The semicircular canals are involved in the coding of angular acceleration of the head and body. Presently, video-nystagmography (VNG) and specifically, caloric testing, is the gold standard for evaluation of semicircular canal function. Caloric irrigation via VNG can only evaluate horizontal semicircular canal function; with this test, there is no way to evaluate the function of the anterior and posterior vertical semicircular canals. The video Head Impulse Test (vHIT) is a relatively new protocol that has the capability to test the function of the horizontal, anterior vertical, and posterior vertical semicircular canals. Because the vHIT system is newly available to clinicians, there is a need to collect normative data, particularly for the vertical semicircular canals. For this study, data was collected from 12 participants with no complaint or history of balance difficulty. Additionally, we compared our data with normative data collected in an earlier study to determine consistency. Lateral average velocity gain measurements were consistent however, a comparison of RALP an LARP velocity gain measurements showed inconsistency.

Book Summary: Dizziness comes in many forms in each age group – some specific to an age group (e.g. benign paroxysmal vertigo of childhood) while others span the age spectrum (e.g., migraine-associated vertigo). This content organizes evaluation and management of the dizzy patient by age to bring a fresh perspective to seeing these often difficult patients.

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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.

The angular vestibulo-ocular reflex (VOR) ensures gaze stability during head rotations by generating eye movements that are equal and opposite to head rotation. The gain of the VOR (eye velocity/head velocity) for natural head movements, therefore, approaches unity in healthy individuals. The VOR has four main anatomic components: the semicircular canals (SCCs) and vestibular nerve in the peripheral vestibular system, the vestibular and ocular motor nuclei in the brainstem, and the extraocular muscles. The SCCs are positioned in three nearly orthogonal planes within the head thereby allowing for the detection of head rotation about any axis in space. The SCCs function as angular accelerometers in a push-pull fashion with two coplanar canals on each side of the head working together, i.e., left and right horizontal SCCs, the right anterior and left posterior SCCs or RALP, and the left anterior and right posterior SCCs or LARP. 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 VOR. The video head impulse test (vHIT) is a relatively 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 in the horizontal and vertical planes. 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. There are no published data concerning both inter- and intra-examiner reliability of the vHIT. The purpose of this study was to establish normal reference intervals and assess the test-retest reliability of the vHIT in young healthy adult participants using the Micromedical vHIT device, two examiners, and a prospective repeated measures design. Each examiner underwent five hours of training on the vHIT device prior to the initiation of the study. The vHIT was administered to each participant (n = 35) by each examiner on two different days. Inter-session interval ranged from 1 to 30 days and examiner order was alternated for successive subjects; canal-plane order was randomized. At each session, participants underwent head impulse testing in each plane resulting in the stimulation of each of the six SCCs. The dependent variable was VOR gain (eye velocity/head velocity) and the effects of examiner, session, eye, and SCC 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. The cut-offs (5th percentiles) for normal VOR gain were 0.76 (right and left horizontal SCCs), 0.68 (right anterior SCC), 0.70 (left anterior SCC), 0.69 (right posterior SCC), and 0.75 (left posterior SCC). There was no significant effect of examiner on VOR gain and the ICCs indicated fair-to-good inter- and intra-examiner reliability with better reliability for the horizontal SCCs than for the posterior and anterior SCCs

The 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 tests of vestibular function involve the measurement of horizontal eye movements produced by stimuli that activates the horizontal semicirculuar canals (hSCCs). 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. There are no published data concerning the examiner reliability of the vHIT. A prospective repeated measures design was used to assess test-retest reliability of the hSCC vHIT in young healthy adult participants (n=44). The vHIT was administered to each participant by each of two different examiners on two different days. A repeated measures analysis of variance was used to determine the effects of examiner, session, and hSCC on the magnitude of VOR gain (eye velocity/head velocity). The intra-class correlation coeffecient and the coefficient of repeatability were used to assess intra- and inter-examiner reliability.

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