Fencing response

{{see also|Abnormal posturing}}

The fencing response is similar to the asymmetrical tonic neck reflex in infants. Like the reflex, a positive fencing response resembles the en garde position that initiates a fencing bout, with the extension of one arm and the flexion of the other.

Tonic posturing preceding convulsion has been observed in sports injuries at the moment of impact{{cite journal |last1=McCrory |first1=P. R. |last2=Berkovic |first2=S. F. |title=Video analysis of acute motor and convulsive manifestations in sport-related concussion |journal=Neurology |date=11 April 2000 |volume=54 |issue=7 |pages=1488–1491 |doi=10.1212/wnl.54.7.1488 |pmid=10751264 |s2cid=43197411 }}{{cite journal |last1=McCrory |first1=P. R |last2=Bladin |first2=P. F |last3=Berkovic |first3=S. F |title=Retrospective study of concussive convulsions in elite Australian rules and rugby league footballers: phenomenology, aetiology, and outcome |journal=BMJ |date=18 January 1997 |volume=314 |issue=7075 |pages=171–174 |doi=10.1136/bmj.314.7075.171 |pmid=9022428 |pmc=2125700 }} where extension and flexion of opposite arms occur despite body position or gravity. The fencing response emerges from the separation of tonic posturing from convulsion and refines the tonic posturing phase as an immediate forearm motor response to indicate injury force magnitude and location.

The neuromotor manifestation of the fencing response resembles reflexes initiated by vestibular stimuli. Vestibular stimuli activate primitive reflexes in human infants, such as the asymmetric tonic neck reflex, Moro reflex, and parachute reflex, which are likely mediated by vestibular nuclei in the brainstem. The lateral vestibular nucleus (LVN; Deiter’s nucleus) has descending efferent fibers in the vestibulocochlear nerve distributed to the motor nuclei of the anterior column and exerts an excitatory influence on ipsilateral limb extensor motor neurons while suppressing flexor motor neurons. The anatomical location of the LVN, adjacent to the cerebellar peduncles (see cerebellum), suggests that mechanical forces to the head may stretch the cerebellar peduncles and activate the LVN. LVN activity would manifest as limb extensor activation and flexor inhibition, defined as a fencing response, while flexion of the contralateral limb is likely mediated by crossed inhibition necessary for pattern generation.{{fact|date=October 2019}}

In simpler terms, the shock of the trauma manually activates the nerves that control the muscle groups responsible for raising the arm. These muscle groups are activated by stimuli in infants for instincts such as grabbing for their mothers or breaking their falls. The LVN has neurons that connect it to motor neurons inside grey matter in the spinal cord, and sends signals to one side of the body that activate motor neurons that cause extension, while suppressing motor neurons that cause flexing. The LVN is located near the connection between the brain and the brain stem, which suggests that excessive force to the head may stretch this connection and thus activate the LVN. The neurons that are stimulated suppress neighboring neurons, which prevents neurons on the other side of the body from being stimulated.

In a survey of documented head injuries followed by unconsciousness, most of which involved sporting activities, two thirds of head impacts demonstrated a fencing response,{{cite journal |last1=Hosseini |first1=Ario H. |last2=Lifshitz |first2=Jonathan |title=Brain Injury Forces of Moderate Magnitude Elicit the Fencing Response |journal=Medicine & Science in Sports & Exercise |date=September 2009 |volume=41 |issue=9 |pages=1687–1697 |doi=10.1249/MSS.0b013e31819fcd1b |pmid=19657303 |doi-access=free |pmc=11421656 }} indicating a high incidence of fencing in head injuries leading to unconsciousness, and those pertaining to athletic behavior. Likewise, animal models of diffuse brain injury have illustrated a fencing response upon injury at moderate but not mild levels of severity as well as a correlation between fencing, blood–brain barrier disruption, and nuclear shrinkage within the LVN, all of which indicate diagnostic utility of the response.

The most challenging aspect to managing sport-related concussion (mild traumatic brain injury, TBI) is recognizing the injury.{{cite journal |last1=Guskiewicz |first1=Kevin M. |last2=Bruce |first2=Scott L. |last3=Cantu |first3=Robert C. |last4=Ferrara |first4=Michael S. |last5=Kelly |first5=James P. |last6=McCrea |first6=Michael |last7=Putukian |first7=Margot |last8=Valovich McLeod |first8=Tamara C. |title=National Athletic Trainers' Association Position Statement: Management of Sport-Related Concussion |journal=Journal of Athletic Training |date=2004 |volume=39 |issue=3 |pages=280–297 |pmid=15514697 |pmc=522153 }} Consensus conferences have worked toward objective criteria to identify mild TBI in the context of severe TBI.{{cite journal |title=Concussion (Mild Traumatic Brain Injury) and the Team Physician |journal=Medicine & Science in Sports & Exercise |date=February 2006 |volume=38 |issue=2 |pages=395–399 |doi=10.1249/01.mss.0000202025.48774.31 |pmid=16531912 |doi-access=free }}{{cite journal |last1=Aubry |first1=Mark |last2=Cantu |first2=Robert |last3=Dvorak |first3=Jiri |last4=Graf-Baumann |first4=Toni |last5=Johnston |first5=Karen |last6=Kelly |first6=James |last7=Lovell |first7=Mark |last8=McCrory |first8=Paul |last9=Meeuwisse |first9=Willem |last10=Schamasch |first10=Patrick |author11=Concussion in Sport (CIS) Group |title=Summary and Agreement Statement of the 1st International Symposium on Concussion in Sport, Vienna 2001 |journal=Clinical Journal of Sport Medicine |date=2002 |volume=12 |issue=1 |pages=6–11 |pmid=11854582 |doi=10.1097/00042752-200201000-00005 }}{{cite journal |last1=Cantu |first1=Robert C. |title=An overview of concussion consensus statements since 2000 |journal=Neurosurgical Focus |date=October 2006 |volume=21 |issue=4 |pages=E3 |doi=10.3171/foc.2006.21.4.4 |doi-access=free |pmid=17112193 }}{{cite journal |last1=McCrory |first1=P |last2=Johnston |first2=K. |last3=Meeuwisse |first3=W. |last4=Aubry |first4=M. |last5=Cantu |first5=R. |last6=Dvorak |first6=J. |last7=Graf-Baumann |first7=T. |last8=Kelly |first8=J. |last9=Lovell |first9=M. |last10=Schamasch |first10=P. |title=Summary and agreement statement of the 2nd International Conference on Concussion in Sport, Prague 2004 |journal=British Journal of Sports Medicine |date=1 August 2005 |volume=39 |issue=Supplement 1 |pages=i78–i86 |doi=10.1136/bjsm.2005.018614 |pmid=15793085 |pmc=1725173 }} However, few tools are available for distinguishing mild TBI from moderate TBI. As a result, greater emphasis has regularly been placed on the management of concussions in athletes than on the immediate identification and treatment of such an injury.

On-field predictors of injury severity can define return-to-play guidelines and urgency of care, but past criteria have either lacked sufficient incidence for effective utility,{{cite journal |last1=de Kruijk |first1=J R |last2=Leffers |first2=P. |last3=Menheere |first3=P. P. C. A. |last4=Meerhoff |first4=S. |last5=Rutten |first5=J. |last6=Twijnstra |first6=A. |title=Prediction of post-traumatic complaints after mild traumatic brain injury: early symptoms and biochemical markers |journal=Journal of Neurology, Neurosurgery & Psychiatry |date=1 December 2002 |volume=73 |issue=6 |pages=727–732 |doi=10.1136/jnnp.73.6.727 |pmid=12438478 |pmc=1757354 }}{{cite journal |last1=McCrory |first1=Paul R. |last2=Berkovic |first2=Samuel F. |title=Concussive Convulsions |journal=Sports Medicine |date=1998 |volume=25 |issue=2 |pages=131–136 |doi=10.2165/00007256-199825020-00005 |pmid=9519401 |s2cid=22738069 }} did not directly address the severity of the injury,{{cite journal |last1=Collins |first1=Michael |last2=Iverson |first2=Grant |last3=Lovell |first3=Mark |last4=McKeag |first4=Douglas |last5=Norwig |first5=John |last6=Maroon |first6=Joseph |title=On-Field Predictors of Neuropsychological and Symptom Deficit Following Sports-related Concussion |journal=Clinical Journal of Sport Medicine |date=2003 |volume=13 |issue=4 |pages=222–229 |pmid=12855924 |doi=10.1097/00042752-200307000-00005 |s2cid=18035638 }} or have become cumbersome and fraught with inter-rater reliability issues.{{cite journal |last1=Gill |first1=Michelle |last2=Windemuth |first2=Ryan |last3=Steele |first3=Robert |last4=Green |first4=Steven M. |title=A comparison of the Glasgow Coma Scale score to simplified alternative scores for the prediction of traumatic brain injury outcomes |journal=Annals of Emergency Medicine |date=January 2005 |volume=45 |issue=1 |pages=37–42 |doi=10.1016/j.annemergmed.2004.07.429 |pmid=15635308 }}

• Stevan Ridley playing in the NFL for the New England Patriots against Baltimore Ravens clashed with Bernard Pollard. Ridley was knocked unconscious, with medical professionals declaring it fencing response. Steven went on to have a full recovery, a long career, and became a Super Bowl champion (XLIX). He has not reported any signs of permanent brain damage since.{{cite web|title=Stevan Ridley's Concussion: Biomechanics of His Injury, 'Fencing Response' |website=Bleacher Report |url=https://bleacherreport.com/articles/1494620-stevan-ridleys-concussion-biomechanics-of-his-injury-fencing-response}}
• Kenny Shaw, NCAA football wide receiver for Florida State, September 17, 2011.{{cite web|url=http://articles.orlandosentinel.com/2011-09-21/sports/os-fsu-oklahoma-sidebar-0918-20110917_1_kenny-shaw-doak-campbell-stadium-fsu-coach-jimbo-fisher |title=FSU's Kenny Shaw OK after being knocked unconscious |publisher=Orlandosentinel.com |accessdate=2015-04-04|archive-url=https://web.archive.org/web/20140608011124/http://articles.orlandosentinel.com/2011-09-21/sports/os-fsu-oklahoma-sidebar-0918-20110917_1_kenny-shaw-doak-campbell-stadium-fsu-coach-jimbo-fisher|archive-date=June 8, 2014}}
• Xiong Fei, professional footballer, after being kicked in the head by Shanghai Shenhua FC teammate Li Jianbin, October 17, 2015.{{cite news |last1=Newell |first1=Sean |title=Chinese Player Knocks Out Teammate with Bicycle Kicks to the Face |url=https://www.vice.com/en/article/chinese-player-knocks-out-teammate-with-bicycle-kicks-to-the-face/ |work=Vice |date=19 October 2015 }}
• Tom Savage, professional American football quarterback for the Houston Texans, December 10, 2017.{{cite news|last1=Schad|first1=Tom|title=NFLPA will review Tom Savage concussion protocol|url=https://www.usatoday.com/story/sports/nfl/texans/2017/12/11/nflpa-review-tom-savage-concussion-protocol-texans-nfl/940168001/|accessdate=December 11, 2017|publisher=USA Today}}
• Donald Parham, professional American football tight end for the Los Angeles Chargers, December 16, 2021.{{cite magazine |last1=Lyons |first1=Dan |title=NBC Sports Medicine Analyst: Donald Parham Experienced the 'Fencing Response' |url=https://www.si.com/nfl/2021/12/17/donald-parham-injury-concussion-fencing-response |access-date=19 October 2022 |magazine=Sports Illustrated |date=December 17, 2021 |language=en-us}}
• Tua Tagovailoa, professional American football quarterback for the Miami Dolphins, Sept. 29, 2022{{cite web |last1=Maadi |first1=Rob |title=Dolphins' Tua Tagovailoa Injury, Fencing Response and NFL Protocol |url=https://www.nbcchicago.com/news/sports/what-to-know-about-dolphins-tua-tagovailoa-injury-fencing-response-and-nfl-protocol/2954985/ |access-date=3 October 2022}} and again on Sept. 12, 2024.{{cite web |last1=Jaques |first1=Marcel |title=What we know about Dolphins QB Tua Tagovailoa's concussion |url=https://www.espn.com/nfl/story/_/id/41239114/tua-tagovailoa-concussion-2024-dolphins-miami |access-date=13 September 2024}}
• Barnabás Varga, Hungarian professional footballer, after a collision with Scotland goalkeeper Angus Gunn in the Euro 2024 Group A match on June 23, 2024.{{Cite web |last=Leeks |first=Jacob |date=2024-06-23 |title=Hungary star stretchered off after sickening collision during Scotland match |url=https://www.mirror.co.uk/sport/football/news/breaking-barnabas-varga-injury-scotland-33091561 |access-date=2024-06-23 |website=The Mirror |language=en}}{{Cite web|url=https://www.sportingnews.com/in/football/news/barnabas-varga-hungary-scotland-euro-2024-updates/645e8b87bec3444513ad4103|title=What happened to Hungary player at Euro 2024? Latest updates after Barnabas Varga receives urgent medical treatment in Scotland match after collision | Sporting News India|date=June 23, 2024|website=www.sportingnews.com}}
• Daniel Sams, Australian cricketer, after a collision with Cameron Bancroft, both trying to go for a catch in the outfield, in their Sydney Thunder game in the BBL against the Perth Scorchers on January 3, 2025.{{Cite web |date=2025-01-03 |title=Big Bash collision: Daniel Sams and Cameron Bancroft have scary clash in Thunder vs. Scorchers BBL match {{!}} Sporting News Australia |url=https://www.sportingnews.com/au/cricket/news/big-bash-collision-sams-bancroft-thunder-scorchers-bbl/722679c58b174693a8dadb31 |access-date=2025-01-06 |website=www.sportingnews.com |language=en-au}}

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Category:Sports medicine