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Normative values of vestibulo-ocular reflex gain obtained through Video Head Impulse Test: an integrative literature review

ABSTRACT

Purpose:

to identify and analyze the available evidence on the reference values of the vestibulo-ocular reflex gain obtained with the video head impulse test.

Methods:

an integrative review based on the PRISMA protocol, searching the ProQuest, EBSCO, PubMed, ScienceDirect, Cochrane Library, LILACS, and SciELO databases with keywords. The studies included were original research articles, systematic reviews, and meta-analyses published since 2009, involving humans, written in English, Spanish and/or Portuguese.

Results:

10,250 studies related to the keywords were found. Of these, 10 articles met the inclusion criteria and were analyzed following the CADE protocol. On the horizontal plane, the values ranged from 0.80 to 1.06, while on the right anterior/left posterior and on the left anterior/right posterior planes, the values ranged from 0.80 to 1.03. Other relevant data for obtaining the gain were analyzed, such as the number of impulses, the assessor’s experience, the patient-object distance, and the percentage of asymmetry.

Conclusion:

little research on the theme, recently developed and published, mostly in European countries, was found. This shows the need for a greater number of studies to strengthen the scientific evidence.

Keywords:
Reference Values; Vestibular Function Tests; Vestibular Nerve

RESUMEN

Objetivo:

identificar y analizar la evidencia disponible sobre los valores de referencia para la ganancia del reflejo vestíbulo ocular, obtenido a través del test de impulso cefálico asistido por video.

Método:

se realizó una revisión integrativa guiada por protocolo PRISMA en las bases de datos Proquest, Ebsco, Pubmed, ScienceDirect, Cochrane Library, LILACS y Scielo de acuerdo a términos claves. Fueron incluídos artículos originales de investigación, revisiones sistemáticas y metaanálisis, publicados desde el año 2009, realizados en humanos y en idiomas inglés, español y portugués.

Resultados:

se encontraron 10.250 estudios relacionados con los términos claves utilizados. 10 artículos cumplieron con los criterios de inclusión y fueron analizados según protocolo CADE. Para plano horizontal los valores varían entre 0.80 y 1.06; mientras que para los planos DerechoAnterior/IzquierdoPosterior e IzquierdoAnterior/DerechoPosterior, los valores oscilan entre 0.80 y 1.03. Se analizaron también otros datos relevantes para la obtención de la ganancia, como la cantidad de impulsos, experiencia del evaluador, distancia paciente-objetivo y porcentaje de asimetría.

Conclusión:

la investigación en torno al tema es escasa, ha sido desarrollada y publicada de manera reciente en países principalmente europeos; demostrando la necesidad de contar con un mayor número de estudios para fortalecer la evidencia científica.

Descriptores:
Valores de Referencia; Pruebas de Función Vestibular; Nervio Vestibular

Introduction

Balance results from integrating the sensory input of visual, vestibular, and proprioceptive systems, mediated by the central nervous system11. Álvarez-Santacruz C, López-Robles M, Hellín Meseguer D. Experiencia con video head impulse testing (v-Hit). Rev. ORL. 2017;8(1):5-15.. The vestibular system comprises the otolithic organs (utricle and saccule) and the semicircular canals (anterior, posterior, and lateral), which function respectively as linear and angular accelerometers22. Lévêque M, Seidermann L, Ulmer E, Chays A. Physiologie vestibulaire: bases anatomiques, cellulaires, immunohistochimiques et e´lectrophysiologiques. Otorhinolaryngologie. Paris: Elsevier Masson; 2009.. The information coming from these structures, once having reached the brainstem by way of the vestibular nerve, establishes various pathways to make connections with multiple systems33. Suárez C. Morfología y función del sistema Vestibular. En: Ramírez Camacho R (ed). Trastornos del equilibrio. Madrid: Mc Graw-Hill Interamericana; 2003. p.3-19.. Hence, quick reflexes are generated, which are useful for standing, head stability in space, and visual stability44. Binetti A. Fisiología vestibular. Revista Faso. 2015;22(1):14-21.. These are the vestibulospinal, vestibulocollic, and vestibulo-ocular reflexes.

Specifically, the vestibulo-ocular reflex (VOR) enables the images to stabilize on the retina when the head moves, moving the eye in the opposite direction to that of the head to keep the image in the center of the visual field55. Herdman S, Clendaniel R. Vestibular rehabilitation. Fourth edition. Philadelphia: F. A Davis Company; 2014.. Traditionally, the peripheral vestibular organs that participate in the VOR have been studied with the caloric test, which was first described by Bárány in 190666. Riveros H, Cohen M, Badía P, Anabalón J, Correa C. Utilidad de la prueba calórica mínima. Rev. Otorrinolaringol. Cir. Cabeza Cuello. 2005;65(3):193-6.. Although this procedure is still in use nowadays, it is a test that only allows for the study of the lateral semicircular canal (SCC). Moreover, it is poorly tolerated by some people when dealing with a nonphysiologic stimulus, causing an intense nauseating reflex11. Álvarez-Santacruz C, López-Robles M, Hellín Meseguer D. Experiencia con video head impulse testing (v-Hit). Rev. ORL. 2017;8(1):5-15.. Another relevant difference is the stimulation speed generated by the caloric test and by the vHIT. The first one generates a low-frequency stimulation (0.003 Hz), while the vHIT generates a physiological stimulation closer to everyday situations - i.e., high-frequency ones (2-5 Hz)77. Redondo-Martínez J, Bécares-Martínez C, Orts-Alborch M, García-Callejo F, Pérez-Carbonell T, Marco-Algarra J. Relationship between Video Head Impulse Test (vHIT) and caloric test in patients with vestibular neuritis. Acta Otorrinolaringol Esp. 2016;67(3):156-61.. The scleral search coil technique, designed by Robinson in 1963, has been considered the gold standard to assess VOR88. Boleas-Aguirre M, Migliaccio A, Carey J. Registro del reflejo vestibulooculomotor con la técnica de la bobina corneal en campo magnético (scleral search coil). Revisión de afecciones vestibulares periférica. Acta Otorrinolaringol Esp. 2007;58(7):321-6.. However, despite its usefulness, it is an expensive, uncomfortable, and invasive procedure for the patient, and of difficult clinical implementation99. Carriel P, Rojas M. Prueba de impulso cefálico: bases fisiológicas y métodos de registro del reflejo vestíbulo oculomotor. Rev. Otorrinolaringol. Cir. Cabeza Cuello. 2013;73(2):206-12., besides being a lengthy performance with complex interpretation1010. Pérez-Fernández N, Gallegos-Constantino V, Barona-Lleo L, Manríque-Huarte R. Exploración clínica y videoasistida del reflejo vestíbulo-oculomotor: Análisis comparativo. Acta Otorrinolaringol Esp. 2012;63(6):429-35..

In 2005, Ulmer and Chays1111. Ulmer E, Chays A. Head Impulse Test de Curthoys & Halmagyi. Un dispositif d'analyse. Ann Otolaryngol Chir Cervicofac. 2005;122(2):84-90. reported using a camera placed in front of the patient to record and register the eye movement in the head impulse test. The purpose was to quantify the function of each SCC. Later, MacDougall, Weber, McGarvie, Halmagyi and Curthoys (2009)1212. MacDougall HG, Weber KP, McGarvie LA, Halmagyi GM, Curthoys IS. The video head impulse test. Diagnostic accuracy in peripheral vestibulopathy. Neurology. 2009;73(14):1134-41. described in detail the procedure currently most used. The vHIT results from the need for a new complementary examination that overcomes the disadvantages of the previous ones1313. Gómez A, Bruna A, Franzoy D, Julio M, Olivares R, Vicencio N. Eficiencia del reflejo vestíbulo ocular mediante la aplicación de la prueba Video Head Impulse Test, en estudiantes de primer año de las Escuelas de Fonoaudiología y de Tecnología Médica de la Universidad de Valparaíso. Rev. Otorrinolaringol. Cir. Cabeza Cuello. 2015;75(2):137-44. and that makes it possible to evaluate the efficiency of the VOR in a simple, objective, and easy performance, without causing discomfort to the patient1414. Silva M, Arias R, Carriel C, Sariego H. Evaluación del Video Head Impulse Test (V-Hit) en el diagnóstico del neurinoma del acústico. Rev. Otorrinolaringol. Cir. Cabeza Cuello. 2015;75(3):213-9.. Also, it evaluates individually the function of the six SCC1515. Halmagyi GM, Weber KP, Aw ST, Todd MJ, Curthoys IS. Impulsive testing of semicircular canal function. In: Kennard C, Leigh RJ (eds). Using eye movements as an experimental probe of brain function. London: Elsevier Science; 2008. p.187-94., and thus, the function of the superior and inferior vestibular nerves1616. Halmagyi M, Curthoys I. The Video Head Impulse Test in clinical practice. Neurol Sci Neurophysiol. NSN. 2018;35(1):1-5..

The vHIT is based on the record of the eye movements with high-speed cameras (250º/seg) placed in goggles adjustable for each patient. By means of a passive, unpredictable, and fast head movement, it makes it possible to determine the efficiency of the VOR, which is the “property of generating slow eye movements almost perfectly compensatory in direction and speed to the head movements”99. Carriel P, Rojas M. Prueba de impulso cefálico: bases fisiológicas y métodos de registro del reflejo vestíbulo oculomotor. Rev. Otorrinolaringol. Cir. Cabeza Cuello. 2013;73(2):206-12.. One of the components of such efficiency is the gain, which is the relationship between the head movement and the displacement of the eyes1717. Alhabib S, Saliba I. Video Head Impulse Test: a review of the literature. Eur Arch Otorhinolaryngol. 2017;274(3):1215-22.. It is one of the values to be analyzed in the results obtained in the examination. It is calculated by dividing the speed of the head movement by the speed of the eye movement. Hence, values close to one indicate similar speeds.

Although the suggested normal values are those close to one, there is an evident need to know the reference values for the analysis of the VOR gain based on a range (minimum and maximum value) that enables a precise vestibular diagnosis. This is particularly so if other associated factors - e.g., age and brand of the equipment used - are considered. Moreover, the value close to one has been informed for the study of the lateral semicircular canal, but not for the anterior and posterior ones.

However, no review has yet grouped the existing studies on the theme, at the same time identifying a consensus between the various published articles. Therefore, the present integrative review aimed to identify and analyze the available evidence on the reference values for the vestibulo-ocular reflex gain, obtained with the video head impulse test.

Methods

Research Strategy

The research team conducted an integrative literature review on reference values for results analysis of the video head impulse test (vHIT). The paper was designed based on guidelines and orientations of the Preferred Reporting Items for Systematic Reviews (PRISMA)1818. Moher D, Liberati A, Tetzlaff J, Altman D, PRISMA Group. Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. Guidelines and Guidance. PLoS Med. 2009;6(7):1-7.,1919. Liberati A, Altman D, Tetzlaff J, Mulrow C, Gotzsche P, Ioannidis J et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. Guidelines and Guidance. PLoS Med. 2009;6(7):1-28.. The first step in the research was to develop the research question for the literature review, which was defined as: “What are the reference values for vestibulo-ocular reflex gain obtained with the video head impulse test?”.

The review was based on a search for studies published in the ProQuest, EBSCO, PubMed, ScienceDirect, Cochrane Library, LILACS, and SciELO databases. Each researcher carried it out in October and November 2019 using combinations of the following descriptors, first in English and then in Spanish and Portuguese: “Normative values” and “video head impulse test”, “Normative data” and “video head impulse test”, “Normative findings” and “video head impulse test”, “Reference values” and “video head impulse test”. The descriptors were combined with the Boolean operator AND.

Selection Criteria

The types of studies included in the search were original research and review articles (either systematic or meta-analysis). The inclusion criteria considered studies published from 2009 to the present, performed in humans. The exclusion criteria encompassed papers unrelated to the purpose and question of this research, those that included exam results of specific otologic pathologies (Ménière’s disease, vestibular neuronitis, vestibular schwannoma), findings in other conditions unrelated to the vestibular system (e.g., bruises in athletes), comparisons between the results of the caloric test and that of Dix-Hallpike, duplicated studies between the databases, irrelevant studies, or those written in languages other than the predefined ones.

In the search, 10,250 potential articles were identified based on the abovementioned combination of descriptors and inclusion criteria. The process of analysis of the articles had three stages. The first one involved reading the titles and abstracts; hence, the clearly irrelevant articles were dismissed. In the second stage, the articles were read in full to verify whether they answered the research question, at the same time applying the exclusion criteria. Lastly, the third stage consisted of the critical analysis of the selected articles, following the Critical Appraisal of Diagnostic Evidence (CADE)2020. Dollaghan CA. The handbook for evidence-based practice in communication disorders. Baltimore: Paul H Brookes Publishing; 2007.. It was independently conducted by the assessors (H.S.P; P.O.D); in case they disagreed, a third assessor was invited (S.R.R) to solve the problem.

Of the 10,250 articles initially found in the databases, 20 were excluded for being duplicated in the search, and 10,219, for being unrelated to the purpose and/or the question of the research. After reading in full the 14 articles evaluated for eligibility, 10 were selected for this review. The identification and characterization of the included articles are presented in Figure 1.

Figure 1:
Flowchart with the selection of the articles.

Literature Review

Based on the combination of descriptors in English, Spanish, and Portuguese, 10,250 potential articles were identified, of which 14 were selected after applying the inclusion and exclusion criteria, having already read the titles and/or abstracts. Four of these articles were dismissed after reading them in full. Hence, 10 articles, which are described in detail in Table 1, were included in the analysis. The results were presented considering the author, year, country, sample size (n), equipment used, planes assessed - horizontal, RALP (right anterior/left posterior), and LARP (left anterior/right posterior) -, and main values obtained according to the ages assessed. Due to the heterogeneity of the equipment used, age ranges, and planes assessed, it was not possible to group the data based on statistical analysis. Thus, the present study is a systematic review without meta-analysis.

Table 1:
Characteristics of the articles selected for the review

The articles analyzed were collected mostly from the PubMed database, followed by EBSCO and ProQuest. The ScienceDirect, LILACS, SciELO, and Cochrane Library databases did not return relevant results with the descriptors used. Regarding the year of publication, although the present research included articles since 2009, the analyzed ones were published only recently, between 2015 and 2018 - i.e., approximately one decade after the vHIT was introduced as a vestibular function assessment procedure. The countries of origin that stood out are European (Germany2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.

27. Lehnen N, Ramaioli C, Sean N, Bartl K, Kohlbecher S, Jahn K et al. Clinical and video head impulses: a simple bedside test in children. J neurol. 2017;264(5):1002-4.
-2828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62. and Spain2222. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.), followed by Korea2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300., Australia2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11., New Zealand2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8., India2525. Bansal S, Kumar S. Assessment of VOR gain function and its test-retest reliability in normal hearing individuals. Eur Arch Otorhinolaryngol. 2016;273(10):3167-73., and the United States2929. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26.. On the other hand, the appreciation did not include any Latin American studies, demonstrating the need for local data.

The age groups studied in the analyzed articles are heterogeneous. Four of them focused mainly on the child and /or youth population2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.

27. Lehnen N, Ramaioli C, Sean N, Bartl K, Kohlbecher S, Jahn K et al. Clinical and video head impulses: a simple bedside test in children. J neurol. 2017;264(5):1002-4.

28. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62.
-2929. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26.; three pieces of research involved young adults and/or adults2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,2525. Bansal S, Kumar S. Assessment of VOR gain function and its test-retest reliability in normal hearing individuals. Eur Arch Otorhinolaryngol. 2016;273(10):3167-73.,3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300.; none of them included exclusively older adults; and three considered a combination of all these age groups2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.

22. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.
-2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.. It should be mentioned that all the studies analyzed included men and women. Regarding the sample size, two studies counted with 274 and 212 subjects2222. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.. Three other studies included from 50 to 91 participants2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.,2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.. Lastly, five authors included 6 to 44 subjects2525. Bansal S, Kumar S. Assessment of VOR gain function and its test-retest reliability in normal hearing individuals. Eur Arch Otorhinolaryngol. 2016;273(10):3167-73.

26. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.

27. Lehnen N, Ramaioli C, Sean N, Bartl K, Kohlbecher S, Jahn K et al. Clinical and video head impulses: a simple bedside test in children. J neurol. 2017;264(5):1002-4.

28. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62.

29. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26.
-3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300.. The quite small samples used in some articles call attention, especially considering the broad age range - which diminishes the validity of the conclusions proposed by the authors. Hence, it is suggested that a greater number of participants be included to obtain data representative of the population, allowing for a reliable statistical analysis.

Concerning the assessed planes, four articles obtained gain values for vestibulo-ocular reflex on the horizontal, RALP, and LARP planes2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.,2525. Bansal S, Kumar S. Assessment of VOR gain function and its test-retest reliability in normal hearing individuals. Eur Arch Otorhinolaryngol. 2016;273(10):3167-73.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.,2929. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26., while six studies only obtained them on the horizontal plane2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2222. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.,2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,2727. Lehnen N, Ramaioli C, Sean N, Bartl K, Kohlbecher S, Jahn K et al. Clinical and video head impulses: a simple bedside test in children. J neurol. 2017;264(5):1002-4.,2828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62.,3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300.. On the horizontal plane, the reference values range from 0.80 to 1.06, while on the RALP and LARP planes, the values range from 0.80 to 1.03. Only one study (which worked with six children aged five to 36 months) reports values lower than 0.802828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62. on the horizontal plane. It was noted that the gain slightly decreases both as the age increases and as the vertical SCCs are studied. Hence, it is proposed that all planes (horizontal, RALP, and LARP) be evaluated to establish a complete reference in relation to the various age ranges.

In six of the analyzed studies, the said planes were assessed using vHIT equipment manufactured by Otometrics (Denmark), followed by two that employed equipment manufactured by Interacoustics (Denmark), one, by Synapsys (France), and one, by SLMed (Korea). It is highlighted that the emphasis of the studies conducted with Otometrics addresses the analysis on the horizontal, RALP, and LARP planes, in a broad age range, from 4 to 95 years. On the other hand, the research with Interacoustics considered only obtaining data from the assessment on the horizontal plane in the child population in one study, and in 60 subjects 20 to 80 years old, grouped by decades in equal numbers. In the case of data obtained with Synapsys and SLMed, all the planes were assessed in 274 children aged one to 15 years in the first case, and only the horizontal plane in a small sample of young adults. Although various brands in the market developed equipment to assess this function, not all of them have reference values for all the planes assessed in the examination, or for the different age ranges. This need is emphasized by Lee et al. (2018)3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300., after showing differences in the vHIT gains in normal subjects depending on the device and analysis method used (Impulse by GN Otometrics versus SLVNG by SLMED Inc.).

Other relevant gain-related data in the selected articles were analyzed, approaching the number of impulses, the assessor’s experience, the patient’s distance to the object, and the percentage of asymmetry between the ears. Concerning the number of head impulses, the results are heterogeneous, describing at least five2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14., 102323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.,2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300., 152828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62., or 202222. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.,2525. Bansal S, Kumar S. Assessment of VOR gain function and its test-retest reliability in normal hearing individuals. Eur Arch Otorhinolaryngol. 2016;273(10):3167-73.,2929. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26. valid impulses on each side or for each canal studied. Also, six of the reviewed articles2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14.,2828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62.

29. Bachmann K, Sipos K, Lavender V, Hunter L. Video Head Impulse Testing in a pediatric population: normative findings. J Am Acad Audiol. 2018;29(5):417-26.
-3030. Lee S, Yoo M, Park J, Kang B, Yang C, Kang W et al. Comparison of Video Head Impulse Test (vHIT) gains between two commercially available devices and by different gain analytical methods. Otol Neurotol. 2018;39(5):297-300. indicate that the assessor was trained and experienced to perform the examination, whereas the other articles do not mention this aspect. As for the patient’s distance to the object, most kept one meter, with exceptions for 1.30 meters2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14., 1.5 meters2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2828. Wenzel A, Eck S, Hülse K, Rohr K, Hörmann K, Umbreit C et al. Development of a new software and test setup for analyzing hVOR in very young children by vHIT. Journal of Vestibular Research. 2017;27(2-3):155-62., and even 1.80 meters2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.. Lastly, regarding the percentage of asymmetry between the ears, great variability was again noticed between the four pieces of research that touch the subject, ranging from 2% to 15%2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2222. Matiño-Soler E, Esteller-More E, Martin-Sanchez J, Martinez-Sanchez J, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the Video Head Impulse Test. Otol Neurotol. 2015;36(3):466-71.,2424. Yang CJ, Lee JY, Kang BC, Lee HS, Yoo MH, Park HJ. Quantitative analysis of gains and catch-up saccades of video-head-impulse testing by age in normal subjects. Clin Otolaryngol. 2016;41(5):1-7.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14..

The articles included in the review were analyzed regarding their methodological quality based on the Critical Appraisal of Diagnostic Evidence (CADE)2020. Dollaghan CA. The handbook for evidence-based practice in communication disorders. Baltimore: Paul H Brookes Publishing; 2007. (Table 2), although some items had to be adapted or dismissed because they did not fit the needs of this review. In summary, the great majority of the studies present at least a good quality level. Three articles2121. Mossman B, Mossman S, Purdie G, Schneider E. Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography. J Otolaryngol Head Neck Surg. 2015;44(29):1-8.,2323. McGarvey L, MacDougall M, Malmagyi G, Burgess A, Weber K, Curthoys I. The Video Head Impulse Test (vHIT) of semicircular canal function-age-dependent normative values of VOR gain in healthy subjects. Front. Neurol. 2015;6(154):1-11.,2626. Wiener-Vacher S, Wiener S. Video Head Impulse Tests with a remote camera system: normative values of semicircular canal vestibulo-ocular reflex gain in infants and children. Front. Neurol. 2017;8(434):1-14. included their findings’ confidence intervals, which reinforces the quality of their analyses. Almost all the studies precisely describe the participants, as well as the methods employed. None of the studies included in this research considered either the positive or the negative likelihood ratio because the original studies did not compare participants with pathologies.

Regarding the said good quality level of the articles, the author of CADE2020. Dollaghan CA. The handbook for evidence-based practice in communication disorders. Baltimore: Paul H Brookes Publishing; 2007. explains that the evidence is compelling when there are few weak or questionable points in the study. The second level is the suggestive category, in which there are questionable points regarding the validity of the studies. Lastly is the equivocal category, in which there are more questionable points than solid ones in the research. The clinical decisions should be aligned with this when adopting new clinical techniques.

Table 2:
Qualitative analysis of the included articles, following the Critical Appraisal of Diagnostic Evidence (CADE)

Conclusion

The present study points out that there is little scientific evidence addressing the normative values for vestibulo-ocular reflex gain obtained with the video head impulse test. The research on the theme has only recently been developed and published, starting in 2015, mostly in European countries, followed by others in different parts of the world. However, Latin American countries still lack references on the subject, which shows the need for a greater number of studies, including normative values to strengthen the scientific evidence.

Altogether, 10 articles were identified and analyzed, which suggest reference values for VOR gain close to one. Specifically, on the horizontal plane, the values ranged from 0.80 to 1.06, while on the RALP and LARP planes they ranged from 0.80 to 1.03. Some differences were noted regarding age and the comparison between vertical and horizontal canals. This points to research that can result in a systematic review with meta-analysis, to make a quantitative analysis of the different variables that can influence the vHIT-measured VOR gain.

The importance of having normative values available lies in their being a reference guide for future comparison with values obtained in the clinical practice. These are essential to medical decision-making regarding the diagnosis, treatment, and follow-up of the health condition of a given population.

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  • Research support source: This study was financed by the Fondo Interno de Investigación de Clínicas Docentes año 2019 (código TAS O000040215/ERP 11600001), of the Universidad Santo Tomás, Chile.

Publication Dates

  • Publication in this collection
    28 Sept 2020
  • Date of issue
    2020

History

  • Received
    20 Apr 2020
  • Accepted
    11 Aug 2020
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