The limits of stability in patients with Ménière's disease

Limits of Stability during a Therapeutic Exercise Intervention for Instability: Progression, Responders' and Non-Responders' Analysis and Predictors

Background/Objectives: Instability is one of the main symptoms in patients with vestibular and neurological disorders and therapeutic exercise interventions are increasing in popularity as a form of treatment. Additionally, the limits of stability measurement are known to be a good tool for balance evaluation and monitoring of these interventions. The aim of this work is to better understand how a specific protocol provokes changes on this variable and to study the characteristics of those who do and do not respond to it. Methods: A retrospective study was developed with the data of 40 patients treated in the Otorhinolaryngology department in Clínica Universidad de Navarra (Madrid, Spain). They had an initial reduction in limits of stability, completed the proposed protocol with home-based and hospital-based exercises and with frequent limits of stability remeasurement, and were assisted to a follow-up retest after 1-2 months. Results: A progressive improvement in limits of stability measure was developed through the intervention and was partially retained at follow-up visit. Several differences were found between those patients who improved with the treatment (responders) and those who did not improve (non-responders). More specifically an initial measure of the limits of stability was able to differentiate those groups with a cut-off data of 56 cm2. Conclusions: The proposed protocol was able to induce motor learning in patients included in this study with good retention after 1-2 months. Furthermore, there is some variability in how patients respond to the treatment. Age and diagnosis should be considered and an interesting cut-off data for clinal decision making was found.

A new paradigm for assessing postural stability

BACKGROUND

The sensory organization test (SOT) is an established and effective method for assessing postural stability and determining fall risk. SOT equilibrium scores are derived from the relationship between an individual's peak sway amplitude and a standard, theoretically-derived normal limits of stability (tLOS). Determining an individual's postural stability and fall risk based on this one-size-fits-all tLOS may overestimate functional equilibrium scores and underestimate fall risk when personal stability limits (pLOS) are reduced.

RESEARCH QUESTION

The purpose of this study is to investigate whether LOS measured from a group of healthy adults is different from the tLOS, and whether SOT equilibrium scores are significantly different when calculated using pLOS versus the standard tLOS.

METHODS

Sixty healthy volunteers were recruited into three age-groups: young (18-39), middle-aged (40-64), and elderly (65-80), with 10 males and 10 females in each age-group. Outcome measures included SOT and LOS. Additional measures o balance perception and functional mobility were obtained including the Activities Balance Confidence (ABC) scale and the timed-up-and-go test (TUG). The tLOS and pLOS were used to calculate standard (tSOT) and personalized (pSOT) equilibrium scores.

RESULTS

The mean pLOS from the group of healthy adults was significantly lower than the tLOS. Consequently, the pSOT equilibrium scores were significantly lower than the standard SOT scores derived using the tLOS.

SIGNIFICANCE

Individual measures of LOS are significantly lower than theoretical estimates of the LOS in healthy adults. This suggests that use of tLOS in the calculation of SOT equilibrium scores often overestimates postural stability and may have implications for the determination of fall risk.

Falls Among People With Bilateral Vestibulopathy: A Review of Causes, Incidence, Injuries, and Methods

Importance

People with bilateral vestibulopathy experience severe balance and mobility issues. Fear and anxiety are associated with reduced activity, which can further affect balance and fall risk. Understanding and intervening on falls in this population is essential. The aims of this narrative review are to provide an overview of the current knowledge and applied methods on fall incidence, causes, and injuries in bilateral vestibulopathy.

Observations

Eleven articles reporting falls incidence in people with bilateral vestibulopathy were deemed eligible, including 3 prospective and 8 retrospective studies, with a total of 359 participants, of whom 149 (42%) fell during the assessed period. When reported, the most common perceived causes of falls were loss of balance, darkness, and uneven ground. Information on sustained injuries was limited, with bruises and scrapes being the most common, and only 4 fractures were reported. As most studies included falls as a secondary, descriptive outcome measure, fall data obtained using best practice guidelines were lacking. Only 6 studies reported their definition of a fall, of which 2 studies explicitly reported the way participants were asked about their fall status. Only 3 studies performed a prospective daily fall assessment using monthly fall diaries (a recommended practice), whereas the remaining studies retrospectively collected fall-related data through questionnaires or interviews. While most studies reported the number of people who did and did not fall, the number of total falls in individual studies was lacking.

Conclusions and Relevance

The findings from this review suggest that falls in people with bilateral vestibulopathy are common but remain an understudied consequence of the disease. Larger prospective studies that follow best practice guidelines for fall data collection with the aim of obtaining and reporting fall data are required to improve current fall risk assessments and interventions in bilateral vestibulopathy.

Menière's disease patients improve specific posturographic parameters following diagnostic intratympanic injection

PURPOSE

Evaluation of specific computerized posturographic parameters in patients with Menière's disease (MD) following the intratympanic injection of gadolinium, a contrast agent, used in radiological diagnosing.

MATERIALS AND METHODS

We have observed 12 adult patients with unilateral Menière's Disease subjected to inner ear magnetic resonance imaging (MRI) examination after intratympanic gadolinium injection (ITG). The diagnoses have been performed according to the guidelines of the American Academy of otolaryngology. Before and after 24 h the ITG, all patients were subjected to the clinical evaluation and computerized posturography (CP), in 4 conditions depending on open/closed eyes and with/without foam cushion under feet.

RESULTS

After ITG, in the affected ear the MRI confirmed the endolymphatic hydrops revealing a thin or even disappeared perilymphatic space. The statokinesigram showed improvement of stability only with closed eyes on a foam cushion. The CP performed 24 h after the contrast intratympanic injection showed a significant reduction of Path Length and Confidence Ellipse Area, due to an improvement of vestibular function on static balance. This improvement could be directly dependent to intratympanic pressure modification mediated by volume of contrast liquid, by "columella effect".

CONCLUSIONS

This study demonstrates the absence of vestibular damage in patients undergoing intratympanic gadolinium infiltration and confirms the relationship between intratympanic pressure and vestibular stability modifications providing positive evidences for an applicative use of CP as a functional assessment to better address diagnosis and follow-up in MD patients treated with intratympanic injections.

An Inexpensive 6D Motion Tracking System for Posturography

Computerized posturography is most often performed with a force plate measuring center-of-pressure (COP). COP is related to postural control actions but does not monitor the outcome of those actions, i.e., center-of-mass (COM) stability. For a more complete analysis of postural control COM should also be measured; however, existing motion tracking technology is prohibitively expensive and overcomplicated for routine use. The objective of this work was to create and validate an inexpensive and convenient stereo vision system which measured a trunk-fixed target's 3D position and orientation relating to COM. The stereo vision system would be complementary to typical force plate methods providing precise 6D position measurements under laboratory conditions. The developed system's measurement accuracy was worst in the inferior-superior axis (depth) and pitch coordinates with accuracy measures 1.1 mm and 0.8°, respectively. The system's precision was worst in the depth and roll coordinates with values 0.1 mm and 0.15°, respectively. Computer modeling successfully predicted this precision with 11.3% mean error. Correlation between in vivo target position (TP) and COP was above 0.73 with COP generally demonstrating larger excursions oscillating around TP. Power spectral analysis of TP revealed 99% of the signal was bound below 1.1 Hz matching expectations for COM. The new complementary measurement method enables identification of postural control strategies and as a result more complete analysis. Stereo vision is a useful complement to typical force plate equipment. The system presented here is inexpensive and convenient demonstrating potential for routine use in clinic and research. In order to use this system in clinic, future work is required in interpretation of this system's data and normal reference values must be established across gender and age in a healthy population followed by values from patients with different pathologies.

Disorders of the inner-ear balance organs and their pathways

Disorders of the inner-ear balance organs can be grouped by their manner of presentation into acute, episodic, or chronic vestibular syndromes. A sudden unilateral vestibular injury produces severe vertigo, nausea, and imbalance lasting days, known as the acute vestibular syndrome (AVS). A bedside head impulse and oculomotor examination helps separate vestibular neuritis, the more common and innocuous cause of AVS, from stroke. Benign positional vertigo, a common cause of episodic positional vertigo, occurs when otoconia overlying the otolith membrane falls into the semicircular canals, producing brief spells of spinning vertigo triggered by head movement. Benign positional vertigo is diagnosed by a positional test, which triggers paroxysmal positional nystagmus in the plane of the affected semicircular canal. Episodic spontaneous vertigo caused by vestibular migraine and Ménière's disease can sometimes prove hard to separate. Typically, Ménière's disease is associated with spinning vertigo lasting hours, aural fullness, tinnitus, and fluctuating hearing loss while VM can produce spinning, rocking, or tilting sensations and light-headedness lasting minutes to days, sometimes but not always associated with migraine headaches or photophobia. Injury to both vestibular end-organs results in ataxia and oscillopsia rather than vertigo. Head impulse testing, dynamic visual acuity, and matted Romberg tests are abnormal while conventional neurologic assessments are normal. A defect in the bony roof overlying the superior semicircular canal produces vertigo and oscillopsia provoked by loud sound and pressure (when coughing or sneezing). Three-dimensional temporal bone computed tomography scan and vestibular evoked myogenic potential testing help confirm the diagnosis of superior canal dehiscence. Collectively, these clinical syndromes account for a large proportion of dizzy and unbalanced patients.

Characterizing Patients with Unilateral Vestibular Hypofunction Using Kinematic Variability and Local Dynamic Stability during Treadmill Walking

Here, we aimed to compare the unstable gait caused by unilateral vestibular hypofunction (UVH) with the normal gait. Twelve patients with UVH and twelve age-matched control subjects were enrolled in the study. Thirty-four markers were attached to anatomical positions of each participant, and a three-dimensional (3D) motion analysis system was used to capture marker coordinates as the participants walked on a treadmill. The mean standard deviation of the rotation angles was used to represent gait variability. To explore gait stability, local dynamic stability was calculated from the trunk trajectory. The UVH group had wider step width and greater variability of roll rotation at the hip than the control group (P < 0.05). Also, the UVH group had lower local dynamic stability in the medial-lateral (ML) direction than the control group (P < 0.05). By linear regression analysis, we identified a linear relationship between the short-term Lyapunov exponent and vestibular functional asymmetry. The result implies that UVH-induced asymmetry can increase posture variability and gait instability. This study demonstrates the potential for using kinematic parameters to quantitatively evaluate the severity of vestibular functional asymmetry. Further studies will be needed to explore the clinical effectiveness of such approaches.

Factors Affecting Postural Instability in Ménière’s Disease

Objective

To assess the influence of factors that can affect the postural instability of Ménière’s disease (MD) patients.

Study Design

Case-control study.

Setting

Outpatient clinic in a university hospital.

Subjects and Methods

Fifty-four definite MD patients and 66 controls were included. Two-legged stance tasks were performed in 4 conditions: eyes open with and without foam rubber and eyes closed with and without foam rubber. We examined 6 variables: the velocity of movement of the center of pressure (COP), the envelopment area traced by the movement of the COP, Romberg’s ratio of velocity and area, and the foam ratios of velocity and area. For patients, stepwise multiple regression analyses were performed to explore the relationship between the 6 variables and the following independent variables: gender, age, the presence of abnormal caloric and/or cervical vestibular evoked myogenic potential (cVEMP) responses, the time elapsed since the last vertigo attack, and the disease duration.

Results

The presence of MD had a significantly positive relationship with all 6 of the variables ( P < .05). The presence of abnormal caloric and/or cVEMP responses had a significantly positive relationship with Romberg’s ratio of velocity ( P < .05) and area ( P < .01). The shorter time interval from last vertigo attack to measurement had a significantly positive relationship with the foam ratio of area ( P < .01).

Conclusion

MD patients show poor postural performance, which is affected by the existence of their peripheral vestibular function and the shorter time interval from last vertigo attack to measurement.

An observed relationship between vestibular function and auditory thresholds in aircraft-maintenance workers

OBJECTIVE

We sought to examine the vestibular function and whether an association exists between vestibular function and hearing thresholds in a group of military aircraft-maintenance workers with exposures to high levels of noise and organic solvents, relative to two different comparison groups.

METHODS

Vestibular function (using functional reach) and hearing (with pure-tone audiometry) were assessed in 601 exposed personnel, compared with two unexposed groups (500 technical trade and 391 nontrade).

RESULTS

Linear regression model showed that functional reach was slightly better for the comparison groups than the exposed group, with only one group being statistically significant, and there was a significant association between vestibular function and auditory thresholds at 500 and 1000 Hz.

CONCLUSION

This study has demonstrated a relationship between low-frequency hearing loss, vestibular dysfunction, anxiety, and depression in an occupational population.

Normal and vestibular patterns in dynamic posturography in patients with Meniere's disease

INTRODUCTION

The Sensory Organization Test of dynamic posturography allows a reliable assessment of the ability of any given patient to maintain a correct stability when conditions in the visual surrounding and/or support surface are deliberately modified. The results of this test can be analyzed according to the norms of the manufacturer of the device or through the application of specific formulae such as those by Cevette.

OBJECTIVES

To evaluate if the Cevette formulae distinguish correctly between the normal and vestibular patterns, as well as observing the differences between these two groups of patients (normal and vestibular), obtained either through standardized calculation or by the Cevette formulae. The work has been restricted to patients diagnosed with unilateral Menière's disease who presented an active form of the disease and who had not suffered a recent crisis.

MATERIAL AND METHODS

63 patients were studied who fulfilled the inclusion criteria for this study. A clinical and instrumental audio-vestibular study was carried out. The results of the sensory organization test were analyzed according to the pattern offered by the device and through the application of the Cevette formulae.

RESULTS

In 63 patients the pattern obtained was normal or vestibular. In 41 the pattern obtained through one system of analysis or the other coincided but in 22 they did not. The analysis of patients using the Cevette formulae offers a higher capacity for clinical discrimination but is not sensitive to the bias introduced by age; however, combined with the classification offered by the device, it manages to differentiate two populations (normal and vestibular) with a very good audio-vestibular correlation.

CONCLUSION

The combined assessment of the results of the sensory organization test using both the equipment analysis and the Cevette formulae provides much better and real information of clinical differences amongst patients with Menière's disease when the result is normal or of vestibular deficiency.