Head position and increased head velocity to optimize video head impulse test sensitivity

Abstract

This study investigated the effects of head position on gain values during video head impulse tests (vHITs). Different head positions were used for vHIT of the horizontal semicircular canals of 20 healthy controls and 18 patients with unilateral vestibular loss (UVL), with head velocities ranging from 150°/s to 200°/s. Differences in vestibulo-ocular reflex gain in the control and patient groups according to head position (0° and 30° downward pitch) were analyzed. In the unaffected control group, the 30° pitched-down position resulted in a mean gain increase of up to 1.0 in both ears (right ear: 0.85 ± 0.26 for head-up and 1.05 ± 0.12 for head-down, p = 0.004; left ear: 0.75 ± 0.18 for head-up and 0.98 ± 0.16 for head-down, p < 0.001). In patients with UVL, the mean gains on the diseased side were 0.92 ± 0.16 in the head-up position and 0.82 ± 0.2 in the head-down position, at similar head velocities (p = 0.046). The pitched-down position also increased the asymmetry between ears in patients with UVL, at the same head velocity. A 30° head-down position can increase vHIT sensitivity, which resulted in increased mean gain in unaffected people and decreased mean gain in most of the patients with UVL in this study. This method may more effectively stimulate the horizontal semicircular canal. This vHIT modification may be helpful for more precisely evaluating vestibular function, thus reducing false-negative findings.