Intra- and Inter-Examiner Reliability of the Video Head Impulse Test

The observation or measurement of eye movement can aid in the detection and localization of vestibular pathology due to the relationship between the function of the vestibular sensory receptors in the inner ear and the eye movements produced by the vestibulo-ocular reflex (VOR). The majority of bedside and laboratory tests of vestibular function involve the observation or measurement of horizontal eye movements (i.e., horizontal VOR) produced by stimuli that activate the horizontal semicircular canals (SCCs) and the superior vestibular nerve. The video head impulse test (vHIT) is a new clinical test of dynamic SCC function that uses a high-speed digital video camera embedded in light-weight goggles to record head and eye movement during passive head rotations. An important precursor to the clinical use of a new diagnostic test is the evaluation of test reproducibility. If test reproducibility is poor, then the test is unlikely to be clinically useful. Currently, there are no published data concerning both inter- and intra-examiner reliability of the vHIT. The purpose of this study was to assess the test-retest reliability of the horizontal SCC vHIT in young healthy adult participants using the Otometrics Impulse vHIT device using a prospective repeated measures design. Forty-four young adults with normal hearing, normal caloric test results, and a negative history of vestibular disorder, neurological disease, open or closed head injury, or cervical spine injury participated in the study. Each examiner underwent one hour of training on the vHIT device prior to the initiation of the study. The vHIT was administered to each participant by each of two different examiners on two different days. Inter-session interval ranged from 1 to 10 days and examiner order was randomized. Each examiner manually rotated each participant’s head in leftward and rightward directions, and VOR gain (eye velocity/head velocity) was calculated for the left and right horizontal SCCs. The effects of examiner, session, and SCC (left horizontal versus right horizontal) on the magnitude of VOR gain were assessed using repeated measures analysis of variance. The intra-class correlation (ICC) coefficient was used to assess intra- and inter-examiner reliability. Preliminary findings obtained in 30 participants indicated that the main effects of examiner, session, and SCC on VOR gain were not significant. The ICCs for both inter-examiner (.847) and intra-examiner reliability (.813 for Examiner 1 and .845 for Examiner 2) were good. Testing was well-tolerated and completed in most participants in ~5 minutes. The vHIT has some important advantages relative to more established laboratory tests of horizontal SCC function including the ability to assess the vertical SCCs, lower cost, shorter test time, greater portability, minimal space requirements, and increased patient comfort. Additional data should be obtained from older participants with normal vestibular function and from patients with vestibular disorders. Within-subject comparisons between the results of the vHIT and the traditional tests of horizontal SCC function (caloric and rotary chair tests) will be important in determining the role of the vHIT in the vestibular test battery