ABSTRACT
<p><b>OBJECTIVES</b>The function of the semicircular canal receptors and the pathway of the vestibulo-ocular reflex (VOR) can be diagnosed with the clinical head impulse test. The aim of the study was to investigate the horizontal VOR by means of video head impulse test in peripheral vestibular disorders.</p><p><b>METHODS</b>Using the vHIT, we examined horizontal semicircular canal VOR in a group of 55 patients and a control group of 20 healthy subjects. The group of patients included 10 cases of vestibular neuritis (VN), 6 cases of vestibular schwannoma (VS), 12 cases of Meniere's disease (MD), and 15 cases of bilateral vestibulopathy (BV), as well as 13 cases of idiopathic sudden hearing loss with vertigo (ISHL).</p><p><b>RESULTS</b>Instantaneous gains of 40 ms, 60 ms and 80 ms of horizontal VOR were 0.88 ± 0.17, 0.94 ± 0.13 and 0.96 ± 0.13, respectively. Regression gain at 60 ms was 0.99 ± 0.11, and asymmetry was 5.6 ± 3.5. Normal range of 60 ms instantaneous gain was > 0.73, normal range of regression gain was > 0.80. Abnormal vHIT was found in VS (100%), VN (90.9%), BV (86.7%), MD (40.0%) and ISHL (38.5%). Three conditions of refixation saccades occurred in cases with abnormal VOR: isolated covert saccades (12.5%), isolated overt saccades (45.0%) and the combination of overt and covert saccades (42.5%).</p><p><b>CONCLUSIONS</b>The vHIT detects abnormal VOR changes in the combination of gain assessment and refixation saccades. Since isolated covert saccades in VOR changes can only be seen with vHIT, peripheral vestibular disorders are likely to be misdiagnosed with the HIT.</p>