Potential Damage from Repeated Concussions

Interviewer:  You've mentioned some of the tragic stories that we've heard of former NFL players, but just in general, what are some of the long term effects of multiple concussions.  What can some of the long term effects be?

Dr. Maroon:  Well, You know, as a neurosurgeon I've been dealing with traumatic brain injury for many years.  We know one severe hit to the head can lead to permanent long term damage.  The gray area is what you're alluding to is the sub-concussive blows.  How many blows to the head before you see a problem?  Well, the imaging that was available to us before simply was inadequate. Even MRI, CT scans, brain scans are almost always normal.  Now we have new imaging techniques, diffusion tensor imaging or high definition fiber tractography, which we can literally follow the axons that leave the cortex, the outer bark, which is what cortex means, where the cells are, and travel through the brain, down to your body and your various organs.  We can see in these millions and millions of fibers if there are any breaks in them by measuring how the water is transported in these axons, and recently there was a paper relative to soccer.  You know, when you're talking about 500 hits to the head a year in Football.  There are drills in soccer where a soccer ball at 40-50 miles an hour, and you sit there practicing hitting.  Well, we know that there now are changes that can be visualized in the brain even though they're asymptomatic.  They have no headache, they have no nausea, they're doing well, but now we can image the brain and see there is some perturbation of some axional flow in these brains.  So we're really in a... We know a lot about concussions, but there's still a big black box that we're trying to shed some light on.