Vestibular/Balance Laboratory

           

The Vestibular/Balance Research Laboratory is located on the Mountain Home VAMC campus. The Vestibular/Balance Research Laboratory receives support from the Rehabilitation Research and Development (RR&D) Service, Department of Veteran Affairs.

People

Faith W. Akin, Ph.D.                                                                                                                                  faith

Director, Vestibular Section

Dr. Akin received her Ph.D. from Vanderbilt University in 1997. She joined the audiology service at the Mountain Home VAMC in 1997 and developed the Vestibular Balance Laboratory in 2000 through funding from the Department of Veteran Affairs Rehabilitation Research & Development. Dr. Akin's research emphasis has been on the clinical use of otolith organ function to supplement the traditional vestibular test battery. Specifically, she and Dr. Murnane have examined cervical vestibular evoked myogenic potential, the ocular vestibular evoked myogenic potential, and the subjective visual vertical tests as tests of vestibular function. Currently, she is using tests of vestibular function and experimental imaging techniques to investigate the vestibular consequences of blast-related mild traumatic injury.

Courtney Hall, Ph.D.                                                                                                                                   hall

Director, Balance Section

Dr. Hall received her Ph.D. in Kinesiology from the University of Texas at Austin. She joined the Vestibular/Balance Research Laboratory in October 2011 as the director of the balance section of the laboratory. Dr. Hall's research has focused on clinical questions that will provide knowledge to develop novel, effective exercise interventions to reduce impairments related to dizziness and imbalance. Dr. Hall's research program is aimed at better understanding age-related (both normal and pathological) changes in balance control and how best to intervene therapeutically to prevent loss of mobility and falls. She has been studying various risk factors impacting mobility and falls for a number of years. Her research to this point has examined the contributions of motor (lower extremity strength and power), sensory (visual and vestibular), and cognitive function to balance control in older adults. Dr. Hall is has two ongoing lines of research. One line of research is how best to intervene to improve the ability to allocate attention to balance and gait under dual-task conditions. The other line of research is to determine whether the addition of vestibular-specific gaze stability exercises reduces symptoms and fall risk in older adults with non-vestibular dizziness.

Owen Murnane, Ph.D.                                                                                                                                           murnane

Investigator/ACOS for Research

Dr. Murnane received his Ph.D. from Syracuse University and was an original member of the Vestibular and Balance Laboratory with Dr. Akin. Dr. Murnane's research has been funded the VA Rehabilitation Research & Development service. Dr. Murnane's research within the laboratory has focused on clinical applications of measures of human vestibular and auditory physiology. Much of Dr. Murnane and Dr. Akin's work over the last decade has focused on ocular and vestibular evoked myogenic potentials. Currently, Dr. Murnane continues to study aging effects of the ocular vestibular evoked myogenic potentials as well as research studying the response characteristics of the video head impulse test and the clinical application of the video head impulse test.

Kristal M. Riska, Au.D., Ph.D.
riska

Investigator

Dr. Riska received her Ph.D. from East Carolina University in 2011. She joined the Vestibular Balance Laboratory in the summer of 2012. Dr. Riska is currently applying for career development funding through the VA Rehabilitation Research & Development service to develop cost and time efficient mechanisms to screen and evaluate individuals with vestibular dysfunction. Dr. Riska's research interests are clinically focused. Specifically, she is interested in improving evidence based clinical practice in the evaluation of dizziness and imbalance. Currently, she is studying epidemiological aspects of dizziness in Veterans as well as conducting research towards developing an effective vestibular screening instrument.

Stephanie Byrd, Au.D.

stephanie           

Project Coordinator

Dr. Byrd received her Au.D from Missouri State University in 2008. She joined the Vestibular Balance Laboratory in the spring of 2009. Dr. Byrd has served as a project coordinator for several VA funded research studies since joining the lab. She currently serves as the project coordinator for Dr. Hall's "Vestibular Rehabilitation and Dizziness in Geriatric Patients" research grant. Although clinically trained, Dr. Byrd enjoys working in the research setting as she has been able to expand her expertise in regards to vestibular assessment, become more effective clinically and directly impact those individuals with dizziness and balance concerns through research.

 

Research Projects and Current Funding

MHREAP Logo

Department of Veterans Affairs

 

Current Projects

Cervical vestibular evoked myogenic potentials as a test of otolith function (VA RR&D CDA I, CDA II, PI: Akin).
Over the past several years, research in the Vestibular/Balance Laboratory at Mountain Home has focused on the cVEMP as a clinical test of saccule/inferior vestibular nerve function. At that time, the cVEMP was not a commercially available vestibular test, so instrumentation and protocols were developed in our laboratory to measure the response (Akin and Murnane, 2001). Sustained contraction of the sternocleidomastoid (SCM) muscle is required during cVEMP acquisition and the SCM muscle is activated by either turning the head laterally while sitting or supine (unilateral activation) or raising the head from supine (bilateral activation). The AC cVEMP is typically obtained by presenting either monaural (unilateral SCM activation) or binaural (bilateral SCM activation) 500 Hz tone bursts (~120 dB peak SPL) via an earphone. Because cVEMP amplitude is influenced by the degree of sternocleidomastoid (SCM) muscle activation, a procedure was developed to control for the effects of tonic electromyography (EMG) level on the cVEMP (Akin and Murnane, 2001). A two-channel EMG recording was obtained simultaneously with the evoked potential recordings. During head rotation to one side, the subjects were provided visual feedback of their EMG amplitude via the computer monitor. Using this recording technique, a series of parametric experiments were conducted to determine the effects of stimulus parameters on cVEMP latency, amplitude, and threshold (Akin et al., 2003).

Effects of aging and noise on the cVEMP (VA RR&D Merit Review E3367R, PI: Akin)
To determine the effect of aging on the cVEMP we measured the tonic EMG level of the SCM muscle during the cVEMP recording. Previous studies on the effect of aging on the cVEMP had not measured directly the tonic EMG level of the SCM muscle during the cVEMP recording. The findings of our study suggested that the decrement in cVEMP amplitude is related to both age-related changes in the vestibular system and age-related changes in the sternocleidomastoid muscle.

To determine the effect of noise on the cVEMP, we recorded cVEMPs in individuals with asymmetric sensorineural hearing loss consistent with a history of noise exposure greater in one ear than the other, and cVEMPs were recorded in age-matched controls. cVEMPS were abnormal in a third of the individuals with noise-induced hearing loss. Furthermore, cVEMP threshold was higher in the NE group than in the control group, and the cVEMP inter-aural asymmetry ratio correlated significantly with the high frequency pure tone average of the ear with the greater noise-induced hearing loss (Akin et al., 2012). These findings demonstrate effects of noise exposure on the cVEMP and suggest that the sacculo-collic pathway may be susceptible to noise-related damage.

Subjective visual vertical during centrifugation as a test of otolith function (VA RR&D Merit Review C6241R; PI: Akin).
Recently, we have examined the clinical utility and obtained normative data for the subjective visual vertical (SVV) test using static and dynamic stimulus conditions. Normative data were obtained in 24 young healthy adults using static and dynamic (unilateral centrifugation) test conditions. Participants were positioned in a darkened rotary chair booth and instructed to indicate the SVV during four test conditions: static, on-axis, off-axis right, and off-axis left. The results revealed that the SVV was < 2° for static and on-axis rotation, and shifted up to 11° during unilateral centrifugation. Test-retest reliability of the SVV was good for all test conditions (Akin et al., 2011b). These normative findings are consistent with other studies using unilateral centrifugation in normal individuals (e.g., Clarke et al., 2001). We have recently completed data collection on experiments designed to determine the effect of age and unilateral vestibular loss on the SVV during centrifugation.

Preliminary evidence of otolith dysfunction related to mTBI/Blast Exposure (VA RR&D Merit Review C6663R, PI: Akin).
Dizziness and balance disorders are common symptoms associated with mild traumatic brain injury (mTBI) or head injury. Numerous studies have provided significant evidence that mTBI or head injury can cause damage to the vestibular system; however, most have limited the vestibular evaluation to assessment of hSCC function. In an ongoing clinical trial, we are collecting data to determine the effect of mTBI and blast exposure on (1) peripheral vestibular system function (specifically, hSCC function, and otolith organ function), (2) central vestibular/CNS function, (3) postural stability, and (4) dizziness-related quality of life. Four subject groups include Veterans complaining of dizziness/imbalance with (1) a history of blast exposure, (2) a history of mTBI, (3) a history of blast exposure and mTBI, and (4) a control group. Each subject is undergoing tests of hSCC function (caloric and rotary chair), tests of otolith function (cVEMPs, oVEMPs, SVV during centrifugation), central vestibular function/CNS function (ocular motor tests, diffusion tensor and susceptibility weighting imaging), gait and balance testing (SOT, Motor Control Test, Dynamic Gait Index), and the Dizziness Handicap Inventory.

Cognitive Training and Dual-task Ability in Older Adults (VA RR&D, VA Merit Pilot grant E7614R, PI: Hall)
The purpose of this project is to determine whether cognitive training provides added benefit to dual-task ability. Historically, therapy has focused on ameliorating impairments of the motor and/or sensory systems; however recent evidence suggests that an impaired ability to allocate attentional (i.e., cognitive) resources to balance during dual-task situations is a powerful predictor of falls. The first aim of the study is to examine whether the inclusion of dual-task practice in balance rehabilitation results in greater benefits to dual-task ability. Participants will receive either standard physical therapy for balance rehabilitation (standard PT) or standard PT plus dual-task practice. The second aim of the study is to examine the extent to which cognitive training to improve cognitive abilities will result in additional benefits to dual-task ability. After completion of PT, participants will complete computerized cognitive training ("brain games").

Vestibular rehabilitation and dizziness in geriatric patients (VA RR&D, VA Merit Review E7613R, PI: Hall)
The goal of this study is to develop novel, effective exercise intervention for older adults with dizziness unrelated to vestibular pathology. The first aim of this study is to examine the extent to which vestibular exercises enhance rehabilitation outcomes (symptoms, balance and fall risk) in older adults with dizziness without vestibular pathology. Older adults with dizziness and normal vestibular function will receive either vestibular-specific gaze stability exercises or placebo eye movement exercises, in additional to balance rehabilitation. The second aim is to determine the degree to which symptom improvement and fall risk reduction are retained after the intervention is completed.

The reproducibility of the video head impulse test (vHIT )(PI: Murnane)
The intra- and inter-examiner reliability of the vHIT will be assessed using two examiners, two test sessions, and two different vHIT devices (Otometrics and Synapsys) in 5 groups of participants: (1) young normal adults, (2) older normal adults, (3) patients with total unilateral vestibular losses, (4) patients with partial unilateral vestibular losses, and (5) patients with bilateral vestibular losses. Based on our preliminary data, we hypothesize that both intra- and inter-examiner reliability of the vHIT for both devices will be good (intra-class correlation coefficients >.80) for all participant groups.

The effect of aging on the video head impulse test (vHIT ) (PI: Murnane)
The vHIT results obtained from the young normal adults will be compared to the results obtained from the older normal adults for each of the two vHIT devices. We hypothesize that the average VOR gain will be significantly lower and that the variability will be significantly greater for the older adults than for the young adults.

Establishment of normal reference intervals for the video head impulse test (vHIT ) (PI: Murnane)
The 95% prediction interval for the distribution of each outcome for normal subjects will be examined, and the reference range will be determined to include 95% of participants. Follow-up analysis will include a comparison of the established normal reference intervals with the range of values for the participants with vestibular loss.

The sensitivity and specificity) of the video head impulse test (vHIT ) (PI: Murnane)
The results of the vHIT will be compared with the results of the reference tests (caloric test for unilateral vestibular losses and rotary chair test for bilateral vestibular losses) in a series of patients referred for vestibular assessment in the Vestibular/Balance Clinic at the Mountain Home VAMC

The use of natural language processing as a mechanism to explore the epidemiology of dizziness within the Veteran population (PI: Riska)
This project utilizes natural language processing to explore the incidence of dizziness within the VA population and to explore the health characteristics of Veteran's complaints of dizziness. Natural language processing is a new technique that allows one to take non-structured data in clinical notes within an electronic medical record and process the data into structured data for analysis. In this way, the study will allow for exploration of characteristics of patients with dizziness.

Student Projects

Current students in the lab are working on research studies involving the video head impulse device, rotary chair, and chart reviews evaluating the efficacy of current clinical evaluation paradigms.

Laura Williams, B.A. Audiology Doctoral Student

Laura is currently a fourth year audiology doctoral student at ETSU. She is completing her capstone project within the Vestibular Balance research laboratory. Laura's capstone project is examining the effectiveness of a triage clinic for patients with BPPV. Laura enjoys the work that she does within the research laboratory as she believes the skills she has developed will lead to her being a better clinician.

Emma Barnard, B.S. Audiology Doctoral Student

Emma is currently a third year audiology doctoral student at ETSU and is beginning work on her capstone project developing normative data for various rotary chair test protocols. Emma enjoys working in the laboratory as she is able to learn more about new and exciting techniques to evaluate vestibular function.

Listed below are previous student projects completed in the Vestibular/Balance Laboratory.

Laura's BPPV Project

Heather's vHIT Project

Amber's SVV Project

Sarah's DVA Project

 

Current Equipment/Technology

Our lab is located at the Mountain Home VA Medical Center. The Vestibular/Balance Laboratory is well equipped to fully investigate all 5 vestibular end-organs in addition to balance and gait.

The Vestibular/Balance Laboratory is equipped with two ICS computerized CHARTR videonystagmography (VNG) systems with water and air caloric stimulators. Two stand-alone video eye movement recorders (RealEyes Monocular, Micromedical Technologies) are used for recording nystagmus in patients with BPPV. There are two rotational chair systems: (1) System 2000 Rotational Vestibular Chair system with micro-centrifuge and subjective visual vertical option (Micromedical Technologies) and (2) I-Portal Neuro-Otologic Test Center (Rotary Chair System) with unilateral centrifugation, off-vertical axis rotation (OVAR), and SVV testing options (Neurokinetics Inc.). Both systems have digital video-oculography for measurement of eye movement. Several video head impulse devices are also available.

The evoked potential section of the the laboratory is equipped with several commercial evoked potential instruments including two Otometrics EP200 systems, a Nicolet Spirit 2000 evoked potential system, and a Bio-Logic multichannel auditory evoked potential and otoacoustic emission systems. In addition, the laboratory contains a Bruel and Kjaer Mini-Shaker, a Bruel and Kjaer power amplifier, a two-channel portable EMG unit (Delsys Bagnoli-2 EMG System), an eight-channel portable EMG unit, (DelSys, Inc., Bagnoli-8), an artificial mastoid (Bruel and Kjaer) and a sound level meter. In addition, the lab has 2 miniature triaxial accelerometers.

The new Gait/Balance section of the laboratory is equipped with a computerized dynamic posturography system (Smart Equitest, NeuroCom) and Long Forceplate attachment with electromyography for balance assessment. The Smart Equitest is also equipped with inVision Dynamic Visual Acuity Test and the Gaze Stabilization Test. In addition, the lab has recently acquired a GaitRite system for gait assessment. The 26-foot GAITRite® system is an electronic walkway to quantify spatiotemporal parameters of gait.

Publications/Presentations/Awards

Publications:

Faith Akin, Ph.D.: 

Akin, FA, Murnane OD, Tampas JW, Clinard C (in revision). The effect of age on the cervical vestibular evoked myogenic potential. Ear and Hearing

Akin FA, Murnane OD (in press). Head Injury and Blast Exposure. Otolaryngology Clinics of North America

Akin FW, Barker F (2009) Vestibular Evoked Myogenic Potentials: Why is monitoring of the EMG important? Insights in Practice, Otometrics.

Akin FW, Murnane OD (2009) The Subjective Visual Vertical Test. Seminars in Hearing, 30(4): 281- 286.

Murnane OD, Akin FW (2009) Vestibular Evoked Myogenic Potentials. Seminars in Hearing, 30(4): 267-280.

Akin FW, Murnane OD (2009) ASHA Perspectives: Clinical Assessment of Otolith Function 13: 29-39.

Akin, F. W. & Murnane, O. D. (2009, February 10). Clinical Assessment of Otolith Function. The ASHA Leader.

Wilson RH, King R, Akin FW. (2009) Unilateral transitory sensorineural hearing loss following a dental procedure. J Am Acad Audiol.;20(3):216-8.

Murnane OD, Akin FW, Lynn SG, Cyr DG (2009) Monothermal caloric screening test performance: a relative operating characteristic (ROC) curve analysis, Ear & Hearing. 30; 313–319.

Akin FW and Murnane OD (2008) Vestibular evoked myogenic potentials, in Balance Function Assessment and Management, Jacobson and Shepard (eds.), Plural Publishing.

Presentations:

Faith Akin, Ph.D.:

Murnane OD, Akin FW, Kelly JK, Tampas J (2009) Ocular Vestibular Evoked Myogenic Potentials: Preliminary Observations, American Academy of Audiology Convention, Dallas, TX.

Pearson A, Akin FW, Murnane OD, Kelly JK (2009) Normative data of the subjective visual vertical test for vestibular assessment, American Academy of Audiology Convention, Dallas, TX.

Murnane OD, Akin FW, Kelly JK, Tampas J (2009) Ocular Vestibular Evoked Myogenic Potentials, American Balance Society Meeting, Phoenix AZ

Murnane OD, Akin FW, Lynn SG, Cyr DG (2009) Monothermal caloric screening test performance: a relative operating characteristic (ROC) curve analysis, American Auditory Society, Phoenix, AZ.

 

Other

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