Vestibular Manifestations of TBI:
Perspectives from the Field and
Lessons for Space
Michael E. Hoffer, CAPT MC USN
Kim R. Gottshall, COL (ret) AMSC USA
Carey Balaban, PhD
Ben J. Balough, CAPT MC USN
TBI a “signature” injury in modern
warfare
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Body armor – other injuries avoided
Improvised explosive device are a
key weapon
Blat exposure account for over 90%
of our battlefield injuries
Urban combat environments create
opportunity for TBI
TBI Mechanisms
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Blunt head trauma
Acceleration/Deceleration Injuries
Blast (even without other injuries)
What’s the issue – Traumatic Brain
Injury (TBI)
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Closed head injury (impact) – work has
been ongoing for 3-4 decades
Acceleration/deceleration injuries – work
has been ongoing for 2-3 decades
Blast
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very little work
mostly from other nations
may not be able to utilize the lessons
learned from other (more heavily studied)
injury patterns
TBI definition*
A traumatically induced structural injury
and/or physiological disruption of brain
function as a result of an external force
that is indicated by new onset or
worsening of at least one of the
following clinical signs, immediately
following the event:
*As developed by the Surgeon Generals’ consensus study
group May-July 2007
TBI Definition - Continued
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Any period of loss of or a decreased level of
consciousness
Any loss of memory for events immediately before or
after the injury
Any alteration in mental state at the time of the injury
(confusion, disorientation, slowed thinking, etc)
Neurological deficits
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Weakness
Loss of balance
Change in vision
Praxis
Paresis/plegia
Sensory loss
Aphasia
Etc.
Intracranial lesion
Common TBI sequela
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Neurocognitive dysfunction
Vestibular disorders
Hearing disorders
Adjustment disorder
Associated PTSD
Severe vs. mild
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Time course of recovery dramatically
different
Response to therapy dramatically
different
Symptoms
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Severe – cognitive with gross muscular
discoordinatioin and severe associated injuries
Mild – different set of symptoms
Three-four decades of work on severe TBI
not very applicable to mild TBI
TBI secondary to combat
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Over 50% of balance disorders in the
civilian population will resolve over time
Less than 20% of war injured balance
disorders will return to duty without
treatment
Sequela from Mild TBI (mTBI) secondary
to blast injury can present months-years
after the injury, can have significant
morbidity, and CANNOT BE IGNORED.
What we know about blunt head
trauma
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Focal lesions at specific sites
(coup/counter-coup)
Pathophysiology is easy to study
due to frequency and sports injuries
Injury patterns being worked out
with high Tesla magnets
CHI Induced Dizziness
Entity
History
Physical Exam
Vestibular Tests
Positional
Vertigo
Positional Vertigo
Nystagmus on Dix-Hallpike test
or modified Dix-Hallpike test
No other abnormalities
Exertional
Dizziness
Dizziness during and right
after exercise
Abnormalities in challenged
gait testing
No other abnormalities
ƒ Episodic Vertigo with
periods of unsteadiness
ƒ Headaches
ƒ Abnormalities in challenged
gait testing
ƒ +/-Abnormalities on head
impulse testing
ƒ Normal static posture tests
ƒ VOR gain, phase, or symmetry
abnormalities
ƒ High frequency VOR
abnormalities
ƒ Normal posturography
ƒ Constant feeling of
unsteadiness worsened by
standing but still present
when sitting or lying down
ƒ Drifting to one side while
walking
ƒ Shifting weight when
standing still
ƒ Abnormalities on standard
gait tests
ƒ +/- Abnormalities on head
impulse testing
ƒ Abnormalities on static
posture tests
ƒ VOR gain, phase, or symmetry
abnormalities
ƒ High frequency VOR
abnormalities
ƒ Abnormal posturography
ƒ Central findings on rotation
chair testing
Migraine
Associated
Dizziness
Spatial
Disorientation
Blast
Blast – Physics
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Any event where individuals or
those around them “feel” a pressure
wave
Damage is done largely by the
pressure wave not the impulse
sound
Basic question
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Determine the difference in
presenting symptoms of blast
induced mild traumatic brain injury
as a function of time
Examine the diagnostic and
management implications of these
differences
Materials and Methods
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Three groups of mild traumatic brain
injury (mTBI) patients divided by time of
presentation
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Acute – seen in under 72 hours from blast in
Iraq
Sub-acute – seen 4-30 days after blast at
NMCSD
Chronic – seen 30-360 days after blast at
NMCSD
All had mTBI secondary to blast as
defined by the DoD definition of TBI
(October 2007)
Materials and Methods
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Acute patients
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History and physical
Dynamic Gait Index (DGI)
Hearing test (Otogram)
Sub-acute and Chronic patients
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History and physical
Rotational chair (details in paper)
Sensory Organization test (Posturography)
DGI
Hearing test
Standardized Instruments (details in paper)
Results
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Groups (Median age 22)
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Acute – 81 Individuals
Sub-Acute – 25 Individuals
Chronic – 42 Individuals
Mild Traumatic Brain Injury after Blast Symptoms Distribution
Group
Acute
Dizziness
Hearing
Vertigo
Loss
Headache
PTSD
98%*
4%*
33%*
72%
2%*
Sub-acute
76%
47%
43%
76%
20%
Chronic
84%
36%
49%
82%
44%
Patterns of Balance Disorders in Sub-acute and
Chronic Blast Exposure
Entity
History
Physical Exam
Vestibular Tests
Positional
Vertigo
Positional Vertigo
Nystagmus on Dix-Hallpike test or
modified Dix-Hallpike test
No other abnormalities
Post-Blast Exercise Induced
Dizziness (PBEID)
Dizziness during and right after exercise
Abnormalities in challenged gait test
during exertion
No other abnormalities
Post-Blast Dizziness (PBD)
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Constant feeling of unsteadiness
when standing and waling worse
with challenging environments
Constant Headache
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Abnormalities in challenged gait
Abnormalities in tandem Romberg
Abnormalities with quick head
motion
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Post-Blast Dizziness with
Vertigo (PBDV)
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Constant feeling of unsteadiness
when standing and waling worse
with challenging environments
Constant Headache
Episodic Vertigo
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Abnormalities in challenged gait
Abnormalities in tandem Romberg
Abnormalities with quick head
motion
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+/- Abnormal posturography
Abnormal target acquisition,
dynamic visual acuity, and gaze
stabilization
+/- VOR gain, phase, or symmetry
abnormalities
+/- Abnormal posturography
Abnormal target acquisition,
dynamic visual acuity, and gaze
stabilization
+/- VOR gain, phase, or symmetry
abnormalities
Blunt vs. Blast – are they different
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Vestibular analysis will give us the
answer
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VOR Analysis
Postural Analysis
VOR Analysis
Materials and Methods
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Patients presenting to our center with TBI
suffered in Iraq from March-September
2006
Divided into three groups – blunt, blast,
mixed
Standard assessment included a detailed
neurotologic exam, standard
questionnaires, rotational chair testing,
and computerized dynamic posturography
Results
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Two groups
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Blunt – 34 males (Ages 19-43, Mean
26)
Blast – 21 males (Ages 20-41, Mean
26)
Mixed group excluded from this
analysis
Comparisons of Dizziness
Blast Injury
Blunt head trauma
6%
24%
35%
47%
59%
PTEID
PTMAD
PTSpD
29%
PTEID
PBD
PBDV
Vestibular-ocular reflex (VOR)
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Blunt – High frequency phase lag
Blast- Low to mid frequency
bilateral phase lead
Symmetry
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Blast – no asymmetry
Blunt – asymmetry present
Other findings
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Hearing
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Blunt - <7%
Blast – 43%
Hearing function showed changes many
months out
{ Central Auditory Processing a major issue
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Cognitive
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Blunt – 17%
Blast – 90%
Phase lead/lag
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Blunt – Phase lag may be a function
of the asymmetry
Blast- May be a function of afferents
with increased activity of
“Irregulars” or decreased activity of
“regulars”
More work needs to be done and is
underway in our consortium
Conclusion
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Objective vestibular testing of VOR
function differentiates blunt vs.
blast head injury in patients injured
in Iraq
Postural Study
Materials and Methods
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Patients presented to our clinic 1
week to 12 months after operational
head injury
Divided into one of three groups
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Primarily blunt
Primarily blast
Primarily mixed
Materials and Methods - Assessment
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History and Physical by two
independent examiners resulting in
diagnostic classification
Work-up as above
Materials and Methods
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Outcome measures
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Comparison of Group mean average
results of sensory organization test
(SOT) pre-treatment vs. posttreatment
Comparison of percent of each group
with abnormal Motor control test (MCT)
Results
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72 patients included in the study –
69 males, 3 females
Average age 24 years of age (1934)
Numbers by diagnostic group
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MAD - 14
PTSD – 19
PBD- 19
PBDV – 20
Comparison of SOT Score
76
74
72
SOT Score
70
68
66
64
62
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58
56
MAD
PTSD
PBD
PBDV
Motor Control Test
50
45
Percent of patients
40
35
30
25
20
15
10
5
0
MAD
PTSD
PBD
PBDV
Results
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SOT comparison
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PBDV, PBD, and PTSD all trended towards
being significantly different then MAD
PBDV, PBD, and PTSD did not differ from each
other
MCT
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no difference between the MAD and PTSD
groups
Significantly higher percentage of abnormality
for PBD and PBDV (blast groups) vs. MAD and
PTSD (blunt groups)
Discussion
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Postural data confirms the
difference between the diagnostic
groups
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SOT – MAD vs. other groups
MCT – Blunt vs. Blast
Blunt and blast mTBI are different
and all lessons learned from one
may not apply to the other
Treatment Results
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Several studies have been done or
are underway
High-light two here
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Study #1 is purely CHI from Iraq
Study #2 is both CHI and blast from
Iraq
Study #1 - CHI
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198 Total Patients
Assigned by two independent
investigators
Distribution of Dizziness Types
26%
27%
BPV
Exercise
PTMAD
8%
39%
Disorientation
Outcome Data
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All patients underwent vestibular
rehabilitation
All migraine patients received
medicines
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Migraine prophylactic medicine
(Verapamil or Topiramate)
Migraine abortive medicine (Triptan)
VOR Abnormalities – 8 Week
Follow-up
100
100
100
90
Percent of Patients
80
76
70
60
Pre-treatment
Post-treatment
50
40
30
20
17
10
0
PTMAD
Spatial Disorientation
Functional Outcome
45
40
35
31.8
30
Weeks
BPV
25
Exertional
20
PTMAD
Disorientation
15
16.7
10
4
5
0.71
1
3.7
7.7
0.43
0
RTW
Symptoms Resolution
Study #2 – Blunt and Blast
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inVision Mirror Tunnel (NeuroCom
International, Clackamas, OR, USA
Testing was performed in a dimly lit room
Test distance was 13 feet
Subjects were seated in a chair with the
cross hair on the display at eye level
The optotype was a letter “E”.
Subjects were asked to report which way
the E was pointing or respond “I don’t
know”
Materials and Methods
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Test Battery
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Perception Time
Target Following
Target Acquisition
Test
Dynamic Visual
Acuity (DVAT)
Gaze Stabilization
(GST)
Dynamic Gait index
Results
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154 patients consented – 82
included in the study
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Fit injury pattern
Fit time of presentation
Successfully completed rehabilitation
Had follow-up data
Demographics
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79 males, 3 females
Average age 24.0 years of age (19-34)
Results of Cognitive Visual-Vestibular Tests
400
50
45
350
40
300
35
250
Score
Score
30
Pre
Post
25
20
Pre
Post
200
150
15
100
10
50
5
0
0
PT
TF
TAH
0.4
180
0.35
160
166
140
0.3
TAV
163
158
140
157
144
136
129
0.25
Pre
Post
0.2
0.15
Score
DVA logMAR
120
100
Pre-treatment
Post-treatment
80
60
0.1
40
0.05
20
0
0
DVAT R
DVAT L
DVAT D
DVAT U
Left
Right
Down
Up
Study Conclusions
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Blast vs. Blunt show different
diagnostic groups and different test
results – they are different injuries
Vestibular disorders from both
groups are treatable in specialized
centers
Conclusions
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TBI treatment strategies developed
over the last thirty years are likely
not be applicable to this group of
patients
More work needs to be done
characterizing the effects of blast on
the brain
The “mixed” group remains
uncharacterized
Lessons for space
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Vestibular disorders seen in very mild TBI
patients may mirror disorders seen in
those undergoing prolonged space fight
Battlefield diagnostic techniques must be
transitioned for use in and after prolonged
space flight
Treatment modalities far forward must be
applied to prolonged space flight
Return to duty/functional concerns are
similar when comparing war fighters to
astronauts
Lessons for space – more granular
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Basic science can be done more
readily on blast injury
Determine relevant blast injuries
that might parallel changes seen in
long term flight then develop
solutions in ground based labs
Take Home Points – Lessons learned
from the ocean
Because after all we are the Navy
Nothing has handles down there
Really??
Lessons we all must heed
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Mild TBI (mTBI) be it blast or blunt IS
THE ISSUE and is not the same as more
severe TBI
Blast is different then blunt
mTBI does not resolve without treatment
but is very amenable to treatment
We must support both basic and clinical
research on mTBI and this work is best
accomplished with an experienced cohort
of investigators
We cannot rely on more severe TBI
research to give us the right answers
Thank you
My colleagues at
TQ Surgical
{ This talk is
dedicated to the
men and women
of the United
States Marine
Corps
“Uncommon valor is
a common virtue”
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