Page 18 - Layout 1

NEUROLOGY &
SLEEP DISORDERS

The pentagram of overt indicators of

By Jonathan Lifschiz, PhD and Joshua A. Beitchmen, MBS

FIGURE 1
child receives a hit to the head and falls to the ground.
A They may not be unconscious, but their arms are held
postured in an unnatural position. Why are they reach-
ing upwards or defensively guarding? Observers are
aghast, confused, and worried.
This event and those like it are indicative of the Fencing Re-
sponse, which identify moderate traumatic brain injury or con-
cussion. Upon impact, if direct or indirect forces of injury
transmit to the brainstem, then an individual’s forearms are held
flexed or extended (typically into the air) for a period lasting up
to several seconds. One expression of the posture resembles a
fencer’s en guarde stance, thereby earning the name Fencing Re-
sponse. Reports of the Fencing Response include all genders,
ages, and activities, including organized sport, domestic violence,
non-accidental trauma, automobile accidents, violent assaults, and
self-inflicted injury.
The Fencing Response originates from motor reflexes in the
brainstem. Concussive forces can be transmitted to the vestibular Schematic illustration of the Fencing Response during a knock-
nuclei (lateral vestibular nucleus (LVN); aka Deiter’s nucleus) and out. A. The individual receives a punch or sudden force to the
mechanically activate primitive reflexes, normally reserved for head. B. After the traumatic blow to the head, the unresponsive
correcting balance. The motor output arises from vestibular ac- individual immediately exhibits posturing of the arms. C. During
tivation of motor nuclei in the anterior column of the spine. The prostration, the rigidity of the extended and flexed arms is re-
reflex is observed as contraction of the limb extensors and re- tained for several seconds as flaccidity gradually returns. Image
laxation of flexors – described as the Fencing Response as shown reprinted from https://en.wikipedia.org/wiki/Fencing_response.
in Figure 1. The Fencing Response is used by healthcare professionals and

18 San Antonio Medicine • August 2018