The trouble with diagnosing chronic traumatic encephalopathy (CTE), a condition that shows up in the overwhelming majority of American football players and other athletes who frequently take blows to the head, is that it can only be diagnosed through an autopsy. And at that point, there’s nothing medicine can do to help the victim.
Researchers at Boston University (the same institution where many of the links between football and CTE were first discovered) have finally found one possible marker for the disease that could be detected in a living person with a simple blood test. Actually being able to diagnose CTE while athletes are alive would mean they could take steps to mitigate the disease before it’s exacerbated with even more hits. Their work was published on Sept. 26 in the journal PLoS One.
CTE is a progressive brain disease caused by a lot of blunt trauma. It typically shows up years after repeated blows to the head, and can lead to symptoms like confusion, depression, aggression, problems with memory, and other forms of cognitive decline. Recently, Aaron Hernandez, an ex-football player who was imprisoned for murder, was found to have had CTE. He killed himself at the age of 27.
Autopsies of people who had CTE show abnormal clusters of a protein called tau throughout the brain, which researchers think kills off neurons. At the moment, this is the only way to definitively test for the condition. The BU team has been looking at a handful of other markers that may indicate a person has CTE. One of these is the protein CLL11, which can circulate in both blood and spinal fluid, which surrounds the brain in the skull. It’s present when there’s any kind of inflammation in the brain, which can be a sign of injury.
For their work, researchers studied the brains from people who had donated their bodies to science—notably, not living people. They found CLL11 was present in the brains of 23 athletes who diagnosed with CTE posthumously. They compared levels of this protein in these players’ brains to levels of the protein in 50 brains belonging to people who died of Alzheimer’s, and 18 brains belonging to people who died for other reasons. CLL11 was highest in the brains of players who had played football for the longest amounts of time, and less concentrated in the brains of people did not have CTE. The fact that it was less prevalent in people who had Alzheimer’s suggests that it’s unique to this type of brain injury, and isn’t just associated with any kind of neurodegeneration.
CLL11 seems to play a role in the way the smallest blood vessels in the brain transport oxygen, Ann McKee, a neurologist and co-author of the study, told the LA Times. Higher levels of CLL11 likely mean these blood vessels start to “leak,” which may lead to symptoms associated with CTE, like inflammation and excess tau protein.
Currently, the biotech company Quanterix in Cambridge, Massachusetts is working with BU researchers to develop a blood test that could detect CLL11 and diagnose CTE in living players. However, it’ll be a little while before this test is available on the market. As mentioned previously, the BU study didn’t actually check blood levels of CLL11 in any living participants, so it’s hard to say how levels of the protein in blood correspond to levels in the brain. They also need to confirm this protein isn’t associated with other kinds of neurodegenerative diseases. Although levels of it in people with Alzheimer’s were lower, it may show up in cases of other kinds of dementia, too. If it does, researchers would have to make sure they understood exactly how much CLL11 is associated with each level of CTE to ensure that future patients get the proper diagnosis.
Although there’s no cure for CTE, a diagnosis while living would give anyone affected a chance to change their lifestyles to try to mitigate the disease. Given the inevitability of getting hit in the head while playing football, for NFL (or college) players, this would probably mean retiring sooner.