Can head sway patterns differentiate between patients with Meniere's disease vs. peripheral vestibular hypofunction?

Background: Meniere's disease (MD) is defined by episodic vertigo, unilateral sensorineural hearing loss and fluctuating aural symptoms. Due to the variable clinical presentation, objective tests of MD may have significant diagnostic utility. Head kinematics derived from a head-mounted display (HMD) have demonstrated to be sensitive to vestibular dysfunction. The purpose of this pilot study was to investigate whether head sway can differentiate between patients with MD, vestibular hypofunction (VH) and healthy controls. Materials/methods: 80 adults (30 healthy controls, 32 with VH, and 18 with MD) were recruited from a tertiary vestibular clinic. All underwent a postural control assessment using the HTC Vive Pro Eye HMD that recorded head sway in the anterior-posterior (AP), medio-lateral (ML), pitch, yaw and roll direction. Participants were tested with 2 levels of visual load: a static versus oscillating star display. Each scene lasted 60 s and was repeated twice. Sway in each direction was quantified using root mean square velocity (VRMS) for the first 20 s and full 60 s of each scene. Results: Static visual: participants with VH showed significantly larger head VRMS than controls in the AP (60 s and 20 s) and pitch (20 s) directions. Dynamic visual: participants with VH showed significantly larger head VRMS than controls all directions for both the 60 and 20 s analysis. Participants with MD did not differ significantly from the control or the VH group. Conclusion: While limited in numbers, Patients with MD had a high variability in head sway in all directions, and their average head sway was between controls and those with VH. A larger sample as well as patients with worse symptoms at time of testing could elucidate whether head sway via HMD could become a viable test in this population. A similar finding between 20- and 60-s scene and the full portability of the system with an in-clinic testing setup could help these future endeavors. Head sway derived from HMD is sensitive to VH and can be clinically useful as an outcome measure to evaluate sensory integration for postural control.

Type of auditory cues and apparatus influence how healthy young adults integrate sounds for dynamic balance.

It is unclear whether the brain handles auditory cues similarly to visual cues for balance. We investigated the influence of headphones and loudspeaker reproduction of sounds on dynamic balance performance when an individual is facing a cognitive challenge. Twenty participants (16 females, aged 19-36) were asked to avoid a ball according to a specific visual rule. Visuals were projected from the HTC Vive head-mounted display in an acoustically controlled space. We varied the environment by adding congruent sounds (sounds coincide with the visual rule) or incongruent sounds (sounds may or may not coincide with the visual rule) as well as creating a multimodal (visual and congruent sounds) vs. unimodal (visual or congruent sounds only) display of stimuli. Sounds were played over headphones or loudspeakers. We quantified reaction time (RT) and accuracy (choosing the correct direction to move) by capturing the head movement. We found that in the absence of sounds, RT was slower with headphones compared to loudspeakers, but the introduction of either congruent or incongruent sounds resulted in faster movements with headphones such that RT was no longer different between apparatus. Participants used congruent sounds to improve accuracy but disregarded incongruent sounds. This suggests that selective attention may explain how sounds are incorporated into dynamic balance performance in healthy young adults. Participants leveraged sounds played over loudspeakers, but not over headphones, to enhance accuracy in a unimodal dark environment. This may be explained by the natural listening conditions created by loudspeakers where sounds may be perceived as externalized.

Weighting of visual and auditory inputs in dancers with and without previous ankle injury.

Elite dance requires highly controlled balance performance in dynamic visual and auditory environments characterized by the use of stage lighting and music. Perturbing visual input is known to influence balance in dancers, but the effects of sounds have not been clearly established. Ankle inversion injuries are common in dancers and may also play a role in dancers' ability to respond to sensory perturbations. The aims of this study were to identify changes in static balance in response to visual or auditory perturbation in elite collegiate dancers with and without a history of ankle injury, and to describe coupling of measurements obtained from the waist and head during balance. Thirty-seven dancers: 22 controls and 15 with a history of ankle sprain, performed single-leg balance under static and dynamic visual and auditory conditions. Dancers demonstrated increased waist sway when viewing a dynamic visual scene and when presented with moving sounds and increased head sway with dynamic visuals. These results did not vary by history of ankle sprain. While dancers appear to dampen the impact of waist sway on head motion during single leg stance, even highly trained dancers may experience challenges controlling balance under perturbing visual and auditory conditions like those present during stage performance.

Contextual sensory integration training vs. traditional vestibular rehabilitation: a pilot randomized controlled trial.

BACKGROUND: We created a clinical virtual reality application for vestibular rehabilitation. Our app targets contextual sensory integration (C.S.I.) where patients are immersed in safe, increasingly challenging environments while practicing various tasks (e.g., turning, walking). The purpose of this pilot study was to establish the feasibility of a randomized controlled trial comparing C.S.I. training to traditional vestibular rehabilitation. METHODS: Thirty patients with vestibular dysfunction completed the Dizziness Handicap Inventory (DHI), Activities-Specific Balance Confidence Scale (ABC), Visual Vertigo Analog Scale (VVAS), Functional Gait Assessment (FGA), Timed-Up-and-Go (TUG), and Four-Square Step Test (FSST). Following initial assessment, the patients were randomized into 8 weeks (once per week in clinic + home exercise program) of traditional vestibular rehabilitation or C.S.I. training. Six patients had to stop participation due to the covid-19 pandemic, 6 dropped out for other reasons (3 from each group). Ten patients in the traditional group and 8 in the C.S.I group completed the study. We applied an intention to treat analysis. RESULTS: Following intervention, we observed a significant main effect of time with no main effect of group or group by time interaction for the DHI (mean difference - 18.703, 95% CI [-28.235, -9.172], p = 0.0002), ABC (8.556, [0.938, 16.174], p = 0.028), VVAS, (-13.603, [-25.634, -1.573], p = 0.027) and the FGA (6.405, [4.474, 8.335], p < 0.0001). No changes were observed for TUG and FSST. CONCLUSION: Patients' symptoms and function improved following either vestibular rehabilitation method. C.S.I training appeared comparable but not superior to traditional rehabilitation. TRIAL REGISTRATION: This study (NCT04268745) was registered on clincaltrials.gov and can be found at https://clinicaltrials.gov/ct2/show/NCT04268745 .

Decrease in head sway as a measure of sensory integration following vestibular rehabilitation: A randomized controlled trial.

OBJECTIVE: The purpose of this study was to determine the extent to which sensory integration strategies via head sway, derived from a Head-Mounted Display (HMD), change in people with vestibular disorders following vestibular rehabilitation. DESIGN: Randomized Controlled TrialSetting:Vestibular Rehabilitation ClinicParticipants:Thirty participants with vestibular dysfunction and 21 age-matched controls. MAIN OUTCOME MEASURES: Participants experienced two levels of visual surround (static or moving 'stars', front to back at 0.2 Hz, 32 mm) and white noise (none or rhythmic) while their head sway was recorded via the HTC Vive. We quantified head sway via Directional Path (DP) and Root Mean Square Velocity (RMSV) in 5 directions: anterior-posterior, medio-lateral, pitch, yaw, and roll and Power Spectral Density in low (PSD 1), medium (PSD 2) and high (PSD 3) frequencies in the anterior-posterior direction. INTERVENTIONS: Participants performed the assessment prior to being randomized into 8-weeks of contextual sensory integration training in virtual reality or traditional vestibular rehabilitation and once again following completion of the intervention. Controls performed the assessment once. Twelve participants dropped out, half due to covid lock-down. We applied an intention to treat analysis. RESULTS: We observed significant increases in AP DP, RMSV and all PSDs with change in visual level. Both intervention groups significantly decreased medio-lateral, pitch and roll DP and RMSV and anterior-posterior PSD 2 with no group differences. Vestibular participants were significantly higher than controls on all outcomes pre rehabilitation. Post rehabilitation they were only significantly higher on PSD 2. Sound was not a significant predictor of head sway in this protocol. CONCLUSIONS: Head sway decreased following vestibular rehabilitation regardless of visual load or type of intervention applied. This change was measured via head kinematics derived from a portable HMD which can serve as a sensitive in-clinic assessment for tracking improvement over time.

Differing postural control patterns in individuals with bilateral and unilateral hearing loss.

OBJECTIVES: Hearing loss (HL) is associated with imbalance and increased fall risk. The mechanism underlying this relationship and differences across types of hearing loss remains unclear. Head mounted displays (HMD) can shed light on postural control mechanisms via an analysis of head sway. PURPOSE: The purpose of this study was to evaluate head sway in response to sensory perturbations in individuals with bilateral (BHL) or unilateral hearing loss (UHL) and compare them to controls. MATERIALS AND METHODS: We recruited 36 controls, 23 individuals with UHL and 14 with BHL. An HMD (HTC Vive) measured head sway while participants stood on the floor, hips-width apart. Stimuli included two levels of visuals and sound. Root Mean Square Velocity (RMSV) and Power Spectral Density (PSD) were used to quantify head sway. RESULTS: Adjusting for age, individuals with BHL had significantly higher anterior-posterior and medio-lateral RMSV than controls and individuals with UHL. Individuals with UHL demonstrated significantly lower response to visual perturbations in RMSV AP and in all 3 frequency segments of PSD compared to controls. Individuals with UHL showed significantly lower movements at high frequencies compared to controls. Sounds or severity of HL did not impact head sway. CONCLUSIONS: Individuals with BHL demonstrated increased sway with visual perturbations and should be clinically assessed for balance performance and fall risk. Individuals with UHL exhibited reduced responses to visual stimuli compared with controls, which may reflect conscious movement processing. Additional studies are needed to further understand the mechanistic relationship between hearing loss and imbalance.

BOXVR Versus Guided YouTube Boxing for Stress, Anxiety, and Cognitive Performance in Adolescents: A Pilot Randomized Controlled Trial.

Background: Adolescents frequently experience high levels of anxiety and stress, which can impede quality of life and academic performance. Boxing as a form of exercise has been shown to have mental health benefits in adults. Methods: This study investigated the impact of boxing exercise with a virtual reality (VR) game vs. with a guided video on anxiety, stress, and executive function in adolescents. Participants were randomly assigned to 1 of 3 cohorts: Oculus Rift BOXVR game (n = 14), boxing with a guided workout video (n = 14), or a non-intervention control (n = 14). The BOXVR and guided video groups participated in 10-minute exercise sessions, 5 times a week for 3 weeks. Results: The groups were comparable at baseline on all outcomes. Only BOXVR participants exhibited a significant (p < 0.001) reduction in stress and significant improvements on the Trail Making Test (TMT) B at weekly checkpoints and follow up. All cohorts showed improvements in executive function on the TMT A. At the end of the study, the BOXVR group reported significantly lower stress levels than the guided video group, and significantly better TMT A & B scores than the control group. Only the control group showed a significant reduction in anxiety but the groups were not significantly different in anxiety at the end of the study. The BOXVR group reported significantly greater enjoyment after each exercise session than the guided video group. Conclusion: BOXVR was shown to be effective in reducing adolescent stress and improving executive function over a three-week period. While larger studies with real-life functional outcomes are necessary, boxing with an immersive VR game represents a potential non-pharmaceutical mode to reduce stress in adolescents that is easy to implement in school settings.

iPhone Accelerometry Provides a Sensitive In-Home Assessment of Age-Related Changes in Standing Balance.

Remote health monitoring has become increasingly important, especially in aging populations. We aimed to identify tasks that are sensitive to age-related changes in balance during fully remote, at-home balance assessment. Participants were 12 healthy young adults (mean age = 26.08 years, range: 18-33) and 12 healthy older adults (mean age = 67.33 years, range: 60-75). Participants performed standing tasks monitored via video conference while their balance was quantified using a custom iPhone application measuring mediolateral center of mass acceleration. We included three stances (feet together, tandem, and single leg) with eyes open or closed, with or without a concurrent cognitive task. Older adults demonstrated significantly more variable center of mass accelerations in tandem (p = .04, ηp2=.25) and significantly higher (p < .01, ηp2=.45) and more variable (p < .01, ηp2=.44) center of mass accelerations in single leg compared with young adults. We also observed that as task challenge increased, balance dual-task cost diminished for older, but not young, adults.

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 Control under Cognitive Load: Evidence of Increased Automaticity Revealed by Center-of-Pressure and Head Kinematics.

How postural responses change with sensory perturbations while also performing a cognitive task is still debatable. This study investigated this question via comprehensive assessment of postural sway, head kinematics and their coupling. Twenty-three healthy young adults stood in tandem with eyes open or wearing the HTC Vive Head-Mounted Display (HMD) with a static or dynamic (i.e., movement in the anterior-posterior direction at 5 mm or 32 mm at 0.2 Hz) 3-wall stars display. On half of the trials, participants performed a cognitive serial subtraction task. Medio-lateral center-of-pressure (COP) path significantly increased with the cognitive task, particularly with dynamic visuals whereas medio-lateral variance decreased with the cognitive task. Head path and velocity significantly increased with the cognitive task in both directions while variance decreased. Head-COP cross-correlations ranged between 0.78 and 0.66. These findings, accompanied by frequency analysis, suggest that postural control switched to primarily relying on somatosensory input under challenging cognitive load conditions. Several differences between head and COP suggest that head kinematics contribute an important additional facet of postural control and the relationship between head and COP may depend on task and stance position. The potential of HMDs for clinical assessments of balance needs to be further explored.

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.

Factors associated with dynamic balance in people with Persistent Postural Perceptual Dizziness (PPPD): a cross-sectional study using a virtual-reality Four Square Step Test.

BACKGROUND: Persistent postural-perceptual dizziness (PPPD) is a condition characterized by chronic subjective dizziness and exacerbated by visual stimuli or upright movement. Typical balance tests do not replicate the environments known to increase symptoms in people with PPPD-crowded places with moving objects. Using a virtual reality system, we quantified dynamic balance in people with PPPD and healthy controls in diverse visual conditions. METHODS: Twenty-two individuals with PPPD and 29 controls performed a square-shaped fast walking task (Four-Square Step Test Virtual Reality-FSST-VR) using a head-mounted-display (HTC Vive) under 3 visual conditions (empty train platform; people moving; people and trains moving). Head kinematics was used to measure task duration, movement smoothness and anterior-posterior (AP) and medio-lateral (ML) ranges of movement (ROM). Heart rate (HR) was monitored using a chest-band. Participants also completed a functional mobility test (Timed-Up-and-Go; TUG) and questionnaires measuring anxiety (State-Trait Anxiety Inventory; STAI), balance confidence (Activities-Specific Balance Confidence; ABC), perceived disability (Dizziness Handicap Inventory) and simulator sickness (Simulator Sickness Questionnaire). Main effects of visual load and group and associations between performance, functional and self-reported outcomes were examined. RESULTS: State anxiety and simulator sickness did not increase following testing. AP-ROM and HR increased with high visual load in both groups (p < 0.05). There were no significant between-group differences in head kinematics. In the high visual load conditions, high trait anxiety and longer TUG duration were moderately associated with reduced AP and ML-ROM in the PPPD group and low ABC and  high perceived disability were associated with reduced AP-ROM (|r| = 0.47 to 0.53; p < 0.05). In contrast, in controls high STAI-trait, low ABC and longer TUG duration were associated with increased AP-ROM (|r| = 0.38 to 0.46; p < 0.05) and longer TUG duration was associated with increased ML-ROM (r = 0.53, p < 0.01). CONCLUSIONS: FSST-VR may shed light on movement strategies in PPPD beyond task duration. While no main effect of group was observed, the distinct associations with self-reported and functional outcomes, identified using spatial head kinematics, suggest that some people with PPPD reduce head degrees of freedom when performing a dynamic balance task. This supports a potential link between spatial perception and PPPD symptomatology.

People with persistent postural-perceptual dizziness demonstrate altered postural strategies in complex visual and cognitive environments.

BACKGROUND: People with PPPD report imbalance, increase in symptoms and impaired function within complex visual environments, but understanding of the mechanism for these behaviors is still lacking. OBJECTIVE: To investigate postural control in PPPD we compared changes in center of pressure (COP) and head kinematics of people with PPPD (N = 22) and healthy controls (N = 20) in response to different combinations of visual and cognitive perturbations during a challenging balance task. METHODS: Participants stood in a tandem position. Static or moving stars (0.2 Hz, 5 mm or 32 mm amplitude, anterior-posterior direction) were displayed through a head-mounted display (HTC Vive). On half the trials, participants performed a serial-3 subtraction task. We measured medio-lateral and anterior-posterior path and acceleration of COP and head. RESULTS: Controls significantly increased all COP and head parameters with the cognitive task whereas PPPD increased only COP ML path and acceleration. Only controls significantly increased head anterior-posterior & medio-lateral acceleration with moving visual load. Cognitive task performance was similar between groups. CONCLUSIONS: We observed altered postural strategies in people with PPPD, in the form of reduced movement with challenge, particularly around the head segment. The potential of this simple and portable head-mounted display setup for differential diagnosis of vestibular disorders should be further explored.

Will virtual rehabilitation replace clinicians: a contemporary debate about technological versus human obsolescence.

This article is inspired by a pseudo Oxford-style debate, which was held in Tel Aviv University, Israel at the International Conference on Virtual Rehabilitation (ICVR) 2019, which is the official conference of the International Society for Virtual Rehabilitation. The debate, between two 2-person teams with a moderator, was organized by the ICVR Program committee to address the question "Will virtual rehabilitation replace clinicians?" It brought together five academics with technical, research, and/or clinical backgrounds-Gerry Fluet, Tal Krasovsky, Anat Lubetzky, Philippe Archambault, W. Geoffrey Wright-to debate the pros and cons of using virtual reality (VR) and related technologies to help assess, diagnose, treat, and track recovery, and more specifically investigate the likelihood that advanced technology will ultimately replace human clinicians. Both teams were assigned a side to defend, whether it represented their own viewpoint or not, and to take whatever positions necessary to make a persuasive argument and win the debate. In this paper we present a recapitulation of the arguments presented by both sides, and further include an in-depth consideration of the question. We attempt to judiciously lay out a number of arguments that fall along a spectrum from moderate to extreme; the most extreme and/or indefensible positions are presented for rhetorical and demonstrative purposes. Although there may not be a clear answer today, this paper raises questions which are related to the basic nature of the rehabilitation profession, and to the current and potential role of technology within it.

Auditory Input and Postural Control in Adults: A Narrative Review.

Importance: An increase in the number of mechanistic studies targeting the association between sound and balance has been observed in recent years, but their results appear equivocal. Observations: A search of PubMed and the Cochrane Database of Systematic Reviews for English-language studies on auditory input and postural control published from database inception through October 31, 2019, yielded 28 articles for review. These articles included 18 (64%) studies of healthy adults, 1 (4%) of participants with Alzheimer disease, 2 (7%) of participants with congenital blindness, 3 (11%) of participants with vestibular loss, and 4 (14%) of participants with diverse levels of hearing loss. Studies varied by the type of audio stimuli (natural vs generated sounds), apparatus (speakers vs headphones), and movement of sounds (eg, stationary, rotational). Most balance measurements involved standing on the floor or foam with eyes open or closed during which sway amount or velocity was quantified. Stationary broadband sounds, including white or environmental noise, may improve balance, but the results regarding stationary pure tone were inconclusive. The implication of moving sounds varied by apparatus (typically destabilizing when headphones were used) and sensory loss (more destabilizing with vestibular or hearing loss but perhaps less with a unilateral cochlear implant). Conclusions and Relevance: Findings from this review suggest that stationary broadband noise can serve as an auditory anchor for balance primarily when projected via speakers and when the balance task is challenging. More research is needed that includes individuals with sensory loss and that tests paradigms using dynamic, ecologically valid sounds; clinicians should also consider auditory cues and the presence of hearing loss in balance and fall-risk assessments.

Static and Dynamic Balance in Adults Undergoing Lumbar Spine Surgery: Screening and Prediction of Postsurgical Outcomes.

INTRODUCTION: Balance and fall risk before and after lumbar surgery was assessed to determine whether balance at baseline predicts long-term postsurgical outcomes. METHODS: Forty-three patients in the United States and Israel performed the single-leg stance (SLS) test, four square step test (FSST), and 8-foot up-and-go (8FUG) test before and 2 to 4 months after lumbar spine surgery. They completed the Oswestry Disability Index (ODI) and pain rating before and 12 months after lumbar surgery. RESULTS: From baseline to follow-up, the SLS time was 3.74 seconds longer (P = 0.01), the FSST time was 1.94 seconds faster (P < 0.001), and the 8FUG time was 1.55 seconds faster (P = 0.02). Before surgery, 26% of the patients were considered high fall risk according to the FSST and 51% according to the 8FUG. Postsurgery, all patients could complete the physical tests, but 26% remained at high fall risk according to the 8FUG and 7.5% according to the FSST. The three physical measures together explained 30% of the variance in postsurgical ODI scores (P = 0.02). Age was not correlated with performance. DISCUSSION: Risk of falling is higher than surgeons suspect. Balance tests (ie, SLS, FSST, and 8FUG) are quick and easy to administer. The findings support the importance of screening for balance and fall risk in adults undergoing lumbar spine surgery.

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.

Head mounted displays for capturing head kinematics in postural tasks.

Tracking head motion in a simple, portable and accurate manner during performance of postural tasks in a virtual reality environment could have important implications for investigating normal and pathological head kinematics. We investigated concurrent validity of head tracking of two Head Mounted Displays (HMDs), Oculus Rift and HTC Vive, vs. a gold-standard motion capture system (Qualisys). Head kinematics of N = 20 healthy young adults was quantified during static and dynamic postural tasks. While wearing the Oculus Rift or HTC Vive, participants observed moving stars (static tasks) or a flying ball (dynamic task). Head kinematics were recorded simultaneously by the Rift or Vive and Qualisys camera system. We calculated head directional path, acceleration in 6 directions and volume of translation movement. Intra-Class Correlations (ICC) and 95% Limits of agreement were calculated. Most ICC values were around 0.9 with several at 0.99 indicating excellent agreement between the HMDs and Qualisys. Weaker agreement was observed for vertical displacement during a static task and moderate agreement was observed pitch and yaw displacement during a dynamic task. A negative bias of a small magnitude (indicating more movement in VR) was observed for most variables in static tasks, while a positive bias was observed for most variables in the dynamic task (indicating less movement in VR). Our results generally support the concurrent validity of Oculus Rift and HTC Vive head tracking during static and dynamic standing tasks in healthy young adults. Specific task- and direction-dependent differences should be considered when planning measurement studies using these novel tools.