Medical Gibberish: Oh God, Oh God, Why Did Jahvid Best’s Arms Do That?

Standout Cal RB Jahvid Best was nearing the end of his 2009 season when he turned the left corner and hurdled an Oregon State defender. There was just enough contact in the air to send him crashing, vulnerably and viciously, onto his shoulders and neck, whiplashing his helmet free. Cal’s celebration was immediately halted and viewers gasped and turned away as the camera zoomed in on an awkwardly angled neck and somehow more awkwardly extended arms.

This was not Jahvid’s first concussion and wouldn’t be his last…in fact, Best’s Lions teammate Nate Burleson said today he thinks Jahvid should retire for the sake of his long-term health (kudos Nate, that’s a rarely expressed opinion these days). There are countless people more qualified than I who have discussed and are researching the long-term effects of concussions and the deeply terrifying implications of chronic traumatic encephalopathy (CTE), so I’ll leave those topics alone for now and attempt to answer a more simple question…what’s up with those arms?

The extension of one or both arms immediately after a concussion is known as the fencing response. The term is due to the extension often being unilateral (one-sided), which causes injured athletes to assume a pose similar to a lunging fencer (“fencer”? Is that right? I feel like there’s probably an unreasonably absurd word for “one who fences”). Anyway, a quick Google search can provide compilation videos of pugilists, hockey players, football players, and countless other athletes demonstrating just how unconscious they’ve been knocked. The response is also fast enough that this uncomfortable-to-witness posture is often formed and held as the athlete is on the way to the ground. It’s also a transient (brief in nature) condition. In Jahvid’s case, you can see his arms and neck beginning to relax as his teammates are still gesturing wildly for aid from the sideline.

To explain the mechanism behind this we’ll need some background but I’ll attempt to keep this brief. The unconscious extension and/or flexion of upper and lower extremities is a well understood effect of serious brain stem injuries.  Pictured below, decerebrate posturing (extension of upper and lower extremities) and decorticate posturing (extension of lower extremities and flexion of distal upper extremities) can be used to form a general prediction of whether a coma patient’s condition is improving or worsening.

These two distinct postures are due to a variety of motor pathways in the brain stem being either severed or left intact and a shift between the two can display whether damage is approaching or receding from the medulla of the brain stem (the seat of much vital function control…an infarct approaching the medulla is a very bad sign). These effects are due to a long lasting interruption of pathway signals and are not transient, like we see during concussions during sports…so while related, don’t likely explain the exact series of events leading to the fencing response.

A piece on concussions at the Bleacher Report claims the fencing response is a regression back to an infantile reflex of extending arms and reaching toward a care-giver…but I can’t find a single piece of evidence backing this and it doesn’t pass the “that sounds like utter nonsense” test. More helpfully, this is an area of some ongoing research, as the presence of the fencing response in both sports and war zones can serve as a signifier of the severity of a concussive brain injury (especially important since it can be easily identified by non-medical professionals). Animal model research at the University of Kentucky show the effect after moderate but not mild brain trauma, although the laboratory definition of “mild” and “moderate” aren’t given explicitly.

I apologize for not having a definite explanation here, but such is the medicine of brain injuries…this stuff is complicated as all hell. Here’s the most likely mechanism of this response. The traumatic impact itself causes a disturbance in neurotransmitter release.  Either an increase or decrease in this release will transiently mimic the more severe responses pictured above. A short-term increase of neurotransmitter in an extension pathway will appear similar to the response caused by the severance of the corresponding flexion pathway, and vice versa. Quickly after impact, neuron function will return to normal and any excessive neurotransmitter present in neuronal synapses will be quickly removed or degraded. These neurons can then return to normal function and the extended limbs will relax, at this point the athlete is probably totally fine and should be reinserted to the game as quickly as possible.


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8 Responses to Medical Gibberish: Oh God, Oh God, Why Did Jahvid Best’s Arms Do That?

  1. Satomtx says:

    On a serious note, best has suffered several more concussions. Should he be stopped from ever playing again?

    • Sponsored by V8 says:

      I would say you can’t forcibly stop someone from doing their job because they might be risking their long-term health. I’m sure it would be in his long-term interests to stop playing football, but I have no idea how much additional risk he’s in. Ultimately, it’s his decision.

  2. Patrick Chewing says:

    Jahvid is doing the Fencing response, which is similar to the fencing reflex and related to traumatic head injuries (as are any primitive reflexes [Moro, Gallant, etc] in adults). I’m not sure if you are implying he is either in decorticate or decerebrate posture; either way, he’s in neither.

    Anyway, I liked the article. My previous comment seems unnecessarily aggressive but I don’t know how to say it any other way. I don’t know protocol on this site, am I supposed to make a joke here?

    • Raysism says:

      Patrick, yours is an odd comment. In the first sentence, you just restate information that’s in SV8’s article. And your confusion in the second sentence seems misplaced. SV8 is very clear that he is not in decorticate or decerebrate posture. In fact, he explicitly delinks the two (“…so while related, don’t likely explain the exact series of events leading to the fencing response.”).

      Anyway, definitely no need to make jokes here, but I was just a little confused by your reply.

    • Sponsored by V8 says:

      Thanks Patrick, glad you liked it. I agree, he’s not in either decorticate or decerebrate postures and there are no rules here…you can do whatever you’d like in the comments.

      But I don’t see your initial unnecessarily aggressive comment in the spam or deleted folders…are you sure you submitted it? Or are you referring to the first paragraph of your comment? If that’s the case, it doesn’t seem unnecessarily aggressive…I’m just not entirely sure what you’re saying…

  3. Raysism says:

    Why did they give the cartoon black guy a 12″ penis?

    • Mangini In A Bottle says:

      That’s a guy?! ohmanohmanohmanohman

      [rocks gently in place, clutching a crusty, discolored t-shirt]

  4. Raysism says:

    The one thing that’s confusing about this article is the big “A” below the video. Is that part of the explanation?

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