A New Method for Gain Calculation in Quantified Visuo-vestibular Interaction Test

OBJECTIVE

To develop a new method to quantify visually-enhanced vestibulo-ocular reflex (VVOR) gain, in patients with vestibular function loss, that is mathematically suitable given the nature of the test, and determine the reliability of the method by comparing results with those of the gold standard, the video head impulse test (vHIT).

MATERIALS AND METHODS

We developed a new method for VVOR gain quantification and conducted a cross-sectional study in patients diagnosed with vestibular function loss and controls, all participants undergoing both a VVOR test and a vHIT. We measured VVOR gain with three different methods: area under the curve (AUC), slope regression, and a Fourier method (VVORAUC , VVORSP , and VVORFR , respectively); and compared these gain values with vHIT gain calculated using the AUC method.

RESULTS

Overall, 111 patients were included: 29 healthy subjects and 82 patients with vestibular function loss. Intraclass correlation coefficients (ICC(1,1)) between gain from the gold standard and each of the VVOR gain methods were: 0.68 (CI: 0.61-0.75) for VVORAUC , 0.66 (CI: 0.58-0.73) for VVORSP and 0.71 (CI: 0.64-0.77) for VVORFR . No interference was found between VVOR gain calculation methods and potentially influential variables considered (p ≥ 0.98).

CONCLUSION

The new method for quantifying VVOR gain showed good concordance with the vHIT method.

LEVEL OF EVIDENCE

2: Individual cross-sectional studies with consistently applied reference standard and blinding (Diagnosis) Laryngoscope, 133:3554-3563, 2023.

Vestibulo-ocular reflex gain values in the suppression head impulse test of healthy subjects

OBJECTIVE

To assess whether there are differences in vestibulo-ocular reflex (VOR) gain for suppression head impulse (SHIMP) and head impulse (HIMP) video head impulse test paradigms, and if so, what are their causes.

METHODS

Prospective multicenter observational double-blind nonrandomized clinical study was performed by collecting 80 healthy subjects from four reference hospitals. SHIMP data was postprocessed to eliminate impulses in which early SHIMP saccades were detected. Differences between HIMP and SHIMP VOR gain values were statistically evaluated. Head impulse maximum velocity, gender, age, direction of impulse, and hospital center were considered as possible influential factors.

RESULTS

A small significant statistical difference between HIMP and SHIMP VOR gain values was found on repeated measures analysis of variance (-0.05 ± 0.006, P < 0.001). Optimized linear model showed a significant influence of age variable on the observed differences for HIMP and SHIMP gain values and did not find influence between gain values differences and maximum head impulse velocity. Both HIMP and SHIMP VOR gain values were significant lower (-0.09, P < 0.001) when the impulses were performed to the left side.

CONCLUSION

We had observed a difference in SHIMP and HIMP gain values not adequately explained by known gain modification factors. The persistence of this slight but significant difference indicates that there are more factors causing lower SHIMP VOR gain values. This difference must to be considered in further studies as well as in the clinical SHIMP testing protocols. We hypothesized that VOR phasic response inhibition could be the underlying cause of this difference.

LEVEL OF EVIDENCE

2b. Laryngoscope, 128:2383-2389, 2018.

Mathematical Methods for Measuring the Visually Enhanced Vestibulo-Ocular Reflex and Preliminary Results from Healthy Subjects and Patient Groups

Background

Visually enhanced vestibulo–ocular reflex (VVOR) is a well-known bedside clinical test to evaluate visuo–vestibular interaction, with clinical applications in patients with neurological and vestibular dysfunctions. Owing to recently developed diagnostic technologies, the possibility to perform an easy and objective measurement of the VVOR has increased, but there is a lack of computational methods designed to obtain an objective VVOR measurement.

Objectives

To develop a method for the assessment of the VVOR to obtain a gain value that compares head and eye velocities and to test this method in patients and healthy subjects.

Methods

Two computational methods were developed to measure the VVOR test responses: the first method was based on the area under curve of head and eye velocity plots and the second method was based on the slope of the linear regression obtained for head and eye velocity data. VVOR gain and vestibulo–ocular reflex (VOR) gain were analyzed with the data obtained from 35 subjects divided into four groups: healthy (N = 10), unilateral vestibular with vestibular neurectomy (N = 8), bilateral vestibulopathy (N = 12), and cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS) (N = 5).

Results

Intra-class correlation index for the two developed VVOR analysis methods was 0.99. Statistical differences were obtained by analysis of variance statistical method, comparing the healthy group (VVOR mean gain of 1 ± 0) with all other groups. The CANVAS group exhibited (VVOR mean gain of 0.4 ± 0.1) differences when compared to all other groups. VVOR mean gain for the vestibular bilateral group was 0.8 ± 0.1. VVOR mean gain in the unilateral group was 0.6 ± 0.1, with a Pearson’s correlation of 0.52 obtained when VVOR gain was compared to the VOR gain of the operated side.

Conclusion

Two computational methods to measure the gain of VVOR were successfully developed. The VVOR gain values appear to objectively characterize the VVOR alteration observed in CANVAS patients, and also distinguish between healthy subjects and patients with some vestibular disorders.

Regulation of Fn14 Receptor and NF-κB Underlies Inflammation in Meniere's Disease

Meniere’s disease (MD) is a rare disorder characterized by episodic vertigo, sensorineural hearing loss, tinnitus, and aural fullness. It is associated with a fluid imbalance between the secretion of endolymph in the cochlear duct and its reabsorption into the subarachnoid space, leading to an accumulation of endolymph in the inner ear. Epidemiological evidence, including familial aggregation, indicates a genetic contribution and a consistent association with autoimmune diseases (AD). We conducted a case–control study in two phases using an immune genotyping array in a total of 420 patients with bilateral MD and 1,630 controls. We have identified the first locus, at 6p21.33, suggesting an association with bilateral MD [meta-analysis leading signal rs4947296, OR = 2.089 (1.661–2.627); p = 1.39 × 10⁻⁰⁹]. Gene expression profiles of homozygous genotype-selected peripheral blood mononuclear cells (PBMCs) demonstrated that this region is a trans-expression quantitative trait locus (eQTL) in PBMCs. Signaling analysis predicted several tumor necrosis factor-related pathways, the TWEAK/Fn14 pathway being the top candidate (p = 2.42 × 10⁻¹¹). This pathway is involved in the modulation of inflammation in several human AD, including multiple sclerosis, systemic lupus erythematosus, or rheumatoid arthritis. In vitro studies with genotype-selected lymphoblastoid cells from patients with MD suggest that this trans-eQTL may regulate cellular proliferation in lymphoid cells through the TWEAK/Fn14 pathway by increasing the translation of NF-κB. Taken together; these findings suggest that the carriers of the risk genotype may develop an NF-κB-mediated inflammatory response in MD.

Vestibulo-Ocular Reflex Stabilization after Vestibular Schwannoma Surgery: A Story Told by Saccades

Objective

To evaluate vestibular compensation via measurement of the vestibulo-ocular reflex (VOR) following vestibular schwannoma surgery and its relationship with changes in saccades strategy after surgery.

Patients

Thirty-six consecutive patients with vestibular schwannomas, without brainstem compression, underwent surgical resection. Patients were recruited from University Hospital of Salamanca, Spain.

Methods

We assessed the age, sex, tumor size, degree of canalicular weakness, and preoperative video head impulse test (gain and saccade organization measured with PR score). Gain and saccade organization were compared with postoperative values at discharge and also at 1, 3, and 6 months. PR scores are a measure of the scatter of refixation saccades.

Results

Patients with normal preoperative caloric function had higher PR scores (saccades were scattered) following surgery compared to patients with significant preoperative canal paresis (p < 0.05). VOR gain and the presence of covert/overt saccades preoperatively did not influence the PR score (p > 0.05), but a group of patients with very low VOR gain (<0.45) and covert/overt saccades before surgery had lower PR scores after surgery. The differences after 6 months were not significant.

Conclusion

Patients with more severe vestibular dysfunction before vestibular schwannoma surgery show significantly faster vestibular compensation following surgery, manifested by changes in VOR gain and PR score. The scatter of compensatory saccades (as measured by the PR score) may be a surrogate early marker of clinical recovery, given its relationship to the Dizziness Handicap Inventory.

A new method to improve the imbalance in chronic unilateral vestibular loss: the organization of refixation saccades

CONCLUSION

VOR adaptation and organization of refixation saccades in a gathered pattern is a process that can be artificially induced in patients with unilateral vestibular loss who have not developed it naturally, improving imbalance and vestibular disability.

OBJECTIVE

To test that temporary grouping of refixation saccades should be linked to better clinical status without gain recovery.

METHODS

A training to induce the refixation saccades into gathered fashion is performed. The outcome measures are handicap level measured by the dizziness handicap index (DHI) and refixation saccades organization pattern measured by a numeric score called 'PR' given by a software developed by the authors. Analysis is done before the training and 1 and 3 months after ending, Non-parametric tests were used for statistical analysis.

RESULTS

This study has included 10 healthy subjects (four males, six females), and 16 patients with chronic unsteadiness due to unilateral vestibular loss (nine vestibular neuritis, four post-surgical vestibular schwannoma, and three cases after intra-tympanic gentamycin in patients with Ménière's disease). The reduction in the DHI score was significant at 1 (p = 0.028) and 3 months (p = 0.042) post-treatment. Also, statistically significant differences were found between the PR score before and PR score 1 (p = 0.005) and 3 months after the treatment (p = 0.003).

Benign paroxysmal positional vertigo in the elderly

BACKGROUND

Benign paroxysmal positional vertigo (BPPV) is the most frequent peripheral vertigo in the elderly. It is a well-characterized entity and generally easy to treat.

OBJECTIVE

To evaluate the main symptoms, time to consult for the problem, vertigo characteristics, treatment and follow-up in patients over 70 with BPPV.

METHODS

This was a retrospective cohort study. Four hundred and four patients were diagnosed to have BPPV (between January 2006 and December 2012); 211 of them were ≥70 years old (mean 77.7 years) and 193 <70 years old (mean 53.82 years).

RESULTS

Patients over 70 with BPPV took longer to consult for the problem (Spearman rho, p = 0.01). The frequency of a clinical presentation consisting of unsteadiness or imbalance without vertigo sensation is higher among elderly patients (χ(2), p = 10(-6)). The effectiveness of the repositioning maneuver is lower than in patients under 70 (χ(2), p = 0.002), and the recurrences are more frequent (χ(2), p = 0.04).

CONCLUSION

BPPV is a frequent entity in the elderly, and it is necessary to take it into account when older patients complain about imbalance. An appropriate treatment with repositioning maneuvers and prolonged follow-up are required in order to detect recurrences.