Characterization of Postural Sway in Patients With Persistent Postural-Perceptual Dizziness (PPPD) Using Wearable Motion Sensors

Evaluation of instability in patients with chronic vestibular syndrome using dynamic stability indicators

Gait abnormalities are common in patients with chronic vestibular syndrome (CVS), and stability analysis and gait feature recognition in CVS patients have clinical significance for diagnosing CVS. This study explored two-dimensional dynamic stability indicators for evaluating gait instability in patients with CVS. The Center of Mass acceleration (COMa) peak of CVS patients was significantly faster than that of the control group (p < 0.05), closer to the back of the body, and slower at the Toe-off (TO) moment, which enlarged the Center of Mass position-velocity combination proportion within the Region of Velocity Stability (ROSv). The sensitivity, specificity, and accuracy of the Center of Mass velocity (COMv) or COMa peaks were 75.0%, 93.7%, and 90.2% for CVS patients and control groups, respectively. The two-dimensional ROSv parameters improved sensitivity, specificity, and accuracy in judging gait instability in patients over traditional dynamic stability parameters. Dynamic stability parameters quantitatively described the differences in dynamic stability during walking between patients with different degrees of CVS and those in the control group. As CVS impairment increases, the patient's dynamic stability decreases. This study provides a reference for the quantitative evaluation of gait stability in patients with CVS.

Postural motion perception during vestibular stimulation depends on the motion perception threshold in persistent postural-perceptual dizziness

Patients with persistent postural-perceptual dizziness (PPPD) perceive postural instability larger than the observed sway. It is unknown whether the concept of postural misperception prevails during vestibular stimulation and whether it may account for the unsteadiness patients complain during body movements. We tested the hypothesis of an abnormal sensory-perceptual scaling mechanism in PPPD by recording objective, perceived, and the reproduced postural sway under various standing conditions, modulating visual and proprioceptive input, by binaural galvanic vestibular stimulation (GVS). We related postural sway speed to individual vestibular motion perceptional thresholds and disease-related PPPD questionnaires in 32 patients and 28 age-matched healthy control subjects (HC). All participants showed normal vestibular function tests on quantitative testing at the time of enrollment. The perception threshold of GVS was lower in patients. Compared to HC, patients showed and perceived larger sway on the firm platform. With GVS, posturo-perceptual ratios did not show group differences. The ratio of reproduced to real postural sway showed no group differences indicating normal postural sway perception during vestibular stimulation. Noticeably, only in patients, reproduced postural instability became larger with lower individual thresholds of vestibular motion detection. We conclude that posturo-perceptual (metacognitive) scaling of postural control seems to be largely preserved in PPPD during GVS. Vestibular stimulation does not destabilize patients more than HC, even in challenging postural conditions. Low individual thresholds of vestibular motion perception seem to facilitate instability and postural misperception on solid grounds. This conclusion is important for an effective physical therapy with vestibular exercises in PPPD.

Characterization of Vestibular Perception in Patients with Persistent Postural-Perceptual Dizziness

OBJECTIVE

To assess vestibular (i.e., passive self-motion) perception in patients diagnosed with persistent postural-perceptual dizziness (PPPD).

STUDY DESIGN

Case-controlled, cross-sectional, observational investigation.

SETTING

Single-center laboratory-based study.

PATIENTS

Thirteen patients with PPPD, 13 age-matched healthy control volunteers. Of those with PPPD, eight had co-occurring vestibular migraine (VM).

INTERVENTIONS

All participants completed a vestibular threshold test battery reflecting perception with predominant inputs from ( a ) the otoliths (1-Hz interaural y -axis translation, 1-Hz superior-inferior z -axis translation), ( b ) the semicircular canals (2-Hz yaw rotation, 2-Hz tilts in the planes of the vertical canal pairs), and ( c ) and canal-otolith integration (0.5-Hz roll tilt).

MAIN OUTCOME MEASURES

Direction-recognition thresholds for each vestibular threshold test condition.

RESULTS

Across all patients with PPPD, higher thresholds for superior-inferior z -translations thresholds in comparison to age-matched healthy control participants were identified ( p < 0.001). Those patients with co-occurring VM and PPPD (PPPD/+VM) displayed significantly higher z -translation thresholds ( p = 0.006), whereas patients with PPPD without VM (PPPD/-VM) displayed significantly higher roll tilt thresholds ( p = 0.029).

CONCLUSIONS

Patients with PPPD did not display a global worsening of passive self-motion perception as quantified by vestibular perceptual thresholds. Instead, patients with PPPD displayed elevated thresholds for only roll tilt and z -translation thresholds, with the relative change in each threshold impacted by the co-occurrence of VM. Because both z -translation and roll tilt motions are reliant on accurate gravity perception, our data suggest that patients with PPPD may exhibit impaired processing of graviceptive cues.

Analysis of postural stability using foam posturography in patients with persistent postural-perceptual dizziness

BACKGROUND/OBJECTIVE

Persistent postural-perceptual dizziness (PPPD) is worsened in a standing posture, or by body movement, or visual stimulation. We aimed to evaluate postural stability in PPPD patients using foam posturography and to investigate the dependence on visual and somatosensory input in the standing posture.

METHODS

Foam posturography was performed on 53 PPPD patients, and data from the PPPD patients were compared with the data from an age- and sex-matched healthy controls. The PPPD patients were divided into four groups based on the findings of vestibular function tests and the effect of vestibular function on posturographic data was examined.

RESULTS

Romberg's ratios were significantly higher in PPPD patients than in controls. The median Romberg's ratios in PPPD patients with normal vestibular function were also higher than those in controls. However, foam ratio was significantly lower in PPPD patients than in controls. The median foam ratios in PPPD patients with vestibular dysfunction were also lower than those in controls.

CONCLUSIONS

In a standing posture, PPPD patients may be more dependent on visual input and less dependent on somatosensory input than healthy subjects. Higher dependence on visual and lower dependence on somatosensory input in PPPD may be a feature unaffected by vestibular function.

Functional Dizziness as a Spatial Cognitive Dysfunction

(1) Background: Persistent postural-perceptual dizziness (PPPD) is a common chronic dizziness disorder with an unclear pathophysiology. It is hypothesized that PPPD may involve disrupted spatial cognition processes as a core feature. (2) Methods: A cohort of 19 PPPD patients underwent psycho-cognitive testing, including assessments for anxiety, depression, memory, attention, planning, and executive functions, with an emphasis on spatial navigation via a virtual Morris water maze. These patients were compared with 12 healthy controls and 20 individuals with other vestibular disorders but without PPPD. Vestibular function was evaluated using video head impulse testing and vestibular evoked myogenic potentials, while brain magnetic resonance imaging was used to exclude confounding pathology. (3) Results: PPPD patients demonstrated unique impairments in allocentric spatial navigation (as evidenced by the virtual Morris water maze) and in other high-demand visuospatial cognitive tasks that involve executive functions and planning, such as the Towers of London and Trail Making B tests. A factor analysis highlighted spatial navigation and advanced visuospatial functions as being central to PPPD, with a strong correlation to symptom severity. (4) Conclusions: PPPD may broadly impair higher cognitive functions, especially in spatial cognition. We discuss a disruption in the creation of enriched cognitive spatial maps as a possible pathophysiology for PPPD.

Predictors of persistent postural-perceptual dizziness (PPPD) and similar forms of chronic dizziness precipitated by peripheral vestibular disorders: a systematic review

BACKGROUND

The literature on predictors of persistent postural-perceptual dizziness (PPPD) following peripheral vestibular insults has not been systematically reviewed.

METHODS

We systematically reviewed studies on predictors of PPPD and its four predecessors (phobic postural vertigo, space-motion discomfort, chronic subjective dizziness and visual vertigo). Investigations focused on new onset chronic dizziness following peripheral vestibular insults, with a minimum follow-up of 3 months. Precipitating events, promoting factors, initial symptoms, physical and psychological comorbidities and results of vestibular testing and neuroimaging were extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

We identified 13 studies examining predictors of PPPD or PPPD-like chronic dizziness. Anxiety following vestibular injury, dependent personality traits, autonomic arousal and increased body vigilance following precipitating events and visual dependence, but not the severity of initial or subsequent structural vestibular deficits or compensation status, were the most important predictors of chronic dizziness. Disease-related abnormalities of the otolithic organs and semi-circular canals and age-related brain changes seem to be important only in a minority of patients. Data on pre-existing anxiety were mixed.

CONCLUSIONS

After acute vestibular events, psychological and behavioural responses and brain maladaptation are the most likely predictors of PPPD, rather than the severity of changes on vestibular testing. Age-related brain changes appear to have a smaller role and require further study. Premorbid psychiatric comorbidities, other than dependent personality traits, are not relevant for the development of PPPD.

Persistent Postural-Perceptual Dizziness: Review and Update on Key Mechanisms of the Most Common Functional Neuro-otologic Disorder

Persistent postural-perceptual dizziness (PPPD) is a functional neuro-otologic (vestibular) disorder manifesting dizziness, unsteadiness, or nonspinning vertigo lasting 3 months or more and exacerbated by upright posture, active or passive motion, and complex visual stimuli. PPPD is the most common cause of chronic vestibular symptoms. Early pathophysiologic models of PPPD emphasized the adverse effects of anxiety on postural control and spatial orientation. More recent concepts added predictive processing of sensory inputs and alterations in motion perception. Herein, a third-generation model incorporates prioritization of postural stability over fluid locomotion to explain symptoms, physiologic and neuroimaging data, and effects of current treatments.

Recurrence quantification analysis of postural sway in patients with persistent postural perceptual dizziness

Background

Persistent postural perceptual dizziness (PPPD) is a common cause of chronic dizziness and imbalance. Emerging evidence suggests that changes in quantitative measures of postural control may help identify individuals with PPPD, however, traditional linear metrics of sway have yielded inconsistent results. Methodologies to examine the temporal structure of sway, including recurrent quantification analysis (RQA), have identified unique changes in dynamic structure of postural control in other patient populations. This study aimed to determine if adults with PPPD exhibit changes in the dynamic structure of sway and whether this change is modulated on the basis of available sensory cues.

Methods

Twelve adults diagnosed with PPPD and twelve age-matched controls, completed a standard battery of quiet stance balance tasks that involved the manipulation of visual and/or proprioceptive feedback. For each group, the regularity and complexity of the CoP signal was assessed using RQA and the magnitude and variability of the CoP signal was quantified using traditional linear measures.

Results

An overall effect of participant group (i.e., healthy controls vs. PPPD) was seen for non-linear measures of temporal complexity quantified using RQA. Changes in determinism (i.e., regularity) were also modulated on the basis of availability of sensory cues in patients with PPPD. No between-group difference was identified for linear measures assessing amount and variability of sway.

Conclusions

Participants with PPPD on average exhibited sway that was similar in magnitude to, but significantly more repeatable and less complex than, healthy controls. These data show that non-linear measures provide unique information regarding the effect of PPPD on postural control, and as a result, may serve as potential rehabilitation outcome measures.

Changes in functional connectivity among vestibulo-visuo-somatosensory and spatial cognitive cortical areas in persistent postural-perceptual dizziness: resting-state fMRI studies before and after visual stimulation

INTRODUCTION

Persistent postural-perceptual dizziness (PPPD) is a functional chronic vestibular syndrome with symptom exacerbation by upright posture, motion, and complex visual stimuli. Among these exacerbating factors, visual exacerbation is the most specific characteristic of PPPD requiring further investigation. We hypothesized that stimulus-induced changes occur in the functional connectivity (FC) rather than simple neural activation that is involved in visual stimulation. The present study aimed to identify the neural basis of PPPD by investigating FC before and after visual stimulation.

METHODS

Eleven patients with PPPD and 11 age- and sex-matched healthy controls (HCs) underwent resting-state fMRI (rs-fMRI) before and after task-based fMRI with visual stimuli.

RESULTS

At pre-stimulus, FC between the vestibular cortex and visual areas was low, while that between the somatosensory and visual areas was high in PPPD compared with that in HCs. FC between the visuospatial (parahippocampal gyrus) and spatial cognitive areas (inferior parietal lobule) was elevated in PPPD even in the pre-stimulus condition, which no longer increased at post-stimulus as observed in HCs. In the post-stimulus condition, FC between the visual and spatial cognitive areas and that between the visual and prefrontal areas increased compared with that in the pre-stimulus condition in PPPD. Task-based fMRI demonstrated that no brain regions showed different activities between the HC and PPPD groups during visual stimulation.

DISCUSSION

In PPPD, vestibular inputs may not be fully utilized in the vestibulo-visuo-somatosensory network. Given that the FC between visuospatial and spatial cognitive areas increased even in HCs after visual stimuli, elevated status of this FC in combination with the high FC between the somatosensory and visual areas would be involved in the visual exacerbation in PPPD. An increase in FC from the visual areas to spatial cognitive and prefrontal areas after visual stimuli may account for the prolonged symptoms after visual exacerbation and anxious status in PPPD.

Gaze instability after exposure to moving visual stimuli in patients with persistent postural-perceptual dizziness

Introduction

Persistent postural-perceptual dizziness (PPPD) is a chronic vestibular syndrome lasting more than 3 months. The core vestibular symptoms are dizziness, unsteadiness, and non-spinning vertigo, which are exacerbated by upright posture or walking, active or passive motion, and exposure to moving or complex visual stimuli. Among these, visual exacerbation is a key feature of PPPD for which the neural mechanisms are unknown. We hypothesized that vestibular symptoms may be exacerbated by visual stimuli through gaze behavioral change after exposure to moving or complex visual stimuli. The study aimed to examine gaze stability after exposure to moving visual stimuli in patients with PPPD.

Methods

Fourteen healthy controls (HCs), 27 patients with PPPD, and 12 patients with unilateral vestibular hypofunction (UVH), showing chronic vestibular symptoms for >3 months, were enrolled in the study. The participants were instructed to fixate on the gazing point at the center of a screen for 30 s before and after 90 s of exposure to moving visual stimuli. Gaze stability, best represented by the bivariate contour ellipse area (BCEA), was compared among three groups, both before and after exposure to the moving visual stimuli. Comparisons between pre- and post-moving visual stimuli in BCEA were also conducted. Correlation between the post/pre ratio of BCEA and vestibular tests, several clinical symptom scales including the Dizziness Handicap Inventory, Niigata PPPD Questionnaire, and Hospital Anxiety and Depression Scale, and the exacerbation of dizziness by exposure to moving visual stimuli was examined in the PPPD group.

Results

BCEA, both before and after exposure to moving visual stimuli in the PPPD group, was not different from that in HC and UVH groups. In the PPPD group, BCEA increased significantly after exposure to moving visual stimuli. The post/pre ratio of BCEA correlated with the occurrence of exacerbation of the dizziness sensation by exposure to moving visual stimuli; however, it did not correlate with vestibular tests or clinical symptom scales.

Conclusion

Patients with PPPD were more likely to exhibit gaze instability after exposure to moving visual stimuli, which potentially exacerbated vestibular symptoms. This phenomenon may help elucidate the neural mechanisms of visual exacerbation in patients with PPPD.

Persistent Postural-Perceptual Dizziness (PPPD) from Brain Imaging to Behaviour and Perception

Persistent postural-perceptual dizziness (PPPD) is a common cause of chronic dizziness associated with significant morbidity, and perhaps constitutes the commonest cause of chronic dizziness across outpatient neurology settings. Patients present with altered perception of balance control, resulting in measurable changes in balance function, such as stiffening of postural muscles and increased body sway. Observed risk factors include pre-morbid anxiety and neuroticism and increased visual dependence. Following a balance-perturbing insult (such as vestibular dysfunction), patients with PPPD adopt adaptive strategies that become chronically maladaptive and impair longer-term postural behaviour. In this article, we explore the relationship between behavioural postural changes, perceptual abnormalities, and imaging correlates of such dysfunction. We argue that understanding the pathophysiological mechanisms of PPPD necessitates an integrated methodological approach that is able to concurrently measure behaviour, perception, and cortical and subcortical brain function.