#1 Title slide: Analysis of Brain Trauma\
Coded as a Diffuse Axonal Injury

Narayan Yoganandan, PhD

Thomas A. Gennarelli, MD

Frank A. Pintar, PhD

Dale Halloway, MA

WI CIREN Center

#2 1997 to 2006 CIREN database was queried for Brain Diffuse Axonal
Injury (DAI).

all restraints systems, with and without airbags, with and without seat
belts were included. So were all impact modes, all clock directions,
frontal, side, and rear impacts. All occupant positions, i.e., drivers,
and passengers in front and rear seats were included. However, ejections
and rollovers were excluded from this initial analysis

#3 With this inclusion and exclusion criteria, 2,823 crashes and 3,178
occupants, i.e., medical cases were found. Out of these, 67 occupants
sustained the injury, amounting to an incidence rate of 2.4%. Occupants
ranged from pediatric to geriatric ages; 15 pediatric (\<16 years) and
52 adults. There were 53 survivors and 14 were fatalities.

#4 Graph showing side impacts dominated the sample with 49 cases,
followed by frontal with 15, and rear impact with three cases.

#5 If all pediatric occupants are removed, the mean age is approximately
during the early adulthood for all impact modes. Because of the sample
size, deviations are large. In fact these data parallel NASS findings.

#6 Height reveals the same pattern, no bias with respect to crash mode;
average height is 160-cm

#7 Weight, a similar finding, no bias with impact mode; average weight
is 75 kg

#8 Mean ∆V about 38 km/h for all modes. For the frontal mode, the mean
velocity is around 40 km/h, within regulatory speeds. Nearside occupants
in lateral impacts have a greater velocity than far-side occupants.

#9 When weight and height data are grouped for the body mass index, the
mean value is around 25 kg/meter squared. Obesity is not significant

#10 All cases had DAI. Looked at other injuries to see whether we can
correlate this injury with specific loading type. Examined injuries from
soft and hard tissue perspectives, brain and bone. Importance was placed
on superficial trauma to the scalp and face. Also included were
fractures to the cranial vault and basilar skull. We also examined
injuries to other body regions such as face and neck.

#11 15 occupants in frontal impacts. Most of the injuries were coded as
DAI to the cerebrum.

#12 Example of evidence of head contact drawn from CT imaging. As seen
from CT scans, injuries are obvious to the superficial structure, scalp.
This is an indication of contact loading to the head. The scalp
abnormality can be seen in all the six images. With 5 mm cuts, the
abnormality extends to about 25 mm on the head. The DAI sustained in
this case can therefore be attributed to head contact loading.

#13 Same evidence as previous slide, but the scalp hematoma is markedly
more obvious.

#14 In cases where scalp laceration, abrasions, or contusions are not
obvious or equivocal in terms of discerning load paths, other injuries
may help. In this case, the occupant sustained facial fractures as shown
on these CT images, although the body region is different. This suggests
facial loading, as literature data are conclusive.

#15 Quasistatic Loading Human Zygoma deflection curves. The human skin
absorbs loads and modulates force tolerance, as shown in this slide.
Presence of skin while does not change force to fracture the facial
bone, deflection needed to fracture is more when the skin is present.
This tolerance is under static forces.

#16 Image of drop apparatus for simulating facial impacts to a steering
wheel. Dynamic Loading**:** Under drop impacts on to the steering wheel,
different pathology occurs. Specimens dropped onto steering wheel
surfaces using a drop tower, showed the following (on next slide)

#17 Single impacts to one side of the facial skeleton produced bilateral
fractures in some cases, and when this study was done some 15 years ago,
2-D and 3-D CT images were used to show the extent of fracture. As you
can see, laboratory produced pathology is similar to the CIREN case is
repeated here. The take home message is that bilateral fractures can
occur with impacts to one side of the face.

#18 Human Facial Fracture Probability as a function of force. These
curves show that approximately 1500 N is required for 50% probability of
fracture

#19 This is another frontal impact, wherein the two head CT images
available are shown. No superficial abnormalities. An interesting
finding is that another body region indicates head contact. C-spine
abnormality in a CT bone window. The axial cut shows a burst fracture
suggesting head contact loading.

#20 Images of apparatus and C-spine fractures. Laboratory studies have
shown that when the head-neck complex is aligned along its stiffest
axis, stabilized, and applied compressive impact to the top of the head,
axial load-induced injuries such as burst fractures can occur, as shown
in these images. CIREN case is similar to this pathology.

#21 Compressive Force-Induced Trauma. The graph as corridors showing
that approximately 3500 N is needed to cause this injury. Thus, head
contact with this level of force is the likely source for brain and neck
injury in this case.

#22 We extended this analysis to derive probability distributions to all
ages, both genders, and different loading rates. Having these
biomechanical information should assist determine injury mechanisms at
organ and component levels.

#23 Injury Analyses: Frontal Impact. There were only three or four cases
of head/face fracture, while 10 cases had some scalp/facial abrasion,
laceration, or contusion implying head contact. However, when all data
were examined, all frontal impact cases has head contact. Thus, DAI is
most likely due to head-contact and direct impact loading

#24 Based on the cumulative frequency distribution, approximately 60%
occurred at 208 and 75% at NCAP speeds, i.e., crashes are within
crashworthiness limits.

#25 Side Impact Type. There were 38 nearside and 10 far-side cases

#26 Image of a head CT with an obvious scalp hematoma. In this case
there was only brain trauma, and seen is external soft tissue swelling
on the left side implying head contact

#27 CT bone and tissue windows of the head with an obvious depressed
skull fracture. Another case of scalp injury and skull fracture, both on
the left side. Skull fracture implies contact. Head contact occurred to
cause fracture and brain trauma

#28 MRI images of the brain and a plain film AP x-ray of the skull. In
this case, there is no clear indication of soft tissue injury. However,
upon examination of injuries to the face, a fractured mandible is seen.
Again fracture to the facial bone implies contact.

#29 Graph summarizing injuries to all 38 nearside occupants. Nine cases
of skull fracture, six cases of face fracture, while 29 cases had some
scalp/facial abrasion, laceration, or contusion implying head contact.

#30 Turning to far-side impacts: 9 cases.

#31 This injury summary is similar in terms of fracture, external soft
tissue involvement, and head contact. Head contact is involved in all
cases.

#32 If we combine all these data from these impact modes, it can be
concluded that head contact, i.e., scalp or facial abrasions,
contusions, or lacerations are involved in a majority of cases; skull
and facial fractures are less common. Let us examine this finding in
light of other biomechanical data.

What level of delta-V is needed to induce brain injuries with minimal
bony fractures?

How does it differ between different impact modes?

#33 Graphic depicting focal and motion (rotation) head (brain) injuries.
If you look at the biomechanics of brain trauma, broadly speaking,
injuries have been classified as focal and head motion induced; DBI
belongs to the latter category. Focal injuries can be effectively
represented by linear accelerations, i.e., HIC. Literature shows that
motion-induced injuries (MII), including DAI, are due to α. Therefore,
one way is to rotate the head. Lot of animal experiments just did that,
i.e., pure rotation without head contact.

What levels of α is needed to cause different severities of MII?

#34 Graph showing how many radians per second squared are required to
induce brain injury. 12,000 radians per second squared are required to
induce a mild DAI. When we assimilated and synthesized all α data from
literature, a simple and statistically-related curve can be derived,
from MC to severe DAI. 12 to 15 k α is needed to induce the type of MII.

#35 Images from a model used to predict the ΔV needed to produce DAI. A
parametric study was done to determine α as function of ΔV in frontal
and side impacts. Very generic modeling approach to get an idea of what
is needed to cause MII. Skull or facial fractures do not occur without
head contact. So, only non-contact scenario was modeled. The model had
full torso restraints, allowing the head-neck complex move freely
without any contact.

It takes a very high ΔV to achieve the level of α needed to cause the
types of severe brain injuries, analyzed here. Approximately 50 mph
vehicle ΔV is needed under side impact. However we do know that this
level of ΔV was uncommon in the current CIREN cases

#36 Examination of NHTSA LINCAP tests: translations accelerations. Low
HIC, low chance of brain injury or skull fracture. With head contact,
get high accelerations and high HIC. Red is a head contact case but with
low HIC. There is an obvious difference in translation accelerations
with and without head contact. As described before, we are interested α
in DAI for MII.

#37 If we compare α in these LINCAP tests, no head contact case had very
low magnitudes. In both head contact cases, whether HIC was above or
below 1000, α was well over 12 k for DAI. Remember, these LINCAP tests
had a ΔV of 15 to 20 mph, speeds associated with DAI identified in the
CIREN database. Fits very well with the current analysis. Thus, it is
quite possible that we can get high α and low HIC with reasonable ΔV to
support the CIREN database records.

#38 Summary: Used CIREN 1997-2006 database

66 cases coded-DAI, AIS 1990/98

Side impacts predominate, \>70%

Pediatric to geriatric age groups

Skull/face involved \> 90% cases

Head contact association exists

Images, clinical reports, & other BR (face, neck)

NCAP tests & laboratory studies

contact-induced metrics

#39 **Acknowledgment: Supported in part by US DOT NHTSA
DTNH22-05-H-41001**