Do “Flash Knockouts” Happen Without Brain Trauma?

Today an interesting article was published by The Athletic with various physicians and experts commenting on knockouts in combat sports.

In the article, titled “Explained: What Happens to a Fighter’s Brain After Suffering a KO?” one of the experts interviewed voiced a controversial opinion that certain ‘flash knockouts‘ can occur without any brain trauma at all.  Specifically when asked “If a fighter is only unconscious for a matter of seconds does that mean the impact on the brain is less severe” professor Mike Loosemore, lead consultant in sport and exercise medicine at the Institute of Sport, Exercise and Health who has worked with the GB Boxing team since 1997 opined as follows:

“Another theory about getting KO’d, which I think has some credence, is the idea of a “flash knockout.” That’s when people get hit, they go down and get up again and are fine. There’s some good evidence that you can overload the cranial nerves – the ones that supply the face and the head – and that if you do, then you become unconscious. But in this case, you don’t become unconscious because of energy transfer to your brain.

There are some moves that martial artists use to target those cranial nerves which do render people briefly unconscious. They don’t have any signs of concussion but they have become unconscious. I think sometimes in boxing when you get those glancing blows down the face and the boxer goes down and gets up again and is fine, it does seem to be this phenomenon of the flash knockdown, which is probably not an energy-transfer-to-the-brain issue, but an overstimulation of the cranial nerves issue.”

If you ever spent any time in a martial arts gym you probably heard similar theories about nerve based KO’s.

I posed this theory on twitter to various physicians and ringside doctors that I am fortunate enough to have follow me.  Many replied and the replies were quite unanimous in dismissing or outright criticizing this theory.  I set them out below.

If you have medical training and have views on the subject please feel free to weigh in.


Update September 19, 2020 – After this article was republished at neurologist and Florida ringside physician Denise weighed in with the following sensible comments:

If you are unconscious, even briefly, it’s an indicator that your brain is not functioning normally. If you are unconscious as the direct result of a blow to your head, your brain is not functioning normally due to trauma. That is a brain injury. As best as we understand it, a very brief loss or alteration (getting your bell rung) of consciousness is rarely dangerous or associated with permanent problems, just so long as the athlete is allowed the proper amount of time to recover back to their baseline. The danger with flash KOs, as we understand it at this time, is if the athlete sustains another brain impact before they have recovered from the first injury, eg. getting hit in the head multiple times immediately following the count. An already mildly concussed brain that is concussed again 30 seconds later puts the athlete at risk for a more severe brain injury.


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