Minnesota Vikings safety Andrew Sendejo landed a devastating hit on former teammate Mike Wallace during last Sunday’s showdown against the Baltimore Ravens that left the wideout with a concussion and Sendejo a one-game suspension. It was an unnecessarily violent hit, one in which Wallace is “lucky” to have “only” suffered a concussion.
However, this article is not about the physiological underpinnings of concussions or their typical recovery timeline.
Instead, it is about something else concussion-related: Wallace’s presentation immediately after the hit displayed a specific sign that is perhaps helpful for determining not only if he suffered a concussion, but also its severity.
As can be seen in the image below, Wallace assumed an involuntarily position known as the fencing response immediately after Sendejo’s hit. It’s called this because the extension — straightening — of one of his upper extremities and the flexion — bending — of the other resembles a fencer in the en garde position.
This position is also commonly seen in children three months of age or younger and is known as the asymmetrical tonic neck reflex (ATNR) — or more commonly known as the fencing reflex — and is assumed when the baby’s head is turned. Basically, the arm that is on the same side to which the head was turned extends and the other flexes.
This is a protective reflex that causes the baby to extend their arm as they brace for impact should they experience a fall to either side of their body.
Despite concussions being a hot-button issue of late, especially in the game of football, surprisingly little research has been conducted on involuntary body position responses and their associated concussion severity. The fencing response has only been researched in one study — found here — and the results may indicate not only concussion severity but also location.
The study contained two parts: the first involved the researchers scouring YouTube for videos in which an individual suffered a head injury, was knocked unconscious and displayed the fencing response and the other involved subjecting mice to a concussion of mild or moderate severity and monitoring to see if they assumed the fencing response.
The YouTube search yielded 35 videos that met the researchers’ criteria and it was noted that in 66 percent of the videos the individual who suffered the head injury displayed a fencing response. Though the small sample size prevents any firm conclusion from being drawn, it would seem to indicate that the fencing response is a pretty common sign of a significant head injury, such as a concussion.
The mice experimentation is perhaps a little more interesting. To put it simply, the researchers inflicted the mice with a concussion utilizing a specialized tool of either mild — defined as being hit with 1.1 atm of force — or moderate (1.19 atm) severity. In all, 63 mice were given concussions — 44 of moderate severity and 19 of mild. Zero of the 19 mice who were inflicted with a mild concussion displayed the fencing response, while a whopping 39 of the 44 mice with a moderate concussion did.
The researchers speculated that because the fencing response presents similarly to that of the ATNR, similar brain structures and neurological pathways must be involved. The lateral vestibular nucleus (LVN) located within the midbrain — which lies between the brain stem and the cerebrum, the outer cortex of the brain — is an integral structure for the ATNR, and thus its volume was estimated in the mice with the mild and moderate concussions as well as the control group.
The LVN in mice with a moderate concussion was found to be scientifically significantly smaller than that of the other two groups. These findings would seem to suggest that moderate concussions are more likely to affect the LVN — aka midbrain — and thus elicit the fencing response.
However, the results of this study should be taken with a healthy amount of salt. First of all, the sample sizes included were incredibly small and, therefore, the odds of revealing misleading results is increased. Second, the study was primarily conducted on mice, not humans, meaning that its findings can only suggest and call for further research, rather than draw conclusions.
However, the results of the study are intriguing and further research should be conducted to help solidify the fencing response’s credibility as a diagnostic tool for concussion severity.
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