The Dynamic Illegible E-test: A Technique for Assessing the Vestibulo-ocular Reflex

Wearable sensor and smartphone assisted vestibular physical therapy for multiple sclerosis: usability and outcomes

Introduction

Vertigo, dizziness, gaze instability and disequilibrium are highly prevalent in people with MS (PwMS) and head movement induced dizziness is commonly reported. Vestibular physical therapy (VPT) is a specialised, non-invasive and effective therapy for these problems but usually involves travel for the person to a specialist center with both personal and carbon costs. The use of wearable sensors to track head movement and smartphone applications to deliver and track programs has potential to improve VPT in MS.

Methods

This study investigated the usability and effects of a commercially available digital VPT system (wearable head sensor, smartphone app and clinician software) to deliver VPT to PwMS. A pre/post treatment design was employed and the primary outcome was the System Usability Scale (SUS). Other patient reported outcomes were the Service User Acceptability Questionnaire (SUTAQ), the Patient Enablement Instrument (PEI) and the Dizziness Handicap Inventory (DHI). Physical outcomes measurements included Mini-BESTest (MB), Modified Dynamic Gait Index (mDGI), Gait Speed (GS), Dynamic Visual Acuity (DVA) and head kinematics and symptoms during exercise.

Results

Sixteen PwMS (14 female), mean age 44(±14) years were recruited to the study and twelve completed VPT. Mean adherence to exercise, measured digitally was 60% (±18.4). SUS scores were high at 81 (±14) and SUTAQ scores also demonstrated high levels of satisfaction and acceptability of the system. Statistically significant improvements in MB (mean change 2.25; p = 0.004), mDGI (median change 1.00; p = 0.008), DVA (median change -1.00; p = 0.004) were found. Head frequencies significantly improved with concurrent decreased intensity of dizziness during head movements (mean change across 4 gaze stabilization exercises was 23 beats per minute; p < 0.05). Non-significant improvements were seen in DHI (p = 0.07) and GS (p = 0.15). 64.5% of follow up visits were conducted remotely (video or phone), facilitated by the system.

Discussion

This study had two main outcomes and benefits for PwMS. Firstly, we showed that the system used was both acceptable and could be used by PwMS. Secondly, we demonstrated an improvement in a range of dizziness, balance and gait metrics with remotely delivered care. This system has the potential to positively impact on MS physiotherapy service provision with the potential to deliver effective remote care.

Validity and Responsiveness of the Portable Warrior Test of Tactical Agility After Rehabilitation in Service Members With Mild Traumatic Brain Injury

OBJECTIVE

The Portable Warrior Test of Tactical Agility (POWAR-TOTAL) is a performance-based test designed to assess active-duty service members diagnosed with mild traumatic brain injuries (mTBIs) and could potentially inform return to duty decisions. To examine the validity and responsiveness of the POWAR-TOTAL measure, this study collected self-reported and performance measures by active-duty service members before and after an episode of physical therapist care.

METHODS

Seventy-four individuals, enrolled in care for mTBI symptoms at 1 of 2 concussion specialty Intrepid Spirit Centers, were examined the week that they initiated physical therapy with the intention to return to active duty. Self-reported measures of concussion symptoms, pain, posttraumatic stress, headache, dizziness, and sleep quality were used, as were concurrent measures of mobility and balance. The POWAR-TOTAL task (motor and cognitive skills in single and dual-task conditions) was administered. Forty-nine active-duty service members returned for posttherapy testing using the same test battery. Effect sizes for change in measures were calculated. Construct validity was assessed by correlating change scores on POWAR with concurrent self-report and mobility measures. Responsiveness was evaluated using an anchor-based approach.

RESULTS

Significant improvements in self-reported and performance-based measures, including POWAR, were observed after therapy with moderate to large effect sizes. Improvement in POWAR performance correlated with improvement in both performance and self-reported measures. After therapy, individuals who registered improvement on the Patient Global Impression of Change scale demonstrated significantly faster POWAR motor performance than those who rated little or no improvement in their condition.

CONCLUSION

The POWAR-TOTAL captured improvement on a military-specific task after completing physical therapy for mTBI and could serve as an indicator of physical recovery and readiness for return to duty.

IMPACT

Challenging cognitive and motor measures for service members may aid in the assessment of recovery and the ability to successfully return to duty after concussion as part of a comprehensive examination approach.

Dynamic Visual Acuity Results in Otolith Electrical Stimulation in Bilateral Vestibular Dysfunction

(1) Background. Patients with bilateral vestibular disease (BVD) experience oscillopsia with a detriment to visual acuity (VA). This VA is driven mainly by the VOR that has two components: rotational and translational. VA can be tested by using dynamic visual acuity (DVA) on a treadmill because both systems are activated. The aim of this study is to compare VA before and after chronic electrical stimulation of the otolith organ. (2) Materials and Method. Five patients suffering from bilateral vestibular dysfunction (BVD), previously implanted with a new vestibular implant prototype, were included in this study with the aim to check VA with and without vestibular implant use (W and W/O) in static, 2 km/h and 4 km/h walking situations. DVAtreadmill was measured on a treadmill with a dynamic illegible E (DIE) test in static and dynamic conditions (while walking on the treadmill at 2 and 4 km/h). The DVA score was registered in a logarithm of the minimum angle of resolution (LogMAR) for each speed. In addition, every patient completed the oscillopsia severity questionnaire (OSQ) and video head impulse test (vHIT) before and after activation of the vestibular implant. (3) Results. The analysis shows a significant difference in OSQ scores and DVA with an improvement in dynamic conditions. Organized corrective saccades during the use of a vestibular implant with no changes in gain were also detected in the video head impulse tests (vHIT). (4) Conclusion. The vestibular implant with otolithic stimulation offers changes in the response of DVA, which makes this paper one of the first to address the possible restoration of it. It is not possible to rule out other contributing factors (presence of covert saccades, somatosensory system, …). More work seems necessary to understand the neurophysiological basis of these findings, but this implant is added as a therapeutic alternative for the improvement of oscillopsia.

Vestibulo-ocular dysfunction in mTBI: Utility of the VOMS for evaluation and management – A review

BACKGROUND: Individuals who have suffered a concussion/mild traumatic brain injury (mTBI) frequently report symptoms associated with vestibular and/or oculomotor dysfunction (VOD) like dizziness, nausea, fatigue, brain fog, headache, gait and neurocognitive impairments which are associated with the development of chronic symptoms. The Vestibular/Ocular Motor Screening (VOMS) tool has been established as a reliable and clinically relevant complement to use alongside a battery of post-concussion tests to improve screening and referral for further evaluation and treatment of VOD. OBJECTIVES: This paper will review the pathoanatomy and symptomatology of common vestibular and oculomotor disorders after concussion, as well as the utility of the VOMS to assist in diagnosis, referral, and management. METHODS: Primary articles were identified using a search via PubMed, Google Scholar, OneSearch, and CINAHL. Search key terms were combinations of “mild traumatic brain injury” or “concussion” or “pursuit” or “accommodation” or “vergence” or “convergence insufficiency” or “saccades” or “vestibulo-ocular reflex” or “vestibular ocular motor screen” or “vestibular rehabilitation”, or “vision rehabilitation” including adult and pediatric populations that were published in print or electronically from 1989 to 2021 in English. Classic papers on anatomy of eye movements, vestibular system and pathological changes in mTBI were also included, regardless of publication date. RESULTS: Objective impairments are commonly found during testing of smooth pursuit, saccades, vergence, accommodation, vestibular ocular reflex, and visual motion sensitivity after mTBI. These deficits can be actively treated with vestibular physical therapy and oculomotor/neuro-optometric vision therapy. VOMS is an efficient and reliable tool that can be used by all healthcare and rehabilitation providers to aid in diagnosis of post-concussion VOD, to help facilitate the decision to refer for further evaluation and treatment to expedite symptomatic post-concussion recovery. CONCLUSIONS: VOD is common after concussion in acute, post-acute, and chronic phases. Once areas of impairments are identified through proper assessment, clinicians can maximize recovery by referring to vestibular physical therapy and/or neuro-optometry to design a targeted treatment program to address individual deficits.

Instrumented Gait Analysis to Identify Persistent Deficits in Gait Stability in Adults With Chronic Vestibular Loss

Importance

Regaining the ability to walk safely is a high priority for adults with vestibular loss. Thus, practitioners need comprehensive knowledge of vestibulopathic gait to design, provide, and/or interpret outcomes of interventions. To date, few studies have characterized the effects of vestibular loss on gait.

Objectives

To investigate the use of an instrumented 2-minute walk test in adults with vestibular loss, to further characterize vestibulopathic gait, and to assess whether those with chronic vestibular loss have enduring gait deficits.

Design, Setting, and Participants

This cross-sectional study, conducted between April 3, 2018, and June 27, 2019, recruited adults 20 to 79 years of age from an academic, tertiary, hospital-based, ambulatory care setting who were healthy or had confirmed unilateral or bilateral vestibular hypofunction. Of the 43 adults who were screened from convenience and referred samples, 2 declined, and 7 were excluded because of health conditions.

Exposures

The main exposure was the instrumented 2-minute walk test, which was conducted with participants using wearable inertial measurement units while they walked a 10-m path at their self-selected speed and turned 180° in their self-selected direction at either end.

Main Outcomes and Measures

The primary measures were spatiotemporal gait metrics (eg, stride length [SL] and peak whole-body turning velocity). Multivariate analysis of variance was used to assess between-group differences. Validity was assessed using the area under the curve from receiver operator characteristic analyses.

Results

Data from 17 healthy adults (mean [SD] age, 39.27 [11.20] years; 13 [76%] female) and 13 adults with vestibular loss (mean [SD] age, 60.50 [10.81] years; 6 [46%] female) were analyzed. Very large between-group differences were found for SL (left) (estimated marginal mean [SE] for healthy vs vestibular groups, 1.47 [0.04] m vs 1.31 [0.04] m; Cohen d, 1.35; 95% CI, 0.18-2.52), SL (right) (estimated marginal mean [SE] for healthy vs vestibular groups, 1.46 [0.04] m vs 1.29 [0.04] m; Cohen d, 1.44; 95% CI, 0.25-2.62), and peak turn velocity (estimated marginal mean [SE] for healthy vs vestibular groups, 240.17 [12.78]°/s vs 189.74 [14.70]°/s; Cohen d, 1.23; 95% CI, 0.07-2.40). The area under the curve was 0.79 (95% CI, 0.62-0.95) for SL (left), 0.81 (95% CI, 0.64-0.97) for SL (right), and 0.86 (95% CI, 0.72-0.99) for peak turn velocity.

Conclusions and Relevance

In this cross-sectional study, instrumented gait analysis had good discriminative validity and revealed persistent deficits in gait stability in those with chronic vestibular loss. The findings of this study suggest that these clinically and functionally meaningful deficits could be targets for vestibular rehabilitation.

Clinical dynamic visual acuity in patients with cerebellar ataxia and vestibulopathy

Deterioration of dynamic visual acuity (DVA) as a result of impaired vestibulo-ocular reflex (VOR) has been well described in peripheral vestibulopathies, however, changes in DVA in patients with degenerative cerebellar ataxias (CA) and its relation to VOR impairment in these patients has not yet been evaluated. Our aim was to assess the alterations of DVA in CA and to evaluate its relation to vestibular function. 32 patients with CA and 3 control groups: 13 patients with unilateral and 13 with bilateral vestibulopathy and 21 age matched healthy volunteers were examined by clinical DVA test, VOR was assessed by video Head Impulse Test and caloric irrigation. The severity of ataxia in CA was assessed by Scale for the assessment and rating of ataxia (SARA). Relationship between DVA and vestibular function in CA patients was examined by linear regressions. DVA impairment was highly prevalent in CA patients (84%) and its severity did not differ between CA and bilateral vestibulopathy patients. The severity of DVA impairment in CA was linked mainly to VOR impairment and only marginally to the degree of ataxia. However, DVA impairment was present also in CA patients without significant vestibular lesion showing that central mechanisms such as impairment of central adaptation of VOR are involved. We suggest that the evaluation of DVA should be a standard part of clinical evaluation in patients with progressive CA, as this information can help to target vestibular and oculomotor rehabilitation.

Detection of VOR dysfunction during the gaze stabilization test: Does target size matter?

BACKGROUND

The Gaze Stabilization Test (GST) identifies vestibulo-ocular reflex (VOR) dysfunction using a decline in target recognition with increasing head velocity, but there is no consensus on target (optotype) size above static visual acuity.

OBJECTIVE

To determine the optimal initial optotype size above static visual acuity to be used during the GST in subjects with unilateral vestibular dysfunction and healthy individuals.

METHODS

Eight subjects with unilateral vestibular dysfunction (UVD) and 19 age-matched, healthy control subjects were studied with the standard GST protocol using two optotype sizes, 0.2 and 0.3 logMAR above static visual acuity (ΔlogMAR). Maximal head velocity achieved while maintaining fixation on both optotypes was measured. Sensitivity, specificity and receiver-operator characteristic area under the curve (ROC AUC) analyses were performed to determine the optimal head velocity cut off point for each optotype, based on ability to identify the lesioned side of the UVD group from the control group.

RESULTS

There was a significant difference in maximal head velocity between the UVD group and control group using 0.2 ΔlogMAR (p = 0.032) but not 0.3 ΔlogMAR (p = 0.061). While both targets produced similar specificities (90%) for distinguishing normal from subjects with UVD, 0.2 ΔlogMAR targets yielded higher sensitivity (75%) than 0.3 logMAR (63%) and accuracy (86% vs 80%, respectively) in detecting the lesioned side in subjects with UVD versus controls with maximal head velocities≤105 deg/s (p = 0.017). Furthermore, positive likelihood ratios were nearly twice as high when using 0.2 ΔlogMAR targets (+ LR 10) compared to 0.3 ΔlogMAR (+ LR 6.3).

CONCLUSION

The 0.2 ΔlogMAR optotype demonstrated significantly superior identification of subjects with UVD, better sensitivity and positive likelihood ratios than 0.3 ΔlogMAR for detection of VOR dysfunction. Using a target size 0.2logMAR above static visual acuity (ΔlogMAR) during GST may yield better detection of VOR dysfunction to serve as a baseline for gaze stabilization rehabilitation therapy.

The Gait Disorientation Test: A New Method for Screening Adults With Dizziness and Imbalance

OBJECTIVE

To develop and evaluate a new method for identifying gait disorientation due to vestibular dysfunction.

DESIGN

The gait disorientation test (GDT) involves a timed comparison of the ability to walk 6.096 m with eyes open versus eyes closed. In this prospective study, participants were grouped based on vestibular function. All participants completed a clinical examination, self-report- and performance-based measures relevant to vestibular rehabilitation, and the tasks for the GDT. Vestibular-impaired participants underwent the criterion standard, videonystagmography and/or rotational chair testing.

SETTING

Ambulatory clinic, tertiary referral center.

PARTICIPANTS

Participants (N=40) (20 vestibular-impaired, 30 women, 49.9±16.1years old) were enrolled from a convenience/referral sample of 52 adults.

MAIN OUTCOME AND MEASURE(S)

We determined test-retest reliability using the intraclass correlation coefficient model 3,1; calculated the minimal detectable change (MDC); examined concurrent validity through Spearman correlation coefficients; assessed criterion validity with the area under the curve (AUC) from receiver operator characteristic analysis; and computed the sensitivity, specificity, diagnostic odds ratio (DOR), likelihood ratios for positive (LR+) and negative (LR-) tests, and posttest probabilities of a diagnosis of vestibulopathy. The 95% confidence interval demonstrates measurement uncertainty.

RESULTS

Test-retest reliability was 0.887 (0.815, 0.932). The MDC was 3.7 seconds. Correlations with other measures ranged from 0.59 (0.34, 0.76) to -0.85 (-0.92, -0.74). The AUC was 0.910 (0.822, 0.998), using a threshold of 4.5 seconds. The sensitivity and specificity were 0.75 (0.51, 0.91) and 0.95 (0.75, 1), respectively. The DOR=57 (6, 541.47), LR+ =15 (2.18, 103.0), and LR- =0.26 (0.12, 0.9). Positive posttest probabilities were 89%-94%.

CONCLUSIONS AND RELEVANCE

The GDT has good reliability, excellent discriminative ability, strong convergent validity, and promising clinical utility.

Development of a Computerized Device for Evaluating Vestibular Function in Locomotion: A New Evaluation Tool of Vestibular Hypofunction

To evaluate vestibular function in the clinic, current assessments are applied under static conditions, such as with the subject in a sitting or supine position. Considering the complexities of daily activities, the combination of dynamic activities, dynamic visual acuity (DVA) and postural control could produce an evaluation that better reflects vestibular function in daily activities.

Objective: To develop a novel sensor-based system to investigate DVA, walking trajectory, head and trunk movements and the chest-pelvis rotation ratio during forward and backward overground walking in both healthy individuals and patients with vestibular hypofunction.

Methods: Fifteen healthy subjects and 7 patients with bilateral vestibular hypofunction (BVH) were recruited for this study. Inertial measurement units were placed on each subject's head and torso. Each subject walked forward and backward for 5 m twice with 2 Hz head yaw. Our experiment comprised 2 stages. In stage 1, we measured forward (FW), backward (BW), and medial-lateral (MLW) walking trajectories; head and trunk movements; and the chest-pelvis rotation ratio. In stage 2, we measured standing and locomotion DVA (loDVA). Using Mann–Whitney U-test, we compared the abovementioned parameters between the 2 groups.

Results: Patients exhibited an in-phase chest/pelvis reciprocal rotation ratio only in FW. The walking trajectory deviation, calculated by normalizing the summation of medial-lateral swaying with 1/2 body height (%), was significantly larger (FW mean ± standard deviation: 20.4 ± 7.1% (median (M)/interquartile range (IQR): 19.3/14.4–25.2)in healthy vs. 43.9 ± 27. 3% (M/IQR: 36.9/21.3–56.9) in patients, p = 0.020)/(BW mean ± standard deviation: 19.2 ± 11.5% (M/IQR: 13.6/10.4–25.3) in healthy vs. 29.3 ± 6.4% (M/IQR: 27.7/26.5–34.4) in patients, p = 0.026), and the walking DVA was also significantly higher (LogMAR score in the patient group [FW LogMAR: rightDVA: mean ± standard deviation:0.127 ± 0.081 (M/IQR: 0.127/0.036–0.159) in healthy vs. 0.243 ± 0.101 (M/IQR: 0.247/0.143–0.337) in patients (p = 0.013) and leftDVA: 0.136 ± 0.096 (M/IQR: 0.127/0.036–0.176) in healthy vs. 0.258 ± 0.092 (M/IQR: 0.247/0.176–0.301) in patients (p = 0.016); BW LogMAR: rightDVA: mean ± standard deviation: 0.162 ± 0.097 (M/IQR: 0.159/0.097–0.273) in healthy vs. 0.281 ± 0.130 (M/IQR: 0.273/0.176–0.418) in patients(p = 0.047) and leftDVA: 0.156 ± 0.101 (M/IQR: 0.159/0.097–0.198) in healthy vs. 0.298 ± 0.153 (M/IQR: 0.2730/0.159–0.484) in patients (p = 0.038)].

Conclusions: Our sensor-based vestibular evaluation system provided a more functionally relevant assessment for the identification of BVH patients.

Considerations for Diagnosis and Management of Concussion

Concussion is an ongoing concern for health care providers. The incidence rates continue to be high and the rate of recovery is variable due to potential risk factors. With no valid biomarkers, diagnosis and assessment of concussion remain a clinical challenge. The heterogeneity in presentation following injury provides an additional level of complexity, requiring the screening and evaluation of diverse body systems, including oculomotor, vestibular, autonomic, psychiatric, cervical, and cognitive symptoms. While a few tools, such as the Vestibular/Ocular Motor Screening and Balance Error Scoring System, have been developed specifically for concussion, the vast majority of tests are adapted from other conditions. Further complicating the process is the overlapping and interactive nature of the multiple domains of postconcussion presentation. This commentary illustrates how clinicians can conceptualize the multiple profiles that present following concussion and describes tools that are available to assist with screening and evaluation of each area. The multifaceted nature of concussion warrants broad clinical screening skills and an interdisciplinary approach to management. J Orthop Sports Phys Ther 2019;49(11):787-798. doi:10.2519/jospt.2019.8855.

Vestibulo-Ocular Responses and Dynamic Visual Acuity During Horizontal Rotation and Translation

Dynamic visual acuity (DVA) provides an overall functional measure of visual stabilization performance that depends on the vestibulo-ocular reflex (VOR), but also on other processes, including catch-up saccades and likely visual motion processing. Capturing the efficiency of gaze stabilization against head movement as a whole, it is potentially valuable in the clinical context where assessment of overall patient performance provides an important indication of factors impacting patient participation and quality of life. DVA during head rotation (rDVA) has been assessed previously, but to our knowledge, DVA during horizontal translation (tDVA) has not been measured. tDVA can provide a valuable measure of how otolith, rather than canal, function impacts visual acuity. In addition, comparison of DVA during rotation and translation can shed light on whether common factors are limiting DVA performance in both cases. We therefore measured and compared DVA during both passive head rotations (head impulse test) and translations in the same set of healthy subjects (n = 7). In addition to DVA, we computed average VOR gain and retinal slip within and across subjects. We observed that during translation, VOR gain was reduced (VOR during rotation, mean ± SD: position gain = 1.05 ± 0.04, velocity gain = 0.97 ± 0.07; VOR during translation, mean ± SD: position gain = 0.21 ± 0.08, velocity gain = 0.51 ± 0.16), retinal slip was increased, and tDVA was worse than during rotation (average rDVA = 0.32 ± 0.15 logMAR; average tDVA = 0.56 ± 0.09 logMAR, p = 0.02). This suggests that reduced VOR gain leads to worse tDVA, as expected. We conclude with speculation about non-oculomotor factors that could vary across individuals and affect performance similarly during both rotation and translation.

Rehabilitation of an Adolescent Equestrian Athlete With a History of Multiple Concussions: A Case Report Describing an Adapted Return-to-Sport Protocol

BACKGROUND

Equestrian riding is a sport with a high risk of concussion. Currently, the literature guiding rehabilitation for concussions in equestrian athletes is limited, especially for directing return to sport.

CASE DESCRIPTION

In this case report, a 14-year-old female equestrian athlete presented to physical therapy following her third concussion in 3 years. Her primary complaints were headaches, dizziness, difficulty concentrating, light sensitivity, and neck pain. On examination, the patient demonstrated reproduction of symptoms during testing of the vestibular-ocular reflex, showed a 3-line symptomatic loss on the dynamic visual acuity test, and had impairments in the joint position error test (1/5 correct on the left, 4/5 correct on the right) and a Balance Error Scoring System (BESS) score of 38/60 errors. A return-to-riding protocol was adapted from general return-to-sport guidelines and tailored to meet the unique demands of the patient's equestrian sport. The protocol included phased progression through no activity, light aerobic activity, moderate aerobic activity, sport-specific nonjumping skills, sport-specific jumping skills, full practice, and return to competition. During the protocol, the patient participated in 8 physical therapy sessions over 4 weeks for vestibular training, aerobic conditioning, and cervical and core exercises, as well as equestrian exercises at her stables.

OUTCOMES

At the final evaluation, the patient reported no symptoms at rest, with exercise, or when testing vestibular-ocular reflex. Improvements were noted in the dynamic visual acuity test, joint position error, and BESS, with changes in the BESS exceeding minimal detectable change. The patient completed the full return-to-riding protocol in 8 weeks and was able to return to equestrian competition without complaints.

DISCUSSION

This case report describes the physical therapy management of an adapted return-to-sport protocol for an equestrian athlete with a history of multiple sport-related concussions.

LEVEL OF EVIDENCE

Therapy, level 5. J Orthop Sports Phys Ther 2018;48(12):934-942. Epub 27 Jul 2018. doi:10.2519/jospt.2018.8214.

A speed-based approach to vestibular rehabilitation for peripheral vestibular hypofunction: A retrospective chart review

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Assessment of vestibulo-ocular function without measuring eye movements

BACKGROUND

The vestibulo-ocular reflex (VOR) maintains stable gaze during head motion. Deficiencies lead to apparent world motion due to incomplete stabilization of eyes in space. VOR measurement requires specialized apparatus, trained operators, and significant setup time.

NEW METHOD

We present a system (VON: vestibulo-ocular nulling) for rapid vestibulo-ocular assessment without measuring eye movements per se. VON uses a head-mounted motion sensor, laptop computer with user input control, and laser target whose position is controlled by the computer. As the head moves, the target is made to move in the same manner with a gain set by the subject. When the subject sets the gain so the target appears stationary in space, it is stationary on the retinas. One can determine from this gain the extent to which the eyes move in space when the head moves, which is the amount by which the VOR is deficient. From this the gain of the compensatory eye movements is derived.

RESULTS

VON was compared with conventional video-based VOR measures. Both methods track expected changes in gain over 20min of adaptation to minifying spectacles. VON measures are more consistent across subjects, and pre-adaptation values are closer to compensatory.

COMPARISON WITH EXISTING METHOD

VON is a rapid means to assess vestibulo-ocular performance. As a functional perceptual measure, it accounts for gaze-stabilizing contributions that are not apparent in the standard VOR, such as pursuit and perceptual tolerance.

CONCLUSIONS

VON assesses functional VOR performance. Future implementations will make VOR assessment widely available to investigators and clinicians.

Comparison of the gaze stabilization test and the dynamic visual acuity test in unilateral vestibular loss patients and controls

OBJECTIVE

Compare the dynamic visual acuity test (DVAT) and gaze stabilization test (GST) in patients with unilateral vestibular loss (UVL) and healthy control subjects using a novel computerized testing system prototype.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary academic referral laboratory.

PATIENTS

Seventeen UVL patients (median age 62 yr) with bithermal caloric asymmetry (≥49%) or ablative surgery and 17 control subjects (median age 57 yr).

INTERVENTION(S)

Diagnostic.

MAIN OUTCOME MEASURE(S)

Comparison of DVAT and GST results during self-generated sinusoidal head movements using transient unpredictable target presentations less than 95 milliseconds in duration.

RESULTS

UVL patients had significantly higher DVAT scores toward the lesioned side compared with controls (p = 0.001) and the non-lesioned side (p = 0.003), but the non-lesioned side was not significantly different from controls (p = 0.157). When comparing GST scores, UVL patients required a slower head velocity to maintain visual acuity with movement toward the lesioned side compared with controls (p < 0.001) and the non-lesioned side (p = 0.004). In addition, UVL patients had significantly lower scores toward the non-lesioned side (p = 0.002) compared to controls. ROC curve analysis identified optimal thresholds for abnormal test results to discriminate the lesioned side from controls. A DVAT score greater than or equal to 0.3 ΔlogMAR provided 65% sensitivity and 88% specificity while a GST score less than or equal to 95 degrees/s provided 71% sensitivity and 100% specificity. When GST results were normal, adding DVAT increased overall sensitivity to 88% with 88% specificity.

CONCLUSIONS

Both GST and DVAT demonstrated reduced gaze stabilization toward the lesioned side in the patient group compared with normal controls. Performing GST first and utilizing DVAT when GST was normal provides optimal identification of patients with vestibular dysfunction.

The effect of vestibulo-ocular reflex deficits and covert saccades on dynamic vision in opioid-induced vestibular dysfunction

Patients with bilateral vestibular dysfunction cannot fully compensate passive head rotations with eye movements, and experience disturbing oscillopsia. To compensate for the deficient vestibulo-ocular reflex (VOR), they have to rely on re-fixation saccades. Some can trigger “covert” saccades while the head still moves; others only initiate saccades afterwards. Due to their shorter latency, it has been hypothesized that covert saccades are particularly beneficial to improve dynamic visual acuity, reducing oscillopsia. Here, we investigate the combined effect of covert saccades and the VOR on clear vision, using the Head Impulse Testing Device – Functional Test (HITD-FT), which quantifies reading ability during passive high-acceleration head movements. To reversibly decrease VOR function, fourteen healthy men (median age 26 years, range 21–31) were continuously administrated the opioid remifentanil intravenously (0.15 µg/kg/min). VOR gain was assessed with the video head-impulse test, functional performance (i.e. reading) with the HITD-FT. Before opioid application, VOR and dynamic reading were intact (head-impulse gain: 0.87±0.08, mean±SD; HITD-FT rate of correct answers: 90±9%). Remifentanil induced impairment in dynamic reading (HITD-FT 26±15%) in 12/14 subjects, with transient bilateral vestibular dysfunction (head-impulse gain 0.63±0.19). HITD-FT score correlated with head-impulse gain (R = 0.63, p = 0.03) and with gain difference (before/with remifentanil, R = −0.64, p = 0.02). One subject had a non-pathological head-impulse gain (0.82±0.03) and a high HITD-FT score (92%). One subject triggered covert saccades in 60% of the head movements and could read during passive head movements (HITD-FT 93%) despite a pathological head-impulse gain (0.59±0.03) whereas none of the 12 subjects without covert saccades reached such high performance. In summary, early catch-up saccades may improve dynamic visual function. HITD-FT is an appropriate method to assess the combined gaze stabilization effect of both VOR and covert saccades (overall dynamic vision), e.g., to document performance and progress during vestibular rehabilitation.

Altered vision during motion: an unusual symptom of cerebellar dysfunction, quantifiable by a simple clinical test

PURPOSE

To report a series of patients with cerebellar dysfunction and altered vision during motion, and to quantify their visual impairment in motion with a simple clinical test.

METHODS

Twenty consecutive patients suffering from cerebellar dysfunction and altered vision during motion were examined between 1994 and 2007. A control group consisted of 20 age- and sex-matched healthy people. All patients had a full neuro-ophthalmic examination. Near visual acuity (NVA) was measured at rest (static NVA) and during chair rotation (dynamic NVA). Distance visual acuity (DVA) was measured at rest (static DVA) and during rotation of the patient's head (dynamic DVA).

RESULTS

Only four of the 20 patients reported altered vision during motion spontaneously. The remaining 16 patients admitted this unusual visual disturbance only when asked specifically. All patients exhibited abnormal eye movements, including saccadic smooth pursuit (20/20), dysmetric saccades (15/20), nystagmus (19/20) and impaired suppression of vestibulo-ocular reflex (VOR) (20/20). During rotation of the examination chair (dynamic NVA), the drop in NVA averaged 5.6 lines (range 1-10 lines). During rotation of the patient's head (dynamic DVA), the drop in DVA averaged only 2.5 lines (range 0-10 lines). For the control group, there was no significant drop in NVA under dynamic conditions.

CONCLUSION

Patients with cerebellar dysfunction rarely complain spontaneously of altered vision during motion. However, specific questioning may bring up this unusual symptom. The use of a simple clinical test, consisting of NVA measurement during rotation of the examination chair (dynamic NVA), allows practitioners to quantify the level of visual impairment in patients presenting altered VOR modulation.

The effects of habituation and gaze stability exercises in the treatment of unilateral vestibular hypofunction: a preliminary results

BACKGROUND AND PURPOSE

The efficacy of both habituation and adaptation exercise interventions in the treatment of unilateral vestibular hypofunction has been demonstrated by previous studies. The purpose of this article is to describe the preliminary results of an ongoing study that compares the effects of these 2 different exercise approaches on outcomes related to vestibular function.

METHODS

Seven participants with unilateral vestibular hypofunction completed a 6-week exercise intervention after random assignment to either habituation exercises or gaze stability (GS) adaptation exercises. The following measures were performed pre- and posttreatment: Dizziness Handicap Inventory to measure the symptom impact, motion sensitivity quotient (MSQ) to assess sensitivity to head movements, and the dynamic visual acuity (DVA) test as a measure of GS during head movements.

RESULTS

After the 6-week intervention, there was an overall improvement in the Dizziness Handicap Inventory, the MSQ score, and both the active and passive DVA. The habituation and GS intervention group participants each demonstrated similar improvements in both the MSQ score and the active and passive DVA measures.

DISCUSSION AND CONCLUSIONS

The improvement in the MSQ score for the GS group and the improvement in the DVA measures for the habituation group were unexpected findings. Head movement, which is required by both exercise interventions, rather than the specific type of exercise may be the critical factor underlying the observed improvements in motion sensitivity and DVA.

Clinical evaluation of dynamic visual acuity in subjects with unilateral vestibular hypofunction

OBJECTIVES

The objectives of this study are threefold: 1) to examine the effect of frequency of head motion on the clinical dynamic visual acuity (DVA) score in subjects with unilateral vestibular hypofunction (UVH); 2) to compare DVA scores between subjects with UVH and subjects with a complete unilateral vestibular deficit; and 3) to establish whether a relationship exists between the extent of the vestibular deficit and the DVA score.

DESIGN

Experimental study.

SETTING

Vestibular outpatient rehabilitation program.

METHODS

A convenience sample of 10 subjects with UVH.

MAIN OUTCOME MEASURES

Dynamic visual acuity scores were recorded using 2 standard acuity charts: Snellen and E-chart. The DVA scores were obtained at slow (0.5 Hz), moderate (1 and 1.5 Hz), and fast (2.0 Hz) frequencies of head motion in the horizontal and the vertical planes. Percentage of caloric weakness was compared with DVA scores in each subject to test whether a relationship exists between the two.

RESULTS

As the frequency of head motion increased, the number of UVH subjects with an abnormal DVA score increased. Subjects with an abnormal DVA score at 1 Hz had the same or higher score as the frequency of the head motion was increased. Spearman correlation analyses revealed low-correlation coefficients between percentage of vestibular paresis at the caloric test and DVA scores (horizontal direction: r = 0.31, p = 0.38 for Snellen chart and r = -0.33, p = 0.35 for the E-chart; vertical: r = 0.05, p = 0.91 for the Snellen chart and r = -0.28, p = 0.50 for the E-chart).

CONCLUSION

Subjects with UVH manifest impaired DVA. The frequency of head motion has an impact on clinical DVA scores in UVH subjects.

Aminoglycoside-Induced Vestibular Injury: Maintaining a Sense of Balance

Objective

To describe the mechanism and risk factors for the development of aminoglycoside-induced vestibular injury and discuss their implications for therapeutic monitoring of aminoglycoside antibiotics.

Data Sources:

A MEDLINE search (1975–January 2008) was performed to identify literature on aminoglycoside-induced vestibular injury and risk factors associated with this outcome and their impact on therapeutic drug monitoring. Additional references were identified through review of bibliographies of identified articles.

Study Selection And Data Extraction:

Data on the mechanisms of vestibular toxicity and its development in association with aminoglycoside exposure were extracted from identified references.

Data Synthesis:

The mechanism leading to the development of irreversible vestibular injury from exposure to aminoglycosides appears to be through the excessive production of oxidative free radicals. This production and subsequent toxicity appears to be a time-dependent process and is unrelated to dose or serum concentration. For similarly designed studies, the pooled incidence of vestibular toxicity is 10.9% for gentamicin, 7.4% for amikacin, 3.5% for tobramycin, and 1.1% for netilmicin. Current evidence suggests that this form of drug toxicity is not restricted to traditionally dosed systemic therapy, since intraperitoneal administration, high-dose once-daily administration, topical inhalation, and eardrop administration have all been associated with the development of this adverse outcome.

Conclusions:

Given the lack of association between serum concentrations and vestibulotoxicity, it is imperative for the pharmacist to interview the patient and not focus solely on maintaining target range drug concentrations. Minimizing the duration of exposure to aminoglycosides is recommended to reduce the risk from this form of drug toxicity.

Pairing virtual reality with dynamic posturography serves to differentiate between patients experiencing visual vertigo

Background

To determine if increased visual dependence can be quantified through its impact on automatic postural responses, we have measured the combined effect on the latencies and magnitudes of postural response kinematics of transient optic flow in the pitch plane with platform rotations and translations.

Methods

Six healthy (29–31 yrs) and 4 visually sensitive (27–57 yrs) subjects stood on a platform rotated (6 deg of dorsiflexion at 30 deg/sec) or translated (5 cm at 5 deg/sec) for 200 msec. Subjects either had eyes closed or viewed an immersive, stereo, wide field of view virtual environment (scene) moved in upward pitch for a 200 msec period for three 30 sec trials at 5 velocities. RMS values and peak velocities of head, trunk, and head with respect to trunk were calculated. EMG responses of 6 trunk and lower limb muscles were collected and latencies and magnitudes of responses determined.

Results

No effect of visual velocity was observed in EMG response latencies and magnitudes. Healthy subjects exhibited significant effects (p < 0.05) of visual field velocity on peak angular velocities of the head. Head and trunk velocities and RMS values of visually sensitive subjects were significantly larger than healthy subjects (p < 0.05), but their responses were not modulated by visual field velocity. When examined individually, patients with no history of vestibular disorder demonstrated exceedingly large head velocities; patients with a history of vestibular disorder exhibited head velocities that fell within the bandwidth of healthy subjects.

Conclusion

Differentiation of postural kinematics in visually sensitive subjects when exposed to the combined perturbations suggests that virtual reality technology could be useful for differential diagnosis and specifically designed interventions for individuals whose chief complaint is sensitivity to visual motion.

Gaze stabilization test: a new clinical test of unilateral vestibular dysfunction

OBJECTIVE

Evaluate the sensitivity, specificity, and reliability of the Gaze Stabilization Test (GST) for detection of unilateral vestibular dysfunction.

STUDY DESIGN

Prospective controlled clinical trial.

SETTING

Tertiary academic referral laboratory.

PATIENTS

Fourteen patients (mean age, 63.8 yr; range, 43-77 yr) with history of vertigo and greater than 50% bithermal caloric asymmetry; 14 control subjects (mean age, 45.8 yr; range, 23-78 yr).

INTERVENTION(S)

Diagnostic test protocol with computerized system of target presentation and head velocity monitoring.

MAIN OUTCOME MEASURE(S)

Comparison of peak head velocity with ipsilesional and contralesional head movement-allowing gaze stability by randomly presenting transient (75 ms) targets of three optotypes above static acuity in patients and healthy subjects during self-generated headshake movements.

RESULTS

GST demonstrated 93% specificity, 64% sensitivity, and a reliability index of 0.91 for the detection of unilateral dysfunction with ipsilesional movement. Peak head velocity in healthy subjects averaged 147 degrees per second, whereas ipsilesional velocities dropped significantly to an average of 84 degrees per second. Surprisingly, peak velocities were also significantly reduced to an average of 112 degrees per second with contralesional movements.

CONCLUSION

GST is a reliable specific test of gaze stability which has diagnostic and rehabilitative applications in patients with vestibular dysfunction. Reduced contralesional velocities may help explain oscillopsia in patients with unilateral dysfunction.

Computerized dynamic visual acuity with volitional head movement in patients with vestibular dysfunction

OBJECTIVES

Patients with uncompensated vestibular dysfunction frequently report blurred vision during head movement, a symptom termed oscillopsia. One way to measure the functional deficit associated with an impaired vestibulo-ocular reflex is by comparing visual acuity from a baseline condition in which there is no head movement to visual acuity obtained during a dynamic condition with head movement. A previously described test incorporated a treadmill upon which patients walked during assessment of visual acuity. The objective of the current investigation was to evaluate an alternative method of assessing dynamic visual acuity that uses volitional head movement instead of walking on a treadmill.

METHODS

Fifteen participants with normal vestibular function and 16 participants with impaired vestibular function were enrolled. All participants performed the visual acuity task under baseline conditions with no movement and also under dynamic conditions that included 1) walking on a treadmill and 2) volitionally moving their head in the vertical plane.

RESULTS

No difference in performance was observed between the treadmill task and the volitional head movement task. Participants with impaired vestibular function performed more poorly under the dynamic conditions than did participants with normal vestibular function.

CONCLUSIONS

The results suggest that the volitional head movement paradigm may be useful in identification of patients with functional deficits of the vestibulo-ocular reflex.

Radiation-induced oscillopsia in nasopharyngeal carcinoma patients

PURPOSE

To apply a battery of audiovestibular function tests and magnetic resonance imaging (MRI) to investigate the causes of oscillopsia in nasopharyngeal carcinoma (NPC) patients after irradiation (RT).

METHODS AND MATERIALS

Of 300 NPC patients, 12 (4%) developed oscillopsia after RT. The mean accumulated radiation dose to the nasopharynx was 112 +/- 30 Gy. Each patient underwent a battery of audiovestibular function tests, including audiometry and the dynamic illegible E, caloric, and rotational tests.

RESULTS

Excluding 3 patients with neck fibrosis who could not perform the head turning movement, the remaining 9 patients displayed 100% abnormal dynamic illegible E test results and 100% abnormal refixation saccades. All 12 patients presented with bilateral hearing loss, caloric reductions, and reduced gains of the vestibular ocular reflex (VOR) on the rotational test, indicating bilateral VOR loss. After excluding tumor relapse and radiation necrosis of the brain by MRI, the oscillopsia in these 12 irradiated NPC patients was attributed to bilateral VOR loss.

CONCLUSION

Radiation-induced oscillopsia in our NPC patients was attributed to bilateral VOR loss, possibly as a result of higher radiation doses. Hence, the therapeutic benefits of a second course of RT are associated with the potential risk of oscillopsia after RT.

Using immersive technology for postural research and rehabilitation

Posture has traditionally been examined by isolating individual control pathways to determine their specific contributions. However, if these pathways are responsive to functional contexts, then their responses may differ when the system is receiving simultaneous inputs from multiple pathways. Thus, we may never fully understand how the central nervous system (CNS) organizes behaviors in the real world from studies conducted in the minimized environment of the laboratory. The consequence of this is that when findings from the laboratory are applied to therapeutic intervention, the intervention may not be appropriate for all circumstances and will not fully meet the needs of the patient. We have united an immersive dynamic virtual environment with motion of a posture platform to record the biomechanical and physiological responses to combined visual, vestibular, and proprioceptive inputs. The virtual environment possesses content, contrast, and texture so that we can examine postural responses as they might occur in a complex, real-world environment. In this paper we specifically describe the factors guiding our choices of virtual technology and present data from young adults, elderly adults, and an individual with bilateral labyrinthine loss to demonstrate how multimodal inputs influence their postural response organization. Significant implications for future experimental and rehabilitation protocols are also discussed.

Outcomes after rehabilitation for adults with balance dysfunction

OBJECTIVES

To assess balance, dynamic gait, and dynamic visual acuity outcomes after a vestibular and balance rehabilitation program and to determine which variables were significantly associated with improved balance and ambulation.

DESIGN

Retrospective case series.

SETTING

Outpatient setting at a tertiary care facility.

PARTICIPANTS

Twenty patients who were seen for vestibular and balance therapy between July 1999 and June 2000.

INTERVENTIONS

A customized exercise program was developed for each patient according to the results of the assessment and included the following interventions, as indicated: gaze stabilization, balance and gait training, and habituation exercises.

MAIN OUTCOME MEASURES

The Dynamic Gait Index (DGI), Berg Balance Scale (BBS), Dynamic Visual Acuity Test (DVAT), and computerized post urography (Sensory Organization Test [SOT]).

RESULTS

The mean change scores for the DGI showed significant improvement for both patients with peripheral vestibular dysfunction and patients with central balance disorders. For the central balance disorders group, the BBS score also showed significant improvement. No difference was noted for pretherapy and posttherapy SOT scores between groups. The total group appeared to show an average improvement of more than 2 lines on the visual acuity chart on the clinical DVAT. Patients who were 66 years or older were 1.5 times more likely to score less than 20 on the DGI, and those whose pretherapy vertical dynamic visual acuity was 20/80 or worse were 1.3 times more likely to score less than 20 on the DGI.

CONCLUSIONS

Patients showed functional improvements in balance, visual acuity, and gait stability after balance and vestibular physical therapy. Age and pretherapy vertical dynamic visual acuity score influenced dynamic gait outcome after a balance rehabilitation program.

A clinical test of dynamic visual acuity for children

OBJECTIVE

Children with sensorineural hearing impairment (SNHI) and concomitant vestibular hypofunction demonstrate deficits in gaze stability that may affect reading. The objective of this study was to develop a reliable, valid clinical test of dynamic visual acuity (DVA) for children.

METHODS

Seventy-six typically developing children, 26 adults and 11 children with sensorineural hearing impairment participated. Visual acuity was tested under three conditions: (1) head stable (static acuity), (2) head tipped forward 30 degrees and passively rotated 30 degrees in the yaw plane at 2 Hz (horizontal dynamic acuity) and (3) head passively moved in the pitch plane 30 degrees at 2 Hz (vertical dynamic acuity, vDVA). The difference, in number of chart lines, between static dynamic acuity was calculated (dynamic acuity score). Based on normative data collected, results were scored as: (1) pass < or =2S.D. from the normative mean and (2) fail > or =2S.D. from normative mean. Children were grouped by age to enable examination of the effect of age on scores.

RESULTS

We found excellent test-retest and inter-tester reliability (ICC(2,2)=0.94 and ICC(3,2)=0.84) for the horizontal dynamic acuity (hDVA) test. Sensitivity, specificity, positive and negative predictive values were 100% to identify children with bilateral vestibular hypofunction (BVH). Although a statistical difference was found, the difference was not clinically significant (all achieved DVA scores <2 lines). The vertical dynamic acuity test was not tolerated by most children, precluding its usefulness.

CONCLUSIONS

The clinical test of horizontal dynamic acuity is a reliable test for children as young as 3 years. It is simple and inexpensive, and will enable identification of those for whom more extensive testing is warranted.

Head-trunk coordination during linear anterior-posterior translations

The purpose of this study was to evaluate the relative contributions of inputs from the vestibular system and the trunk to head-trunk coordination. Twelve healthy adults and 6 adults with diminished bilateral labyrinthine input (LD) were seated with their trunk either fixed to the seat or free to move. Subjects received 10-cm, 445-cm/s(2) anterior-posterior ramps and 0.35- to 4.05-Hz sum-of-sines translations while performing a mental distraction task in the dark. Kinematics of the head and trunk were derived from an Optotrak motion analysis system and a linear accelerometer placed on the head. EMG signals were collected from neck and paraspinal muscles. Data were tested for significance with multivariate ANOVA (MANOVA) and Bonferroni post hoc analyses. Initial linear and angular head acceleration directions differed in healthy subjects when the trunk was fixed or free, but did not differ in LD subjects. Peak head angular accelerations were significantly greater with the trunk fixed than when free, and were greater in LD than in control subjects. EMG response latencies did not differ when the trunk was fixed or free. Low-frequency phase responses in the healthy subjects were close to 90 degrees and had a delayed descent as frequency increased, suggesting some neural compensation that was absent in the LD subjects. Results of this study revealed a strong initial reliance on system mechanics and on signals from segmental receptors. The vestibular system may act to damp later response components and to monitor the position of the head in space secondary to feedback from segmental proprioceptors rather than to generate the postural reactions.

Idiopathic Bilateral Vestibular Loss

We describe the clinical and laboratory features of 13 patients with bilateral loss of peripheral vestibular sensitivity of no known cause. In the office, screening for this condition was possible using illegible e-testing and examination of the patient for refixation saccades after brisk head movements while attempting visual fixation. Diagnosis was confirmed by bilaterally reduced caloric responses (<20 degrees/second on all 4 caloric irrigations) and abnormally low gain of the vestibulo-ocular reflex on rotational chair testing. The mean age of the patients was 68 years. We noted two patterns of symptom onset: onset associated with vertigo (10 patients) and insidious progressive disequilibrium not associated with vertigo (3 patients). Only 38 % of the patients complained of subjective oscillopsia. The subjects performed poorly on platform posturography, particularly when deprived of visual and somatosensory feedback. When associated with vertigo, bilateral vestibular loss may be the result of bilateral sequential vestibular neuritis; when not associated with vertigo, disequilibrium may be caused by slow, symmetrical loss of peripheral function as a result of aging. Although the subjects in this report were elderly, idiopathic bilateral vestibular loss has been reported in patients of all ages.