Page 149 - NNS 2014 Program & Abstract Book

Non-penetrating eye (retina) and brain injuries, often caused by
blast overpressure (BOP) shock waves, have emerged as a signif-
icant threat to warfighters in current theaters of operation. Previous
research using rodent models of BOP demonstrated reproducible
injury to the eye and brain, as assessed by electroretinography
(ERG) and histopathology. We further characterized this BOP in-
jury model by examining the effect of various head orientations in
relation to the oncoming BOP wave on the extent of eye injury in
the rat.
Adult male rats were secured in a compressed air driven shock tube
with either the right eye (side-on) or the snout (face-on) facing toward
the oncoming shock wave and then exposed to a single 20 psi BOP
wave. The animals were then assessed at 1, 7 and 14 days post-blast
along with non-blasted sham animals utilizing ERG measurements
and histopathological assessments.
At 2 weeks post-blast, side-on blasted rats versus sham animals
showed significantly decreased ERG waveform amplitudes (ap-
proximately 30% from shams) and severe neuronal degrada-
tion within the retina and brain visual processing centers which
could indicate functional visual deficits in the blasted animals.
However, the face-on blasted rats showed minimal ERG waveform
decrement or histopathologic evidence of injury, quite similar to
sham animals.
We have demonstrated a reproducible method of studying BOP-
induced eye and brain injuries in rats. Differences in eye and brain
injury between the side-on and face-on orientation might be due to
deflection of the shock wave away from the eyes in the face-on
animals, owing, in part, to the conical morphology of the rodent
skull. We conclude that the side-on orientation offers a reproducible
model of BOP-induced eye and visual processing center brain injury
in the rat and that it is suitable for further preventive and treatment
paradigms.
Key words
blast injury, eye injury, TBI, vision processing centers
D2-12
A NEW MODEL OF TRAUMATIC BRAIN INJURY (TBI) SI-
MULATING PENETRATING INJURIES USING A CAPTIVE
BOLT IN SWINE
Scultetus, A.H.1,2, Haque, A.1, Pappas, G.M.1, Carballo, N.1, Arnaud,
F.G.1,2, Auker, C.R.1,2, McCarron, R.M.1,2
1Naval Medical Research Center, Silver Spring, U.S.A.
2Uniformed Services University of the Health Sciences, Bethesda,
U.S.A.
TBI induced by explosives/blast is the predominant head injury
mechanism in current military conflicts. However, no model ac-
curately mimics direct brain impact injuries by shrapnel or flying
objects. In lateral fluid percussion, fluid wave transmission to the
intact dura does not provide the complexity of injury seen in blast.
While blast injuries performed in a tube replicate the ideal blast
wave found in open-air explosions, they omit injuries due to
shrapnel or flying objects. Open-field explosions have a less con-
trollable environment, making it more difficult to standardize. We
propose the use of a captive bolt to simulate brain injury secondary
to direct skull impact of flying objects and resulting penetrating
brain injury.
We built a customized plexiglas structure that held a concussion
stunning captive bolt gun in place and provided adjustments for angle
and depth of bolt impact. Sixteen anesthetized swine (30 kg) had scalp
removed on the frontal part of the head. The tip of the gun was placed
perpendicular to the exposed skull at a distance of 2.5cm. Yellow
single cartridges (175m/s) were used to inflict a single hit on the
frontoparietal lobe. Animals were invasively monitored for 6 hours.
After euthanasia, a full necropsy was performed.
Bolt impact produced multiple skull fractures with non-lethal brain
penetration, resulting in acute hypotension, apnea, bradycardia and
intracranical hypertension. Gross necropsy showed consistent injury
patterns. Hemorrhage volumes, fibrin deposits and neuronal loss were
quantifiable in histopathology and were significantly higher than in
fluid percussion control animals.
In this model, we showed a reproducible method of simulating
penetrating traumatic brain injury in swine. This model may be
helpful in studying open, penetrating, traumatic injuries similar to the
ones encountered in combat or civilian head trauma casualties.
Key words
captive bolt, penetrating head injury model, swine
D2-13
COMBINED HYPOXEMIA & HEMORRHAGIC SHOCK
WORSEN MOTOR BUT NOT COGNITIVE FUNCTION
AFTER PENETRATING BALLISTIC-LIKE BRAIN INJURY
Leung, L.Y., Deng-Bryant, Y., Flerlage, W.J., Winter, M., Bustos, F.,
Shear, D.A., Tortella, F.C.
Walter Reed Army Institute of Research, Silver Spring, USA
The purpose of this study was to determine the extent to which ad-
ditional insults, such as hypoxemia (HX) and hemorrhagic shock
(HS), may worsen neurofunctional deficits following unilateral frontal
penetrating ballistic-like brain injury (PBBI) in rats. Adult Sprague-
Dawley rats were randomly assigned into 6 groups: (1) Sham (2) 5%
PBBI (3) 10% PBBI (4) HX + HS, (5) 5%PBBI + HX + HS, (6)
10%PBBI + HX + HS. In the combined injury groups, HX (PaO2 = 30-
40 mm Hg) was initiated 5 minutes following PBBI or sham proce-
dures and maintained for 30 minutes. After restoring normoxia, HS
(MAP = 40 mmHg) was initiated and maintained for 30 minutes.
Motor function was assessed using the rotarod task at 7 and 14 days
post-injury (DPI) and cognitive function was assessed in the Morris
water maze (MWM) task from 13-17 DPI. PBBI produced significant
decrements in motor performance (vs. sham and HX + HS groups) that
were more prominent following 10% PBBI vs. 5% PBBI. Additional
insults (HX + HS) significantly worsened motor functions following
5% PBBI but not 10% PBBI. Both 5% and 10% PBBI produced
significant spatial learning and memory deficits in the MWM task (vs.
sham control and HX + HS groups) with increased deficits evident
following 10% PBBI vs. 5% PBBI. However, while rats subjected to
the 5% PBBI + HX + HS injury combination showed a trend toward
worsened cognitive performance (vs. 5% PBBI), this was not statis-
tically significant. No difference in cognitive performance was de-
tected between 10% PBBI and 10% PBBI + HX + HS groups. Overall
these results suggest that 10% unilateral frontal PBBI produces motor
and cognitive deficits which may exceed a sensitivity threshold ca-
pacity. In contrast, 5% PBBI produces a lower, albeit significant,
magnitude of deficits and thus provides a more sensitive screen for
evaluating the cumulative effects of additional insults. Additionally,
the current results suggest that the cumulative effects of additional
insults such as HX + HS may have more overt effects on motor vs.
cognitive abilities in the PBBI model.
Key words
cognitive, hemorrhagic shock, hypoxemia, motor, neurobehavior,
penetrating ballistic-like brain injury
A-117