Moderate and severe brain injuries can be seen via diagnostic imaging.  Concussions can not be seen via imaging but by definition come with clinically significant symptoms which themselves should be a red flag for athletes that they have suffered harm from brain trauma.  Sub concussive brain trauma, on the other hand, remains diagnostically elusive.  A fundamental safety question in combative sports is when has an athlete been exposed to too much career ‘mileage’.  For athletes who chose to pursue these dangerous endeavours when are they being exposed to too much career harm?  A recent study published in the Journal of Neurotrauma making progress in this regard.

In the recent study, titled Dynamic Blood Brain Barrier Regulation in Mild Head Trauma, the authors studied a group of professional mixed martial arts fighters and adolescent rugby players.  The athletes had baseline MRI testing and follow up post competition / post season testing.  The athletes also used instrumented mouthguards documenting the number of impacts they were exposed to.  The authors then performed linear regression between the Blood Brain Barrier disruption defined by increased gadolinium contrast extravasation on dynamic contrast-enhanced (DCE-MRI) imaging on MRI and multiple biomechanical parameters indicating the severity of impacts recorded using instrumented mouthguards in professional MMA fighters.  The data revealed that the sub concussive hits measured related to the blood brain barrier imaging available via the MRI.  As the study’s lead author noted “Our findings for the first time suggest that repetitive head trauma can lead to an MRI signal that we can definitively link to the number and severity of impacts to the head”.

The full abstract reads as follows:

While the diagnosis of moderate and severe TBI is readily visible on current medical imaging paradigms (MRI and CT scanning), a far greater challenge is associated with the diagnosis and subsequent management of mild TBI (mTBI), especially concussion which by definition is characterized by a normal CT. To investigate whether the integrity of the blood-brain barrier (BBB) is altered in a high risk population for concussions, we studied professional mixed martial arts (MMA) fighters and adolescent rugby players. Additionally, we performed the linear regression between the BBB disruption defined by increased gadolinium contrast extravasation on dynamic contrast-enhanced (DCE-MRI) imaging on MRI and multiple biomechanical parameters indicating the severity of impacts recorded using instrumented mouthguards in professional MMA fighters. MMA fighters were examined pre-fight for a baseline and again within 120 hours post competitive fight, while rugby players were examined pre-season and again post-season or post-match in a sub-set of cases. DCE-MRI, serological analysis of BBB biomarkers, and an analysis of instrumented mouthguard data was performed. Here, we provide pilot data that demonstrates disruption of the BBB in both professional MMA fighters and rugby players, dependent on the level of exposure. Our data suggest that biomechanical forces in professional MMA and adolescent rugby can lead to BBB disruption. These changes on imaging may serve as a biomarker of exposure of the brain to repetitive sub-concussive forces and mTBI.