Are Subconcussive Events Actually Concussions?

Is a subconcussive event a concussive event that only affects one part of the brain? Learn more about what research is showing, and hopes to show in the future.

See all videos with Dr. David Hovda.

You know people are looking at this term subconcussive events, and are these accumulative, and can these produce long-term problems. And my first response to that is scientific-- is that I--I don't know. I don't think so--I don't know. I don't have any scientific evidence to suggest that that's the case. It could be the case that--we're missing it in the clinical realm because we just don't measure it very often. I mean I don't know how many times a 4 year old bumps his head on a coffee table or how many times dad--you know--gets his bell rung-- you know--very lightly when he was playing flag football when he was in college, and does that make him now an attorney rather than a doctor or a republican rather than a democrat or something like that. You just don't know. But all teasing aside, I don't think there is such a thing as a subconcussive event, and this is from science. And this was work that was done by Yoichi Katayama. He was gentleman--director and chairman of neurosurgery now at-- at Nihon University. And while I was at UCLA, we looked at the different levels of severity of the injury that we could induce and tissue and in animals, and it was--There was not a problem until you reached a particular threshold. This wasn't a linear event. So there wasn't this subconcussive thing and then you get this concussion. It was--it was either nothing and then the whole brain went into concussion. And this is a proposal that has been around since 1944. It was originally described by a gentleman by the name of Earl Walker and Denny-Brown and a gentleman by the name of Liaw, and he describes __________. And so--A) At this point, I do not have any scientific evidence that there is such a thing as a subconcussive syndrome. B) If there is, it's probably not global. One of the things I disagree with the-- some of the Colorado guidelines and the recent guidelines for the National Football League, in terms of concussion severity, is that I really don't think-- I think there is such a thing as severity of concussion, but I think it's more important to understand what type of concussions. And a very good example is perhaps the blast-type concussions that you are getting in Iraq and Afghanistan are different than the type of concussions that the National Football League are getting. So you may have these, what you think are subconcussive events, but they really are a concussive event for a particular part of the brain where the rest of the brain is not. And it may be that regional change that occurs over time. But that's something we need--we would like to learn more about.
Posted on BrainLine October 18, 2011.

About the author: David Hovda, PhD

David Hovda, PhD is the director of the UCLA Brain Injury Research Center. He is past president of the National Neurotrauma Society and past president of the International Neurotrauma Society.  He has served as chair of study sections for the National Institute for Neurological Disease and Stroke.

David Hovda

Produced by Noel Gunther, Ashley Gilleland, and Brian King, BrainLine.