Abstract Background 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. Methods 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. Results 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. Conclusion 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.
Storm et al. (Sun,) studied this question.