also works with the Boston University CTE Center, was quoted by Josh Cooper of Yahoo Sports:

We have plenty of medical and scientific evidence that brain trauma leads to CTE. In fact the experts from the Department of Defense and the National Institute of Health are both on record saying they personally believe that CTE is caused by brain trauma.

Ray Slover of the Chicago Tribune wrote the following:

Gary Bettman might have been speaking as a lawyer as well as head of the National Hockey League this week when he said there was no established link between concussions and chronic traumatic encephalopathy.

He also might have been the NHL equivalent of an ostrich sticking his head in the sand or a climate-change denier. Bettman’s stand certainly seems to fly in the face of medical evidence.

Keith Olbermann named Mr. Bettman the worst person in the sports world on his May 22, 2015 television program.

For all this rhetoric, perhaps it’s important to take a step back and try to acknowledge that we know only what we know. Perhaps we should turn to the experts for their understanding of CTE and its causes. This is a relatively new disease entity, so new in fact, that there was not a standardized set of criteria to make the diagnosis. In February 2015, a consensus conference was held by the National Institutes of Health. The diagnosis can only be made at autopsy, when abnormal tau proteins are found irregularly scattered within the depths of brain tissue and cells. The abnormal protein “pathology has only been found in individuals exposed to brain trauma, typically multiple episodes.  How common this pathology occurs at autopsy and the nature and degree of trauma necessary to cause this neurodegeneration remain to be determined.”

The “to be determined” is a big step for science when it comes to cause and effect. In the presentation of the group’s consensus, Dr. Ann McKee, of the CTE Center, wrote the following bullet points:

“Relationship between concussion, subconcussion and CTE is unclear”

  • Concussion, subconcussion and post-concussion syndrome: most likely reversible states of neuronal and axonal derangement
  • CTE- a latent, progressive neurodegenerative disease.
  • Repetitive injury superimposed on unresolved injury may initiate a series of metabolic and cytoskeletal disturbances that trigger a pathological cascade leading to CTE in susceptible individuals
  • The number of concussions does not correlate with CTE or predict CTE
  • However, the severity of CTE is significantly associated with length of exposure in American football, and it is likely that this is a result of the cumulative effects of subconcussive injury

There is still much work to be done to build on the initial finding of the CTE group. Many more brains need to be analyzed, since a sampling bias needs to be removed from the research. The brain banks that accept tissue donated from athletes and their families who suspect that a major neurologic problem exist. This may skew what might be happening in the general population. Many people have minor head injuries and perhaps the Tau deposition is more commonly spread throughout the population than presently known. The special pathology tests are not routinely done on every autopsy, but the deposits of tau protein in CTE differs than the same protein distribution in Alzheimer’s Disease. Volunteers from the general public are being recruited to keep diaries of their lives and donate their brains science. This will not be a short term project.

A great doctor or scientist knows what they know and what they don’t. It is hard to pursue the mysteries of the human body. Mr. Bettman reminded us that while we think we might know some answers, there are significant gaps in our understanding of the brain. Head trauma may cause CTE but we don’t know how many are needed, how severe or how often they might occur and what victims are more susceptible to the disease. We do not know how to make the diagnosis when people are alive, nor how to treat them to prevent the development of CTE. And we don’t know how to treat CTE should the symptoms be recognized. The bottom line is that we don’t know very much.





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