Patterns of Vestibular Impairment in Bilateral Vestibulopathy and Its Relation to Etiology

Mechanisms underlying treatment effects of vestibular noise stimulation on postural instability in patients with bilateral vestibulopathy

BACKGROUND

Previous studies indicate that imbalance in patients with bilateral vestibulopathy (BVP) may be reduced by treatment with low-intensity noisy galvanic vestibular stimulation (nGVS).

OBJECTIVE

To elucidate the potential mechanisms underlying this therapeutic effect. In particular, we determined whether nGVS-induced balance improvements in patients are compatible with stochastic resonance (SR)-a mechanism by which weak noise stimulation can paradoxically enhance sensory signal processing.

METHODS

Effects of nGVS of varying intensities (0-0.7 mA) on body sway were examined in 19 patients with BVP standing with eye closed on a posturographic force plate. We assumed a bell-shaped response curve with maximal sway reductions at intermediate nGVS intensities to be indicative of SR. An established SR curve model was fitted on individual patient outcomes, and three experienced human raters had to judge whether responses to nGVS were consistent with the exhibition of SR.

RESULTS

nGVS-induced reductions of body sway compatible with SR were found in 12 patients (63%) with optimal improvements of 31 ± 21%. In 10 patients (53%), nGVS-induced sway reductions exceeded the minimally important clinical difference (optimal improvement: 35 ± 21%), indicative of strong SR. This beneficial effect was more likely in patients with severe vestibular loss (i.e. lower video head impulse test gain; R = 0.663; p = 0.002) and considerable postural imbalance (baseline body sway; R = 0.616; p = 0.005).

CONCLUSIONS

More than half of the assessed patients showed robust improvements in postural balance compatible with SR when treated with nGVS. In particular, patients with a higher burden of disease may benefit from the non-invasive and well-tolerated treatment with nGVS.

Multi-frequency VEMPs improve detection of present otolith responses in bilateral vestibulopathy

Objective

To investigate whether multi-frequency Vestibular Evoked Myogenic Potential (VEMP) testing at 500, 750, 1,000, and 2,000 Hz, would improve the detection of present dynamic otolith responses in patients with bilateral vestibulopathy (BV).

Methods

Prospective study in a tertiary referral center. BV patients underwent multi-frequency VEMP testing. Cervical VEMPs and ocular VEMPs were recorded with the Neuro-Audio system (v2010, Neurosoft, Ivanovo, Russia). The stimuli included air-conducted tone bursts of 500, 750, 1,000, and 2,000 Hz, at a stimulation rate of 13 Hz. Outcome measures included the percentage of present and absent VEMP responses, and VEMP thresholds. Outcomes were compared between frequencies and type of VEMPs (cVEMPs, oVEMPs). VEMP outcomes obtained with the 500 Hz stimulus, were also compared to normative values obtained in healthy subjects.

Results

Forty-nine BV patients completed VEMP testing: 47 patients completed cVEMP testing and 48 patients completed oVEMP testing. Six to 15 % more present VEMP responses were obtained with multifrequency testing, compared to only testing at 500 Hz. The 2,000 Hz stimulus elicited significantly fewer present cVEMP responses (right and left ears) and oVEMP responses (right ears) compared to the other frequencies (p ≤ 0.044). Using multi-frequency testing, 78% of BV patients demonstrated at least one present VEMP response in at least one ear. In 46% a present VEMP response was found bilaterally. BV patients demonstrated a significantly higher percentage of absent VEMP responses and significantly higher VEMP thresholds than healthy subjects, when corrected for age (p ≤ 0.002). Based on these results, a pragmatic VEMP testing paradigm is proposed, taking into account multi-frequency VEMP testing.

Conclusion

Multi-frequency VEMP testing improves the detection rate of present otolith responses in BV patients. Therefore, multi-frequency VEMPs should be considered when evaluation of (residual) otolith function is indicated.

Vestibular contributions to linear motion perception

Vestibular contributions to linear motion (i.e., translation) perception mediated by the otoliths have yet to be fully characterized. To quantify the maximal extent that non-vestibular cues can contribute to translation perception, we assessed vestibular perceptual thresholds in two patients with complete bilateral vestibular ablation to compare to our data in 12 young (< 40 years), healthy controls. Vestibular thresholds were assessed for naso-occipital ("x-translation"), inter-aural ("y-translation"), and superior-inferior ("z-translation") translations in three body orientations (upright, supine, side-lying). Overall, in our patients with bilateral complete vestibular loss, thresholds were elevated ~ 2-45 times relative to healthy controls. No systematic differences in vestibular perceptual thresholds were noted between motions that differed only with respect to their orientation relative to the head (i.e., otoliths) in patients with bilateral vestibular loss. In addition, bilateral loss patients tended to show a larger impairment in the perception of earth-vertical translations (i.e., motion parallel to gravity) relative to earth-horizontal translations, which suggests increased contribution of the vestibular system for earth-vertical motions. However, differences were also noted between the two patients. Finally, with the exception of side-lying x-translations, no consistent effects of body orientation in our bilateral loss patients were seen independent from those resulting from changes in the plane of translation relative to gravity. Overall, our data confirm predominant vestibular contributions to whole-body direction-recognition translation tasks and provide fundamental insights into vestibular contributions to translation motion perception.

[Rehabilitation in bilateral vestibulopathy: trends and perspectives]

A review of the literature on rehabilitation methods for bilateral vestibulopathy is presented using RSCI, Scopus and PubMed databases. The principles and effectiveness of physical vestibular rehabilitation, vestibular implants, galvanic vestibular stimulation, and biofeedback-based sensory substitution and augmentation systems are described. The advantages and disadvantages of each method and perspectives for their improvement are presented.

Bilateral vestibulopathy: a clinical update and proposed diagnostic algorithm

Bilateral vestibulopathy (BVP) is characterized by its heterogeneous and chronic nature with various clinical presentations and multiple etiologies. This current narrative review reflects on the main insights and developments regarding clinical presentation. In addition, it proposes a new diagnostic algorithm, and describes available and potential future therapeutic modalities.

Neurological update: neuro-otology 2023

Much has changed since our last review of recent advances in neuro-otology 7 years ago. Unfortunately there are still not many practising neuro-otologists, so that most patients with vestibular problems need, in the first instance, to be evaluated and treated by neurologists whose special expertise is not neuro-otology. The areas we consider here are mostly those that almost any neurologist should be able to start managing: acute spontaneous vertigo in the Emergency Room-is it vestibular neuritis or posterior circulation stroke; recurrent spontaneous vertigo in the office-is it vestibular migraine or Meniere's disease and the most common vestibular problem of all-benign positional vertigo. Finally we consider the future: long-term vestibular monitoring and the impact of machine learning on vestibular diagnosis.

The Need for Vestibular Implants in a Tertiary Referral Ear, Nose, and Throat Center and Its Relation to Hearing Status

BACKGROUND

Patients with bilateral vestibulopathy (BVP) are at increased risk of falling and have poor quality of life. Several research groups are currently developing and investigating vestibular implants to treat BVP. The goal was to identify how many patients can be considered eligible for vestibular implantation.

METHODS

The objective vestibular implantation criteria for research were applied to the results of the caloric irrigation test, the sinusoidal harmonic acceleration test, the video head impulse test, and the cervical and ocular vestibular evoked myogenic potential tests.

RESULTS

Vestibular implant eligibility was situated between 3.6% and 15.7% (semicircular canal implant: 3.6%; otolith implant: 15.7%; combined implant: 4.8%). Only 16 out of the 29 patients (55%) eligible for a vestibular implant had bilateral severe-to-profound hearing loss. The remaining 45% (13/29) thus have better hearing in at least 1 ear.

CONCLUSION

Vestibular implant eligibility in an ear, nose, and throat department was situated between 3.6% and 15.7%, depending on the type of implant that was considered. In addition, the data showed that 45% of the eligible patients had normal-to-moderate hearing in at least 1 ear. In other words, only recruiting patients with (bilateral) severe-to-profound hearing loss for vestibular implantation leads to the systematic exclusion of about half of the candidates. Structure-preserving surgical techniques are thus a major future challenge in the field of vestibular implantation.

Construct validity and reliability of the Bilateral Vestibulopathy Questionnaire (BVQ)

Background

The Bilateral Vestibulopathy Questionnaire (BVQ) is a recently developed 54-item Patient Reported Outcome Measure (PROM) that evaluates the clinically important symptoms of bilateral vestibulopathy (BVP) and its impact on daily life. This study aimed to assess the construct validity and reliability of the BVQ in a large BVP cohort.

Methods

Patients diagnosed with BVP were asked to complete a set of questionnaires, including the BVQ, the EuroQol-5D-5L, the Health Utilities Index, the Dizziness Handicap Inventory, the Hospital Anxiety and Depression Scale, and the Oscillopsia Severity Questionnaire. The construct validity of the BVQ was evaluated by confirmatory and exploratory factor analyses (CFA and EFA), followed by hypotheses testing and known groups validity. Structural properties were explored for each individual item. Reliability was assessed by testing the internal consistency of the BVQ constructs (Cronbach's alpha) and test-retest reliability [intraclass correlation coefficients (ICCs)].

Results

A total of 148 patients with BVP (50% women, mean age 66 years) completed the set of questionnaires. The CFA did not show a satisfactory model in the original BVQ. However, the EFA showed a four-factor solution with 20 Likert-scale items related to oscillopsia, imbalance, emotion, and cognition. The succeeding CFA provided evidence for construct validity and an acceptable model of fit. Hypothesis testing confirmed that this shortened version validly measures the constructs to be measured. Statistically significant differences in scores between known groups were found, providing further support for good construct validity. The structural properties were acceptable. Cronbach's alpha confirmed good internal consistency for the four constructs, ranging from 0.80 to 0.89. The ICCs of the 20 Likert-scale items and four visual analog scale (VAS) items were interpreted as good (range 0.76-0.93).

Conclusion

This study showed evidence of good construct validity of the new shortened version of the BVQ, consisting of four constructs with a total of 20 Likert-scale items and four VAS items. The final 24-item BVQ proved to be a reliable and valid multi-item PROM that captures the clinically important symptoms of BVP and evaluates its impact on daily life. Consequently, the BVQ enables the gathering of high-level evidence of treatment effectiveness in a systematic and quantitative manner.