Quantification and localization of vestibular loss in unilaterally labyrinthectomized patients using a precise rotatory test.

Unilateral vestibular loss was characterized using a high torque rotatory test and spectral analysis. The vestibulo-ocular reflex (VOR) of unilaterally labyrinthectomized patients was measured during passive body rotation using sinusoidal (0.5-3 Hz) and pseudo-random (0.5-5 Hz) stimulation 1) while the patient fixated an earth-fixed target and 2) during fixation of a moving target. Asymmetrical responses towards the labyrinthectomized side (as postulated by Ewald's second law) were exhibited by all patients at and above approximately 2 Hz sinusoidal stimulation and during random stimulation under illuminated conditions. The most pronounced gain loss and minimal response variability between subjects was observed during VOR suppression (moving target fixation) and random stimulation. Therefore, clinical quantification as well as the side detection of peripheral vestibular loss is best based on a fixation suppression task under fully lit conditions with a random stimulus.