Sustained deviation of torsional eye position associated with transient semicircular canal stimulation

Background: Vestibular stimulation causes postural unsteadiness accompanied by a sensation of tilt. Aims/Objectives: The mechanism of the sensation of tilt needs to be assessed by accurate calculation of the rotational axis of torsional eye position under various vestibular stimulations. Material and Methods: Twenty-two healthy subjects participated in the study. Thirteen subjects underwent bilateral vestibular stimulation by on-axis yaw rotation under various head positions, and eighteen subjects underwent unilateral vestibular stimulation by caloric irrigation under various head positions. Listing’s Plane was plotted for the eye movement data obtained by three-dimensional video-oculography. Results: The offset of Listing’s Plane showed sustained deviation of torsional eye position that was more prominent in head positions that stimulated lateral semicircular canals more than vertical semicircular canals. There was a less prominent and directionally reversed offset in head positions that stimulated vertical canals more than lateral semicircular canals. Conclusion and Significance: The sustained torsional eye position was validated by accurate assessment using Listing’s Plane. The mechanism behind the deviation may be due to a combination of multiple anatomical components within the vestibular apparatus, with potentially stronger influence from lateral semicircular canals.