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OBJECTIVE: To determine the ability of patients with unilateral Ménière's disease (MD) to reach the corresponding limits of stability and to define the existence of directional constraints. PATIENTS: 112 patients with unilateral MD and 30 normal age-matched subjects with no history of equilibrium problems. METHODS: A computerized dynamic posturography system was used to test the ability of subjects to displace their centre of pressure (COP) to the corresponding limits of stability. The eight targets used were separated by 45 degrees to form a circle around the subject who had to displace their COP to the target. Reaction time, velocity, accuracy and an overall evaluation of the intended movement towards and away from the target were analysed. Other characteristics of the patients were also assessed. RESULTS: A small but significant correlation was found between auditory and vestibular deficit and the different variables studied in the limits of stability test. Three factors were derived from variables obtained with short displacements, and the results are significantly different between patients and controls and are correlated with the period since the last vertigo spell, the level of disability, hearing loss and vestibular deficit. CONCLUSIONS: Dynamic balance is moderately impaired in patients with Ménière's disease. [ABSTRACT FROM AUTHOR]

The Spanish neurohistologist Santiago Ramón y Cajal (1852-1934) is widely regarded as the father of modern Neuroscience. In addition to identifying the individuality of cells in the nervous system (the neuron theory) or the direction followed by nerve impulses (the principle of dynamic polarization), he described numerous details regarding the organization of the different structures of the nervous system. This task was compiled in his magnum opus, "Textura del Sistema Nervioso del Hombre y los Vertebrados," first published in Spanish between 1899 and 1904, and later revised and updated in French as "Histologie du système nerveux de l'homme et des vertébrés" between 1909 and 1911 for wider distribution among the international scientific community. Some of Cajal's findings are fundamental to our understanding of the anatomy and histology of the vestibular system. He depicted the nerve endings in the sensory epithelia, the structure of the vestibular nerve and Scarpa ganglion, afferent vestibular fibers, vestibular nuclei, lateral vestibulospinal tract, vestibulocerebellar connections, and the fine structure of the cerebellum. However, most of these pioneering descriptions were published years earlier in Spanish journals with limited circulation. Our study aimed to gather Cajal's findings on the vestibular system and identify his original publications. After this endeavor, we claim a place for Cajal among the founders of anatomy and histology of the vestibular system., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Espinosa-Sanchez, Perez-Fernandez, de Castro and Batuecas-Caletrio.)

Background: Rafael Lorente de Nó was a neuroscientist that worked alongside two of the giants of Medicine, the Nobel Prize winners Cajal and Bárány., Objective: To describe the contributions of Lorente de Nó to vestibular neuroscience., Methods: Detailed review of the publications of Lorente de Nó and analysis of the archives from Junta para Ampliación de Estudios e Investigaciones Científicas at Residencia de Estudiantes (Madrid, Spain), Casa de Salud Valdecilla at Hospital Universitario Marqués de Valdecilla (Santander, Spain), Becker Medical Library at Washington University (St. Louis, MO, USA), Rockefeller Archive Center (Sleepy Hollow, New York, NY, USA), Archivo Fernando de Castro (Madrid, Spain), Biblioteca Nacional de España (Madrid, Spain) and Legado Cajal at Instituto Cajal (Madrid, Spain). Most of this material is unpublished and includes over a hundred letters to or from Lorente., Results: Lorente de Nó made a substantial contribution to our understanding of the vestibular system. Amongst these, he meticulously detailed the course of the vestibular nerve and its central projections. He described the vestibulo-ocular reflex as the consequence of an integration of the various nuclei and connections across the vestibular system, rather than a simple three-neuron arc. He also highlighted the role of the reticular formation in the generation of the fast phase of the nystagmus., Conclusions: Lorente de Nó was a pioneer of modern neuro-otology, having made outstanding contributions to vestibular neuroscience, forging novel discoveries that still burn true today.

Background: The number of intratympanic gentamicin (ITG) injections needed to achieve vertigo control in patients with intractable Ménière's disease (MD) may vary from a single dose to several instillations. Changes in different vestibular test results have been used to define an endpoint of treatment, including the decrease of the vestibulo-ocular reflex (VOR) gain elicited by the head-impulse test., Objective: To assess the accuracy of the VOR gain reduction after horizontal canal stimulation, as measured with the video head-impulse test (vHIT) 1 month after the first intratympanic injection, in predicting the need for one or more instillations to control vertigo spells in the long term., Methods: The VOR gain reduction was calculated in 47 patients submitted to (ITG) therapy 1 month after the first instillation., Results: Single intratympanic treatment with gentamicin has a 59.6% efficacy in vertigo control in the long term. Hearing change in the immediate period after treatment (1 month) is not significant to pre-treatment result and is similar for patients who needed multiple doses due to recurrence. Chronic disequilibrium and the need for vestibular rehabilitation were less frequent in patients with a good control of vertigo with just one single injection of gentamicin. A fair accuracy was obtained for the VOR gain reduction of the horizontal canal (area under the curve = 0.729 in the Receiver Operating Characteristic analysis) in predicting the need for one or more ITG., Conclusions: Single intratympanic treatment with gentamicin is an effective treatment for patients with MD. That modality of treatment has very limited damaging effect in hearing. The degree of vestibular deficit induced by the treatment is significant as measured by the reduction in the gain of the VOR but not useful for prognostic purposes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wegmann-Vicuña, Manrique-Huarte, Calavia-Gil, Martín-Sanz, Marques and Perez-Fernandez.)

Objective: Main objectives for this study were to develop a quantification method to obtain a Perez-Rey (PR) score adapted to the VVOR test and to evaluate the correlation of the PR score obtained with quantified VVOR with the PR score of the vHIT test., Methods: A new PR score calculation method for quantified VVOR test was developed using the MATLAB computational software based on saccadic response time latency variability between each head oscillation cycle of the VVOR test. Retrospective correlation between PR scores in VVOR and vHIT tests, performed in the same vHIT testing session for patients with vestibular neuritis and vestibular neurectomy, was performed to correlate new PR (VVOR) score with the classic PR (vHIT) score., Results: Thirty patients were included: 11 post-neurectomy and 19 subacute vestibular neuritis. Pearson's correlation coefficient (R2) for the overall sample was 0.92 (p < 0.001) and 95% confidence interval was 0.85 -0.96. In the linear mixed-effects statistical model developed, only PRVHIT and PRVVOR scores showed statistical association in Wald X2 test (p = 0.008)., Conclusion: The new developed PR score for synchronization measurement of saccadic responses in VVOR testing is a valid method that outputs synchronization values and highly correlates with PR score in vHIT test.

Objectives/hypothesis: Characterize the state of vestibular compensation of subjects diagnosed with acute unilateral vestibulopathy (AUV) of peripheral origin according to the temporal organization pattern of the refixation saccades (Perez and Rey (PR) score)., Study Design: Retrospective cross-sectional study using previously collected clinical data from a tertiary referral center., Methods: Following the vestibular compensation criteria defined by Eisenman, we used the video head impulse test as the main vestibular function test and compared the results with other traditional tests: rotatory chair test (ROT), caloric test, videonystagmography, clinical situation (CLIN), and the Dizziness Handicap Inventory (DHI) questionnaire from 28 subjects (17 men, 11 women), average age 60.21 years, who were in a compensated and noncompensated vestibular situation. We used the PR score to measure the differences between the study groups. A cluster was developed to define a cutoff point that objectively distinguishes the vestibular compensation status., Results: Significant differences in the PR score were found in the state of vestibular compensation in the ROT test (P = .01), DHI (P = .04), and CLIN (P = .023). The vestibular compensation criteria that groups the original variables (PR-CLUSTER) cutoff point was 55 (P = .019)., Conclusions: The PR score is a measure of temporal organization of the refixation saccades that enables us to distinguish clearly and objectively the vestibular situation of subjects with AUV. We suggest its clinical application., Level of Evidence: NA Laryngoscope, 2020., (© 2020 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: The main sequences used to assess degree of endolymphatic hydrops (EH) are the 3D- inversion-recovery (IR) with real reconstruction and the 3D- fluid-attenuated inversion recovery (FLAIR)., Objectives: The purpose of this study is to describe and compare both sequences., Material and Methods: Forty-two consecutive patients diagnosed with probable or definite Ménièr´s disease were referred for hydrops MR examination. Vestibular and cochlear EH in both sequences were read by two independent radiologists, unaware of the patient's clinical status. The primary study endpoint was the concordance in the hydrops detection and severity with both imaging sequences. This was assessed using the Cohen's kappa Κ statistic for disease grading and Pearson Χ 2 test to test the difference in detection rates of hydrops. Statistical significance was defined as two-sided p  < .05., Results: We obtained an excellent overall concordance, with a kappa of 0.821, ( p  < .001) when comparing hydrops detection. The degree of concordance is higher in vestibular hydrops than in cochlear hydrops. The 3D-IR sequence detected more hydrops than the 3D FLAIR, (62 vs. 39.5%, p  < .03)., Conclusion: The 3D-IR sequence seems to be superior to the 3D-FLAIR for the assessment of EH. Significance: The 3D-IR sequence should be considered as a standalone parameter for a shorter and optimized EH magnetic resonance imaging protocol.

Objective: To evaluate the effect of artifacts on the impulse and response recordings with the video head impulse test (VHIT) and determine how many stimuli are necessary for obtaining acceptably efficient measurements., Methods: One hundred fifty patients were examined using VHIT and their registries searched for artifacts. We compared several variations of the dataset. The first variation used only samples without artifacts, the second used all samples (with and without artifacts), and the rest used only samples with each type of artifact. We calculated the relative efficiency (RE) of evaluating an increasingly large number of samples (3 to 19 per side) when compared with the complete sample (20 impulses per side)., Results: Overshoot was associated with significantly higher speed (p = 0.005), higher duration (p < 0.001) and lower amplitude of the impulses (p = 0.002), and consequent higher saccades' latency (p = 0.035) and lower amplitude (p = 0.025). Loss of track was associated with lower gain (p = 0.035). Blink was associated with a higher number of saccades (p < 0.001), and wrong way was associated with lower saccade latency (p = 0.012). The coefficient of quartile deviation escalated as the number of artifacts of any type rose, indicating an increment of variability. Overshoot increased the probability of the impulse to lay on the outlier range for gain and peak speed. Blink did so for the number of saccades, and wrong way for the saccade amplitude and speed. RE reached a tolerable level of 1.1 at 7 to 10 impulses for all measurements except the PR score., Conclusions: Our results suggest the necessity of removing artifacts after collecting VHIT samples to improve the accuracy and precision of results. Ten impulses are sufficient for achieving acceptable RE for all measurements except the PR score.

Objective: To investigate the main effects of some testing and analysis variables on clinically quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) results using video head impulse test., Methods: This prospective observational clinical study included 19 healthy participants who underwent the VVOR and VORS tests. The effect of demographic variables, head oscillation frequency, rotation direction, visual acuity and analysis time window width and location of the recorded tests on the quantified results of both VVOR and VORS were evaluated. And specifically, for the VORS test the effect of cognitive reinforcement of the participant during testing was evaluated., Results: A statistically significant difference was observed among the VVOR, non-reinforced VORS, and reinforced VORS tests for mean gain values of 0.91 ± 0.09, 0.6 ± 0.15, and 0.57 ± 0.16, respectively (p < 0.001). The optimized linear mixed-effect model showed a significant influence of frequency on the gain values for the reinforced and non-reinforced VORS tests (p = 0.01 and p = 0.004, respectively). Regarding the gain analysis method, statistically significant differences were found according to the short time interval sample location of the records for the initial location of the VVOR test (p < 0.006) and final location of the reinforced VORS test (p < 0.023)., Conclusion: Significant differences were observed in the gain values according to VVOR and VORS testing. Head oscillation frequency is a significant factor that affects the gain values, especially in VORS testing. Moreover, in VORS testing, participant concentration has a significant effect on the test for obtaining suppression gain values. When a short time interval sample is considered for VVOR and VORS testing, intermediate time samples appear the most adequate for both tests., Significance: The quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) tests have recently been added to the assortment of available clinical vestibular tests. However, despite the clinical validity of these quantified tests that appear to be of increasing clinical interest, the effects of most of the clinical testing methods and mathematical variables are not well defined. In this research we describe what are the main collecting and analysis variables that could influence to the VVOR and VORS tests. Specially for VORS test, participant concentration on test tasks will have positive effect on the measured vestibulo-ocular reflex (VOR) suppression., Competing Interests: Declaration of Competing Interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper., (Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objectives: Oscillopsia is a disabling condition for patients with bilateral vestibular hypofunction (BVH). When the vestibulo-ocular reflex is bilaterally impaired, its ability to compensate for rapid head movements must be supported by refixation saccades. The objective of this study is to assess the relationship between saccadic strategies and perceived oscillopsia., Design: To avoid the possibility of bias due to remaining vestibular function, we classified patients into two groups according to their gain values in the video head impulse test. One group comprised patients with extremely low gain (0.2 or below) in both sides, and a control group contained BVH patients with gain between 0.2 and 0.6 bilaterally. Binary logistic regression (BLR) was used to determine the variables predicting oscillopsia., Results: Twenty-nine patients were assigned to the extremely low gain group and 23 to the control group. The BLR model revealed the PR score (saccades synchrony measurement) to be the best predictor of oscillopsia. Receiver operating characteristic analysis determined that the most efficient cutoff point for the probabilities saved with the BLR was 0.518, yielding a sensitivity of 86.6% and specificity of 84.2%., Conclusions: BVH patients with higher PR values (nonsynchronized saccades) were more prone to oscillopsia independent of their gain values. We suggest that the PR score can be considered a useful measurement of compensation.

Background: Classical posturography techniques have been recently enhanced by the use of different motion tracking devices, but for technical reasons they are not used to track directly the body spatial position of a subject., Objective: To describe and clinically evaluate a wireless inertial measurement unit-based mobile system to track body position changes., Methods: The developed system used a calculus transformation method using the acceleration data corrected by Kalman and Butterworth filters to output position data. A prospective non-randomized clinical study involving 15 healthy subjects was performed to evaluate the agreement between the confidence ellipse areas synchronously measured by the new developed system and a classical posturography system while performing a modified clinical test of sensory interaction in balance., Results: The overall intra-class correlation index was 0.93 (CI 0.89, 0.96). Grouped by conditions, under conditions 1-4, Pearson's correlation was 0.604, 0.78, 0.882, and 0.81, respectively., Conclusion: The developed wireless inertial measurement unit-based posturography system was valid for tracking the sway variances in normal subjects under habitual clinical testing conditions. Further studies are needed to validate this system on patients and also under other posture conditions.

This paper presents a classification and definitions for types of nystagmus and other oscillatory eye movements relevant to evaluation of patients with vestibular and neurological disorders, formulated by the Classification Committee of the Bárány Society, to facilitate identification and communication for research and clinical care. Terminology surrounding the numerous attributes and influencing factors necessary to characterize nystagmus are outlined and defined. The classification first organizes the complex nomenclature of nystagmus around phenomenology, while also considering knowledge of anatomy, pathophysiology, and etiology. Nystagmus is distinguished from various other nystagmus-like movements including saccadic intrusions and oscillations.View accompanying videos at http://www.jvr-web.org/ICVD.html.

Objective: This study aimed to evaluate the changes in the VOR gain after intratympanic gentamicin therapy and to correlate them with the mid-term effects on the control of vertigo, in a population of Menière's disease patients., Study Design: The study design was a prospective "Outcomes research.", Setting: Tertiary referral center., Patients: This study included 20 patients with unilateral Menière's disease refractory to medical therapy for at least 1 year, and treated with an on demand intratympanic gentamicin protocol., Intervention: Therapeutic., Main Outcome Measure: Audiometry, caloric testing, and a vHIT before beginning the protocol were performed. Patients underwent weekly vHIT assessments until a significant gain reduction was observed. Subsequently we performed vHIT tests 1 month after the therapy completion, and then every 3 months for at least 1 year., Results: Complete vertigo control (class A) was achieved in 14 patients at the 12-month follow-up assessment. We observed a significant reduction in VOR gain values at the 3-week follow-up assessment. We found a significant correlation between the 1-month posttreatment ipsilateral hVOR gain and the rate of vertigo recurrence after the first IT gentamicin treatment (p = 0.012; r = 0.400). At the mid-term assessment, 10 patients exhibited a significant partial recovery of the hVOR gain., Conclusions: The delayed effect of intratympanic gentamicin and the subsequent gain restoration are factors that may influence the patients' outcome. The feasibility of the vHIT system makes it a useful tool to monitorize the VOR changes.

Introduction: Middle ear application of gentamicin is a common medical treatment for uncontrolled Ménière's disease. The objective of the study was to evaluate the impact of endolymphatic hydrops on inner ear delivery., Methods: Perilymph gentamicin concentrations and correlation with endolymphatic hydrops in an animal model were assessed. A group of 24 guinea pigs was submitted to surgical obstruction of the endolymphatic sac and duct of the right ear. Gentamicin was applied either to the right ear's round window niche or through a transtympanic injection. Perilymph specimens were collected at different times. Histologic morphometry was used to evaluate both turn-specific and overall hydrops degree., Results: In animals with endolymphatic hydrops, lower concentrations of gentamicin were observed after 20 or 120 minutes of exposure and in both types of administration, when compared to controls. This difference reached statistical significance in the round window niche application group (Mann-Whitney, p = 0,007). A negative correlation between perilymphatic gentamicin concentration and hydrops degree could be observed in both groups, after 120 minutes of exposure (Spearman correlation, round window niche p<0,001; TT p = 0,005)., Conclusions: The study indicates that the endolymphatic hydrops degree has a negative interference on the delivery of gentamicin into the inner ear following middle ear application., Competing Interests: The authors have declared that no competing interests exist.

Objectives: To evaluate the ability of saccadic strategies developed during vestibular compensation to reduce the effect of an impaired vestibulo-ocular reflex (VOR) on a retinal smear and image motion sensation., Design: Twenty patients with unilateral vestibular loss were examined with a video head impulse test before and after vestibular rehabilitation (VR) with the use of gaze stabilization and refixation saccades training. Head and eye velocity functions were processed to infer the retinal eccentricity, and through its correlation with visual acuity (VA), several measurements are proposed to evaluate the influence of VR on saccades behavior and visual performance. To isolate the effect of saccades on the findings and avoid bias because of gain differences, only patients whose VOR gain values remained unchanged after VR were included., Results: Improved contribution of covert saccades and reduction of overt saccades latency were measured after VR. We found significant differences when assessing both the interval less than 70% VA (50.25 ms), which is considered the limit of a moderate low vision, and less than 50% VA (39.515 ms), which is the limit for severe low vision. Time to recover a VA of 75% (near normal) was reduced in all the patients (median: 56.472 ms)., Conclusion: Despite the absence of VOR gain improvement, patients with unilateral vestibular loss are able to develop saccadic strategies that allow the shortening of the interval of retinal smear and image motion. The proposed measurements might be of use to evaluate VR outcomes and visually induced impairment.

Objective: To estimate how much could intratympanic gentamicin (ITG) interfere with the vestibular-ocular reflex (VOR) parameters on instrumental head impulse test (HIT), either with scleral search coil or video head impulse test and, eventually, foresee the control of vertigo crisis in unilateral intractable Ménière's disease (MD)., Methods: A literature search was conducted in PubMed, Scopus, Web of Science and Cochrane search engines. The search terms used were "vestibular ocular reflex", "head impulse test", "gentamicin," and "Meniere's disease". Limitations included text availability to be full text, species to be humans and language to be English. All study types were included. 89 articles were screened identifying four eligible studies were identified. Studies were included after consensus of the authors. Meta-analysis was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data was analysed using Review Manager software., Results: Instrumental HIT, after ITG for MD, demonstrated, in the treated ear, a decreased gain in the horizontal, posterior and superior semicircular canals (SCC), of 0.36 (0.26; 0.47; 95% CI), 0.35 (0.22; 0.48; 95% CI) and 0.28 (0.21; 0.35; 95% CI), respectively. Gain asymmetry increases between the treated and non-treated ear of 23.78 (7.22; 40.35; 95% CI), 32.01 (12.27; 51.76; 95% CI) and 17.49 (9.99; 24.99; 95% CI), were similarly detected in the horizontal, posterior and superior SCC, respectively. Significantly smaller gain values after the first treatment were observed for a single injection group versus multiple injection group in the horizontal (p=0.002) and superior SCCs (p=0.016)., Conclusions: Instrumental HIT is effective in evaluating the SCC function after ITG for intractable unilateral MD. VOR gain changes in the direction of the treated ear in the three SCC have been clearly registered. An increased reduction of the VOR gain in the horizontal and anterior SCC also seemed to foresee the control of vertigo crisis. Still, after meta-analysis, the small number of patients' data available did not allow to define a treatment end-point value. This review also indicated that further and better-designed studies are warranted., (Copyright © 2018 Elsevier B.V. All rights reserved.)

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., (© 2018 The American Laryngological, Rhinological and Otological Society, Inc.)

Patients with inner ear damage associated with bilateral vestibular impairment often ask "how much damage do I have." Although there are presently three clinical methods of measuring semicircular canal vestibular function; electronystagmography (ENG or VENG), rotatory chair and video head-impulse (VHIT) testing; none of these methods provides a method of measuring total vestibular output. Theory suggests that the slow cumulative eye position can be derived from the rotatory chair test by multiplying the high frequency gain by the time constant, or the "Gain Tc product." In this retrospective study, we compared the Gain Tc in three groups, 30 normal subjects, 25 patients with surgically induced unilateral vestibular loss, and 24 patients with absent or nearly absent vestibular responses due to gentamicin exposure. We found that the Gain Tc product correlated better with remaining vestibular function than either the gain or the time constant alone. The fraction of remaining vestibular function was predicted by the equation R = (Gain Tc /11.3) - 0.6. We suggest that the Gain Tc product answers the question "how much damage do I have," and is a better measure than other clinical tests of vestibular function.