The combination of multiple concussions combined with repetitive sub-concussive head trauma is the biggest risk factor for chronic traumatic encephalopathy. Now we have evidence that suggests repetitive sub-concussive head trauma alone, without concussion, can lead to damage to the blood brain barrier. Damage to the blood brain barrier can result in increased inflammation in the brain, and contribute to neurodegenerative processes.
S100B is a serum biomarker of blood brain barrier integrity.
A study published in 2013 measured S100B and antibodies to S100B in football players throughout a season. The researchers wanted to see what the impact of repetitive sub-concussive head trauma had on the blood brain barrier, and whether sub-concussive head trauma could elicit an auto-immune response to S100B. They also performed diffusion tensor imaging before and after the season, to determine if changes in serum S100B auto-antibodies correlated to changes seen on the diffusion tensor imaging. They went one step further, and looked to see if there was a correlation of S100B auto-antibodies to impulse control scores and balance stability scores utilizing the BESS test.
What these researchers found was that elevated S100B levels do occur in football players that experience sub-concussive head trauma during the game. The players with the most sub-concussive hits to the head had the highest levels of S100B post-game. They showed that players with the highest repeated spikes in S100B levels throughout the season, also had the highest levels of serum S100B auto-antibodies. Diffusion tensor imaging and BESS results were significantly correlated with auto-antibody blood levels of S100B, which were, as stated earlier, dependent upon the magnitude of sub-concussive hits to the head.
The take-home message here, is that, sports involving repetitive sub-concussive hits to the head generate blood brain barrier disruption that can trigger production of auto-antibodies, which may become a risk factor for the early onset of neurodegeneration. Not only do we have direct damage to the blood brain barrier from a concussion, if that person is involved in high-impact sports, they may already have blood brain barrier dysfunction and permeability, as a result of their sport.
Reference:
Marchi, N., Bazarian, J. J., Puvenna, V., Janigro, M., Ghosh, C., Zhong, J., . . . Janigro, D. (2013). Consequences of repeated blood-brain barrier disruption in football players. PLoS One, 8(3), e56805. doi:10.1371/journal.pone.0056805
