Page 155 - NNS 2014 Program & Abstract Book

Hyperphosphorylated tau positivity has not been unequivocally
demonstrated or excluded in any subjects to date. These results reflect
the challenge in validating tau for a large animal model with limited
species-specific positive controls and highlights the need for caution,
and additional confirmatory measures before reaching unequivocal
conclusions regarding the pathophysiology of trauma and tauopathy in
immaturity and across species.
Key words
immaturity, large animal model, tauopathy, TBI
D2-28
COMPUTATIONAL INVESTIGATION OF BRAIN NEURO-
TRAUMA BIOMECHANICS UNDER BLAST
Sarvghad Moghaddam, H., Rezaei, A., Karami, G., Ziejewski, M.
North Dakota State University, Fargo, USA
Due to moral and technical limitations for experimental studies on
blast-induced traumatic brain injury, computational methods such as
finite element (FE) analysis serve as the most common tools in the
engineering sciences to study the biomechanics of brain neuro-
trauma. In this research, a numerical study was carried out on the
interaction of blast shockwaves with the head. The tissue level pa-
rameters such as shear stress, shear strain, and intracranial pressure
(ICP) as well as the kinematic parameters such as linear acceleration
of brain were recorded to provide an evaluation of injury related
parameters. Due to the structural inhomogeneity of the human head
as well as different tolerances and functions of head components, the
head response to blast waves can differ with respect to the impact
location of shockwaves on the head. Accordingly, four different
blast scenarios were performed based on the approaching blast
waves from the front, back, top, and side of the head to highlight the
effect of blast directionality on the head response. A detailed vali-
dated FE head model including most anatomical features of the
human head was employed. Ls-Dyna, a nonlinear explicit FE solver
was used to carry out all simulations. In order to comply with the
lung injury threshold, a 520 kPa blast overpressure was generated
around the head. The primary results showed the development of
peak ICP and shear stress values inside the brain mainly at the coup
site, the parietal lobe, and the brainstem. However, a comparison of
brain biomechanics at different directions revealed that the side blast
produced the highest peak values for both tissue and kinematic pa-
rameters, hence imposing higher risks of neurotrauma. However,
while kinematical responses are addressed as main injury predictors
in most studies, our correlational analysis did not indicate a direct
relationship between tissue and kinematic parameters for all direc-
tions. Hence, the tissue level parameters were ascertained as a more
reliable injury criterion. The observations from the present study
may be considered in the design of protective headgears.
Key words
blast induced neurotrauma, computational biomechanics, directionality,
finite element analysis, tissue level parameters, traumatic brain injury
D2-29
EFFECT OF SPACE CONFINEMENT ON THE LEVEL OF
BLAST INDUCED TRAUMATIC BRAIN INJURY
Rezaei, A., Sarvghad Moghaddam, H., Salimi Jazi, M., Karami, G.,
Ziejewski, M.
North Dakota State University, Fargo, USA
Blast-induced assaults to the head can impose traumatic injuries to
the head brain. Parameters such as the intensity of blast and the
media significantly influence the level of brain neurotrauma. Se-
vere blast scenarios are expected in confined spaces. According to
some observations, the rate of fatality and morbidity in confined
spaces has shown a significant increase compared to similar open-
space blast scenarios. The aim of this study is to examine the in-
fluence of confinement on different injury-related biomechanical
parameters such as the brain intracranial pressure (ICP), shear
stress, and strain. Investigations are conducted on a 50th percentile
finite element human head model exposed to blast at different lo-
cations in a confined space. The head model employed in this study
consisted of essential components for accurate computational
analysis and has been validated against cadaveric experiments. The
results of the investigations indicate that in such complex envi-
ronments, besides the direct blast wave incidents similar those in
open spaces, human head would also experience reflection waves
from the surrounding walls. Such reflected waves extend a longer
duration of load which intensifies the level of brain injury. Ad-
ditionally, for the locations close to walls where the magnitudes of
the reflected waves from neighboring wall are the highest, the peak
values of ICP and shear stress of the brain are drastically amplified.
It is concluded that the duration and magnitude of reflected waves
applied on the human head could be several times larger when the
head is placed at the corners of the confined space. While the brain
is prone to traumatic injuries in confined spaces the severity and
fatality of blast-induced trauma would remarkably be elevated
when the head is located near the walls and particularly at the
corners.
Key words
biomechanical parameters, blast injury, blast media, computational
biomechanics, confined space, finite element analysis
D2-30
LIMITED EVIDENCE OF BRAIN INJURY IN RATS EXPOSED
TO EXPLOSIVE-DRIVEN PRIMARY BLAST
Leonessa, F.1 , Kovacs, S.K.1, Murphy, E.1, Pan, H.1, Kitces, E.1, Sarkar,
S.1, Magnuson, J.1, Gabriel, L.1, Martin, S.1, Parks, S.3, Swauger, P.3,
Brooks, K.3 , Carlisle, A.2, Lipsky, R.2, Buonora, J.1, Mueller, G.1
1Uniformed Services University of the Health Sciences, Bethesda,
MD, USA
2George Mason University, Fairfax, VA, USA
3Ora Inc., Fredericksburg, VA, USA
Explosive blast has been a major cause of brain injury in recent war
theaters. Blast can cause injury by different mechanisms, but the
specific contribution of shock wave transmission across tissues,
(‘‘primary’’ mechanism of injury by blast) is still unclear. We ex-
plored the neurobehavioral and neuropathological outcome in an-
esthetized and restrained rats exposed to explosive-generated blast
waves, under conditions aimed to minimize non primary mecha-
nisms of injury. The outcome was evaluated across a range of peak
blast overpressures and pulse durations, at different angles of ex-
posure, in the presence and absence of chest protection. Results
suggest very mild levels of brain injury even at blast intensities
approaching thresholds of lung injury-related lethality, both in the
absence (21 psi) and presence of torso protection (50 psi). Neuro-
logical scores, motor coordination, spatial learning, parameters of
anxiety were not affected. Loss of startle response was most likely
A-123