Search

Suffering an acute asymmetry in vestibular function (i.e., vestibular neuritis) causes increased sway. Non-causal studies report associations between lateral semicircular canal function and balance ability, but direct links remain controversial. We investigate the immediate effect on body sway after unilateral vestibulo-ocular reflex (VOR) gain down adaptation simulating acute peripheral vestibular hypofunction. Eighteen healthy adults, mean age 27.4 (± 12.4), stood wearing an inertial measurement device with their eyes closed on foam before and after incremental VOR gain down adaptation to simulate mild unilateral vestibular neuritis. Active head impulse VOR gain was measured before and after the adaptation to ensure VOR gain adaptation. Percentage change for VOR gain was determined. Sway area was compared before and after VOR adaptation. VOR gain decreased unilaterally exceeding meaningful change values. Sway area was significantly greater immediately after VOR gain down adaptation, but quickly returned to baseline. In a subset of subjects VOR gain was re-assessed and found to remain adapted despite sway normalization. These results indicate that oculomotor adaptation targeting the lateral semicircular canal VOR pathway has an immediate, albeit transient increase in body sway. Rapid return of body sway to baseline levels suggests dynamic sensory reweighting between vestibular and somatosensory inputs to resolve the undesirable increased body sway. [ABSTRACT FROM AUTHOR]

BACKGROUND: Patients with cerebellar ataxia report oscillopsia, "bouncy vision" during activity, yet little is known how this impacts daily function. The purpose of this study was to quantify the magnitude of oscillopsia and investigate its relation to vestibulo-ocular reflex (VOR) function and daily activity in cerebellar ataxia. METHODS: 19 patients diagnosed with cerebellar ataxia and reports of oscillopsia with activity were examined using the video head impulse test (vHIT), Oscillopsia Functional Index (OFI), and clinical gait measures. Video head impulse data was compared against 40 healthy controls. RESULTS: OFI scores in ataxia patients were severe and inversely correlated with gait velocity (r = –0.55, p < 0.05), but did not correlate with VOR gains. The mean VOR gain in the ataxic patients was significantly reduced and more varied compared with healthy controls. All patients had abnormal VOR gains and eye/head movement patterns in at least one semicircular canal during VHIT with passive head rotation. CONCLUSIONS: Patients with cerebellar ataxia and oscillopsia have impaired VOR gains, yet severity of oscillopsia and VOR gains are not correlated. Patients with cerebellar ataxia have abnormal oculomotor behavior during passive head rotation that is correlated with gait velocity, but not magnitude of oscillopsia. [ABSTRACT FROM AUTHOR]

Background: A clinical pattern of damage to the auditory, visual, and vestibular sensorimotor systems, known as multi-sensory impairment, affects roughly 2% of the US population each year. Within the population of US military service members exposed to mild traumatic brain injury (mTBI), 15-44% will develop multi-sensory impairment following a mild traumatic brain injury. In the US civilian population, multi-sensory impairment-related symptoms are also a common sequela of damage to the vestibular system and affect ~ 300-500/100,000 population. Vestibular rehabilitation is recognized as a critical component of the management of multi-sensory impairment. Unfortunately, the current clinical practice guidelines for the delivery of vestibular rehabilitation are not evidence-based and primarily rely on expert opinion. The focus of this trial is gaze stability training, which represents the unique component of vestibular rehabilitation. The aim of the Incremental Velocity Error as a New Treatment in Vestibular Rehabilitation (INVENT VPT) trial is to assess the efficacy of a non-invasive, incremental vestibular adaptation training device for normalizing the response of the vestibulo-ocular reflex.Methods: The INVENT VPT Trial is a multi-center randomized controlled crossover trial in which military service members with mTBI and civilian patients with vestibular hypofunction are randomized to begin traditional vestibular rehabilitation or incremental vestibular adaptation and then cross over to the alternate intervention after a prescribed washout period. Vestibulo-ocular reflex function and other functional outcomes are measured to identify the best means to improve the delivery of vestibular rehabilitation. We incorporate ecologically valid outcome measures that address the common symptoms experienced in those with vestibular pathology and multi-sensory impairment.Discussion: The INVENT VPT Trial will directly impact the health care delivery of vestibular rehabilitation in patients suffering from multi-sensory impairment in three critical ways: (1) compare optimized traditional methods of vestibular rehabilitation to a novel device that is hypothesized to improve vestibulo-ocular reflex performance, (2) isolate the ideal dosing of vestibular rehabilitation considering patient burden and compliance rates, and (3) examine whether recovery of the vestibulo-ocular reflex can be predicted in participants with vestibular symptoms.Trial Registration: ClinicalTrials.gov NCT03846830 . Registered on 20 February 2019. [ABSTRACT FROM AUTHOR]

The vestibulo-ocular reflex (VOR) maintains stable vision during rapid head rotations by rotating the eyes in the opposite direction to the head. The latency between onset of the head rotation and onset of the eye rotation is 5–8 ms in healthy humans. However, VOR latency can be 3–4 times larger in patients treated with intra-tympanic gentamicin. A prior study showed that latency can be trained with head rotations at 0.2 Hz. We sought to determine how the VOR is affected when a delay between vestibular and visual stimuli is added during adaptation training with high-frequency head rotations (impulses), where the VOR is the main vision-stabilizing system. Using a variant of the incremental VOR adaptation technique, the delay between head rotation onset and movement onset of a visual target was gradually increased. With this training, the instantaneous VOR gain demand (= target/head velocity) varied from less than unity to greater than unity during each head impulse, albeit in a consistent and repeatable way. We measured the active and passive VOR gain and latency before and after VOR adaptation training in healthy normal subjects. There was no significant change in VOR latency across subjects; however, there was a significant decrease in VOR gain of − 6.0 ± 4.5%. These data suggest that during high-frequency head rotations delay/latency is interpreted as a changing instantaneous VOR gain demand. Although the gain demand in this study had a complex trajectory, adaptation was evident with the VOR seeming to use an average of the instantaneous gain demand. [ABSTRACT FROM AUTHOR]

The study objective was to understand how the contralesional labyrinth contributes to gaze and gait stability after unilateral vestibular deafferentation (UVD). Head impulse testing (vHIT) was completed in 37 individuals [22 women (59%); age 52.13 ± 11.59 yr, mean ± SD] with UVD from vestibular schwannoma resection. Compensatory saccades (CS) and vestibulo-ocular reflex (VOR) gain were analyzed for both ipsilesional and contralesional impulses. Gait speed (10-m walk test) and endurance (2-min walk test) were collected for 35 individuals. CS were recruited during contralesional head rotation regardless of VOR gain on either the ipsilesional [ρ = 0.21 (-0.14, 0.57); Spearman rank (95% confidence interval)] or contralesional side [ρ = -0.04 (-0.42, 0.35)]. Additionally, the latency of these CS (151.19 ± 52.41 ms) was similar to that of CS generated during ipsilesional rotation (165.65 ± 21.62 ms; P = 0.159). CS recruited during ipsilesional vHIT were of a higher velocity (P < 0.001) and greater frequency (P < 0.001) compared with contralesional CS. VOR gain asymmetry was significantly correlated with gait speed [ρ = -0.37 (-0.73, -0.01)], yet individual VOR gain was not correlated [ipsilesional: ρ = 0.17 (-0.20, 0.55); contralesional: ρ = -0.18 (-0.52, 0.15)]. Our data reveal CS are recruited at similar latencies without correlation to VOR gain or direction of head rotation, and that the central integration of ipsilesional and contralesional vestibular afference correlates with gait. Together, our data suggest the brain considers vestibular afference from both sides when generating related behavioral output after UVD.NEW & NOTEWORTHY After unilateral vestibular deafferentation, compensatory saccades (CS) have similar latencies regardless of the direction of head rotation, and those CS generated during contralesional head rotation are unrelated to extent of vestibular loss. Additionally, the extent of asymmetry in residual vestibular function, not the extent of vestibular loss, correlates with gait speed. Our data suggest a common mechanism is responsible for the generation of CS and restoration of gait speed in vestibular compensation. [ABSTRACT FROM AUTHOR]

Introduction: Benign paroxysmal positional vertigo (BPPV) of the horizontal semicircular canal (hSCC) can present with otoconia blocking its lumen (canalith jam), with signs and symptoms that make it difficult to distinguish from central nervous system pathology. Objective: Here we report two cases of canalith jam affecting the hSCC and offer a theoretical mechanism based on known vestibular neurophysiology. Methods: We use video‐oculography to document the canalith jam and show the moment the otoconia loosen. Results: Canalith jam is a rare form of BPPV remedied with repositioning maneuvers. Conclusion: Clinicians should consider canalith jam as a mechanism for BPPV when the nystagmus is (a) Direction fixed with fixation removed and during positional testing; (b) Velocity dependent on supine head position; (c) Converts to geotropic directional changing nystagmus. [ABSTRACT FROM AUTHOR]

This is a review summarizing the development of vestibulo-ocular reflex (VOR) adaptation behavior with relevance to rehabilitation over the last 10 years and examines VOR adaptation using head-onbody rotations, specifically the influence of training target contrast, position and velocity error signal, active vs. passive head rotations, and sinusoidal vs. head impulse rotations. This review discusses optimization of the single VOR adaptation training session, consolidation between repeated training sessions, and dynamic incremental VOR adaptation. Also considered are the effects of aging and the roles of the efferent vestibular system, cerebellum, and otoliths on angular VOR adaptation. Finally, this review examines VOR adaptation findings in studies using whole body rotations. [ABSTRACT FROM AUTHOR]

Introduction: A significant population of our wounded veterans suffer long-term functional consequences of visual deficit, disorientation, dizziness, and an impaired ability to read. These symptoms may be related to damage within the otolith pathways that contribute to ocular alignment. The purpose of this study was to compare perception of vertical and torsional ocular alignment between veterans and healthy controls in an upright and supine test position. Materials and methods: Veterans (n = 26) with reports of dizziness were recruited from the East Orange Veterans Administration Hospital. Healthy controls (n = 26) were recruited from both Johns Hopkins University and the East Orange VA. Each subject performed 20 trials each of a novel vertical and torsional binocular alignment perception test. Veterans underwent semicircular canal and otolith pathway function testing. Results: 88% of the Veterans had an absent otolith response. Only the veterans had an abnormally large variability in perception of both vertical and torsional ocular alignment, and in both upright and supine position. Neither post-traumatic stress disorder, nor depression contributed to the misperception in binocular alignment. Conclusions: Our novel method of measuring vertical and torsional misalignment distinguishes veterans with dizziness from healthy controls. The high prevalence of absent otolith function seems to explain this result. Further studies are needed to better understand the fundamental mechanism responsible for the increased variability of perception of binocular alignment. [ABSTRACT FROM AUTHOR]

BACKGROUND: Vestibular rehabilitation is a sub-specialization within the practice of physical therapy that includes treatments designed to reduce gaze instability. Gaze stability exercises are commonly given for head rotations to the left and right, even in subjects with one healthy vestibular system (as in unilateral loss). Few studies have investigated the difference in the angular vestibular ocular reflex gain (aVOR) measured in the acute phase after deafferentation for ipsilesional head rotations that move the head away from center or towards center. OBJECTIVE: The purpose of this study was to compare differences in acute aVOR gain when the head was passively rotated outward from an initially centered position (neck neutral) versus the head being rotated inward. METHODS: We recorded head and eye velocity using video head impulse test equipment in patients with unilateral vestibular pathology scheduled for tumor resection via retrosigmoid approach (n=5) or labyrinthectomy due to Meniere's disease (n=2). RESULTS: We found 1) no difference in the ipsilesional aVOR gain for inward or outward directed head impulse rotations and 2) head velocity is inversely correlated with aVOR gain for ipsilesional but not contralesional rotations. CONCLUSIONS: Bedside testing of the ipsilesional aVOR following acute vestibular ablation can be done with head impulse rotations to either side. In the acute stages, physical therapists should prescribe ipsilesional and contralesional gaze stability exercises. [ABSTRACT FROM AUTHOR]

Purpose: This paper focuses on motor learning within the saccadic and vestibulo-ocular reflex (VOR) oculomotor systems, vital for our understanding how the brain keeps these subsystems calibrated in the presence of disease, trauma, and the changes that invariably accompany normal development and aging. We will concentrate on new information related to multiple time scales of saccade motor learning, adaptation of the VOR during high-velocity impulses, and the role of saccades in VOR adaptation. The role of the cerebellum in both systems is considered. Methods: Review of data involving saccade and VOR motor learning. Results: Data supports learning within the saccadic and VOR oculomotor systems is influenced by 1). Multiple time scales, with different rates of both learning and forgetting (seconds, minutes, hours, days, and months). In the case of forgetting, relearning on a similar task may be faster. 2). Pattern of training, learning and forgetting are not similarly achieved. Different contexts require different motor behaviors and rest periods between training sessions can be important for memory consolidation. Conclusions: The central nervous system has the difficult task of determining where blame resides when motor performance is impaired (the credit assignment problem). Saccade and VOR motor learning takes place at multiple levels within the nervous system, from alterations in ion channel and membrane properties on single neurons, to more complex changes in neural circuit behavior and higher-level cognitive processes including prediction. [ABSTRACT FROM AUTHOR]

Studies on motor learning typically present a constant adaptation stimulus, corresponding to the desired final adaptive state. Studies of the auditory and optokinetic systems provide compelling evidence that neural plasticity is enhanced when the error signal driving adaptation is instead adjusted gradually throughout training. We sought to determine whether the angular vestibulo-ocular reflex (aVOR) may be adaptively increased using an incremental velocity error signal (IVE) compared with a conventional constant and large velocity-gain demand (x2). We compared the magnitude of aVOR gain change for these two paradigms across different motion contexts (active and passive). Seven individuals with normal vestibular function and six individuals with unilateral vestibular hypofunction (UVH) were exposed to the IVE and x2 (“control”) aVOR demand tasks. Each subject participated in 10 epochs of 30 active head impulses over a 15 min aVOR gain increase training session separately for the IVE and x2 paradigms, separated by either seven days (normal subjects) or 14 days (UVH subjects). For both normal and UVH subjects, both paradigms led to aVOR gain increase during the training session. For the normal subjects, the IVE paradigm led to larger aVOR gain change after training compared to the x2 paradigm, for both active (mean 17.3 ± 4% vs. mean 7.1 ± 9%, P = 0.029) and passive (mean 14.2 ± 5% vs. 4.5 ± 8%, P = 0.018) head impulses. For subjects with UVH, IVE produced a greater change in aVOR gain for active head impulses (mean 18.2 ± 9.2% vs. mean −6 ± 3.8%, P = 0.003). However, aVOR gains for passive head impulses were less consistent after IVE, with only two subjects displaying greater aVOR gain with this incremental paradigm. Some individuals generated compensatory saccades that occurred in the same direction of the deficient aVOR during either training paradigm. Our data suggest that the aVOR is modifiable when the velocity error signal is presented incrementally, and that this adaptation stimulus is particularly effective in the case of unilateral vestibular hypofunction. This has implications for programs of vestibular rehabilitation, where active head rotation is prescribed as a means to improve gaze stability. [ABSTRACT FROM AUTHOR]

Motor learning in the vestibular system can be differentially obtained depending upon the context for which the vestibulo-ocular reflex (VOR) has been exposed. Manipulating head orientation relative to gravity is an example of a contextual cue that can elicit independent VOR gains. We were interested in examining retention of short-term VOR adaptation when the adapting stimulus was paired with a novel contextual cue. Two sets of non-human primate VOR adaptation experiments were designed to assess the influence of head position relative to gravity on retention of the pitch VOR. First, the pitch VOR of three squirrel monkeys was adapted for 3 h using minimizing (×0.45) spectacles and a sum-of-sines stimulus (20°/s at 0.5, 1.1, 2.3, and 3.7 Hz) while the animals were positioned left ear down (LED adaptation). Pitch VOR gains were measured in the adapted position (LED) and two non-adapted positions (upright, UP) or right ear down (RED). In the second set of experiments, the pitch VOR was adapted in an upright head position (same adapting stimulus as used in LED) and tested in UP, LED or RED. No head immobility or darkness restrictions were imposed on the animals after the initial adaptation exposure. The pitch VOR gains were measured during the acceleration ( G A) and constant velocity ( G V) portions of 1,000°/s2–150°/s step responses and during 0.5, 2.0, and 4.0 Hz sinusoids with velocities varying from 20 to 100°/s. All measures of VOR gain for UP, LED, and RED were done immediately after the adaptation and for three subsequent days and at post-adaptation day 7 (PAD 7). When tested in the adapting position, all experiments showed immediate reduction in G A and G V compared with pre-adaptation levels. For LED adaptation experiments, the pitch G A and G V gains were significantly reduced for as long as 7 days. Some retention of the LED-adapted VOR gain also occurred when testing in the RED position. No retention of pitch VOR G A or G V existed for the UP position after adaptation in LED. After the UP-adapt experiments, no retention of the G A or G V was found when tested in the adapting position. Interestingly, however, some retention of G A and G V did exist when the UP-adapted animals were tested in LED or RED. Data from sinusoidal rotations followed a similar adaptation pattern as the step responses. Our findings show that after only 3 h of adaptation exposure, adaptation of the pitch VOR gain is retained for several days. This long-term retention of VOR adaptation after short-term exposure appears to be the result of inducing adaptation with an atypical combination of movement and position for the monkey (LED-adapt). Our results indicate that head orientation relative to gravity is an effective context for retaining learned VOR gains in addition to restricting mobility or keeping animals in the dark. We also show that the adapting head position determines the magnitude of VOR adaptation. [ABSTRACT FROM AUTHOR]

The recruitment of extra-vestibular mechanisms to assist a deficient angular vestibulo-ocular reflex (aVOR) during ipsilesional head rotations is well established and includes saccades of reduced latency that occur in the direction of the lesioned aVOR, termed compensatory saccades (CS). Less well known is the functional relevance of these unique saccades. Here we report a 42 y.o. male diagnosed with right unilateral vestibular hypofunction due to vestibular neuronitis who underwent a vestibular rehabilitation program including gaze stabilization exercises. After three weeks, he had a significant improvement in his ability to see clearly during head rotation. Our data show a reduction in the recruitment and magnitude of CS as well as improved peripheral aVOR gain (eye velocity/head velocity) and retinal eye velocity. Our data suggest an inverse, dynamic relationship between the recruitment of CS and the gain of the aVOR. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine if the angular vestibulo-ocular reflex (VOR) in response to pitch, roll, left anterior-right posterior (LARP), and right anterior-left posterior (RALP) head rotations exhibited the same linear and nonlinear characteristics as those found in the horizontal VOR. Three-dimensional eye movements were recorded with the scleral search coil technique. The VOR in response to rotations in five planes (horizontal, vertical, torsional, LARP, and RALP) was studied in three squirrel monkeys. The latency of the VOR evoked by steps of acceleration in darkness (3,000°/s² reaching a velocity of 150°/s) was 5.8±1.7 ms and was the same in response to head rotations in all five planes of rotation. The gain of the reflex during the acceleration was 36.7 ±15.4% greater than that measured at the plateau of head velocity. Polynomial fits to the trajectory of the response show that eye velocity is proportional to the cube of head velocity in all five planes of rotation. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20°/s, the VOR gain did not change with frequency (0.74±0.06, 0.74 ±0.07, 0.37±0.05, 0.69±0.06, and 0.64±0.06, for yaw, pitch, roll, LARP, and RALP respectively). The VOR gain increased with head velocity for sinusoidal rotations at frequencies ≥4 Hz. For rotational frequencies ≥4 Hz, we show that the vertical, torsional, LARP, and RALP VORs have the same linear and nonlinear characteristics as the horizontal VOR. In addition, we show that the gain, phase and axis of eye rotation during LARP and RALP head rotations can be predicted once the pitch and roll responses are characterized. [ABSTRACT FROM AUTHOR]

Examines the anatomy and physiology of the vestibular system and to describe the neurophysiological mechanisms responsible for the vestibulo-ocular abnormalities in patients with vestibular hypofunction. Function of the vestibular system; Peripheral vestibular anatomy; Vestibular afferent physiology; Incidence and prevalence of dizziness in the U.S.; Difference between vestibular and nonvestibular causes of dizziness.

Background and Purpose. The head thrust test (HTT) is used to assess the vestibulo-ocular reflex. Sensitivity and specificity for diagnosing unilateral vestibular hypofunction (UVH) in patients following vestibular ablation is excellent (100%), although sensitivity is lower (35%-39%) for patients with nonsurgically induced UVH. The variability of the test results may be from moving the subject's head outside the plane of the lateral semicircular canals as well as using a head thrust of predictable timing and direction. The purpose of this study was to examine sensitivity and specificity of the horizontal HTT in identifying patients with UVH and bilateral vestibular hypofunction (BVH) when the head was flexed 30 degrees in attempt to induce acceleration primarily in the lateral semicircular canal and the head was moved unpredictably. Subjects. The medical records of 176 people with and without vestibular dysfunction (n=79 with UVH, n=32 with BVH, and n=65 with nonvestibular dizziness) were studied. Methods. Data were retrospectively tabulated from a de-identified database (ie, with health information stripped of all identifiers). Results. Sensitivity of the HTT for identifying vestibular hypofunction was 71% for UVH and 84% for BVH. Specificity was 82%. Discussion and Conclusion. Ensuring the head is pitched 30 degrees down and thrust with an unpredictable timing and direction appears to improve sensitivity of the HTT. [ABSTRACT FROM AUTHOR]

Introduction: Aging is associated with loss of balance, with falls being one of the leading causes of death among the elderly in the USA. Gaze stabilization exercises (GSE) improve balance control in vestibular populations and could be useful to prevent falls in healthy individuals. However, the extent to which aging affects head kinematics in GSE is unknown. Methods: Forty-eight younger (n = 25, 24 ± 6 years, 60% female) and older (n = 23, 66 ± 5 years, 56% female) adults completed six 30-s GSE. Participants were asked to maintain gaze fixation on a stationary target while continuously performing head movements in pitch (e.g., vertical) and yaw (e.g., horizontal) directions. The visual target was placed on the wall 1 m or 2 m away or handheld at arm's length. Head kinematics were recorded with an inertial measurement unit placed on the back of the participants' head. Results: Older adults took significantly more time (e.g., delay) to complete cycles of head rotation in both pitch and yaw compared to younger participants across all GSE. Such delay was further increased during yaw head rotation while fixating gaze of the 1 m target. The average peak velocity (APV) and average angular displacement (AAD), however, were equivalent between groups in all GSE. Conclusion: Aging leads to the maintenance of head rotation APV and AAD at the expense of delayed cycles of head rotation, suggesting an age-dependent prioritization strategy (e.g., adapt duration first, range second) during continuous head movements. The distance of the visual target and head movement direction influenced elderly performance and should be considered when prescribing GSE to older populations. [ABSTRACT FROM AUTHOR]

Presents a case report which described a physical therapy for motion sickness in a 34-year-old woman. Purpose of the report; Case description; Discussion on habituation therapy, which focused on the use of provocative visual and vestibular stimuli and balance training with gradual increase of difficulty.

Introduction: Spatial navigation, the ability to move through one's environment, is a complex skill utilized in everyday life. The effects of specific vestibular end-organ deficits and hearing impairments on spatial navigation have received little to no attention. We hypothesized that hearing impairment adversely affects spatial navigation and that bimodal impairments (vestibular and hearing) further impair navigation ability. Methods: Data from 182 participants in the Baltimore Longitudinal Study of Aging who had interpretable results for the video head impulse test (vHIT), cervical vestibular evoked myogenic potentials (cVEMP) and ocular vestibular evoked myogenic potentials (oVEMP), audiometric testing, and the triangle completion test (TCT) were retrospectively analyzed. Multiple linear regression, controlling for age, sex, and cognition, was employed to identify predictors of TCT performance in terms of end-point error, angle deviation, and distance walked. Results: oVEMP abnormalities were associated with larger end-point error (p = 0.008) and larger angle deviation (p = 0.002) but were not associated with distance walked (p = 0.392). Abnormalities on cVEMP testing and vHIT were not associated with distance walked (p = 0.835, p = 0.300), end-point error (p = 0.256, p = 0.808), or angle deviation (p = 0.192, p = 0.966). Compared with normal-hearing adults, hearing-impaired adults walked a shorter distance during the TCT (p = 0.049) but had a similar end-point error (p = 0.302) and angle deviation (p = 0.466). There was no interaction between vestibular and hearing function for predicting spatial navigation ability. Conclusion: In this cohort analysis, utricular dysfunction and hearing impairment were associated with poorer spatial navigation performance. We postulate that hearing impairment negatively affects one's ability to use real-time, intrinsic auditory cues and/or prior experience to guide navigation. Plain Language Summary: Spatial navigation, the ability to move through one's environment, is a complex skill utilized in everyday life. The effects of specific balance and hearing deficits on spatial navigation have not been extensively studied. Thus, we analyzed data from 182 participants in the Baltimore Longitudinal Study of Aging who completed balance, hearing, and spatial navigation tests to determine if hearing impairment may adversely affect spatial navigation and if combined deficits in balance and hearing further impair navigation ability. Our analyses accounted for the confounding effects of age, sex, and cognition on aspects of spatial navigation performance. We found that deficits in hearing and in the balance organ that senses horizontal translational movements were associated with worse performance on spatial navigation. However, deficits in the balance organs that sense vertical translational movements and horizontal rotational movements were not associated with worse spatial navigation ability. Surprisingly, we found that those with combined balance and hearing deficits did not perform significantly worse on spatial navigation than those with deficits in either balance or hearing alone. We believe that the abnormal function of the horizontal translational movement sensors likely explains the gait disorientation experienced by persons with inner ear problems. Additionally, we propose that hearing deficits impede one's ability to use real-time sound cues to guide navigation. Many of our participants had mild deficits; thus, further research on the effects of more severe balance and hearing deficits on spatial navigation is needed to gain a better understanding of how different sensory inputs contribute to spatial navigation ability. [ABSTRACT FROM AUTHOR]

BACKGROUND: Managing acute vertigo/dizziness for inpatients requires valid communication between the various healthcare professionals that triage such life-threatening presentations, yet there are no current scaling methods for managing such acute vertigo symptoms for inpatients. OBJECTIVE: To describe the development and validation of the Krems Acute Vertigo/Dizziness Scale (KAVEDIS), a new instrument for tracking subjective symptoms (vertigo, dizziness) and gait impairment across four unique vestibular diagnoses (Menière's disease, benign paroxysmal positional vertigo, peripheral vestibular hypofunction, and vestibular migraine) over a one-year period after inpatient hospital admission. METHODS: Retrospective data collection study from KAVEDIS scale and chart documentation. RESULTS: The KAVEDIS scale can significantly distinguish scores from admission to discharge in three of four vestibular diagnoses. The documented course of subjective vestibular symptoms and gait disturbances were correlated in all four groups. CONCLUSION: We suggest that KAVEDIS documentation among inpatients admitted with acute vertigo/dizziness may improve communication between the various intervening clinicians and help to raise concern in cases of symptomprogression. [ABSTRACT FROM AUTHOR]

People with multiple sclerosis (PwMS) who report dizziness often have gaze instability due to vestibulo-ocular reflex (VOR) deficiencies and compensatory saccade (CS) abnormalities. Herein, we aimed to describe and compare the gaze stabilization mechanisms for yaw and pitch head movements in PwMS. Thirty-seven PwMS (27 female, mean ± SD age = 53.4 ± 12.4 years old, median [IQR] Expanded Disability Status Scale Score = 3.5, [1.0]. We analyzed video head impulse test results for VOR gain, CS frequency, CS latency, gaze position error (GPE) at impulse end, and GPE at 400 ms after impulse start. Discrepancies were found for median [IQR] VOR gain in yaw (0.92 [0.14]) versus pitch-up (0.71 [0.44], p < 0.001) and pitch-down (0.81 [0.44], p = 0.014]), CS latency in yaw (258.13 [76.8]) ms versus pitch-up (208.78 [65.97]) ms, p = 0.001] and pitch-down (132.17 [97.56] ms, p = 0.006), GPE at impulse end in yaw (1.15 [1.85] degs versus pitch-up (2.71 [3.9] degs, p < 0.001), and GPE at 400 ms in yaw (-0.25 [0.98] degs) versus pitch-up (1.53 [1.07] degs, p < 0.001) and pitch-down (1.12 [1.82] degs, p = 0.001). Compared with yaw (0.91 [0.75]), CS frequency was similar for pitch-up (1.03 [0.93], p = 0.999) but lower for pitch-down (0.65 [0.64], p = 0.023). GPE at 400 ms was similar for yaw and pitch-down (1.88 [2.76] degs, p = 0.400). We postulate that MS may have preferentially damaged the vertical VOR and saccade pathways in this cohort. [ABSTRACT FROM AUTHOR]

The vestibulo-collic reflex generates neck motor commands to produce head-on-trunk movements that are essential for stabilizing the head relative to space. Here we examined the effects of vestibular loss on head-on-trunk kinematics during voluntary behavior. Head and trunk movements were measured in individuals with vestibular schwannoma before and then 6 weeks after unilateral vestibular deafferentation via surgical resection of the tumor. Movements were recorded in 6 dimensions (i.e., 3 axes of rotation and 3 axes of translation) using small light-weight inertial measurement units while participants performed balance and gait tasks. Kinematic measures differed between individuals with vestibular schwannoma (at both time points) and healthy controls for the more challenging exercises, namely those performed in tandem position or on an unstable surface without visual input. Quantitative assessment of the vestibulo-ocular reflex (VOR) revealed a reduction in VOR gain for individuals with vestibular schwannoma compared to control subjects, that was further reduced following surgery. These findings indicated that the impairment caused by either the tumor or subsequent surgical tumor resection altered head-on-trunk kinematics in a manner that is not normalized by central compensation. In contrast, we further found that head-on-trunk kinematics in individuals with vestibular schwannoma were actually comparable before and after surgery. Thus, taken together, our results indicate that vestibular loss impacts head-on-trunk kinematics during voluntary balance and gait behaviors, and suggest that the neural mechanisms mediating adaptation alter the motion strategies even before surgery in a manner that may be maladaptive for long-term compensation. [ABSTRACT FROM AUTHOR]

Head kinematics are altered in individuals with vestibular schwannoma (VS) during short duration gait tasks [i.e., Functional Gait Assessment (FGA)], both before and after surgery, yet whether these differences extend to longer duration gait exercises is currently unknown. Here we examined the effects of vestibular loss and subsequent compensation on head kinematics in individuals with VS during gait exercises of relatively extended versus short duration (< 10 versus 30 s), compared to age-matched controls. Six-dimensional head movements were recorded during extended and short duration gait exercises before and then 6 weeks after sectioning of the involved vestibular nerve (vestibular neurectomy). Standard functional, physiological, and subjective clinical assessments were also performed at each time point. Kinematics were differentially altered in individuals with vestibular loss at both time points during extended versus short duration exercises. Range of motion was significantly reduced in extended tasks. In contrast, movement variability predominately differed for the short duration exercises. Overall, our results indicate that quantifying head kinematics during longer duration gait tasks can provide novel information about how VS individuals compensate for vestibular loss, and suggest that measurements of range of motion versus variability can provide information regarding the different strategies deployed to maintain functional locomotion. [ABSTRACT FROM AUTHOR]

Head kinematics are altered in individuals with vestibular schwannoma (VS) during short duration gait tasks [i.e., Functional Gait Assessment (FGA)], both before and after surgery, yet whether these differences extend to longer duration gait exercises is currently unknown. Here we examined the effects of vestibular loss and subsequent compensation on head kinematics in individuals with VS during gait exercises of relatively extended versus short duration (< 10 versus 30 s), compared to age-matched controls. Six-dimensional head movements were recorded during extended and short duration gait exercises before and then 6 weeks after sectioning of the involved vestibular nerve (vestibular neurectomy). Standard functional, physiological, and subjective clinical assessments were also performed at each time point. Kinematics were differentially altered in individuals with vestibular loss at both time points during extended versus short duration exercises. Range of motion was significantly reduced in extended tasks. In contrast, movement variability predominately differed for the short duration exercises. Overall, our results indicate that quantifying head kinematics during longer duration gait tasks can provide novel information about how VS individuals compensate for vestibular loss, and suggest that measurements of range of motion versus variability can provide information regarding the different strategies deployed to maintain functional locomotion. [ABSTRACT FROM AUTHOR]

Background: A better understanding of how vestibular asymmetry manifests across tests is important due to its potential implications for balance dysfunction, motion sickness susceptibility, and adaptation to new environments. Objective: We report the results of multiple tests for vestibular asymmetry in 32 healthy participants. Methods: Asymmetry was measured using perceptual reports during unilateral centrifugation, oculomotor responses during visual alignment tasks, vestibulo-ocular reflex gain during head impulse tests, and body rotation during stepping tests. Results: A significant correlation was observed between asymmetries of subjective visual vertical and verbal report during unilateral centrifugation. Another significant correlation was observed between the asymmetries of ocular alignment, vestibulo-ocular reflex gain, and body rotation. Conclusions: These data suggest that there are underlying vestibular asymmetries in healthy individuals that are consistent across various vestibular challenges. In addition, these findings have value in guiding test selection during experimental design for assessing vestibular asymmetry in healthy adults. [ABSTRACT FROM AUTHOR]

Background: Balance stabilization exercises are often prescribed to facilitate compensation in individuals with vestibular schwannoma (VS). However, both the assessment and prescription of these exercises are reliant on clinical observations and expert opinion rather than on quantitative evidence. The aim of this study was to quantify head motion kinematics in individuals with vestibular loss while they performed commonly prescribed balance stability exercises.Methods: Using inertial measurement units, head movements of individuals with vestibular schwannoma were measured before and after surgical deafferentation and compared with age-matched controls.Results: We found that individuals with vestibular schwannoma experienced more variable head motion compared to healthy controls both pre- and postoperatively, particularly in absence of visual input, but that there was little difference between preoperative and postoperative kinematic measurements for our vestibular schwannoma group. We further found correlations between head motion kinematic measures during balance exercises, performed in the absence of visual input, and multiple clinical measurements for preoperative VS subjects. Subjects with higher head motion variability also had worse DVA scores, moved more slowly during the Timed up and Go and gait speed tests, and had lower scores on the functional gait assessment. In contrast, we did not find strong correlations between clinical measures and postoperative head kinematics for the same VS subjects.Conclusions: Our data suggest that further development of such metrics based on the quantification of head motion has merit for the assessment and prescription of balance exercises, as demonstrated by the calculation of a "kinematic score" for identifying the most informative balance exercise (i.e., "Standing on foam eyes closed"). [ABSTRACT FROM AUTHOR]

BACKGROUND: Geographical location is known to affect health outcomes; however, evidence regarding whether location affects healthcare for persons suspected to have vestibular dysfunction is lacking. OBJECTIVE: To investigate whether location affects healthcare seeking and outcomes for adults with symptoms of vestibular pathology. METHODS: We assessed for regional disparities associated with demographics, diagnosis, chronological factors, and financial expenditures from Americans who participated in the Vestibular Disorders Association registry (N = 905, 57.4±12.5 years, 82.7% female, 94.8% White, and 8.1% Hispanic or Latino). Respondents were grouped per geographical regions defined by the United States Census Bureau. RESULTS: There were no significant between-region differences for age (p = 0.10), sex (p = 0.78), or ethnicity (p = 0.24). There were more Asian respondents in the West versus the Midwest (p = 0.05) and more Black respondents in the South versus the West (p = 0.05). The time to first seek care was shorter in the Northeast (17.3 [SD = 49.5] weeks) versus the South (42.4 [SD = 83.7] weeks), p = 0.015. The time from the first healthcare visit to receiving a final diagnosis was shorter in the Northeast (46.5 [SD = 75.4] weeks) versus the South (68.9 [SD = 89.7] weeks), p = 0.015. Compared to the Midwest, fewer respondents in the Northeast reported "no" out-of-pocket financial impact, p = 0.039. CONCLUSIONS: Geographical location affects healthcare seeking and outcomes for persons suspected to have vestibular dysfunction. [ABSTRACT FROM AUTHOR]

Individuals with peripheral or central vestibular dysfunction recruit compensatory saccades (CSs) in response to high acceleration, yaw head impulses. Although CSs have been shown to be an effective strategy for reducing gaze position error (GPE) in individuals with peripheral hypofunction, for individuals with central vestibular dysfunction, the effectiveness of CS is unknown. The purpose of our study was to compare the effectiveness of CS, defined as the ability to compensate for head velocity and eye position errors, between persons with central and peripheral vestibular dysfunction. We compared oculomotor responses during video head impulse testing between individuals with unilateral peripheral vestibular deafferentation, a disorder of the peripheral vestibular afferents, and individuals with multiple sclerosis, a condition affecting the central vestibular pathways. We hypothesized that relative to individuals with peripheral lesions, individuals with central dysfunction would recruit CSs that were delayed and inappropriately scaled to head velocity and GPE. We show that CSs recruited by persons with central vestibular pathology were not uniformly deficient but instead were of a sufficient velocity to compensate for reductions in VOR gain. Compared to those with peripheral vestibular lesions, individuals with central pathology also recruited earlier covert CS with amplitudes that were better corrected for GPE. Conversely, those with central lesions showed greater variability in the amplitude of overt CS relative to GPE. These data point to a unique role for peripheral and central vestibular inputs in the recruitment of CS and suggest that covert CSs are an effective oculomotor strategy for individuals with multiple sclerosis. [ABSTRACT FROM AUTHOR]

Objective To determine if vestibular evoked myogenic potential (VEMP) responses change during inversion in patients with superior canal dehiscence syndrome (SCDS) compared to controls. Methods Sixteen subjects with SCDS (mean: 43, range 30–57 years) and 15 age-matched, healthy subjects (mean: 41, range 22–57 years) completed cervical VEMP (cVEMP) in response to air conduction click stimuli and ocular VEMP (oVEMP) in response to air conduction 500 Hz tone burst stimuli and midline tap stimulation. All VEMP testing was completed in semi-recumbent and inverted conditions. Results SCDS ears demonstrated significantly larger oVEMP peak-to-peak amplitudes in comparison to normal ears in semi-recumbency. While corrected cVEMP peak-to-peak amplitudes were larger in SCDS ears; this did not reach significance in our sample. Overall, there was not a differential change in o- or cVEMP amplitude with inversion between SCDS and normal subjects. Conclusions Postural-induced changes in o- and cVEMP responses were measured in the steady state regardless of whether the labyrinth was intact or dehiscent. Significance VEMP responses are blunted during inversion. Although steady-state measurements of VEMPs during inversion do not increase diagnostic accuracy for SCDS, the findings suggest that inversion may provide more general insights into the equilibration of pressures between intracranial and intralabyrinthine fluids. [ABSTRACT FROM AUTHOR]

Objective: To compare the sensitivity and specificity of ocular vestibular evoked myogenic potentials (oVEMPs) using 2 electrode montages for the diagnosis of superior canal dehiscence syndrome (SCDS). Subjects: 16 SCDS patients (17 affected-SCDS ears, 15 contralateral-SCDS ears) and 12 controls (24 ears). Methods: oVEMPs were recorded in response to 500-Hz tone bursts using 2 electrode montages. For both montages the active electrode was placed approximately 5 mm below each eye and a ground electrode on the sternum. For montage 1 (standard), the reference electrode was centered 2 cm below each active electrode. For montage 2, the reference electrode was placed on the chin. Results: For either montage, the separation between oVEMP amplitudes in affected-SCDS ears and controls was significant (p < 0.001), with excellent sensitivity and specificity (>90%). Conclusion: oVEMP recordings with the standard montage remain a reliable method for evaluation of SCDS. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objective: To compare the sensitivity and specificity of ocular vestibular evoked myogenic potentials (oVEMPs) using 2 electrode montages for the diagnosis of superior canal dehiscence syndrome (SCDS).Subjects: 16 SCDS patients (17 affected-SCDS ears, 15 contralateral-SCDS ears) and 12 controls (24 ears).Methods: oVEMPs were recorded in response to 500-Hz tone bursts using 2 electrode montages. For both montages the active electrode was placed approximately 5 mm below each eye and a ground electrode on the sternum. For montage 1 (standard), the reference electrode was centered 2 cm below each active electrode. For montage 2, the reference electrode was placed on the chin.Results: For either montage, the separation between oVEMP amplitudes in affected-SCDS ears and controls was significant (p < 0.001), with excellent sensitivity and specificity (>90%).Conclusion: oVEMP recordings with the standard montage remain a reliable method for evaluation of SCDS. [ABSTRACT FROM AUTHOR]

While active dynamic visual acuity (DVA) has been shown to improve with gaze stabilization exercises, we sought to determine whether DVA during passive head impulses (pDVA) would also improve following a rehabilitation course of vestibular physical therapy (VPT) in patients with unilateral and bilateral vestibular hypofunction. VPT consisted of gaze and gait stabilization exercises done as a home exercise program. Scleral search coil was used to characterize the angular vestibulo-ocular reflex (aVOR) during pDVA before and after VPT. Mean duration of VPT was 66 ± 24 days, over a total of 5 ± 1.4 outpatient visits. Two of three subjects showed improvements in pDVA with a mean reduction of 43% (LogMAR 0.58 to 0.398 and 0.92 to 0.40). Our data suggest improvements in pDVA may be due in part to improvements in aVOR velocity and acceleration gains or reduced latency of the aVOR. Each subject demonstrated a reduction in the ratio of compensatory saccades to head impulses after VPT. Preliminary data suggest that active gaze stability exercises may contribute to improvements in pDVA in some individuals. [ABSTRACT FROM AUTHOR]

The bedside examination associated with their clinical history remains the most critical means to accurately diagnose the cause for most of the signs and symptoms related to pathology of the cerebellum and vestibular system in patients presenting with dizziness and imbalance. This paper focuses on those critical bedside examinations, suggests when laboratory testing might be useful to confirm the clinical suspicion, and considers the shared neural circuitry within the visual and vestibular systems to offer an algorithmic approach in conducting the clinical bedside examination. [ABSTRACT FROM AUTHOR]

Objective Deficits in vestibular function increase the risk for falls while turning. However, the clinical assessment of turning in patients with vestibular dysfunction is lacking, and evidence is limited that identifies the effectiveness of vestibular physical therapy in improving turning performance. The purpose of this study was to quantify walking and turning performance during the instrumented Timed "Up & Go" (TUG) test using body-worn inertial measurement units (IMUs). Novel instrumented TUG parameters were investigated for ability to distinguish patients with unilateral vestibular deafferentation (UVD) from control groups and discriminate the differences in turning parameters of patients with UVD following vestibular physical therapy. Methods Thirty-eight individuals were recruited following UVD surgery: 26 age-matched veteran controls with reports of dizziness not from a peripheral vestibular origin, and 12 age-matched healthy controls. Participants were donned with IMUs and given verbal instructions to complete the TUG test as fast as safely possible. The IMU-instrumented and automated assessment of the TUG test provided component-based TUG parameters, including the novel walk:turn ratio. Among the participants with UVD, 19 completed an additional instrumented TUG testing after vestibular physical therapy. Results The walk:turn time ratio showed that turning performance in patients with UVD before rehabilitation is significantly more impaired than both the individuals with nonperipheral conditions and healthy controls. Vestibular rehabilitation significantly improved turning performance and "normalized" their walk:turn time ratio compared with healthy controls. The duration of the straight walking component in individuals with UVD before vestibular physical therapy, however, was not significantly different compared with that component in people after vestibular physical therapy and in healthy controls. Conclusion The IMU-instrumented TUG test can be used to distinguish individuals with vestibular deafferentation and to objectively quantify the change in their turning performance after vestibular physical therapy. Impact The IMU-based instrumented TUG parameters have the potential to quantify the efficacy of vestibular physical therapy and be adopted in the clinic. [ABSTRACT FROM AUTHOR]

The angular and linear vestibulo-ocular reflex responses are greater when viewing near targets to compensate for the relatively larger translation of the eyes with respect to the target. Our aim was to measure vestibular evoked myogenic potentials using a lateral ocular electrode montage (oVEMP) with a laterally applied stimulus using a mini-shaker during both far- and near-viewing (vergence) distances to determine whether vergence affects the oVEMP response as it does the semicircular canal vestibulo-ocular reflex response. Our results show that during vergence, the p1 and n1-p1 amplitude of the lateral oVEMP response increases significantly, whereas the latencies do not change significantly. We suggest that the physiological basis for this vergence-mediated amplitude increase in potentials may be the same as those already documented using transient linear head accelerations. Our data also suggest that irregular vestibular afferents are likely mediating the vergence-mediated gain increase during linear head accelerations because only irregular afferents are stimulated during short, transient 500 Hz stimuli. [ABSTRACT FROM AUTHOR]

Gaze stability is the ability of the eyes to fixate a stable point when the head is moving in space. Because gaze stability is impaired in peripheral vestibular loss patients, gaze stabilization exercises are often prescribed to facilitate compensation. However, both the assessment and prescription of these exercises are subjective. Accordingly, here we quantified head motion kinematics in patients with vestibular loss while they performed the standard of care gaze stability exercises, both before and after surgical deafferentation. We also correlate the head kinematic data with standard clinical outcome measures. Using inertial measurement units, we quantified head movements in patients as they transitioned through these two vestibular states characterized by different levels of peripheral damage. Comparison with age-matched healthy control subjects revealed that the same kinematic measurements were significantly abnormal in patients both pre- and post-surgery. Regardless of direction, patients took a longer time to move their heads during the exercises. Interestingly, these changes in kinematics suggest a strategy that existed preoperatively and remained symmetric after surgery although the patients then had complete unilateral vestibular loss. Further, we found that this kinematic assessment was a good predictor of clinical outcomes, and that pre-surgery clinical measures could predict post-surgery head kinematics. Thus, together, our results provide the first experimental evidence that patients show significant changes in head kinematics during gaze stability exercises, even prior to surgery. This suggests that early changes in head kinematic strategy due to significant but incomplete vestibular loss are already maladaptive as compared to controls. [ABSTRACT FROM AUTHOR]

BACKGROUND: The gain (eye-velocity/head-velocity) of the angular vestibuloocular reflex (aVOR) during head impulses can be increased while viewing near-targets and when exposed to unilateral, incremental retinal image velocity error signals. It is not clear however, whether the tonic or phasic vestibular pathways mediate these gain increases. OBJECTIVE: Determine whether a shared pathway is responsible for gain enhancement between vergence and adaptation of aVOR gain in patients with unilateral vestibular hypofunction (UVH). MATERIAL AND METHODS: 20 patients with UVH were examined for change in aVOR gain during a vergence task and after 15-minutes of ipsilesional incremental VOR adaptation (uIVA) using StableEyes (a device that controls a laser target as a function of head velocity) during horizontal passive head impulses. A 5 % aVOR gain increase was defined as the threshold for significant change. RESULTS: 11/20 patients had >5% vergence-mediated gain increase during ipsi-lesional impulses. For uIVA, 10/20 patients had >5% ipsi-lesional gain increase. There was no correlation between the vergence-mediated gain increase and gain increase after uIVA training. CONCLUSION: Vergence-enhanced and uIVA training gain increases are mediated by separate mechanisms and/or vestibular pathways (tonic/phasic). The ability to increase the aVOR gain during vergence is not prognostic for successful adaptation training. [ABSTRACT FROM AUTHOR]

BACKGROUND: Embedded within most rapid head rotations are gaze shifts, which is an initial eye rotation to a target of interest, followed by a head rotation towards the same target. Gaze shifts are used to acquire an image that initially is outside of the participant's current field of vision. Currently, there are no tools available that evaluate the functional relevance of a gaze shift. OBJECTIVE: The purpose of our study was to measure dynamic visual acuity (DVA) while performing a gaze shift. METHODS: Seventy-one healthy participants (42.79±16.89 years) and 34 participants with unilateral vestibular hypofunction (UVH) (54.59±20.14 years) were tested while wearing an inertial measurement unit (IMU) sensor on the head and walking on a treadmill surrounded by three monitors. We measured visual acuity during three subcomponent tests: standing (static visual acuity), while performing an active head rotation gaze shift, and an active head rotation gaze shift while walking (gsDVAw). RESULTS: While doing gsDVAw, patients with Left UVH (n = 21) had scores worse (p = 0.023) for leftward (0.0446±0.0943 LogMAR) head rotation compared with the healthy controls (–0.0075±0.0410 LogMAR). Similarly, patients with right UVH (N = 13) had worse (p = 0.025) gsDVAw for rightward head motion (0.0307±0.0481 LogMAR) compared with healthy controls (–0.0047±0.0433 LogMAR). As a whole, gsDVAw scores were worse in UVH compared to the healthy controls when we included the ipsilesional head rotation on both sides gsDVAw (0.0061±0.0421 LogMAR healthy vs. 0.03926±0.0822 LogMAR UVH, p = 0.003). Controlling for age had no effect, the gsDVAw scores of the patients were always worse (p < 0.01). CONCLUSION: The gaze shift DVA test can distinguish gaze stability in patients with UVH from healthy controls. This test may be a useful measure of compensation for patients undergoing various therapies for their vestibular hypofunction. [ABSTRACT FROM AUTHOR]

Objective The modified Clinical Test of Sensory Interaction and Balance (mCTSIB) is used to clinically assess vestibular sensory integration (VSI), the process by which the central nervous system integrates vestibular afference to maintain balance. The rate and effects of impaired VSI (IVSI) on prosthetic mobility in people with lower limb amputation (LLA) is unknown. The objective of this study was to use the mCTSIB to classify VSI in active community ambulators with LLA and to examine the relationship between IVSI and prosthetic mobility, as measured by the Component Timed Up and Go (cTUG) test. Methods This was a cross-sectional study with a convenience sample of 130 community ambulators with unilateral LLA. Classification of VSI was determined based on a time-based pass/fail mCTSIB performance. Participants were classified as having normal sensory integration (NSI) if they could balance for 30 seconds in every mCTSIB condition. Participants who failed condition 4 exclusively were classified as IVSI. Prosthetic mobility, as measured by the cTUG, was compared between NSI and IVSI groups. Results Of the 130 participants, 29 (22%) were classified as IVSI and 95 (73%) were classified as having NSI. Prosthetic mobility significantly differed between IVSI and NSI groups, with IVSI participants performing all components of the cTUG significantly slower. Medium to large effect sizes were found between groups during cTUG. Conclusions These results suggest that 1 in 5 community ambulators with LLA have IVSI, with associated limitations in balance confidence and prosthetic mobility. Impact The ability to integrate vestibular information was found to have a strong relationship with prosthetic mobility in active community ambulators with LLA, especially with performing a 180-degree step turn. Physical therapists can use the mCTSIB to classify sensory integration during prosthetic rehabilitation and develop an appropriate balance intervention. Lay Summary Active adults with LLA can use information from their senses to maintain their standing balance. Adults with LLA who have difficulty balancing on foam with closed eyes were slower to get in and out of a chair, walk, and perform a 180-degree step turn. [ABSTRACT FROM AUTHOR]

BACKGROUND: Exposure to brain injury via blast or blunt mechanisms disrupts multiple sensorimotor systems simultaneously. Large numbers of US Gulf War era and Operation Iraqi/Enduring Freedom veterans with traumatic brain injury (TBI) are suffering the symptom of dizziness – presumed due to "Multi-Sensory Impairment", a clinical pattern of damage to the auditory, visual and vestibular sensorimotor systems. OBJECTIVE: To describe the oculomotor response to rapid head rotation in a population of veterans with dizziness. We also describe the reliability of using the video head impulse test (vHIT) in a veteran population. METHODS: We used the vHIT to evaluate the vestibular-ocular reflex (VOR) gain and presence of compensatory saccades (CS) in each semicircular canal of 81 veterans (31% TBI) with dizziness. Data was collected using the ICS Otometric™ vHIT. Data was processed using both the Otometric™ software and custom software written in MATLAB™. This data was evaluated through Kruskal-Wallis rank-sum test and analysis of regression. RESULTS: Veterans with dizziness recruit CS in all semicircular canal planes even though their VOR gain is normal. The vHIT is a reliable clinical test to quantify the metrics of the VOR and CS in veterans. CONCLUSION: Veterans with dizziness symptoms use compensatory saccades in all planes of semicircular canal rotation, despite having normal peripheral VOR gain during rapid head rotation. The video head impulse test is a stable measure of vestibular slow phase and metrics of compensatory saccades in veterans with dizziness. [ABSTRACT FROM AUTHOR]

The healthy vestibulo-ocular reflex (VOR) ensures that images remain on the fovea of the retina during head rotation to maintain stable vision. VOR behavior can be measured as a summation of linear and nonlinear properties although it is unknown whether asymmetric VOR adaptation can be performed synchronously in humans. The purpose of the present study is twofold. First, examine whether the right and left VOR gains can be synchronously adapted in opposing directions. Second, to investigate whether the adaptation context transfers between both sides. Three separate VOR adaptation sessions were randomized such that the VOR was adapted Up-bilaterally, Down-bilaterally, or Mixed (one side up, opposite side down). Ten healthy subjects completed the study. Subjects were tested while seated upright, 1 meter in front of a wall in complete dark. Each subject made active (self-generated) head impulse rotations for 15 min while viewing a gradually increasing amount of retinal slip. VOR training demand changed by 10% every 90 s. The VOR changed significantly for all training conditions. No significant differences in the magnitude of VOR gain changes between training conditions were found. The human VOR can be simultaneously driven in opposite directions. The similar magnitude of VOR gain changes across training conditions suggests functionally independent VOR circuits for each side of head rotation that mediate simultaneous and opposing VOR adaptations. NEW & NOTEWORTHY Our results indicate that humans have the adaptive capacity for concurrent and opposing directions of vestibuloocular reflex (VOR) motor learning. Context specificity of VOR adaptation is dependent on the error signal being unilateral or bilateral, which we illustrate via a lack of VOR gain transfer using unique adaptive demands. [ABSTRACT FROM AUTHOR]

Background Small, innate asymmetries between the left and right otolith organs can cause ocular misalignment with symptoms that include double vision and motion sickness. Additionally, ocular misalignment affects nearly 5% of the US population. We have developed a portable, non-invasive technology that uses subjective perception of binocular visual signals to estimate relative binocular alignment. New method and results The Vertical Alignment Nulling (VAN) and Torsional Alignment Nulling (TAN) tests ask subjects to view one red and one blue line on a tablet computer while looking through color-matched red and blue filters so that each eye sees only one of the lines. Subjects align the red and blue lines, which are initially vertically offset from one another during VAN or rotated relative to one another during TAN, until they perceive a single continuous line. Ocular misalignments are inferred from actual offsets in the final line positions. During testing, all binocular visual cues are eliminated by employing active-matrix organic light-emitting diode (AMOLED) technology and testing in darkness. VAN and TAN can accurately account for visual offsets induced by prisms, and test-retest reliability is excellent, with resolution better than many current standard clinical tests. Comparison with existing method(s) VAN and TAN tests are similar to the clinical Lancaster red-green test. However, VAN and TAN employ inexpensive, hand-held hardware that can be self-administered with results that are quickly quantifiable. Conclusions VAN and TAN provide simple, sensitive, and quantitative measures of binocular positioning alignment that may be useful for detecting subtle abnormalities in ocular positioning. [ABSTRACT FROM AUTHOR]

Summary A major focus in neurobiology is how the brain adapts its motor behavior to changes in its internal and external environments [ 1, 2 ]. Much is known about adaptively optimizing the amplitude and direction of eye and limb movements, for example, but little is known about another essential form of learning, “set-point” adaptation. Set-point adaptation balances tonic activity so that reciprocally acting, agonist and antagonist muscles have a stable platform from which to launch accurate movements. Here, we use the vestibulo-ocular reflex—a simple behavior that stabilizes the position of the eye while the head is moving—to investigate how tonic activity is adapted toward a new set point to prevent eye drift when the head is still [ 3, 4 ]. Set-point adaptation was elicited with magneto-hydrodynamic vestibular stimulation (MVS) by placing normal humans in a 7T MRI for 90 min. MVS is ideal for prolonged labyrinthine activation because it mimics constant head acceleration and induces a sustained nystagmus similar to natural vestibular lesions [ 5, 6 ]. The MVS-induced nystagmus diminished slowly but incompletely over multiple timescales. We propose a new adaptation hypothesis, using a cascade of imperfect mathematical integrators, that reproduces the response to MVS (and more natural chair rotations), including the gradual decrease in nystagmus as the set point changes over progressively longer time courses. MVS set-point adaptation is a biological model with applications to basic neurophysiological research into all types of movements [ 7 ], functional brain imaging [ 8 ], and treatment of vestibular and higher-level attentional disorders by introducing new biases to counteract pathological ones [ 9 ]. [ABSTRACT FROM AUTHOR]

Globally, there are 3 million people living with multiple sclerosis (PLW-MS). A large proportion of PLW-MS have abnormal vestibular function tests that suggest central vestibular lesions. Yet, data regarding vestibular-ocular control in PLW-MS is limited. Thus, we aimed to further characterize compensatory saccade (CS) behavior in PLW-MS. We analyzed video head impulse data from four groups of six age- and sex-matched adults: people living with mild MS (PLW-mild-MS, people living with moderate MS (PLW-moderate-MS), people living with unilateral vestibular deafferentation (PLW-UVD), and healthy controls (HC). PLW-moderate-MS had lower lateral canal vestibulo-ocular reflex (VOR) gain bilaterally compared to PLW-mild MS (p < 0.001), HC (p < 0.001), and PLW-UVD (p < 0.001). CS frequency was higher for impulses towards the less affected side in PLW-moderate-MS versus the more (p = 0.01) and less (p < 0.001) affected sides in PLW-mild-MS. CS latency was shorter (p < 0.001) and CS peak velocity was lower (p < 0.001) with impulses towards the more affected side versus the less affected side in PLW-moderate-MS. However, CS peak velocity with impulses towards each side was similar in PLW-mild-MS (p = 0.12). Gaze position error (GPE) was larger after impulses towards the more affected side versus the less affected side in PLW-moderate-MS (p < 0.001) and PLW-mild-MS (p < 0.001). MS-related disability was moderately associated with VOR gain (p < 0.001) and GPE (p < 0.001). Additionally, we identified micro-saccades and position correcting saccades that were uniquely employed by PLW-MS as compensatory gaze stabilizing strategies. In PLW-MS, the characteristics of compensatory oculomotor behavior depend on the extent of residual VOR gain. [Display omitted] • People living with moderate multiple sclerosis often fail to generate compensatory saccades. • People living with mild multiple sclerosis tend to over-compensate for gaze position error. • The absence of saccades to compensate for low VOR gain may suggest internuclear ophthalmoplegia. [ABSTRACT FROM AUTHOR]

As part of the National Institutes of Health Toolbox initiative, we developed a low-cost, easy-to-administer, and time-efficient test of vestibular and visual function. A computerized test of dynamic visual acuity (cDVA) was used to measure the difference in visual acuity between head still and moving in yaw. Participants included 318 individuals, aged 3 to 85 years (301 without and 17 with vestibular pathology). Adults used Early Treatment of Diabetic Retinopathy Study (ETDRS) optotypes; children used ETDRS, Lea, and HOTV optotypes. Bithermal calorics, rotational chair, and light box testing were used to validate the cDVA. Analysis revealed that the cDVA test is reliable for static (intraclass correlation coefficient [ICC] >/=­ 0.64) and dynamic (ICC >/= 0.43--V0.75) visual acuity. Children younger than 6 years old were more likely to complete cDVA with Lea optotypes, but reliability and correlation with ETDRS was better using HOTV optotypes. The high correlation between static acuity and light box test scores (r = 0.795), significant difference of cDVA scores between those with and without pathology (p >/=­ 0.04), and the good to excellent sensitivity (73%) and specificity (69%) establish that the cDVA is a valid and reliable measure of visual acuity when the head is still and moving, as well as a good proxy of vestibular function to yaw rotation. [ABSTRACT FROM AUTHOR]

Effective navigation requires the ability to keep track of one's location and maintain orientation during linear and angular displacements. Path integration is the process of updating the representation of body position by integrating internally-generated self-motion signals over time (e.g., walking in the dark). One major source of input to path integration is vestibular afference. We tested patients with reduced vestibular function (unilateral vestibular hypofunction, UVH), patients with aberrant vestibular function (benign paroxysmal positional vertigo, BPPV), and healthy participants (controls) on two linear path integration tasks: experimenter-guided walking and target-directed walking. The experimenter-guided walking task revealed a systematic underestimation of self-motion signals in UVH patients compared to the other groups. However, we did not find any difference in the distance walked between the UVH group and the control group for the target-directed walking task. Results from neuropsychological testing and clinical balance measures suggest that the errors in experimenter-guided walking were not attributable to cognitive and/or balance impairments. We conclude that impairment in linear path integration in UVH patients stem from deficits in self-motion perception. Importantly, our results also suggest that patients with a UVH deficit do not lose their ability to walk accurately without vision to a memorized target location. [ABSTRACT FROM AUTHOR]

The article presents a study on the vestibular dysfunction among older people in the U.S. It is stated that balance dysfunction can be impairing and worse, it can lead to falls. With this, differences by sociodemographic characteristics, the association between vestibular dysfunction and the risk of falls were evaluated. Data indicated that 35.4% of adults aged 40 years and older had vestibular dysfunction and that the occurrence of vestibular dysfunction increased with age. It added that patients with vestibular dysfunction and who reported symptoms such as dizziness have a 12-fold increase in the odds of falling.

Background: Amongst the most challenging diagnostic dilemmas managing patients with vestibular symptoms (i.e. vertigo, nausea, imbalance) is differentiating dangerous central vestibular disorders from benign causes. Migraine has long been recognized as one of the most common causes of vestibular symptoms, but the clinical hallmarks of vestibular migraine are notoriously inconsistent and thus the diagnosis is difficult to confirm. Here we conducted a prospective study investigating the sensitivity and specificity of combining standard vestibular and neurological examinations to determine how well central vestibular disorders (CVD) were distinguishable from vestibular migraine (VM).Method: Twenty-seven symptomatic patients diagnosed with CVD and 36 symptomatic patients with VM underwent brain imaging and clinical assessments including; 1) SVV bucket test, 2) ABCD2, 3) headache/vertigo history, 4) presence of focal neurological signs, 5) nystagmus, and 6) clinical head impulse testing.Results: Mean absolute SVV deviations measured by bucket testing in CVD and VM were 4.8 ± 4.1° and 0.7 ± 1.0°, respectively. The abnormal rate of SVV deviations (> 2.3°) in CVD was significantly higher than VM (p < 0.001). Using the bucket test alone to differentiate CVD from VM, sensitivity was 74.1%, specificity 91.7%, positive likelihood ratio (LR+) 8.9, and negative likelihood ratio (LR-) 0.3. However, when we combined the SVV results with the clinical exam assessing gaze stability (nystagmus) with an abnormal focal neurological exam, the sensitivity (92.6%) and specificity (88.9%) were optimized (LR+ (8.3), LR- (0.08)).Conclusion: The SVV bucket test is a useful clinical test to distinguish CVD from VM, particularly when interpreted along with the results of a focal neurological exam and clinical exam for nystagmus. [ABSTRACT FROM AUTHOR]

Background: The use of vestibular rehabilitation principles in the management of gaze and postural stability impairments in people with multiple sclerosis (PwMS) has shown promise in pilot work completed in our lab and in a recently published randomized clinical trial (RCT). However, further work is needed to fully quantify the gaze and postural impairments present in people with multiple sclerosis and how they respond to rehabilitation.Methods/design: The study is a single blind RCT designed to examine the benefit of a gaze and postural stability (GPS) intervention program compared to a standard of care (SOC) rehabilitation program in dizzy and balance impaired PwMS. Outcomes will be collected across the domains of body structure and function, activity, and participation as classified by the World Health Organization International Classification of Functioning, Disability, and Health (ICF). Our primary outcomes are the Dizziness Handicap Inventory (DHI) and the Functional Gait Assessment (FGA). Secondary outcomes include other measures of gaze and postural stability, fatigue, and functional mobility. Participants who are interested and eligible for enrollment will be consented prior to completing a baseline assessment. Following the baseline assessment each participant will be randomized to either the GPS or SOC intervention group and will complete a 6 week treatment period. During the treatment period, both groups will participate in guided exercise 3x/week. Following the treatment period participants will be asked to return for a post-treatment evaluation and again for a follow-up assessment 1 month later. We anticipate enrolling 50 participants.Discussion: This study will be an innovative RCT that will utilize gaze and postural stability metrics to assess the efficacy of vestibular rehabilitation in PwMS. It will build on previous work by examining measures across the ICF and improve the current evidence base for treating PwMS.Trial Registration: ClinicalTrials.gov, May 29th 2018, NCT03521557 . [ABSTRACT FROM AUTHOR]