Comparison of two systems for the video head impulse test (vHIT) for the lateral semicircular canal: description of results from normal and pathological subjects.

Lilian Felipe

doi:10.1590/0004-282x-anp-2020-0301

Abstract

The video head impulse test (vHIT) is a recent technique for functional evaluation of semicircular canals (SSCs). The vHIT examines eye movements at high frequencies of stimulation and provides an objective assessment of the functioning of the high-frequency domain of the vestibular system. To describe the results from vHIT performed using two systems. All subjects were evaluated through an audiological and otoneurological battery of tests and were diagnosed as normal or abnormal by an otorhinolaryngologist. The results from two systems: 1. ICS Impulse (Otometrics/Natus, Denmark) and 2. EyeSeeCam (InterAcoustics, Denmark) were recorded. The same operator delivered every impulse to every subject. The head impulses were performed while the operator was standing behind the subject, using both hands on the top of the subject's head, well away from the goggles strap and forehead skin. Two calibrations were completed in each system, prior to beginning the test. Test parameters were recorded through both systems for healthy subjects with no history or complaint of any vestibular disorder (N = 12; M/F = 5/7; age 35.1 ± 13.5 y) and for pathological subjects with a diagnosis of unilateral or bilateral vestibular disorder (N = 15; M/F = 7/8; age 53.4 ± 16.7 y). The vHIT is an important tool for otoneurological complementary evaluation. Both systems are reliable for vestibular disorders. The EyeSeeCam seems to reject fewer data and provides more information to include in diagnostics. Because of the small sample, there is a need for further in-depth comparison of both systems.

Highlights

The vestibular system is mainly engaged in three bodily functions: image stabilization, postural control and space orientation
Qualitative comparison showed that the two systems gave similar results, albeit that in one particular case, the results from the ICS Impulse were opposite to those from the EyeSeeCam[10]
Quantitative comparison showed clear deviations between the two systems, which may have been caused by: (1) the data processing method, since the ICS Impulse uses the ratio of peak velocities of head and eye movements whereas the EyeSeeCam uses linear regression of the complete velocity traces; (2) physical and detection differences between the goggles, for example: goggle weight, sensitivity and temporal resolution of the camera, sensitivity of the accelerometers and accuracy of the pupil tracking software; or (3) no standardization technique was applied to ensure that the two systems were positioned on the subjects’ heads with similar tension; variation in movement of the goggles relative to the head during application of the impulse cannot be fully ruled out[11]

Summary

Introduction

The vestibular system is mainly engaged in three bodily functions: image stabilization, postural control and space orientation. Proper integration of diagnostic tools during examination is a requirement for good clinical practice, in order to pinpoint the cause and location (central/peripheral) of the vestibular deficit[2]. These tools include, but are not limited to, a caloric test, head impulse test (HIT), oculomotor investigation, use of a rotating/translating chair, vestibular evoked myogenic potential (VEMP) and posturography[3]. Conclusions: The vHIT is an important tool for otoneurological complementary evaluation Both systems are reliable for vestibular disorders.

Objectives

Methods

Results

Conclusion