From Axon to Action: The Devil of Brain Trauma Is in the Details

Curator's Note

While it may seem intuitive to measure brain trauma, specifically the most intense trauma associated with contact sports (CTE: Chronic Traumatic Encephalopathy), in concussions, the current growing body of evidence suggests that the everyday, ostensibly 'trivial' trauma is causing this degenerative brain disease, as opposed to the accumulation of large, concussive trauma.

How does this affect behavior? Why is it that athletes in contact sports are statistically more likely to suffer depression? Why is it that people suffering from chronic pain (surely an occasional byproduct of CTE given that the symptoms of brain trauma can involve emesis, dizziness, motor impairment, photophobia, and memory loss) are six times more likely to report suicidal thoughts?

The case of Owen Thomas (diagnosed with CTE at age 21), prompts a closer look. Whether or not CTE caused his suicide is not the task of this essay, but perhaps emphasizing potential correlations are important enough. To explain why, scientists are looking at axons. Experiments with axons have been highlighted off the work of Douglas Smith at the University of Pennsylvania, where he builds miniature brains out of rat neurons, which are then 'hit' with controlled puffs of air to simulate brain trauma at a molecular level.

To recap from those static A&P lectures none of us enjoyed, the axon is like a paperboy, sending neurological news, referred to as neurotransmitters, to "homes" called dendrites. The findings show that as axons stretch upon trauma (vulnerable months after an initial stretch), like a worn rubber band, they lose their elasticity after swelling, where proteins then block the proper neural absorption until the axons fall apart (called Diffuse Axonal Injury). 

This "traffic jam" of hoarded proteins, caused by the sudden acceleration/deceleration of the head, destroys axonal connections, which are important for the function of neurotransmitters that can do wonderful things: they inform sociability (seratonin), optimism, and persistence (dopamine), and even, as love expert and anthropologist, Helen Fisher has argued, the characteristics that model our capacity for romantic love, such as excessive energy, sleeplessness, loss of appetite, and the type of acute memory for new stimuli that allows us to keep from perceiving time spent with an intimate partner as trivial (associated with norepinephrine). CTE is a stark example of how intimate the connection between physiology and psychology is: a disorder that threatens the chemical constitution which helps define how we think.


A great explanation of CTE and the ramifications of brain injuries in sports.  It is haunting to think of these effects tormenting former, current, and future athletes.  And by starkly addressing the effects of CTE on a more personal level, the culture of toughness/hyper-masculinity that dominates these sports is destabilized.  Even the "toughest" athlete is humanized by focusing on whether or not they will be able to feel love, show optimism in life, and so on.  Perhaps this is the type of education that has to dominate our discussion of the brain in contact sports, how it impacts the quality of life that we all desire regardless of our athletic prowess.

I am also intrigued by your point on the trivial trauma, which is something touched on by Stephen as well.  We are so focused on preventing the catastrophic blow, even going so far in sports like football to design new armor for protection (as David Epstein pointed out earlier this week), that we may be avoiding a more disastrous issue of this trivial trauma that accumulates over time.  How do we regulate these sports/activities if the mundane activities associated with them are causing such disastrous consequences? 

Going back to Steve Granelli's post from earlier in the week, wrestling fans wanted so desperately to have a cause for what Chris Benoit did, blaming all sorts of culprits.  And if CTE was to blame, wrestling fans wanted to blame the chair shots to the head for causing his concussions.  But wrestlers such as Mick Foley have stated that they got some concussions from routinely falling on the mat, something all wrestlers do very often.  What if these routine activities in wrestling, and by extension football, MMA, hockey, and so on are indeed causing the accumulation of trivial trauma?  Is there a future for contact sports if this is the case?


Well, when you chop a tree down, do you use one swing, or a lot of 'little' ones? That a progressive brain disease caused by brain trauma is brought on by a general accumulation of blows, as opposed to the odd 'big hit', makes sense in theory.

Owen Thomas' case highlights something else though. Chris Henry's brain (the former Cincinnati Bengal), for example, contained an apolipoprotein E3 allele: the same gene found in most brains with CTE, suggesting, as could be the case with Owen Thomas, that some people are simply genetically predisposed to this disease. The science is still too raw at this point though.

Right after posting this, an article by R. Douglas Fields enlightened me to the role of glial cells (which make up 85% of the cells in the brain), typically thought of as mere "support" for neurons, may be just as important for information processing as neurons are. When it comes to mental illness, the key to treating it may be in targeting these cells (microglia, like trash receptacles, clear waste in the brain, which atrophy in a case like Alzheimer's, for example). The better our understanding (which is limited), the better we can think about solutions, which at this point, barring an outright ban, is providing athletes with the best available care possible.

The NFL is on the right track with the ImPACT test. But I'd like to see something more comprehensive than what is currently offered, along with making them mandatory after certain periods, regardless of whether or not athletes have been diagnosed with a concussion. Might simple questionnaires be helpful? Does an athlete's personality change over time because of accumulated brain trauma? We know this is true based on what we know of dementia, but might personality questionnaires clue us in on the more subtle changes? After two years of competition, does an athlete still strongly agree to 'finding unpredictable situations exhilirating'? Do they still strongly agree with the statement 'I am more enthusiastic than most people'? Might these answers change over time? Seems like a simple way of identifying the possible presence of depression without being overt about it. Because CTE cannot be observed in a live brain, we can't locate the fire, so we've gotta track the smoke. 

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