Diagnosis and Treatment of 

Vestibular Disorders in mTBI

1War Related Illness & Injury Study Center, Veterans Administration, 

East Orange, NJ, USA

2Dept of Pharmacology & Physiology, Rutgers Biomedical Health 

Sciences, Newark, NJ, USA

3Electrical & Electronic Engineering, National University of Ireland 

Galway, Ireland

Jorge M Serrador, PhD

Associate Professor
Poll Question:

What type of vestibular damage do you 

think may be more common in mTBI with 

blast exposure?

1) Unilateral Canal

2) Unilateral Otolith

3) Bilateral Canal

4) Bilateral Otolith

5) None
What does vestibular 

dysfunction look like?
Acute Vestibular Disorder
Chronic Vestibular Disorder
Research Approach

 Assess balance system a number of ways

 Posturography – sway while standing with eyes 

open and closed

 Vestibular Ocular Reflex – focused on otolith 

funciton by examining ocular torsion during roll tilt as 

well as unilateral centrifugation
Postural Sway in Veterans
Assessing Ocular Torsion
Assessing Otolith Function
Findings
Assessing Unilateral Damage
Findings
Findings
Findings
Clinical Relevance

 Long term effects of blast exposure are 

still not understood

 Vestibular problems may contribute to 

some of the poorly understood symptoms 

in returning veterans

 Working on new treatments for vestibular 

problems
Can we improve vestibular function? 
Is noise always a bad thing? 
Can Noise Improve a Picture? 
Can Noise Improve a Picture? 
Can Noise Improve a Picture? 
Does this work in physiological 

systems? 
Stochastic Resonance

Application of stochastic noise has been shown to 

demonstrated improvements in detecting weak 

signals in several sensory systems including 

crayfish mechanoreceptors (Douglass et al, 1993) 

and rat cutaneous afferents (Collins et al, 1996).

Human studies have shown improved signal 

detection of hippocampal CA1 neurons (Stacey and 

Durand, 2000) and sensory tactile nerves (Collins et 

al, 1996) .

Application of stochastic noise galvanic vestibular 

stimulation has been shown to improve response to 

a platform perturbation (Pavlik et al, 1999)
Basis of Stochastic Resonance
Basis of Stochastic Resonance
Basis of Stochastic Resonance
Can we improve vestibular function? 
Methods

20 Veterans (22-71 yrs) 

Ocular Counter Roll measurements made 

during sinusoidal roll tilt of 25 degrees at 

0.03125 Hz, 0.125 Hz, and 0.25 Hz for both 

control and sub threshold stochastic noise 

trials.

Stochastic noise galvanic vestibular 

stimulation was bipolar 

Veterans also completed Posturography 

Group of subjets also completed tandem 

stand testing with eyes closed during sham 

and stimulation trials.




Does this improvement in ocular 

counter-roll result in functional 

improvements?



Poll Question:

What type of vestibular damage do you 

think may be more common in mTBI with 

blast exposure?

1) Unilateral Canal

2) Unilateral Otolith

3) Bilateral Canal

4) Bilateral Otolith

5) None
Summary

 mTBI may be associated with unilateral

otolith damage that may underlie some

symptoms

 These deficits may not be found during

bilateral tests

 Application of subsensory GVS using a

specific noise paradigm can improve VOR

and balance
Vestibular Consequences of 

Mild Traumatic Brain Injury 

and Blast Exposure

Faith W. Akin, Ph.D.

VA Medical Center 

Mountain Home, TN

East Tennessee State University

Johnson City, TN
Disclaimer 

The views expressed in this article are those 

of the authors and do not necessarily 

reflect the position or policy of the 

Department of Veterans Affairs or the 

United States government.
Poll Question

What is your primary role in VHA?

1) Clinician

2) VA Researcher

3) Non-VA Researcher

4) Management/policy maker

5) Other
Dizziness and War-Related Injuries 

Caveness & Nielson (1961) reported that 56% of 

407 Korean conflict veterans with head injury 

complained of giddiness & vertigo

Robert Bárány (1910) 

association between head 

injury and dizziness 
Scope of the Problem

15% to 78% patients with head injury report 

dizziness/vertigo

Symptoms often last for 6 months or longer 

following the head trauma/blast exposure

 Van Campen et al., 1999; Cohen et al. 2002
 

 

Sensory Input Central Processing Motor Output

Visual

Vestibular

Proprioceptive

Vestibular 

Nuclear 

Complex

Cerebellum

Motor

Neurons

Overview of Balance System
Vestibular Sensory Organs

Semicircular Canals

Otolith Organs
Vestibulo-ocular Reflex (VOR)

Vestibular ganglion

Vestibular nucleus

Ocular motor nuclei

Goal is to stabilize gaze 

during angular head 

acceleration
Tests of Horizontal Semicircular 

Canal (hSCC)/Superior Vestibular Nerve Function

Binaural Bithermal Caloric Test

Rotary Chair Test (SHA, step velocity)
Ocular Motor Function

Gaze-Evoked Nystagmus

Smooth Pursuit

Saccades

Optokinetic Nystagmus

Fixation Suppression

Abnormalities suggest possible central 

pathology (brainstem/cerebellar)
Otolith Organs 

Utricle and saccule 

located in vestibule 

Stimulus is linear 

acceleration, tilt, & 

gravity 

Saccule 

Utricle 

otoconia 
Benign Paroxysmal Positioning Vertigo 

(BPPV) and Head Injury

BPPV is a common vestibular disorder 

associated with head injury

10 – 25% of head trauma patients develop BPPV 

Proctor et al., 1956; Barber, 1964; Davies & Luxon, 1995
Mechanism for BPPV: canalithiasis

Free-floating otoconia in the endolymph 

 Hall, Ruby, & McClure, 1979

Accounts for short duration of vertigo and nystagmus

Basis for modern approaches to treatment 

 

 

Brandt & Steddin, 1993
Management of BPPV 

Canalith Repositioning Therapy

Efficacy rate: 80-100% 

 Fife et al. 2008 

 Bhattacharyya et al. 2008 

 Fife, 2009 
Tests of Otolith Function

Cervical vestibular evoked myogenic potentials

Ocular vestibular evoked myogenic potentials

Subjective visual vertical or ocular torsion

Centrifugation or tilt
Vestibular Evoked Myogenic Potentials (VEMPs)

Short latency electromyogram evoked by high-level 

sound or vibration stimuli 

Recorded from surface electrodes over the tonically

contracted muscles 

Cervical VEMP (cVEMP): sternocleidomastoid m.

Ocular VEMP (oVEMP): Inferior oblique extraocular m.
Left SCM m. Activation/ 

Left Ear Stimulation

Left SCM

Right SCM

P1

N1

Cervical VEMP Recording

Asymmetry Ratio (AR): 

100 x (AmpL – AmpS ) / (AmpL + AmpS ) 

< 

> 

Vestibular Nuclei

Midline Utricle

MVST

CN XI

> 

SCM m.

Cervical VEMP Pathway

Saccule Inferior

Vestibular n.

Air conduction stimulus

500-Hz Tone bursts
Ocular VEMP Recording 

Bone conduction (BC) vibration

N1

P1

> 

> > 

Vestibular 

Nuclei

Superior

Vestibular

Nerve

Utricle

Midline

MLF

CN III Inferior 

Oblique m.

Saccule

oVEMP Pathway

Asymmetry Ratio (AR): 

100 x (AmpL – AmpS ) / (AmpL + AmpS ) P1

N1
Vestibulo-Spinal Pathways

Serve to modulate posture

Two components 

 Medial vestibulo-spinal tract 

 Lateral vestibulo-spinal tract 

Burt, 1993
Balance Testing

Can assess static or dynamic balance function

e.g., Posturography Sensory Organization Test
N hSCC

Otolith 

organ

Ocular 

motor

Gait/

balance

Davies & Luxon 1995 100 51% - 8% - 

Ernst et al. 2005 63 19% 25% 5% 27%

Dae Lee et al. 2011 28 7% 54% - - 

Shupak et al. 1993 5 40% - - - 

Van Campen et al. 1999 30 7% - 7% 37%

Cohen et al. 2002 17 0% - - 4%

Scherer et al. 2011* 11 27% 17% 45% - 

Literature Review: 

Abnormal vestibular function test findings in 

individuals with dizziness/imbalance related to 

TBI/blast exposure
TBI/Blast 

N = 51

Control

N = 21

Age 37 (10) 26 (5)

MMSE 29 (1.8) 30 (.4)

PTSD 92% 0%

Tinnitus 98% 14%

Sensorineural

Hearing Loss

67% 0%

Mountain Home VAMC study: Preliminary findings
Symptom N (%)

Vertigo 25 (49%)

Imbalance 45 (88%)

Lateropulsion 26 (52%)

Lightheadedness 37 (73%)

Oscillopsia 3 (6%)

Symptom characteristics of mTBI/blast group (n = 51) 
Number of blasts Number of Veterans

0 3 

1-2 13

3-5 6 

5+ 29 

History of blast exposure for 51 Veterans

Time since worst exposure

Range = 6 months – 10 years

Mean (SD) = 5 years 9 mos (30 mos) 

4 Veterans with symptoms ≥ 20 years
0

20

40

60

80

100

Saccades Tracking Gaze 

Nystagmus

Fixation

TBI/Blast

Control

Tests of Central Vestibular Function Normal Findings (%) 
0

20

40

60

80

100

Caloric Test Rotary 

Chair

oVEMP cVEMP

TBI/Blast

Control

Tests of Peripheral Vestibular Function Normal Findings (%) 

hSCC/SVN 

utricle/SVN saccule/IVN 

* 

*p = 0.014 
Further evidence

Histological studies and cVEMP studies in 

humans and animals suggest that the saccule 

may be particularly susceptible to noise-related 

damage.

Kerr & Byrne, 1975; Ylikoski, 1987; 

Akdogan et al., 2009; Hsu et al,. 2008; 

Fetoni et al,. 2009; Wang et al., 2006; 

Wang & Young, 2007; Akin et al. 2012
0 

20 

40 

60 

80 

100 

SOT DGI FAP Gait 

Velocity

TBI/Blast

Control

Tests of Gait and Balance

Normal Findings (%)

* 

* p ≤ 0.01

* * 
Case Study: History 

• 22 year old male c/o imbalance and

lightheadedness with onset 1 year ago

• Hx of > 300 blast exposures (security for

explosive ordnance clearance team)

• Diagnosed with mTBI and PTSD

• Noise-induced sensorineural hearing loss

worse AD and constant tinnitus AU
Case Study: Ocular Motor Test Results

No gaze evoked or spontaneous nystagmus

Saccades WNL

Tracking WNL

Normal fixation suppression
Case Study: hSCC Tests Results

Bithermal Binaural Caloric Test

Caloric nystagmus 

symmetrical and WNL

Rotary Chair Test

WNL 
Case Study: Otolith Organ Test Results

Cervical VEMPs (AC) Ocular VEMPs (BC)

P1

N1

Left SCM

Right SCM

N1

N1

P1 Left Eye

Right Eye

Absent cVEMP on the right side

Right saccule/IVN dysfunction

Symmetrical oVEMPs 

WNL 

P1
Case Study: Balance & Gait Tests

• Dynamic Gait Index = 19

(abnormal)

• Functional Ambulation

Profile = 88

(abnormal)

• Gait velocity = 63 cm/s

 (abnormal)

Sensory Organization Test

Abnormal composite equilibrium score
Future Directions

• Consider otolith assessment in individuals

with dizziness following mTBI/blast

• Functional consequences

– Relationship b/w vestibular findings and

functional impact

• Rehabilitation?

– Vestibular exercises (gaze stability) based on VOR

(hSCC) dysfunction

• CNS abnormalities (imaging)
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Wang Y-P, Hsu W-C, Young Y-H (2006). Vestibular evoked myogenic potentials in acute acoustic trauma. Otol Neurotol, 27: 956-

61.

Wang Y-P, Young Y-H (2007). Vestibular-evoked myogenic potentials in chronic noise-induced hearing loss. Otolaryngol Head 

Neck Surg, 137: 607-11.

Ylikoski J (1987). Impulse noise induced damage in the vestibular end organs of the guinea pig: A light microscopic study. Acta

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Acknowledgements

• Colleagues: Owen Murnane PhD, Courtney

Hall PhD, Kristal Riska PhD, Amber Pearson

AuD, Stephanie Byrd AuD, Kip Kelly PhD

• VHA RR&D Merit Review (C6663R)

• VHA RR&D Auditory & Vestibular Dysfunction

Research Enhancement Award Program