Christina Bennett, M.S.
You have probably seen the headlines touting the latest
football player to be diagnosed with the rare degenerative brain disease called
chronic traumatic encephalopathy (CTE). CTE was first diagnosed in NFL football
player Mike Webster in 2002 and has continued to grab the public’s attention.
Experts believe that repeated hits to the head are the cause
of CTE. These brain injury events include both those labeled as concussions and
brain injuries less severe. People at risk for CTE are those who play contact
sports, such as football, soccer, rugby, wrestling, and boxing. Also, people in
the military who participate in combat are at risk too. Typically, these at-risk
athletes and military personnel have acquired several brain injuries for many
One challenge with learning more about CTE is the condition
can be diagnosed only after death because an autopsy is needed to look for
specific changes in the brain. Also, no such cure exists, making research that
studies this disease particularly warranted. As such, preventing brain injuries
in the first place, and in turn lowering the risk for CTE, is key.
Symptoms of CTE often do not show for years, even decades,
after repeated head injuries. Some symptoms include difficulty thinking,
changes in behavior (such as aggression, depression, and suicidal actions),
memory loss, and reduced motor function. As CTE progresses, dementia may occur.
Often, people mistake some of these symptoms as signs of aging.
In a person with CTE, the brain is slowly deteriorating and
eventually loses tissue mass. In fact, the progression of CTE can be broken
down into four stages, and by the fourth stage, the brain mass has decreased by
50 percent. Tau protein, a molecule that forms deposits and distinct tangles in
a brain afflicted with CTE, is believed to play a role. Tau protein function is
also disrupted in Alzheimer’s disease, but the pattern of tau deposits and
tangles in CTE is different from what is seen in Alzheimer’s.
The good news is researchers are making strides. For the
first time, authors of a recent study linked brain inflammation in football athletes
to CTE. To conduct the study, authors selected 66 former football players who
had died and donated their brains to a brain bank and 16 non-athletes to serve
as the control group. This study was published in the journal Acta Neuropathologica Communications on
October 28, 2016.
Specifically, Jonathan Cherry and the other study authors
found that the longer an athlete played the high-contact game, the greater the risk
of developing CTE. With each brain injury comes inflammation, which is the
body’s way of protecting the brain, but these repeat brain injuries and therefore
prolonged inflammation may be the reason why CTE develops. The potential for
these findings is that molecules that participate in inflammation could help
diagnosis CTE in living people and even be targets for treatments.
However, not all experts accept these findings just yet. More
research is needed to determine how exactly CTE develops. Inflammation is not
the only process that occurs after brain injury, so other processes could be
involved too. Also, this particular study was limited by its being
retrospective, meaning the researchers looked at events in the past, and the
brain tissue studied was that of athletes who chose to donate, not those who
were randomly selected.
Despite these limitations, previous findings support this
study’s reasoning. For example, in an earlier study, these authors showed that the
number of years of repeated head injuries correlated with a higher stage of CTE
in athletes and military personnel. Also, other researchers have shown
molecules involved in brain inflammation for degenerative brain diseases to
promote tau protein disarray, suggesting brain injury and CTE are linked. Findings
have also linked degenerative brain diseases to brain inflammation. Future
studies are certainly needed, but this one serves as a good start.
Cherry JD, Tripodis Y, Alvarez VE, et al.
Microglial neuroinflammation contributes to tau accumulation in chronic
traumatic encephalopathy. Acta
Neuropathologica Communications. 2016;4:112.
McKee AC, Stein TD, Kiernan PT, Alvarez VE. The
neuropathology of chronic traumatic encephalopathy. Brain Pathol. 2015;25(3):350-364.
McKee AC, Cantu RC, Nowinski CJ, et al. Chronic
traumatic encephalopathy in athletes: progressive tauopathy following
repetitive head injury. J Neuropathol Exp
Neurol. 2009;68(7): 709-735.
Safinia C, Bershad EM, Clark HB, et al. Chronic
Traumatic Encephalopathy in Athletes Involved with High-impact Sports. J Vasc Interv Neurol. 2016;9(2):34-48.
What is CTE? Concussion Legacy Foundation
Chronic traumatic encephalopathy. Mayo Clinic