Insight into postural control in unilateral sensorineural hearing loss and vestibular hypofunction.

This pilot study aimed to identify postural strategies in response to sensory perturbations (visual, auditory, somatosensory) in adults with and without sensory loss. We tested people with unilateral peripheral vestibular hypofunction (N = 12, mean age 62 range 23-78), or with Unilateral Sensorineural Hearing Loss (USNHL, N = 9, 48, 22-82), or healthy controls (N = 21, 52, 28-80). Postural sway and head kinematics parameters (Directional Path in the anterior-posterior and medio-lateral directions (sway & head); pitch, yaw and roll (head) were analyzed in response to 2 levels of auditory (none, rhythmic sounds via headphones), visual (static, dynamic) and somatosensory cues (floor, foam) within a simulated, virtual 3-wall display of stars. We found no differences with the rhythmic auditory cues. The effect of foam was magnified in the vestibular group compared with controls for anterior-posterior and medio-lateral postural sway, and all head direction except for medio-lateral. The vestibular group had significantly larger anterior-posterior and medio-lateral postural sway and head movement on the static scene compared with controls. Differences in pitch, yaw and roll emerged between vestibular and controls only with sensory perturbations. The USNHL group did not increase their postural sway and head movement with the increased visual load as much as controls did, particularly when standing on the foam. They did not increase their medio-lateral sway with the foam as much as controls did. These findings suggest that individuals with USNHL employ a compensatory strategy of conscious control of balance, the functional implications of which need to be tested in future research.

Contextual sensory integration training via head mounted display for individuals with vestibular disorders: a feasibility study.

PURPOSE: Virtual reality (VR) interventions can simulate real-world sensory environments. The purpose of this study was to test the feasibility of a novel VR application (app) developed for a Head Mounted Display (HMD) to target dizziness, imbalance and sensory integration in a functional context for patients with vestibular disorders. Here we describe the design of the app as well as self-reported and functional outcomes in vestibular patients before and after participating in vestibular rehabilitation using the app. MATERIAL AND METHODS: Our app includes a virtual street, airport, subway or a park. The clinician controls the visual and auditory load including several levels of direction, amount and speed of virtual pedestrians. Clinicians enrolled 28 patients with central (mild-traumatic brain injury [mTBI] or vestibular migraine) and peripheral vestibular disorders. We recorded the Simulator Sickness Questionnaire, Visual Vertigo Analogue Scale (VVAS), Dizziness Handicap Inventory (DHI), Activities-Specific Balance Confidence Scale (ABC), 8-foot up and go (8FUG) and Four-Step Square Test (FSST) before and after the intervention. RESULTS: Within the 15 patients who completed the study, 12 with peripheral hypofunction showed significant improvements on the VVAS (p = 0.02), DHI (p = 0.008) and ABC (p = 0.02) and a small significant improvement on the FSST (p = 0.015). Within-session changes in symptoms were minimal. Two patients with mTBI showed important improvements, but one patient with vestibular migraine, did not. CONCLUSION: HMD training within increasingly complex immersive environments appears to be a promising adjunct modality for vestibular rehabilitation. Future controlled studies are needed to establish effectiveness.IMPLICATIONS FOR REHABILITATIONVirtual Reality allows for gradual introduction of complex semi-real visual environments.Within VR training patients can re-learn to maintain balance when presented with a sensory conflict in a safe environment.Head Mounted Display training appears to be a promising adjunct modality for vestibular rehabilitation.Portability and affordability of the hardware and software enhance the potential clinical outreach.

Postural and Head Control Given Different Environmental Contexts.

Virtual reality allows for testing of multisensory integration for balance using portable Head Mounted Displays (HMDs). HMDs provide head kinematics data while showing a moving scene when participants are not. Are HMDs useful to investigate postural control? We used an HMD to investigate postural sway and head kinematics changes in response to auditory and visual perturbations and whether this response varies by context. We tested 25 healthy adults, and a small sample of people with diverse monaural hearing (n = 7), or unilateral vestibular dysfunction (n = 7). Participants stood naturally on a stable force-plate and looked at 2 environments via the Oculus Rift (abstract "stars;" busy "street") with 3 visual and auditory levels (static, "low," "high"). We quantified medio-lateral (ML) and anterior-posterior (AP) postural sway path from the center-of-pressure data and ML, AP, pitch, yaw and roll head path from the headset. We found no difference between the different combinations of "low" and "high" visuals and sounds. We then combined all perturbations data into "dynamic" and compared it to the static level. The increase in path between "static" and "dynamic" was significantly larger in the city environment for: Postural sway ML, Head ML, AP, pitch and roll. The majority of the vestibular group moved more than controls, particularly around the head, when the scenes, especially the city, were dynamic. Several patients with monaural hearing performed similar to controls whereas others, particularly older participants, performed worse. In conclusion, responses to sensory perturbations are magnified around the head. Significant differences in performance between environments support the importance of context in sensory integration. Future studies should further investigate the sensitivity of head kinematics to diagnose vestibular disorders and the implications of aging with hearing loss to postural control. Balance assessment and rehabilitation should be conducted in different environmental contexts.

Weighting and reweighting of visual input via head mounted display given unilateral peripheral vestibular dysfunction.

We translated a well-established laboratory paradigm to study sensory integration into a Head-Mounted-Display (HMD). In the current study, a group of 23 individuals with unilateral vestibular dysfunction and 16 age-matched controls observed moving spheres projected from the Oculus Rift. We confirmed increased visual weighting with an unstable surface and decreased visual weighting (i.e., reweighting) with increased visual amplitude. We did not observe significant differences in gains and phases between individuals with vestibular dysfunction and age-matched controls. The vestibular group increased sway in mid and high frequencies significantly more than controls with the change in surface or visual amplitude. Mild visual perturbations within HMDs carry the potential to become a useful portable assessment of postural control in individuals with vestibular disorders.

An Oculus Rift Assessment of Dynamic Balance by Head Mobility in a Virtual Park Scene: A Pilot Study.

Postural sway does not differentiate between balance disorders. Head kinematics within a salient, immersive environment could potentially help identifying movement patterns that are unique to vestibular dysfunction. We describe a virtual park scene, where participants are asked to avoid a virtual ball approaching their head, to target dynamic balance and quantify head movement strategy. Sixteen patients with vestibular dysfunction and 16 healthy controls were wearing the Oculus Rift and performed the "park" scene on floor and stability trainers. Significant between-group differences emerged in head path (patients rotated their head sideways more), head acceleration (controls had higher acceleration, especially on translation movements), and peak frequency (controls peaked around the frequency of the ball whereas patients were variable). Those findings demonstrated good to excellent test-retest reliability. There were no significant between-group differences in postural sway parameters. Future studies should establish norms across different levels of balance dysfunction and investigate the underlying mechanism leading to the movement strategy observed.

Control Mechanisms of Static and Dynamic Balance in Adults With and Without Vestibular Dysfunction in Oculus Virtual Environments.

BACKGROUND: Deficits in sensory integration and fear of falling in complex environments contribute to decreased participation of adults with vestibular disorders. With recent advances in virtual reality technology, head-mounted displays are affordable and allow manipulation of the environment to test postural responses to visual changes. OBJECTIVES: To develop an assessment of static and dynamic balance with the Oculus Rift and (1) to assess test-retest reliability of each scene in adults with and without vestibular hypofunction; (2) to describe changes in directional path and sample entropy in response to changes in visuals and surface and compare between groups; and (3) to evaluate the relation between balance performance and self-reported disability and balance confidence. DESIGN: Test-retest, blocked-randomized experimental design. SETTING: Research laboratory. PARTICIPANTS: Twenty-five adults with vestibular hypofunction and 16 age- and sex-matched adults. METHODS: Participants stood on the floor or stability trainers while wearing the Oculus Rift. For 3 moving "stars" scenes, they stood naturally. For a "park" scene, they were asked to avoid a virtual ball. The protocol was repeated 1-4 weeks later. OUTCOME: Anteroposterior and mediolateral center-of-pressure directional path and sample entropy were derived from a force plate. RESULTS: We observed good to excellent reliability in the 2 groups, with most intraclass correlations above 0.8 and only 2 at approximately 0.4. The vestibular group had higher directional path for the stars scenes and lower directional path for the park scene compared with controls, with large variability in the 2 groups. Sample entropy decreased with more challenging environments. In the vestibular group, less balance confidence strongly correlated with more sway for the stars scenes and less sway for the park scene. CONCLUSION: Virtual reality paradigms can shed light on the control mechanism of static and dynamic postural control. Clinical utility and implementation of our portable Oculus Rift assessment should be further studied. LEVEL OF EVIDENCE: II.

A virtual reality head stability test for patients with vestibular dysfunction.

BACKGROUND: The contribution of visual information to standing balance in patients with vestibular dysfunction varies between patients. Sensitive tools to detect kinematic response to visual perturbation are needed to individualize treatment. OBJECTIVE: Using the Oculus Rift headset and sensors, we developed a novel virtual reality (VR) test of head stability (HST) in response to visual perturbation. During the test, head movements were tracked in six degrees-of-freedom. The purpose of this pilot study was to test the sensitivity of the VR_HST to differences between patients with vestibular dysfunction and controls. METHODS: Seventeen patients and 16 controls performed static balance tasks with eyes closed (feet together or tandem on floor and foam) and observing 'moving stars' (amplitude 32 mm, frequency 0.2 Hz) via the Oculus (tandem). Directional Path and Root Mean Square Velocity were calculated for postural and head oscillations. RESULTS: Postural sway differed significantly between groups when standing on foam with feet together and on floor while observing the 'moving stars' task. Head oscillations were larger among patients, primarily in pitch, yaw, and roll rotation. CONCLUSIONS: The VR_HST was found to be sensitive to differences between small and diverse groups. Its clinical utility should be studied in larger samples of patients with vestibular dysfunction.

Special tools for the assessment of balance and dizziness in individuals with mild traumatic brain injury.

INTRODUCTION: Although a majority of patients following minor traumatic brain injury recover to their pre-morbid functional level, persistent activity and participation limitations can occur in the refractory patient. These long-term consequences of brain injury may only become apparent months to years after the injury. In order to quantify these long-term sequella, laboratory, clinical and functional outcome measures may not only identify needed areas of treatment, but may also assist in determining the impact of the treatment on the individuals function. PURPOSE: The aim of this manuscript is to review the clinical utility of vestibular laboratory testing and the bedside vestibular examination in patients following mild traumatic brain injury. In addition, the validity and inter-observer reliability of functional outcome measures commonly used in individuals with mTBI will also be reviewed. SUMMARY: Because of the diffuse pathology seen with mTBI, multiple tests are needed to determine the resultant impairment and their impact on the patient's activity level and participation level. Laboratory test and bedside tests of vestibular impairment are reviewed. Functional outcome measures including the Dynamic Gait Index, the Functional Gait Assessment, the Balance Error Scoring System, and Dual Task Performance are reviewed for their appropriateness in quantifying the effect of mTBI at activity level and participation level of the individual. CONCLUSION: TBI rehabilitation services are increasingly exemplified by the needs of patients, rather than by the underlying pathology or diagnosis. Basing treatment decisions and treatment timing on laboratory, clinical, and functional testing can optimize the rehabilitation outcome.

Vestibular rehabilitation following mild traumatic brain injury.

INTRODUCTION: Vertigo, dizziness, and imbalance are a symptom complex that is commonly found following concussion. Early metabolic changes following concussion may lead to worsening of the injury and symptoms in individuals not properly managed from the outset. When symptoms do not recover spontaneously, skilled vestibular rehabilitation can be an effective modality in an attempt to normalize the individual's vestibular responses. PURPOSE: The purpose of this review is to appraise the current and accepted methods available to the skilled clinician in quantifying and treating vestibular dysfunction following concussion. Incidence and prognostic indicators will be reviewed along with common barriers to recovery. SUMMARY: Vestibular Rehabilitation following concussion utilizes similar tools and techniques employed when treating those solely with peripheral pathology. The clinician must not only have a solid understanding of when and why certain exercises are required, but also be willing to accept that less exercise may be indicated in this population. As injury to the system following mild traumatic brain injury can include both peripheral and central structures, the duration of therapy and the time to recovery may be prolonged. Co-morbidities including cognitive and behavioral issues, visual-perceptual dysfunction, metabolic dysfunction, and autonomic dysfunction may hamper the effectiveness of the traditional Vestibular Rehabilitation approach. As successful treatment does not occur in a vacuum, working closely with other disciplines well versed in treating these co-morbid issues will help the individual to obtain optimal recovery. CONCLUSION: Vestibular Rehabilitation is an effective modality for managing dizziness, vertigo, and imbalance following concussion. Careful consideration of the acuity of the injury, along with effective management of co-morbid conditions will optimize the result.