Evaluation on Effectiveness of a New System as well as Analysis on Optimal Horizontal Eye Position for Vertical Video Head Impulse Test.

OBJECTIVE: To compare the performances among three different systems for video head impulse test (vHIT), and to identify an optimal target angle for precisely evaluating the function of vertical semicircular canals in vHIT. METHODS: A two-center prospective study was done. Participants were sit 1.2 m away from the wall in a noise-proved room that dedicated for vHIT experiments. During the comparison experiments, similar settings were ensured in both hospitals, with the same distance to wall and angle of staring. For each equipment, the procedures followed the developers' recommendations. The same examiner performed the comparison between two systems in one location. For the eye-position projects, targets were placed on the wall sequentially at the pre-marked lines for different angles. For the comparison projects, 9 and 13 participants were recruited, respectively. Any participant with otologic or vestibular disorders was excluded. A total of 26 healthy participants were recruited in the eye-position experiments, 16 of which were further involved in inter-examiner tests. RESULTS: Our evaluations of three different systems showed that a new vHIT system, VertiGoggles® ZT-VNG-I (VG) performed as good as the long-tested Otometrics® ICS impulse (Oto) and EyeSeeCam® (ESC). During the comparison, we validated 25-degree, instead of right ahead at 0 degree, is a better place to set the targets when torsion was applied at vertical semicircular canal planes. CONCLUSION: The new VG system is good for clinical practices. Furthermore, we proposed a new protocol to set the targets 25 degrees from right ahead after tilting head 45 degrees to evaluate vertical canals during vHIT.

Are gain values significantly altered by manual data selection when performing the video Head Impulse Test (v-HIT) on all six semicircular canals with two different v-HIT systems.

BACKGROUND: It has not yet been tested whether averaged gain values and the presence of pathological saccades are significantly altered by manual data selection or if data selection only done by the incorporated software detection algorithms provides a reliable data set following v-HIT testing. OBJECTIVE: The primary endpoint was to evaluate whether the averaged gain values of all six SCCs are significantly altered by manual data selection with two different v-HIT systems. METHOD: 120 subjects with previously neither vestibular nor neurological disorders underwent four separate tests of all six SCCs with either EyeSeeCam® or ICS Impulse®. All v-HIT test reports underwent manual data selection by an experienced ENT Specialist with deletion of any noise and/or artifacts. Generalized estimating equations were used to compare averaged gain values based on unsorted data with averaged gain values based on the sorted data. RESULTS: EyeSeeCam®: Horizontal SCCs: The estimate and the p-value (shown in parenthesis) for the right lateral SCC and the left lateral SCC were 0.00004 (0.95) and 0.00087 (0.70) respectively. Vertical SCCs: The estimate varied from -0.00858 to 0.00634 with p-values ranging from 0.31 to 0.78. ICS Impulse®: Horizontal SCCs: The estimate and the p-value for the right lateral SCC and the left lateral SCC were 0.00159 (0.18) and 0.00071 (0.38) respectively. Vertical SCCs: The estimate varied from 0.00217 to 0.01357 with p-values ranging from 0.00 to 0.17. Based upon the averaged gain value from the individual SCC being tested, 148 tests before and 127 after manual data selection were considered pathological. CONCLUSION: None of the two v-HIT systems revealed any clinically important effects of manual data selection. However, 21 fewer tests were considered pathological after manual data selection.

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.

Horizontal Vestibulo-Ocular Reflex Gain Measures During Convergence Using a Monocular Video Technique.

HYPOTHESIS: Vestibulo-ocular reflex (VOR) response measures during convergence, which are clinically important to measure peripheral vestibular organ function during rotational and translational rapid head movements, can be implemented using existing clinically available monocular video-oculography (VOG) systems. BACKGROUND: We have developed and validated a monocular VOG technique that allows for accurate measurement of the convergence angle immediately before a rapid translational or rotational head movement. METHODS: We recorded binocular eye movements while subjects performed active or passive horizontal head impulses while viewing near and far targets. We calculated the convergence angles and VOR gains using monocular and binocular methods and compared them with a geometric model. RESULTS: The monocular VOG technique resulted in convergence angle and VOR gain (eye velocity/head velocity) calculations that differed by ∼10% compared with values calculated using the binocular data. CONCLUSIONS: The monocular VOG technique can be clinically implemented using any unmodified, commercially available, monocular VOG system, provided its camera can be positioned to track either eye. Many vestibular clinics already have access to such systems. This method makes possible reliable measurement of the near-viewing horizontal angular VOR during the head impulse test, the translational VOR during the head heave test in patients, and the clinical measurement of convergence insufficiency.

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.

Power spectra prognostic aspects of impulsive eye movement traces in superior vestibular neuritis.

Since usefulness of power spectra (PS) analysis was demonstrated in many fields of electrophysiology, the aims of the present study were to evaluate differences in frequency domain values of eye velocity traces between a group of 60 healthy subjects (HC) and 35 matched superior vestibular neuritis (VN) patients and to determine prognostic aspects of such values in terms of superior VN recovery. PS calculated on video head impulse test traces was compared between HC and during the acute stage of vertigo (T1) and after 3 months (T2) in superior VN patients. A multiple regression and desirability model between Δ (T2gain - T1gain) vestibulo-ocular reflex (VOR) gain and five prognostic factors were employed. Significant PS differences within the 7.8-16.6 Hz domain were found between superior VN and HC. A significant negative correlation was found between the 7.8-16.6 Hz domain unitary PS value and Δ VOR gain (ß = - 0.836). The desirability model depicted a cutoff value of the unitary PS equal to 1.82 in order to obtain a Δ VOR gain rate at least equal to 0.1. Present findings could be a further step for monitoring those superior VN patients with systemic risk factors and high risk of VOR incomplete recovery. Graphical abstract In the top left, healthy control (HC) and superior vestibular neuritis (VN) subjects were screened by means of video head impulse test. In the top right, significant differences in power spectra values were depicted within the 7.8-16.6 Hz domain when comparing the two groups of subjects. In the bottom center, the desirability model depicts a cutoff value of the power spectra equal to 1.82 in order to obtain a Δ vestibulo-ocular reflex gain rate at least equal to 0.1.

Effects of Device on Video Head Impulse Test (vHIT) Gain.

BACKGROUND: Numerous video head impulse test (vHIT) devices are available commercially; however, gain is not calculated uniformly. An evaluation of these devices/algorithms in healthy controls and patients with vestibular loss is necessary for comparing and synthesizing work that utilizes different devices and gain calculations. PURPOSE: Using three commercially available vHIT devices/algorithms, the purpose of the present study was to compare: (1) horizontal canal vHIT gain among devices/algorithms in normal control subjects; (2) the effects of age on vHIT gain for each device/algorithm in normal control subjects; and (3) the clinical performance of horizontal canal vHIT gain between devices/algorithms for differentiating normal versus abnormal vestibular function. RESEARCH DESIGN: Prospective. STUDY SAMPLE: Sixty-one normal control adult subjects (range 20-78) and eleven adults with unilateral or bilateral vestibular loss (range 32-79). DATA COLLECTION AND ANALYSIS: vHIT was administered using three different devices/algorithms, randomized in order, for each subject on the same day: (1) Impulse (Otometrics, Schaumberg, IL; monocular eye recording, right eye only; using area under the curve gain), (2) EyeSeeCam (Interacoustics, Denmark; monocular eye recording, left eye only; using instantaneous gain), and (3) VisualEyes (MicroMedical, Chatham, IL, binocular eye recording; using position gain). RESULTS: There was a significant mean difference in vHIT gain among devices/algorithms for both the normal control and vestibular loss groups. vHIT gain was significantly larger in the ipsilateral direction of the eye used to measure gain; however, in spite of the significant mean differences in vHIT gain among devices/algorithms and the significant directional bias, classification of "normal" versus "abnormal" gain is consistent across all compared devices/algorithms, with the exception of instantaneous gain at 40 msec. There was not an effect of age on vHIT gain up to 78 years regardless of the device/algorithm. CONCLUSIONS: These findings support that vHIT gain is significantly different between devices/algorithms, suggesting that care should be taken when making direct comparisons of absolute gain values between devices/algorithms.

Effect of Goggle Slippage on the Video Head Impulse Test Outcome and Its Mechanisms.

OBJECTIVES: The aim of this study was to quantitatively measure the tightness of the goggle strap during the video head impulse test (vHIT) and to identify slippage-induced artifacts according to tightness. We aimed to elucidate the mechanism of faulty gain caused by goggle slippage and explain the typical artifacts associated with it. SUBJECTS AND METHODS: An endotracheal tube cuff manometer was coupled to the EyeSeeCam vHIT system (Interacoustics, Assens, Denmark) to monitor strap tightness. The instantaneous gain (40, 60, and 80 ms) and regression gain were compared in eight healthy subjects under the following strap tightness conditions: loose (25 cm H2O), tight (35 cm H2O), and very tight (45 cm H2O). To elucidate the mechanism of faulty gain caused by goggle slippage, a fake fixed pupil with a vestibule ocular reflex (VOR) gain of 0 was attached to the subject's eyelid. The faulty gain recording pattern was analyzed as the tightness of the strap was decreased. RESULTS: The most common slippage-induced artifacts were: 1) initial backward eye movement toward the head movement, 2) acceleration bumps, 3) high gain, and 4) deceleration bumps. At 40 ms, the gain was significantly lower in the 25 cm H2O condition (0.68 ±â€Š0.32 cm H2O) compared with the 45 cm H2O condition (0.90 ±â€Š0.26 cm H2O). At 80 ms, the gain was higher for the 25 cm H2O condition (1.24 ±â€Š0.27 cm H2O) compared with the 45 cm H2O condition (1.16 ±â€Š0.30 cm H2O). These findings were progressively more obvious as the tightness of the strap decreased in a dose-dependent manner. When the fake pupil was recorded, initial backward eye movement toward the head movement (negative VOR gain) and eye tracing mimicking a small VOR (positive VOR gain) were recorded, despite the fake pupil having absolutely no movement. These artifact recordings are presumed to be related to the faulty low (40 ms) and high (80 ms) gain calculation. CONCLUSIONS: Slippage-induced artifacts are presumed to be because of the slingshot-like movement of the goggles during head movement in three different phases (lagging, overshooting, and bouncing of the goggles). Monitoring the pressure of the strap tightness may be a solution for minimizing this slippage. A strap tightness of at least 45 cm H2O is required for reliable vHIT recording and gain calculations.

Relación entre el video head impulse test (vHIT) y la prueba calórica en el estudio evolutivo de pacientes con neuritis vestibular / Relationship between video head impulse test (vHIT) and caloric test in patients with vestibular neuritis

Introducción y objetivos: La prueba calórica es hasta ahora la prueba de referencia para el diagnóstico y el examen de una hipofunción vestibular unilateral. El video head impulse test (vHIT) valora el reflejo vestíbulo-oculomotor, mediante el registro videoasistido de la maniobra impulsiva. Se pretende comparar la variación de los resultados del vHIT y la prueba calórica en pacientes con neuritis vestibular respecto a su estado inicial en diferentes puntos de su evolución, y comprobar su grado de correlación entre sí y con el test Dizziness Handicap Inventory (DHI). Métodos: Exploración en la misma sesión mediante vHIT y prueba calórica de 20 pacientes con neuritis vestibular. Valoración de la correlación de dichas pruebas entre sí y con el test DHI en 2 momentos diferentes de la evolución para cada paciente. Resultados: La asimetría de la ganancia del vHIT y la paresia canalicular de la prueba calórica no evidenciaron una correlación lineal entre ellas. Tampoco se apreció una correlación entre el DHI y la recuperación de los parámetros de estas 2 pruebas. Las sacadas Covert mantienen una velocidad similar mientras están presentes en el vHIT, mientras que las Overt disminuyen su velocidad con el tiempo. Conclusiones: El vHIT y la prueba calórica muestran diferentes respuestas del reflejo vestíbulo-oculomotor, dado que exploran diferentes frecuencias del mismo. No se ha encontrado una correlación entre el vHIT, la prueba calórica y el DHI a lo largo de la evolución de la neuritis vestibular, siendo pruebas complementarias entre sí (AU)

Introduction and objectives: The caloric test is the gold standard for the loss of vestibular function diagnosis. The Video Head Impulse Test (vHIT) assesses the same reflex by using a video- assisted examination of the impulsive maneuver. We intend to compare the variation of results of the vHIT and the caloric test in patients with vestibular neuritis with respect to their initial condition at two different moments of their evolution and to check the level of correlation between them and with that of the DHI test. Methods: We explored 20 patients with neuritis by using both vHIT and the caloric test on the same day. We assessed the correlation between these two tests and with the DHI test for each patient at two different moments of their evolution. Results: We calculated gain asymmetry and compared it with the canal paresis, but we found neither a linear correlation between them, nor a correlation between the DHI test or improvement of these two other tests. We conclude that the covert saccades maintain a similar speed whilst present in the VHIT, but the overts diminish their speed over time. Conclusions: The VHIT and the caloric test show different responses of the vestibulo-ocular reflex, because they stimulate different frequencies of this reflex. No correlation was found between the VHIT, the caloric test and the DHI test. The tests appear to complement one another (AU)

The horizontal computerized rotational impulse test.

Whole-body impulsive rotations were used to overcome several limitations associated with manual head impulse testing. A computer-controlled rotational chair delivered brief, whole-body, earth-vertical axis yaw impulsive rotations while eye movements were measured using video-oculography. Results from an unselected group of 20 patients with dizziness and a group of 22 control subjects indicated that the horizontal computerized rotational head impulse test (crHIT) is well-tolerated and provides an estimate of unidirectional vestibulo-ocular reflex gain comparable to results from caloric testing. This study demonstrates that the horizontal crHIT is a new assessment tool that overcomes many of the limitations of manual head impulse testing and provides a reliable laboratory-based measure of unilateral horizontal semicircular canal function.

The video head impulse test during post-rotatory nystagmus: physiology and clinical implications.

The aim of this study was to test the effects of a sustained nystagmus on the head impulse response of the vestibulo-ocular reflex (VOR) in healthy subjects. VOR gain (slow-phase eye velocity/head velocity) was measured using video head impulse test goggles. Acting as a surrogate for a spontaneous nystagmus (SN), a post-rotatory nystagmus (PRN) was elicited after a sustained, constant-velocity rotation, and then head impulses were applied. 'Raw' VOR gain, uncorrected for PRN, in healthy subjects in response to head impulses with peak velocities in the range of 150°/s-250°/s was significantly increased (as reflected in an increase in the slope of the gain versus head velocity relationship) after inducing PRN with slow phases of nystagmus of high intensity (>30°/s) in the same but not in the opposite direction as the slow-phase response induced by the head impulses. The values of VOR gain themselves, however, remained in the normal range with slow-phase velocities of PRN < 30°/s. Finally, quick phases of PRN were suppressed during the first 20-160 ms of a head impulse; the time frame of suppression depended on the direction of PRN but not on the duration of the head impulse. Our results in normal subjects suggest that VOR gains measured using head impulses may have to be corrected for any superimposed SN when the slow-phase velocity of nystagmus is relatively high and the peak velocity of the head movements is relatively low. The suppression of quick phases during head impulses may help to improve steady fixation during rapid head movements.

Video head impulse testing (VHIT) in the pediatric population.

OBJECTIVES: VHIT is the first vestibular test to evaluate all six semicircular canals. This test has advantages over the rotary chair and caloric tests in evaluating children since it does not require fear-inducing darkness or provocation of dizziness. The goal of this study was to review our initial experience with VHIT in children and adolescents at a pediatric vestibular program. METHODS: Results using the ICS Impulse VHIT device in 33 patients <20 years of age were retrospectively reviewed. Rotary chair testing was used to designate 26 subjects into groups with normal (n=20) and abnormal (n=6) lateral semicircular canal (LSC) function for comparison. RESULTS: Ages ranged from 3 to 19 years (mean 13±4.3) with no statistically significant difference in mean lateral canal gains between age groups (3-10, 11-14, 15-19 years, respectively) by one-way ANOVA, p=0.111. LSC VHIT gain of <0.7 demonstrated sensitivity of 66.7%, specificity of 100%, positive predictive value of 100%, negative predictive value of 90.9% for detecting abnormal LSC function. Corrective saccades demonstrated 100% sensitivity and 100% specificity for detecting abnormal LSC function. VHIT gain <0.7 in an anterior (n=7) or posterior (n=9) canal was only found in subjects with a clinical history and abnormal findings on other tests indicative of a diagnosis involving the affected canal (e.g. benign paroxysmal positioning vertigo, vestibular neuritis, etc.). CONCLUSION: VHIT is an effective test for evaluating semicircular canal function in children and offers major potential advantages over rotary chair and caloric testing.

A study of the relationship between the video head impulse test and air calorics.

The video head impulse test (vHIT) has been proposed as an objective approach to detect peripheral vestibular disorder in a clinical setting. Data from several studies indicate that the vHIT is a useful addition to the vestibular test battery and can give complementary information to caloric testing. This study explores the relationship between lateral canal vestibular occular reflex gain measured using the vHIT system and canal paresis indicated using air calorics in a sample of patients attending a clinic for balance disorder. Sensitivity and specificity of the vHIT test relative to calorics was studied for a clinical sample of 51 patients (20 male, 31 female) who attended a private clinic for balance disorders. vHIT gains were compared to the manufacturer's normative range and to data from a normative study using 30 young volunteers. Of 14 patients in the clinical sample that had significant canal paresis indicated by air calorics, only 4 showed a significant abnormality in either canal using a measurement of vHIT gain. vHIT gain does not correlate with canal paresis as indicated by air caloric testing. vHIT gain appears relatively insensitive to peripheral vestibular disorder as indicated by air caloric testing, although patients that had no caloric response on one side showed abnormal vHIT gain. vHIT testing may be a useful addition to the existing vestibular test battery, but it does not appear to be an alternative to it.

Reading while moving: the functional assessment of VOR.

The head impulse test (HIT) is nowadays recognized as the gold standard for clinical testing of the angular vestibulo-ocular reflex (VOR). By imposing unpredictable, abrupt head rotations in canal pairs' planes it aims at unveiling the dysfunction of the semicircular canal towards which the head is rotated based on Ewald's II law. Functional testing of the VOR aims at assessing the ability of the reflex to stabilize gaze in space and thus allow clear vision during head movements. The HIT device (HITD) approach exploits impulsive head rotations spawning a range of angular accelerations while requiring subjects to identify optotypes briefly displayed on a screen. Here we also recorded eye movements, so that the evaluation of the individual subject is based both on the VOR gain and on the percentage of correct answers with respect to a population of controls. Here we used the HITD to study 14 patients suffering from vestibular neuritis and 7 of those were re-tested after three months. We found that the HITD was able to unveil the ipsilesional deficit and the contralesional impairment, together with the improvement in the follow-up test.