Auditory and Vestibular Effects of Repeated Low-Level Blast

PI: Robin Pinto, Au.D.

AI: Holly Burrows, Au.D., LTC Philip Littlefield, MD, Douglas Brungart, Au.D. Lina Kubli, Ph.D.

Disclaimer

• The views expressed in this presentation are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government

Objectives

• Overview: Methods of Entry School, Marince Corps Base, Quantico VA

• Previous “Breacher” research studies

• Auditory and vestibular effects of repeated low-level blast research study

– Methods

– Results

• Conclusions

Marine Corps Base Quantico (MCB) Methods of Entry School (MOES)/

Goettege Demo Range

https://youtu.be/euZbLuGNFgU

High-Level Blasts vs Low-Level Blasts

> 4 PSI < 4 PSI

Effects of Blast Pressure on Structures and the Human Body

http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-125/125-ExplosionsandRefugeChambers.pdf

Previous Breacher Studies

Tate, Charmaine M., et al. "Serum brain biomarker level, neurocognitive performance, and self-reported symptom changes in soldiers repeatedly exposed to low-level blast: a breacher pilot study." Journal of neurotrauma 30.19 (2013): 1620-1630.

Baker, Andrew J., et al. "Controlled blast exposure during forced explosive entry training and mild traumatic brain injury." Journal of Trauma and Acute Care Surgery 71.5 (2011): S472-S477.

Auditory/Vestibular System Blast Measures

Primary Objective: Determine if Breachers are at risk of injury during standard training practices.

BREACHER 1 (students)

• Investigate the audiometric and vestibular consequences of repeated exposure to low-level blasts (comprehensive evaluation at Walter Reed National Military Medical Center – WRNNMC)

BREACHER 2

• Identify any acute effects of blast exposure (abbreviated evaluation on demolition range at Quantico)

Weapons Training Battalion (WTB), Quantico VA

• “Breacher” - instructors for Methods of Entry Course (MOEC)

• “Engineers” for MOEC (controls)

SUBJECT POPULATION

Equipment: Demo Range vs Hospital

BREACHER 2 Goettege Demo Range & WRNMMC

Comprehensive evaluation Abbreviated evaluation

Baseline Demographics

Participation in Evaluation Sessions

Study Duration

Subject # Walter Reed Observation Period (months)

Breacher

1 2 8

4 2 8

12 2 6

13 2 15

14 2 9

MEAN 9.2

Engineer

2 3 17

3 3 17

6 2 8

9 3 15

MEAN 14.3

Dependent Measures

Comprehensive (testing at WRNMMC)

• Hearing (4 hours) – Otoscopy

– Air & bone conduction thresholds

– Immitance

– Otoacoustic emissions (distortion product: DPOAEs)

– Speech intelligibility tests

– Central Auditory Processing tests

• Vestibular/Balance (4 hours) – Ocular motor tests

– Spontaneous

– Positional/positioning tests

– Head shake test

– Caloric testing

– SVV

– Rotational testing

– Dynamic visual acuity

– Vestibular Evoked Myogenic Potential (cervical and ocular)

– Posturography

– Gan’s Sensory Organization Performance Test

• Questionnaires (30 minutes) – Dizziness Handicap Inventory

– Vestibular Visual Analog Scale

– Functional Hearing Questionnaire

– Neurobehavioral Symptom Inventory (NSI)

– Speech, Spatial, and Qualities of Hearing Questionnaire (SSQ)

– Tinnitus and Hearing Survey (THS)

Abbreviated (testing at Quantico) • Hearing (10 minutes)

– Otoscopy

– Air conduction thresholds

– Otoacoustic emissions (distortion product: DPOAEs)

• Vestibular/Balance (15 minutes) – Ocular motor

– Spontaneous/positional

– Dynamic visual acuity

– Gan’s Sensory Organization Performance Test

• Questionnaires (5 minutes) – Dizziness Handicap Inventory

– Vestibular Visual Analog Scale

– Functional Hearing Questionnaire

VESTIBULAR/BALANCE RESULTS

t

Breachers Engineers Site p-Values Variable S N Mean SD S N Mean SD MCB WRB Slope Subject Site

Neurobehavioral Symptom Inventory (0-88) 11 51 1.3 (0.3) 4 22 1.5 (0.2) 50 23 0.40 0.34 0.75

Visual Analog Scale (0-10)

Vertigo 11 50 0.24 (0.11) 4 19 1.2 (1.2) 50 19 0.47 0.09 0.35 Oscillopsia 11 50 0.22 (0.13) 4 19 0.5 (0.2) 50 19 0.79 0.06 0.57 Motion Intolerance 11 50 0.79 (1.51) 4 19 0.8 (0.4) 50 19 0.92 0.67 0.67 Dysequilibrium 11 50 0.26 (0.15) 4 19 0.8 (0.6) 50 19 0.12 0.05 0.36

Videonystagmography

Spontaneous Nystagmus (% present) 11 57 5.30 (11.9) 4 24 3.13 (6.3) 55 26 0.17 0.45 0.34 Gaze Nystagmus (% present) 11 57 11.4 (12.0) 4 24 2.3 (4.7) 55 26 0.89 0.21 0.06 Optokinetic Nystagmus (% abnormal) 10 47 0.0 (0.00) 4 24 13.8 (20.2) 48 23 0.10 0.20 Saccades (% abnormal) 11 57 0.0 (0.00) 4 24 2.4 (4.8) 55 26 0.17 0.32 Smooth Pursuit (% abnormal) 10 47 0.0 (0.00) 4 21 17.4 (27.1) 45 23 0.06 0.19 Post Headshake Nystagmus (% abnormal) 10 48 6.8 (12.3) 4 24 15.0 (13.8) 49 23 0.17 0.59 0.63 Positional Nystagmus (% abnormal) 10 48 41.7 (36.8) 4 24 31.2 (32.3) 49 23 0.38 0.69 0.95 Upbeat Positional 10 48 24.1 (21.8) 4 24 17.2 (34.4) 49 23 0.38 0.84 0.71 Caloric (% asymmetry between sides) 10 15 10.8 (6.8) 4 10 6.8 (0.9) 0 25 0.88 0.28 Caloric (% with abnormal asymmetry) 10 14 5.0 (15.8) 4 10 0.0 (0.0) 0 24 0.39 0.55

VEMP

Cervical (% abnormal) 10 14 7.5 (16.9) 4 11 0.0 (0.0) 0 25 0.39 0.40 Right P1 (msec) 10 14 17.0 (2.2) 4 11 16.0 (0.4) 0 25 0.91 0.39 Right N1 (msec) 10 14 25.9 (2.4) 4 11 23.5 (2.5) 0 25 0.97 0.13 Left P1 (msec) 9 13 18.0 (1.8) 4 11 16.6 (1.1) 0 24 0.79 0.18 Left N1 (msec) 9 13 26.1 (1.9) 4 11 24.4 (3.1) 0 24 0.08 0.25 Ocular (% abnormal) 10 13 30.0 (42.2) 4 11 41.7 (50.0) 0 24 0.66

Rotary Chair

VOR Suppression (% abnormal) 8 13 0.0 (0.0) 4 8 0.0 (0.0) 0 21 1.00 1.00 0.01 Hz SHA Gain Average 10 15 0.5 (0.1) 4 8 0.4 (0.1) 0 23 0.41 0.41 Phase (degrees) 10 15 36.6 (7.0) 4 8 44.6 (3.7) 0 23 0.61 0.05 Asymmetry (MAD) 10 15 4.2 (2.1) 4 7 3.6 (4.5) 0 22 0.99 0.74 0.08 Hz SHA Gain Average 10 15 0.6 (0.1) 4 9 0.5 (0.1) 0 24 0.75 0.33 Phase (degrees 10 15 0.7 (3.5) 4 9 0.0 (6.1) 0 24 0.24 0.79 Asymmetry (MAD) 10 15 4.4 (4.5) 4 9 9.2 (4.9) 0 24 0.16 0.11 0.32 Hz SHA Gain Average 10 15 0.6 (0.1) 4 9 0.6 (0.2) 0 24 0.09 0.75 Phase (degrees) 10 15 0.6 (4.2) 4 8 -4.4 (7.9) 0 23 0.06 0.14 Asymmetry (MAD) 10 15 4.6 (3.4) 4 9 4.7 (2.6) 0 24 0.17 0.98 60° Step Test % Abnormal 6 9 16.7 (40.8) 4 8 37.5 (47.9) 0 17 0.48 Decay Times (s) Pre clockwise 7 10 14.3 (5.6) 4 7 12.9 (3.7) 0 17 0.39 0.67 Post clockwise 7 10 21.0 (5.8) 4 8 15.0 (7.6) 0 18 0.41 0.18 Pre counterclockwise 7 10 14.1 (2.3) 4 8 14.2 (2.1) 0 18 0.39 0.93 Post counterclockwise 7 10 14.1 (7.5) 4 8 11.7 (7.8) 0 18 0.62 0.63 Peak Eye Velocities (degrees/s) Pre clockwise 7 10 -51.1 (11.0) 4 8 -45.9 (13.4) 0 18 0.94 0.49 Post clockwise 7 10 41.8 (11.8) 4 8 49.8 (20.3) 0 18 0.18 0.42 Pre counterclockwise 7 10 48.7 (15.1) 4 8 48.8 (14.8) 0 18 0.88 0.99 Post counterclockwise 7 10 -48.8 (8.1) 4 8 -53.7 (20.4) 0 18 0.25 0.58 % with asymmetries 7 10 0.7 (14.4) 4 8 3.2 (1.4) 0 18 0.72 0.75 Unilateral Centrifugation Test (degrees) Mean Subjective Visual Vertical 10 15 0.3 (0.8) 4 11 -1.1 (2.4) 0 26 0.37 0.13 Right mean 10 14 -5.5 (3.5) 4 9 -3.4 (2.8) 0 23 0.47 0.31 Center mean 10 15 -1.5 (2.5) 4 9 -3.3 (1.1) 0 24 0.07 0.20 Left mean 10 15 0.3 (3.0) 4 8 -1.3 (1.3) 0 23 0.72 0.34

Dynamic Visual Acuity

Up Loss (LogMAR) 9 54 0.06 (0.03) 4 24 0.12 (0.04) 56 22 0.46 0.07 0.16 Down Loss (LogMAR) 9 54 0.04 (0.02) 4 24 0.12 (0.03) 56 22 0.98 0.01 0.13 Right Loss (LogMAR) 9 54 0.08 (0.04) 4 23 0.11 (0.02) 56 21 0.53 0.27 0.66 Left Loss (LogMAR) 9 54 0.06 (0.04) 4 21 0.11 (0.06) 55 20 0.56 0.45 0.40

Posture and Balance

SOT Composite (1-100) 10 15 85.1 (4.4) 4 11 82.5 (5.9) 0 26 0.09 0.38 Motor Control Composite (msec) 5 7 89.9 (57.7) 4 7 127.8 (9.2) 0 14 0.50 0.24

Upbeat positional nystagmus by test session

Subject # Walter Reed MCB Quantico

Breacher

1 2 of 2 4 of 6

4 0 of 1 0 of 9

5 0 of 1 1 of 2

7 0 of 1 0 of 2

8 1 of 1 1 of 3

10 0 of 1 No data

11 1 of 1 No data

12 0 of 2 3 of 4

13 0 of 2 4 of 8

14 Excluded (nicotine nystagmus)

15 No Data 0 of 2*

Engineer

2 3 of 3 3 of 3

3 0 of 3 0 of 5

6 0 of 2 0 of 1

9 0 of 3 0 of 4

The presence of upbeat positional nystagmus correlated with a history of trauma

HEARING RESULTS

Baseline Evaluation HEARING: behavioral & objective measures

Air conduction thresholds Distortion Product Otoacoustic Emissions (DPOAEs)

HEARING (threshold), Post blast vs Baseline

Post blast: better hearing than baseline

HEARING (OAEs), Post blast vs Baseline

Post blast: better hearing than baseline

Baseline Evaluation HEARING: SPEECH IN NOISE

• 8 different ‘noise’ conditions

• Speech reception thresold (SRT) measured

• The lower the SRT, the better.

Questionnaire Results

• None of the questionnaires showed any evidence of systemic changes over time in the Breacher population.

• There was also no difference between the Breachers and Engineers, or between the MCB and WRB administrations of the test.

• The Neurobehavioral symptom inventory (NSI) scores were within normal range for a non-clinical deployed population.

Aim 1: Investigate the audiometric and vestibular consequences of repeated exposure to low-level blasts.

• Hypothesis 1: Through repeated testing over several years, subtle changes in audiologic and vestibular function may become detectable in MOEC breacher instructor cadre members.

• Hypothesis 2: Any changes in auditory and vestibular function found within the MOEC breacher instructor cadre will vary according to the level of blast exposure (i.e. between those who serve as primary instructors, and those who serve in an administrative or support role, such as Engineer controls).

Aim 2: Identify any acute effects of blast exposure.

• Hypothesis 3: There will be more symptoms and audio-vestibular abnormalities in those immediately and directly exposed to a blast when compared to their baseline evaluations.

Breacher Study - Discussion

• We are the first to make a control group for comparison, and the demographics show a good match.

• The assessments used in this study were all standard of care in the clinical evaluation of dizzy and hearing-impaired patients, and included the most sophisticated clinical measures currently available. We were more than exhaustive in all of the measures that we collected.

• This is a cohort with a limited number of subjects (11 Breachers and 4 Engineer controls), but this is as good as group can do with the way these courses are set up.

• This is mostly a negative study, which is not exactly an exciting way to conclude several years of work, but it is something that the scientific mind must accept. What really matters is that the Breachers are safe.

Conclusions

• This study looked at auditory and vestibular symptoms and function using multiple standard of care measures, but did not identify any changes over the 17 month study period.

• There were baseline differences between the Breachers and the Engineer control group, as well as between those with and without prior mTBI. In particular, the presence of upbeat positional nystagmus correlated with a history of trauma. While we have seen this in our clinical mTBI population, this has not been described elsewhere before. This relationship is worth further investigation.

• Overall, the Breachers appear to be safe at the current levels of blast exposures, but the number of subjects, the small control group, and limited compliance with follow-up evaluations limits this prospective cohort.

• While the study period is the longest to date, it still may be too short to detect long-term deterioration of function in this population.