Effect of Gaze Angle during the Vertical Video Head Impulse Test across Two Devices in Healthy Adults and Subjects with Vestibular Loss

Objective:To evaluate the effect of gaze angle on vertical vestibulo-ocular reflex (VOR) gain using two different video head impulse (vHIT) devices in healthy adults and subjects with bilateral vestibular loss (BVL).Study Design:Prospective study.Setting:Hospital research laboratory.Subjects:Twenty-four healthy adults (mean [standard deviation {SD}] age = 32 [4.8]; 23-42; 8 men) and four subjects with previously diagnosed BVL (mean age [SD] = 32 [8.2]; 21-40; 3 men) participated.Intervention:Vertical canal vHIT was administered with two different devices using three gaze angles (-45 degrees, 0 degree, +45 degrees). These devices have different gain calculation algorithms and different head and gaze angle protocols.Main Outcome Measures:Vertical canal gain and presence or absence of reset saccades.Results:A significant stepwise reduction in vHIT gain was noted as gaze moved away from the plane of the canals stimulated (from-45 degrees to 0 degree, to +45 degrees) for both healthy adults and subjects with BVL. vHIT gain was able to separate the two groups using gaze angles-45 degrees and 0 degree.Conclusions:In spite of their differences in gain algorithm and recommended head position and gaze angle, each device was able to appropriately separate healthy adults from subjects with BVL with high sensitivity/specificity.