Quantitative Analysis of Saccade Gain in Video Head Impulse Testing

Abstract

Objective To quantitatively analyze corrective saccade (CS) gain and further characterize the specific relationship between vestibulo-ocular reflex (VOR) gain and CS gain in patients with vestibular loss and healthy controls. Study Design Prospective combined with retrospective study. Setting Affiliated Sixth People’s Hospital, Shanghai Jiao Tong University. Subjects and Methods Forty patients with unilateral vestibular loss and 40 participants with normal vestibular function were subjected to video head impulse testing (vHIT). The analysis of the horizontal semicircular canal VOR and CS gains was based on individual head impulses. Results The patient group had significantly higher CS gain and lower VOR gain than the control group ( P < .001). While there was no significant correlation between VOR and CS gains in the control group after adjusting for age and sex ( P = .689), VOR gain negatively correlated with CS gain in the patient group ( r = −0.853, P < .001). The specific relationship between VOR and CS gains was characterized as y = −1.17x + 1.12 (x: VOR gain, y: CS gain; r 2 = 0.732, P < .001) in the patient group. Conclusions In healthy participants, CS was not correlated with VOR gain, suggesting that CS is not due to VOR hypofunction. In patients with unilateral vestibular loss, CS was closely associated with VOR gain and can almost correct gaze position errors required for visual stabilization. CS gain could be an important indicator to diagnose vestibular loss and help physicians identify abnormal vHIT curves caused by artifacts and irregular practices.