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

Fractional Amplitude of Low-Frequency Fluctuation and Voxel-Mirrored Homotopic Connectivity in Patients with Persistent Postural-Perceptual Dizziness: Resting-State Functional Magnetic Resonance Imaging Study

Purpose: Persistent postural-perception dizziness (PPPD) is a chronic subjective form of dizziness characterized by the exacerbation of dizziness with active or passive movement, complex visual stimuli, and upright posture. Therefore, we aimed to analyze the resting-state functional magnetic resonance imaging (fMRI) in patients with PPPD using fractional amplitude of low-frequency fluctuation (fALFF) and voxel-mirrored homotopic connectivity (VMHC) and evaluate the correlation between abnormal regions in the brain and clinical features to investigate the pathogenesis of PPPD. Methods: Thirty patients with PPPD (19 females and 11 males) and 30 healthy controls (HCs; 18 females and 12 males) were closely matched for age and sex. The fALFF and VMHC methods were used to investigate differences in fMRI (BOLD sequences) between the PPPD and HC groups and to explore the associations between areas of functional abnormality and clinical characteristics (dizziness, anxiety, depression, and duration). Result: Compared to the HC group, patients with PPPD displayed different functional change patterns, with increased fALFF in the right precuneus and decreased VMHC in the bilateral precuneus. In addition, patients with PPPD had a positive correlation between precuneus fALFF values and dizziness handicap inventory (DHI) scores, and a negative correlation between VMHC values and the disease duration. Conclusions: Precuneus dysfunction was observed in patients with PPPD. The fALFF values correlated with the degree of dizziness in PPPD, and changes in VMHC values were associated with the duration of dizziness, suggesting that fMRI changes in the precuneus of patients could be used as a potential imaging marker for PPPD.

Persistent Challenges: A Comprehensive Review of Persistent Postural-Perceptual Dizziness, Controversies, and Clinical Complexities

Persistent postural-perceptual dizziness (PPPD) is a chronic and disabling disorder characterized by persistent dizziness, unsteadiness, and imbalance. It often arises without an identifiable cause and is exacerbated by upright posture, active or passive movement, and exposure to moving or complex visual stimuli. This complex pathophysiology and the psychological dimensions of its symptomatology pose a significant challenge to clinicians. PPPD presents diagnostic challenges and a lack of standardized treatment options, underscoring the need for multidisciplinary approaches encompassing pharmacotherapy, vestibular rehabilitation, and psychological interventions for effective management. Bridging the gaps in understanding PPPD requires collaborative efforts across disciplines, emphasizing integrated research approaches and patient support networks to enhance care and improve outcomes. This review explores the challenges, controversies, and clinical complexities of PPPD, highlighting the importance of a patient-centered approach.

Clinical, Biomarker, and Research Tests Among US Government Personnel and Their Family Members Involved in Anomalous Health Incidents

Importance

Since 2015, US government and related personnel have reported dizziness, pain, visual problems, and cognitive dysfunction after experiencing intrusive sounds and head pressure. The US government has labeled these anomalous health incidents (AHIs).

Objective

To assess whether participants with AHIs differ significantly from US government control participants with respect to clinical, research, and biomarker assessments.

Design, Setting, and Participants

Exploratory study conducted between June 2018 and July 2022 at the National Institutes of Health Clinical Center, involving 86 US government staff and family members with AHIs from Cuba, Austria, China, and other locations as well as 30 US government control participants.

Exposures

AHIs.

Main Outcomes and Measures

Participants were assessed with extensive clinical, auditory, vestibular, balance, visual, neuropsychological, and blood biomarkers (glial fibrillary acidic protein and neurofilament light) testing. The patients were analyzed based on the risk characteristics of the AHI identifying concerning cases as well as geographic location.

Results

Eighty-six participants with AHIs (42 women and 44 men; mean [SD] age, 42.1 [9.1] years) and 30 vocationally matched government control participants (11 women and 19 men; mean [SD] age, 43.8 [10.1] years) were included in the analyses. Participants with AHIs were evaluated a median of 76 days (IQR, 30-537) from the most recent incident. In general, there were no significant differences between participants with AHIs and control participants in most tests of auditory, vestibular, cognitive, or visual function as well as levels of the blood biomarkers. Participants with AHIs had significantly increased fatigue, depression, posttraumatic stress, imbalance, and neurobehavioral symptoms compared with the control participants. There were no differences in these findings based on the risk characteristics of the incident or geographic location of the AHIs. Twenty-four patients (28%) with AHI presented with functional neurological disorders.

Conclusions and Relevance

In this exploratory study, there were no significant differences between individuals reporting AHIs and matched control participants with respect to most clinical, research, and biomarker measures, except for objective and self-reported measures of imbalance and symptoms of fatigue, posttraumatic stress, and depression. This study did not replicate the findings of previous studies, although differences in the populations included and the timing of assessments limit direct comparisons.

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.

Treating Psychiatric Symptoms in Persistent Postural Perceptual Dizziness

Persistent postural perceptual dizziness (PPPD) is a functional neurological disorder characterized by troublesome feelings of dizziness and might be precipitated by vestibular events, postural changes, psychopathologies, and/or a person's perceptual experiences. The diagnosis is confirmed by assessing a patient's history. A variety of psychiatric symptoms are associated with PPPD; anxiety and depression are the most common. Psychotherapy and pharmacotherapy can be clinically helpful in reducing psychiatric symptoms and dizziness. Early intervention improves prognosis.

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.

The Effects of Vibro-Tactile Biofeedback Balance Training on Balance Control and Dizziness in Patients with Persistent Postural-Perceptual Dizziness (PPPD)

BACKGROUND

Patients with persistent postural-perceptual dizziness (PPPD) frequently report having problems with balance control. Artificial systems providing vibro-tactile feedback (VTfb) of trunk sway to the patient could aid recalibration of "falsely" programmed natural sensory signal gains underlying unstable balance control and dizziness. Thus, the question we examine, retrospectively, is whether such artificial systems improve balance control in PPPD patients and simultaneously reduce the effects of dizziness on their living circumstances. Therefore, we assessed in PPPD patients the effects of VTfb of trunk sway on balance control during stance and gait tests, and on their perceived dizziness.

METHODS

Balance control was assessed in 23 PPPD patients (11 of primary PPPD origin) using peak-to-peak amplitudes of trunk sway measured in the pitch and roll planes with a gyroscope system (SwayStar™) during 14 stance and gait tests. The tests included standing eyes closed on foam, walking tandem steps, and walking over low barriers. The measures of trunk sway were combined into a Balance Control Index (BCI) and used to determine whether the patient had a quantified balance deficit (QBD) or dizziness only (DO). The Dizziness Handicap Inventory (DHI) was used to assess perceived dizziness. The subjects first underwent a standard balance assessment from which the VTfb thresholds in eight directions, separated by 45 deg, were calculated for each assessment test based on the 90% range of the trunk sway angles in the pitch and roll directions for the test. A headband-mounted VTfb system, connected to the SwayStar™, was active in one of the eight directions when the threshold for that direction was exceeded. The subjects trained for 11 of the 14 balance tests with VTfb twice per week for 30 min over a total of 2 consecutive weeks. The BCI and DHI were reassessed each week and the thresholds were reset after the first week of training.

RESULTS

On average, the patients showed an improved balance control in the BCI values after 2 weeks of VTfb training (24% p = 0.0001). The improvement was greater for the QBD patients than for the DO patients (26 vs. 21%), and greater for the gait tests than the stance tests. After 2 weeks, the mean BCI values of the DO patients, but not the QBD patients, were significantly less (p = 0.0008) than the upper 95% limit of normal age-matched reference values. A subjective benefit in balance control was spontaneously reported by 11 patients. Lower (36%), but less significant DHI values were also achieved after VTfb training (p = 0.006). The DHI changes were identical for the QBD and DO patients and approximately equal to the minimum clinical important difference.

CONCLUSIONS

These initial results show, as far as we are aware for the first time, that providing VTfb of trunk sway to PPPD subjects yields a significant improvement in balance control, but a far less significant change in DHI-assessed dizziness. The intervention benefitted the gait trials more than the stance trials and benefited the QBD group of PPPD patients more than the DO group. This study increases our understanding of the pathophysiologic processes underlying PPPD and provides a basis for future interventions.

A comparison of placebo and nocebo effects on objective and subjective postural stability: a double-edged sword?

Background: Positive expectations (i.e., placebo effect) can improve postural control during quiet standing. This raises an important question: if postural control is susceptible to positive expectations, is it possible to elicit the opposite, a decline in postural stability, simply by suggesting a performance impairment (i.e., nocebo) will take place? Yet no studies have examined the nocebo effect on balance performance. To better understand both phenomena, comparative studies, which include both placebo and nocebo conditions, are needed.

Method: Forty-two healthy adults were initially assessed for objective (center of pressure movement) and subjective (perceived) postural stability and performance expectations. Participants were then randomly assigned in equal numbers to a placebo (positive expectation), nocebo (negative expectation) or control (no suggestion) group. Participants in the placebo/nocebo groups were deceptively administered an inert capsule described as a potent supplement which would either positively or negatively influence their balance performance. Objective and subjective postural stability, and performance expectations were reassessed 20 min later.

Results: The nocebo procedure evoked an increase in COP sway movements and reduced perceived stability compared to a control group. The placebo group presented with reductions COP sway movements and increased perceived stability following expectation manipulation. Compared to the control group, the placebo group showed a significantly higher performance expectation whilst the nocebo group showed a significantly lower performance expectation. Regression analyses also revealed that performance expectations following the placebo/nocebo procedure significantly predicted perceptions of postural instability (i.e., perceived performance), accounting for around 50% of the variance. These results remained even when controlling for actual performance (i.e., objective postural stability).

Conclusion: Our findings indicate that positive and negative performance expectations evoked by instructional manipulation can profoundly influence both objective and subjective postural stability. Postural control—and perceptions regarding such—are clearly susceptible to expectation manipulation, which could have important practical implications and repercussions on testing, training interventions and rehabilitation programs. Positive and negative expectancies are a double-edged sword for postural control.