# Vestibular and visual influence on postural stability and egomotion perception in persistent postural-perceptual dizziness (PPPD)

## TL;DR

The study explores how PPPD patients experience dizziness and balance issues when exposed to visual and vestibular stimuli, revealing differences in their perception and stability compared to healthy individuals.

## Contribution

The study introduces a novel approach to understanding PPPD by examining the effects of combined visual and vestibular stimuli on postural sway and egomotion perception.

## Key findings

- PPPD patients showed increased postural sway compared to healthy controls during vestibular and combined stimuli but not during visual stimuli alone.
- Egomotion perception was consistently higher in PPPD patients across all conditions, indicating a non-linear relationship with postural sway.
- Multisensory stimulation reduced visual sensitivity and postural misperception in PPPD patients during quiet stance.

## Abstract

Patients suffering from persistent postural-perceptual dizziness (PPPD) often experience postural instability that worsens when exposed to visual motion stimuli. We investigated how different visual motion stimuli affect patients’ postural sway and their perceived egomotion during stance.

28 PPPD patients and 26 gender and healthy control subjects (HC) underwent posturographic measurements on a firm or foam platform while being exposed to either vestibular or visual motion stimuli or their combination. Vestibular stimuli were applied via 1.3 mA galvanic vestibular stimulation (GVS) or a sham stimulus. Visual stimulation (VS) was performed via 20-s video snippets of a silent movie, flow-field animation, or a rollercoaster video from the driver’s perspective. Outcome measures included postural sway speed (PSS) and perceived egomotion, collected via self-ratings after each trial.

Compared to HC, PSS of PPPD patients was higher on a firm surface during vestibular stimulation alone and combined visual–vestibular stimulation (except during rollercoaster VS) but not during VS alone. These group differences disappeared on foam, except during the baseline (noVS, noGVS) condition. Egomotion perception was rated consistently higher by PPPD participants in all conditions but in a non-linear ratio.

Our visual motion stimuli were capable of eliciting different magnitudes of perceived egomotion and postural sway without significant group differences in postural sway challenging the notion of increased visual sensitivity in PPPD. Multisensory stimulation alleviates visual sensitivity and counteracts postural misperception in quiet stance. Patients’ non-linear increase of egomotion with increasing postural sway differs from HC and reflects a non-linear perceptual-postural scaling as a crucial mechanism in PPPD.

The online version contains supplementary material available at 10.1007/s00415-026-13653-z.