VOR gain calculation methods in video head impulse recordings.

BACKGROUND: International consensus on best practices for calculating and reporting vestibular function is lacking. Quantitative vestibulo-ocular reflex (VOR) gain using a video head impulse test (HIT) device can be calculated by various methods. OBJECTIVE: To compare different gain calculation methods and to analyze interactions between artifacts and calculation methods. METHODS: We analyzed 1300 horizontal HIT traces from 26 patients with acute vestibular syndrome and calculated the ratio between eye and head velocity at specific time points (40 ms, 60 ms) after HIT onset ('velocity gain'), ratio of velocity slopes ('regression gain'), and ratio of area under the curves after de-saccading ('position gain'). RESULTS: There was no mean difference between gain at 60 ms and position gain, both showing a significant correlation (r2 = 0.77, p < 0.001) for artifact-free recordings. All artifacts reduced high, normal-range gains modestly (range -0.06 to -0.11). The impact on abnormal, low gains was variable (depending on the artifact type) compared to artifact-free recordings. CONCLUSIONS: There is no clear superiority of a single gain calculation method for video HIT testing. Artifacts cause small but significant reductions of measured VOR gains in HITs with higher, normal-range gains, regardless of calculation method. Artifacts in abnormal HITs with low gain increased measurement noise. A larger number of HITs should be performed to confirm abnormal results, regardless of calculation method.

Separating posterior-circulation stroke from vestibular neuritis with quantitative vestibular testing.

OBJECTIVE: To separate vestibular neuritis (VN) from posteriorcirculation stroke (PCS) using quantitative tests of canal and otolith function. METHODS: Video Head-Impulse tests (vHIT) were used to assess all three semicircular canal pairs; vestibulo-ocular reflex (VOR) gain and saccade metrics were examined. Cervical and ocular-Vestibular-Evoked Myogenic Potentials (c- and oVEMP) and Subjective Visual Horizontal (SVH) were used to assess otolith function. RESULTS: For controls (n = 40), PCS (n = 22), and VN (n = 22), mean horizontal-canal VOR-gains were 0.96 ± 0.1, 0.85 ± 0.3 and 0.40 ± 0.2, refixation-saccade prevalence was 71.9 ± 41, 90.7 ± 57, 209.2 ± 62 per 100 impulses and cumulative-saccade amplitudes were 0.9 ± 0.4°, 2.4 ± 2.2°, 8.0 ± 3.5°. Abnormality-rates for cVEMP, oVEMP and SVH were 38%, 9%, 72% for PCS, and 43%, 50%, 91% for VN. A gain ≤0.68, refixation-saccade prevalence of ≥135% and cumulative-saccade amplitudes ≥5.3° separated VN from PCS with sensitivities of 95.5%, 95.5%, and 81.8%, and specificities of 68.2%, 86.4% and 95.5%. VOR-gain and saccade prevalence when combined, separated VN from PCS with a sensitivity and specificity of 90.9%. Abnormal oVEMP asymmetry-ratios were of low sensitivity (50%) but high specificity (90.9%) for separating VN from PCS. CONCLUSION: vHIT provided the best separation of VN from PCS. VOR-gain, refixation-saccade prevalence and amplitude were effective discriminators of VN from PCS. SIGNIFICANCE: vHIT and oVEMP could assist early identification of the aetiology of Acute Vestibular Syndrome in the Emergency Room.

The vestibular implant: Opinion statement on implantation criteria for research.

This opinion statement proposes a set of candidacy criteria for vestibular implantation of adult patients with bilateral vestibulopathy (BVP) in a research setting. The criteria include disabling chronic symptoms like postural imbalance, unsteadiness of gait and/or head movement-induced oscillopsia, combined with objective signs of reduced or absent vestibular function in both ears. These signs include abnormal test results recorded during head impulses (video head impulse test or scleral coil technique), bithermal caloric testing and rotatory chair testing (sinusoidal stimulation of 0.1 Hz). Vestibular implant (VI) implantation criteria are not the same as diagnostic criteria for bilateral vestibulopathy. The major difference between VI-implantation criteria and the approved diagnostic criteria for BVP are that all included vestibular tests of semicircular canal function (head impulse test, caloric test, and rotatory chair test) need to show significant impairments of vestibular function in the implantation criteria. For this, a two-step paradigm was developed. First, at least one of the vestibular tests needs to fulfill stringent criteria, close to those for BVP. If this is applicable, then the other vestibular tests have to fulfill a second set of criteria which are less stringent than the original criteria for BVP. If the VI-implantation is intended to excite the utricle and/or saccule (otolith stimulation), responses to cervical and ocular vestibular evoked myogenic potentials must be absent in addition to the above mentioned abnormalities of semicircular canal function. Finally, requirements for safe and potentially effective stimulation should be met, including implanting patients with BVP of peripheral origin only, and assessing possible medical and psychiatric contraindications.

Effects of parameters of video head impulse testing on visually enhanced vestibulo-ocular reflex and vestibulo-ocular reflex suppression.

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.

Video Head Impulse Testing: From Bench to Bedside.

Over 30 years ago, the head impulse test (HIT) was measured with search coil recordings and it provided robust evidence for a new test of vestibular function that could detect impairment of a single semicircular canal, that is, the lateral canal. Over the next two decades, the diagnostic spectrum of HIT was expanded to the testing of vertical canals, differentiation of central from peripheral vestibulopathy, and incorporation of visual interaction-the suppressed head impulse. However, HIT measurement was limited to very few specialized laboratories that were able to maintain the time-consuming and expensive operation of the scleral search coil system, which is the gold standard in eye movement recording. The video HIT (vHIT) was validated for the first time over 10 years ago, against the search coils, and its introduction into dizzy clinics worldwide has revolutionized the practice of neuro-otology. Here we review the basic physiology, practical aspects, and clinical application of the vHIT.

The functional head impulse test: Comparing gain and percentage of correct answers.

OBJECTIVES: The video head impulse test (vHIT) provides as output a gain value that summarizes the behavior of the vestibulo-ocular reflex as the ratio of a measure of eye movement to the corresponding measure of head movement and is not directly informative of the functional effectiveness of the motor response. The functional HIT (fHIT) is based on the ability to recognize the orientation of a Landolt C optotype that briefly appears on a computer screen during passive head impulses imposed by the examiner over a range of head accelerations; accordingly fHIT is a functional measurement of the vestibular-ocular reflex since it measures the capability to keep clear vision and to read during head movement. METHODS: We compared the results of the fHIT with those of the vHIT and the results of the Dizziness Handicap Inventory (DHI) questionnaire in a group of 27 vestibular neuritis patients recorded acutely and at 3-months follow-up. RESULTS: Both the vHIT and fHIT exams correctly classified all patients as abnormal on the affected side when tested in the acute phase. After a 3-month follow-up, both were able to show that compensation phenomena had occurred. Otherwise the data from the two techniques were not correlated. More specifically, the fHIT detected more abnormalities than the vHIT, for head rotation toward the healthy side, both in the acute phase and after 3 months, and for head rotation toward the affected side after 3 months. The asymmetry indices, that compare the performance of the healthy to the affected side, also were larger for the fHIT than for the vHIT both at onset and after 3 months. There was no significant correlation between the different vHIT and fHIT parameters and indices, or with the DHI values after 3 months. CONCLUSIONS: The fHIT data are able to detect a difference between the healthy and the affected side in the acute phase, and they show an improvement after 3 months. fHIT detects more abnormalities than vHIT, but both these techniques lack a correlation with the DHI score.

Evaluating the Diagnostic Accuracy of the Head-Impulse Test: A Scoping Review.

Importance: Vestibular symptoms rank among the most common complaints in medicine worldwide. Underlying disorders manifested by these symptoms are generally associated with an impairment of the vestibular-ocular reflex and can be assessed with different diagnostic procedures. In recent years, an increasing number of diagnostic test accuracy studies comparing various head-impulse test (HIT) methods with other diagnostic procedures have been published but not systematically reviewed. Objective: To conduct a scoping review and describe key characteristics of the growing number of diagnostic studies in patients presenting with vestibular symptoms. Evidence Review: In April 2017, published studies were identified through searches of 4 bibliographic databases: Medline, Science Citation Index Expanded, the Cochrane Library, and ScienceDirect. Studies were included if they provided diagnostic accuracy data (sensitivity and specificity) for any HIT method with reference to any other vestibular test or clinical diagnosis in patients with vestibular symptoms. Study key characteristics were extracted, and the current literature was described narratively. All analysis took place between June 2017 and July 2018. Findings: We identified a total of 27 diagnostic studies (including 3821 participants). There were disagreements between diagnostic test accuracy data both within and between studies when different HIT methods were compared with other diagnostic procedures. The proportion of correctly identified people having the disease (sensitivity) ranged between 0% and 100% (median, 41%), whereas the proportion of correctly identified people without the disease (specificity) was higher and ranged between 56% and 100% (median, 94%). Conclusions and Relevance: Based on the studies included in this review, sensitivity, specificity, and, more importantly, the risk of misdiagnosis and associated undertreatment or overtreatment cannot be reliably estimated by HIT methods for patients with vestibular symptoms. We recommend that further diagnostic studies consider (1) multiple possible underlying causes of vestibular symptoms and multiple test thresholds, (2) a representative sample of patients with and without the disease, and (3) reporting guidelines for diagnostic test accuracy studies.

Confiabilidad interevaluador de la prueba video head impulse test en estudiantes de primer año de la generación 2016 de la Escuela de Fonoaudiología de la Universidad de Valparaíso Casa Central / Inter-rater reliability of the video head impulse test in students from the School of Speech and Language therapist of the University of Valparaiso main campus class 2016

RESUMEN Introducción: El video head impulse test es un método rápido, no invasivo y cómodo para evaluar el reflejo vestíbulo ocular, el cual está siendo utilizado con mayor frecuencia en la evaluación de pacientes con alteraciones del equilibrio. Sin embargo, en Chile se evidencia una falta de estudios relacionados a la confiabilidad interevaluador de dicha prueba. Objetivo: Determinar el nivel de concordancia de los resultados de la eficiencia del reflejo vestíbulo ocular de los canales semicirculares horizontales, obtenidos mediante la aplicación de la prueba video head impulse test, por parte de 3 evaluadores. Material y método: Estudio cuantitativo, correlacional, no experimental transversal descriptivo, con muestreo no probabilístico, de participación voluntaria. La prueba video head impulse test fue aplicada por 3 examinadores a 30 estudiantes que cumplieron con los criterios de inclusión. Resultados: El método de Bland y Altman mostró gran concordancia en las mediciones realizadas entre los 3 examinadores. La correlación intraclase para la ganancia del canal semicircular horizontal derecho e izquierdo fue de 0,85 y 0,91 respectivamente y de 0,75 para el valor de asimetría. Conclusión: El estudio mostró una confiabilidad interevaluador adecuada de la prueba video head impulse test para la evaluación de los canales semicirculares horizontales.

ABSTRACT Introduction: The video head impulse test is a rapid, non-invasive and comfortable method for the evaluation of the vestibulo-ocular reflex that is being used more often in the evaluation of patients with balance disorders. In Chile there is a lack of studies related to the inter-rater reliability for this test. Aim: To determine the level of agreement on the results for the vestibulo-ocular reflex of the horizontal semicircular canals obtained by the execution of the video head impulse test by 3 raters. Material and method: Quantitative, correlational, non-experimental, cross-sectional descriptive study with a type of non-probability sampling with voluntary participation. The video head impulse test was applied by 3 raters to 30 students who fulfilled the inclusion criteria. Results: The Bland-Altman method demonstrated good agreement in the measurements made between the 3 raters. The inter-rater reliability for the gain of the left and right horizontal semicircular canals was 0.85 and 0.91 respectively and 0.75 for the asymmetry value. Conclusion: The study showed an adequate inter-rater reliability for the video head impulse test in the evaluation of the horizontal semicircular canals.

Reliability and comparison of gain values with occurrence of saccades in the EyeSeeCam video head impulse test (vHIT).

The vHIT (video head impulse test) investigates the vestibular function in two ways: a VOR (vestibulo-ocular reflex) gain value and a head impulse diagram. From the diagram covert and overt saccades can be detected. Evaluation of the vestibular function based on vHIT depends on both parameters. There is a lack of knowledge regarding the reliability of the two parameters. The objective was to investigate the reliability of vHIT by comparing gain values between examiners on the same subjects, and to see how differences affected the occurrence of saccades. SUBJECTS: 25 subjects who had undergone cochlear implant (CI) surgery. Subjects were tested using the vHIT by two of four different examiners. Two judges interpreted the occurrence of saccades in the diagram. MAIN OUTCOME MEASURES: VOR gain values and the occurrence of saccades in the diagram. Differences in gain values between examiners varied from 0.2 to 0.58 with an average of 0.14 (95 % CI 0.12-0.16) on the right ear and 0.17 (95 % CI 0.15-0.19) on the left ear. Occurrences of saccades in the same patient were reproduced in 93 % of the cases by all examiners. Kappa's coefficient on the occurrence of saccades was 0.83. Interclass correlation coefficient (ICC) of the gain values between examiners ranged from 0.62 to 0.70. Differences in gain values amongst examiners did not seem to affect the occurrence of saccades in the same patient. The occurrence of saccades, therefore, seems to be more reliable than the gain value in the evaluation of the vestibular function. Interpretation of vHIT results should, therefore, first depend on the occurrence of saccades and second on the gain value.