Visual-Vestibular Modification of Egomotion Perception in Patients With Persistent Postural-Perceptual Dizziness in...

Persistent postural-perceptual dizziness (PPPD) has been classified by the Bárány Society as a chronic functional dizziness disorder with perceived unsteadiness. Symptoms typically worsen by upright posture or exposure to moving visual stimuli or complex visual patterns. The specific visual features remain poorly defined. We investigated how visual, vestibular, and combined visual-vestibular stimulation affects egomotion perception in PPPD patients, comparing responses in upright and supine positions to those of age-matched healthy controls (HC).

Participants performed a self-rating of perceived egomotion in two sessions with two different body positions: supine and upright standing. During both sessions, participants were exposed to three types of visual stimulation designed to differ by the degree of elicited egomotion: a black-and-white silent movie, a flow field animation, and a rollercoaster video from the driver's perspective. Each visual stimulus was presented in combination with one of three binaural vestibular galvanic stimulation conditions (GVS): no stimulation (noGVS), fixed intensity stimulation (fixGVS: 1.3 mA), or sham (sham: 1.3 mA).

PPPD patients consistently reported stronger egomotion than HC, regardless of the stimulation condition. Both visual and vestibular inputs robustly influenced egomotion perception in standing and supine positions. Egomotion perception of PPPD patients in the standing, compared to the supine position, was larger during rollercoaster stimulation.

Our findings challenge the notion of generalized visual hypersensitivity in PPPD. They rather point to a context-dependent alteration of egomotion perception during upright stance. Differences disappear with concomitant vestibular stimulation supporting the need for vestibular rehabilitation in PPPD.