Yamaguchi et al.
Journal of NeuroEngineering and Rehabilitation
https://doi.org/10.1186/s12984-022-01068-6(2022) 19:92

Open Access

RESEARCH

Temporal virtual reality‑guided, dual‑task,
trunk balance training in a sitting position
improves persistent postural‑perceptual
dizziness: proof of concept
Tomoya Yamaguchi1,2, Toru Miwa1,2,3* , Kaoru Tamura1, Fumiko Inoue1, Naomi Umezawa1, Toshiki Maetani1,
Masahiko Hara4,5 and Shin‑ichi Kanemaru1

Abstract
Background: Persistent postural-perceptual dizziness (PPPD) is a newly defined disorder characterized by functionaldizziness. Due to its recent discovery, definitive treatment for PPPD has not been established; therefore, this study
aimed to assess the effectiveness of virtual reality (VR)-guided, dual-task, trunk balance training for the managementof PPPD using the mediVR KAGURA system.
Methods: We analyzed data of patients who presented with PPPD from January 1, 2021, to February 28, 2021. The
VR group included patients who underwent mediVR KAGURA-guided training for 100 tasks (10 min). Patients with
PPPD who received standard treatment and rehabilitation were assigned to the control group. Equilibrium tests were
performed at baseline and immediately after mediVR KAGURA-guided training to examine its effectiveness in improv‑
ing static and dynamic balance. Additionally, clinical questionnaires related to balance disorders were administered atbaseline and 1 week after mediVR KAGURA-guided training to examine its effects on balance-related symptoms. The
primary outcome was improvements in static and dynamic balance and Niigata PPPD Questionnaire (NPQ) scores.
Results: VR-guided training using mediVR KAGURA improved objective outcomes, including static and dynamic pos‑tural stability, after a single 10-min training session. Additionally, mediVR KAGURA-guided training improved scores on
the Hospital Anxiety and Depression Scale and NPQ 1 week after the 10-min training session.
Conclusion: VR-guided training using mediVR KAGURA represents a viable method for managing balancing ability,
anxiety, and symptoms in patients with PPPD. Such training provides a safe and cost-effective solution for PPPD man‑agement. Further studies are required to evaluate the clinical efficacy of this strategy.
Trial registration: Institutional Ethics Committee of Kitano Hospital, approval number: 1911003. Registered 18 Decem‑ber 2019, https://​kitano.​bvits.​com/​rinri/​publi​sh_​docum​ent.​aspx?​ID=​426.
Keywords: Virtual reality, Persistent postural-perceptual dizziness, Rehabilitation*Correspondence: t-miwa@omu.ac.jp
3
Department of Otolaryngology, Osaka Metropolitan University Schoolof Medicine, 1‑4‑3 Asahi‑machi, Abeno‑ku, Osaka 545‑8585, Japan
Full list of author information is available at the end of the article

Background
Persistent postural-perceptual dizziness (PPPD) is afunctional dizziness disorder characterized by a chronic
vestibular syndrome lasting for > 3 months, typically preceded by acute vestibular symptoms [1]. According to
the International Classification of Diseases 11th edition,© The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which
permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to theoriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images orother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line
to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory
regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of thislicence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecom‑mons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Yamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

PPPD was previously referred to as phobic postural vertigo (PPV) or chronic subjective dizziness (CSD) [2].
PPPD presents as core vestibular symptoms including
dizziness, unsteadiness, or non-spinning vertigo, and it
is exacerbated during upright posture/walking, active or
passive movement, or exposure to complex visual stimuli[2]. The disorder is caused by long-term maladaptation toa neuro-otological, medical, or psychological event thattriggered vestibular symptoms. Additionally, it is considered within the spectrum of other functional neurological disorders.
The core dogma that explains PPPD is “sensory weighting” [1, 3–9]. The postural control system involves a complex organization of visual, vestibular, and somatosensory
inputs, which are relayed to the musculoskeletal systemby the central nervous system [10]. Normal postural
stability occurs due to a balance among the “weights”
of these three types of sensory input and accurate processing of signals from the central nervous system tomotile organs. In patients with PPPD, the processing of
spatial orientation information shifts to favor visual overvestibular and somatosensory inputs, and there is a failure of higher-order cortical mechanisms to modulate
visual, vestibular, and somatosensory inputs [1, 4–9].
Thus, patients with PPPD exhibit altered and disorganized “sensory weighting” in the central nervous system[1, 3–9]. An intractable and persistent disease usually
implies a higher degree of maladaptation, more severe
disability, and more ingrained illness beliefs. Althoughprevious studies have suggested the long-term benefitsof early treatment for PPV and CSD [11, 12], definitive
treatment for PPPD based on randomized controlled
trials has yet to be approved. However, numerous studies have investigated therapeutic strategies for managing
PPPD, including selective serotonin reuptake inhibitorsand serotonin-norepinephrine reuptake inhibitors [1, 13],
vestibular rehabilitation [13–15], cognitive-behavioral
therapy [16–18], and electrical stimulation [19, 20].
Virtual reality (VR) technology has been recently introduced in a variety of clinical settings, including physical,
occupational, cognitive, and psychological rehabilitation
or training [21, 22]. In particular, physicians and therapists have expressed interest in the application of VR
technology to balance training in patients with neurological disorders such as stroke [21, 22]. Research has
indicated that this technology can be applied for posthospitalization rehabilitation in patients with walking
disabilities, particularly older adults presenting withdisuse syndrome [23]. VR technology also has the potential to overcome the scarcity of human and economic
resources in rehabilitation medicine [24]; however, theclinical efficacy of VR rehabilitation relative to traditional
methods remains unclear [21, 22, 25, 26]. Although a few

Page 2 of 10

reports regarding VR rehabilitation for walking or balance training using a Wii Fit system (Nintendo, Kyoto,
Japan) have been published, none have validated whether
the use of VR technology can improve walking or balancein patients with chronic vestibular disorders [27, 28]. A
recent study reported successful management of muscle
atrophy or cerebellar ataxia resistant to traditional therapeutic management using mediVR KAGURA-guided,dual-task balance training (mediVR KAGURA, mediVR,
Inc., Toyonaka, Japan, commercially available since February 4, 2019) [29, 30]. The mediVR KAGURA system
was developed to help patients regain their walking ability by improving dual-task processing and trunk balance[29, 30].
In the present study, we investigated the effectivenessof VR-guided, dual-task trunk balance training using themediVR KAGURA system for the management of PPPD.

Methods
Participants

Patients with PPPD at our hospital from January 1, 2021,
to February 28, 2021, were recruited for the current
study. Inclusion criteria were as follows: (i) age between
20 and 100 years; (ii) score of > 27 on the Niigata PPPD
Questionnaire (NPQ), as described in Additional file 1[31]; (iii) visit to the hospital more than twice between
January 1, 2020, and December 31, 2020. Patients who
presented with comorbidities (asthma and uncontrolled
cardiac, pulmonary, gastrointestinal, renal, hepatic,
endocrine, musculoskeletal, or oncological disorders)that would prevent them from completing the study were
excluded. Clinical diagnosis of vestibular disorders thatpreceded PPPD was based on the diagnostic criteria published by the Japan Society for Equilibrium Research [32,33] and the Bárány Society [2].
Study design and outcome measures

We randomly divided the patients into two groups: theVR-guided training group (VR group) and the conventional physiotherapy group (control group). Patientsin the VR group underwent VR-guided training using
mediVR KAGURA for 100 tasks, which took approximately 10 min. In the VR group, equilibrium tests were
performed at baseline and immediately after mediVR
KAGURA-guided training to examine its effects on staticand dynamic balance. In the control group, equilibrium
tests were performed at baseline and 10 min after thephysiotherapist performed conventional physiotherapy
related to vestibular compensation via the vestibulo-ocular reflex. Additional assessments using clinical questionnaires evaluating vestibular disorders were performed
at baseline and 1 week after mediVR KAGURA-guided
training or conventional physiotherapy to examine theYamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

Page 3 of 10

effects on symptoms related to vestibular disorders. Allevaluations were blinded. All patients were treated with
anti-vertigo/dizziness medications; other medications
administered for comorbidities were not limited. Additionally, all patients were instructed to perform vestibular
rehabilitation three times per day at home to acquire vestibular compensation via the vestibulo-ocular reflex.
The primary outcome was the effect of VR on static anddynamic trunk balance and NPQ scores in patients with
PPPD.
Detailed methods for VR training

In the 3D virtual space, the participants were instructedto catch falling red or blue objects or touch fixed red
or blue targets with their right- or left-hand controllers, respectively. The training was performed with thepatient in a sitting position to ensure safety, as training
while standing is prohibited according to the manufacturer’s instructions. The mediVR KAGURA system provides a video game-like training environment to enhance
motivation and ensure adherence. The therapist can help
patients undergo training in a dual-task fashion, utilizing various levels of physical and cognitive stimulation
through seven parameters. These parameters include
the distance, angle, height, and size of the object; size ofthe controller; inter-task interval; and falling speed ortime limit for each task (Fig. 1; Additional file 2). In addition, the therapist is permitted to encourage patients todecrease their tension and promote effective training.
Cognitive stimulation was designed to emulate how
cognitive and attention functions are processed during
each activity. For example, participants were instructedto catch red objects using the right-hand controller andblue objects using the left-hand controller. Differentiation of object colors emulates the cognitive processing
required to differentiate traffic signals. Considering theseven parameters, recognizing a new object in 3D spaceand reaching a response in a timely manner emulates the
cognitive processing involved in hazard perception andfacilitates hazard avoidance in daily life (Fig. 1; Additional
file 2).
The VR system places a radar screen at the center ofthe head-mounted display to indicate the direction of thenext task, and the patient must refer to this radar screen
regularly. Some gaming characteristics have been added
to divert attention away from the radar screen while evaluating or training the patient’s attentiveness.
Detailed assessment methods

Methodological details and criteria regarding thequestionnaires and equilibrium tests are described in
Additional file 1. The clinical questionnaires administered included the NPQ [31], the Dizziness Handicap

Fig. 1 Image during VR training. VR virtual reality

Inventory (DHI) [34, 35], the Hospital Anxiety andDepression Scale (HADS) [36, 37], orthostatic dysregulation (OD) questionnaires [38, 39], Graybiel’s motion
sickness test [40], and the Pittsburgh Sleep Quality Index(PSQI) [41, 42].
Equilibrium tests included stabilometry with or without foam posturography to assess steady-state posturalcontrol [43], while the Foulage stepping test was used toassess dynamic postural control. During stabilometry,the patients were instructed to stand on a strain-gauge
force platform (GP-5000 stabilometer; Anima, Tokyo,
Japan) for 60 s with their eyes open or closed and with orwithout foam rubber [44]. As described above, the postural control system involves the complex organization ofvisual, vestibular, and somatosensory inputs. Foam rubber posturography can assess sensory “dependence” or“weighting” among these three types of input [44]. Whenpatients stand on a foam rubber force platform with
their eyes closed, somatosensation from the foot andvisual stimuli is reduced, which results in altered sensory
weighting of vestibular inputs. Thus, this setup can indirectly reflect the function of the peripheral and central
vestibular systems due to reductions in visual and somatosensory input [44]. To assess vestibular weighting, thevelocity of the center of pressure (COP) was calculated
in the eyes closed/foam rubber conditions (VCF; lower
values indicate improvement in PPPD). Studies haveindicated that Romberg’s ratio, which compares postural
sway in eyes-open and eyes-closed conditions involving
a foam rubber platform, may reflect visual dependenceYamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

in a standing posture [44]. To assess visual weighting,the velocity of the Romberg’s ratio was calculated (VRF;
lower values indicate improvement in PPPD). To assess
somatosensory weighting, the velocity of the foam ratios(ratio of a measured parameter with or without thefoam rubber platform) was calculated in the eyes-closed
position (VFCF; higher values indicate improvementin PPPD). Measurements were performed under background noise conditions (approximately 50 dB).
Dynamic equilibrium was assessed using the Foulage
test (FT) [45–47], which involves a quantified stepping
test regulated at 120 bpm using a metronome. In this test,
the patient is instructed to stand upright with both arms
at the sides of the body and with closed feet, with the toes
continuously touching the plate, allowing for alternatingchanges in the height of the heel only (rise of approximately 2–6 cm) [45, 46, 48]. Dynamic Romberg’s ratios(eyes-closed /eyes-open FT value; area of the front–backwidth of the locus) were assessed, with lower values
indicative of PPPD improvement [45, 46, 48].
Statistical analyses

Power and sample size calculations were conducted using
the PS software (Ver. 3.1.6, Vanderbilt University, Nashville, TN, USA) [49]. This study aimed to include at least
10 patients to yield a power ≥ 0.80, assuming a medium
effect size (i.e., d = 0.80 [50]) and an α ≤ 0.05. All statistical analyses were performed using GraphPad Prism version 8.0.0 for Windows, GraphPad Software, San Diego,
California USA (www.​graph​pad.​com). An unpaired t-test
and Fisher’s exact test were used to compare age and sex
between the groups, respectively. Parametric data related
to questionnaire and equilibrium test results before
and after training were assessed using paired t-tests,
while non-parametric data related to these results wereassessed using Mann–Whitney U-tests. Residual plots
were used to confirm the accuracy of the assumptions
made for outcomes. Statistical significance was set at
P < 0.05. Evaluations were determined as “not applicable” if the calculated sample size after data collection was
found to be insufficient for statistical analysis.

Results
Participants

Fourteen patients underwent mediVR KAGURA-guided
training; however, two patients did not consent to share
their data. Therefore, twelve patients (3 men, 9 women;mean age ± standard deviation (SD): 58.0 ± 17.1 years)
were included in the VR group. The control group
included 14 patients (3 men, 11 women; mean age ± SD:
63.5 ± 15.9 years). Detailed participant information isshown in Table 1.

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Table 1 Patient characteristicsAge
Sex (M:F)
PrecedingvestibulardiseaseVR group (n = 12)

Control group(n = 14)

P-value

58.0 ± 17.1

63.5 ± 15.9

0.12a

3:11

0.67b

Meniere’s disease: 11
BPPV: 1

Meniere’s disease: 12
BPPV: 2NA

3:9

VR virtual reality, BPPV benign paroxysmal positional vertigoaUnpaired t-testb

Fisher’s exact test

Static postural stability was improved by mediVR
KAGURA‑guided training in patients with PPPD

To examine changes in static postural stability after
mediVR KAGURA-guided training in patients with
PPPD, we assessed changes in the parameters of vestibular weighting (VCF), visual weighting (VRF), and somatosensory weighting (VFCF) before and after training.
The VR group demonstrated a significant improvementin VFCF after mediVR KAGURA-guided training compared to that before training (Fig. 2a–c, VCF: P = 0.16,
VRF: P = 0.31, VFCF: P = 0.02 [Cohen’s d = 1.41]), suggesting somatosensory re-weighting in the vestibular control system. While no such improvement wasobserved in the control group (Fig. 2d–f, VCF: P = 0.98,
VRF: P = 0.30, VFCF: P = 0.08).
Dynamic postural stability was partly improved by mediVR
KAGURA‑guided training in patients with PPPD

To examine changes in dynamic postural stability after
mediVR KAGURA-guided training in patients with
PPPD, we compared changes in Foulage test [45, 46,48]. The VR group exhibited significant improvement in
the dynamic Romberg’s ratio, while no such improvement was observed in the control group (Fig. 3a, VR
group: P = 0.003 [Cohen’s d = 2.42]; Fig. 3b, control
group: P = 0.34), which suggests visual re-weighting or
desensitization.
Subjective symptoms and anxiety related to PPPD
improved after mediVR KAGURA‑guided training

Responses to clinical questionnaires related to vestibular disorders were analyzed at baseline and after themediVR KAGURA-guided training to examine changes
in subjective symptoms. In the VR group, significant
improvements in scores for the HADS-A, NPQ, and all
NPQ subcategories relative to baseline were observed
following mediVR KAGURA-guided training (Fig. 4a–d, i, NPQ: P = 0.005 [Cohen’s d = 2.20], NPQ uprightYamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

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Fig. 2 Static postural stability after mediVR KAGURA-guided training. a, d Changes in control group and VR group VCF parameters related tovestibular weighting: P = 0.96 (r = 0.13), P = 0.16 (r = 0.12), respectively. b, e Changes in control group and VR group VRF parameters related to visual
weighting: P = 0.67 (r = 0.12). P = 0.31 (r = 0.15), respectively. c, f Changes in control group and VR group VFCF parameters related to somatosensory
weighting: P = 0.04 (r = 0.53), P = 0.02 (r = 0.58), respectively. Blue indicates the control group, and red indicates the VR group. Bars indicate themean ± SD. VR virtual reality, VCF velocity of COP in the eyes-closed/foam rubber condition, VRF velocity of Romberg’s ratio with foam rubber, VFCF
velocity of foam ratio in the eyes-closed/foam rubber condition, SD standard deviation

Fig. 3 Dynamic postural stability after mediVR KAGURA-guided
training. a, b Dynamic Romberg’s ratios in the (a) control group(P = 0.34, r = 0.12) and (b) VR group (P = 0.003, r = 0.80). Blue indicatesthe control group, and red indicates the VR group. Bars indicate themean ± SD. VR virtual reality, SD standard deviation

posture/walking: P = 0.02 [Cohen’s d = 1.67], NPQ
movement: P = 0.005 [Cohen’s d = 2.06], NPQ visual
stimulation: P = 0.002 [Cohen’s d = 2.42], HADS-A:
P = 0.01 [Cohen’s d = 1.78]). There were no significant
differences in other parameters between baseline andafter mediVR KAGURA-guided training (DHI: P = 0.08,
DHI-P: P = 0.18, DHI-E: P = 0.06, DHI-F: P = 0.16,
HADS-D: P = 0.24, OD: P = 0.17, PSQI: P = 0.50, Graybiel’s motion sickness score: P = 0.31).
In the control group, there were no significant differences in any parameter except for the deteriorationof visual stimulation in the NPQ (Fig. 4e–h, j, NPQ:
P = 0.43, NPQ upright posture/walking: P = 0.20, NPQ
movement: P = 0.13, NPQ visual stimulation: P = 0.02
[Cohen’s d = 1.27], HADS-A: P = 0.19, DHI: P = 0.07,
DHI-P: P = 0.38, DHI-E: P = 0.10, DHI-F: P = 0.17,
HADS-D: P = 0.24, OD: P = 0.37, PSQI: P = 0.32, Graybiel’s motion sickness score: P = 0.06).

Yamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

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Fig. 4 Subjective symptoms of PPPD after mediVR KAGURA-guided training and conventional physiotherapy. a–d Control group: NPQ: P = 0.40,
r = 0.20 (a), NPQ upright posture/walking: P = 0.32, r = 0.23 (b), NPQ movement: P = 0.12, r = 0.30 (c), and NPQ visual stimulation: P = 0.02, r = 0.52
(d). e–h VR group: NPQ: P = 0.005, r = 0.74 (e), NPQ upright posture/walking: P = 0.02, r = 0.65 (f), NPQ movement: P = 0.005, r = 0.72 (g), and NPQ
visual stimulation: P = 0.002, r = 0.77 (h). i, j HADS-A: P = 0.15, r = 0.24 in the control group and P = 0.01, r = 0.67 in the VR group. Blue indicates thecontrol group, and red indicates the VR group. Bars indicate the mean ± SD. PPPD persistent postural-perceptual dizziness, VR virtual reality, NPQ
Niigata PPPD Questionnaire, HADS Hospital Anxiety and Depression Scale, SD standard deviation

Discussion
In this study, we aimed to determine the effectiveness of
VR-guided training for the management of PPPD using
the mediVR KAGURA system. Patients with PPPD
exhibited improvements in objective outcomes, including static and dynamic postural stability (somatosensory

and visual re-weighting), immediately after the mediVR
KAGURA-guided training session. Additionally, thistraining improved anxiety and scores for all NPQ subcategories after 1 week. Consequently, these findings
broaden the possibilities of PPPD management using
mediVR KAGURA-guided rehabilitation.

Yamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

PPPD is a syndrome that unifies the key features of
PPV, CSD, and other related disorders [2]. Research has
demonstrated that the mechanisms underlying PPPD
include the stiffening of postural control, a shift in spatial orientation information processing to favor visualover vestibular inputs, and failure of higher-order corticalmechanisms to modulate the first two processes [1, 4–9].
Psychological and functional comorbidities develop frommaladaptive cognitive-behavioral responses, including
acrophobia, anxiety or depressive disorders, and functional gait abnormalities. Therefore, current strategies for
managing PPPD include therapy for comorbidities suchas vestibular diseases, re-weighting of sensory inputs forpostural control [13–15], and desensitization to increase
tolerance to perceived stimuli [16–18].
In this study, mediVR KAGURA-guided training
resulted in improvements in NPQ scores, static postural
stability (somatosensory weighting), dynamic postural
stability (visual weighting), and even short-term rehabilitation. We speculate that re-tuning, desensitization, andre-weighting attenuated impairments in balance control
by improving cognitive and motor function in patientswith PPPD. The use of conventional approaches for quantitative assessments of performance during postural balance training may be ineffective for PPPD [26, 29]. VR
creates multiple interactive, multimodal sensory stimuli
that offer unique advantages over other approaches inneurorehabilitation. VR facilitates an easy, prompt, quantitative, and replicable training method by accurately setting the distance, angle, height, or other parameters in a
3D virtual space [26, 29]. The therapist’s only responsibility is to adjust these parameters by inputting numbers on
the operating panel of the computer. Moreover, the randomly programmed VR-training tasks may require significantly more precise postural control. Consequently,
the tailor-made, optimized, and unpredictable mediVR
KAGURA-guided tasks can result in greater improvements in postural and trunk balance when comparedwith conventional approaches, even when performed
in a sitting position. Previous research has indicatedthat the use of VR during neurorehabilitation improvescognitive and motor function [21], with several studies
reporting benefits in relation to upper limb function, balance, and gait [51]; neuromotor monitoring of recovery[52]; strength fitness and skills [53], range of motion forthe shoulder, and spasticity [54]. In this study, mediVR
KAGURA-guided training promoted sensory re-weighting in patients with PPPD, resulting in improvementof subjective symptoms. This finding suggests that reweighting of somatosensory inputs and desensitization
to visual inputs via mediVR KAGURA-guided training
are important for symptom improvement in patientswith PPPD. We speculated that adequate and optimized

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VR-guided rehabilitation can have a greater effect on
PPPD.
Our findings also indicated that anxiety scores
improved following mediVR KAGURA-guided training when compared with those observed in the control
group. This outcome highlights the benefits of using
tailor-made, optimized, and unpredictable mediVR
KAGURA-guided training tasks and therapist-guided
relaxation techniques. During our mediVR KAGURAguided rehabilitation sessions, the patient was constantly
required to think of the next task to time the fall of thenext object and perform the reaching movements in atimely manner, emulating the conditions necessary for
hazard perception and avoidance. These methods may
be useful for patients with PPPD who are unable to imagine the variables associated with real-world situations. A
previous study reported psychological and cognitive benefits when older adults utilized adapted VR devices, suchas improvements in attention or memory and decreased
depressive symptoms [21, 55]. Taken together, the available evidence indicates that VR devices can be used as
effective tools to motivate patients during rehabilitation
sessions [56], to improve spatial orientation and attention in daily life activities [57], and to improve pain relief
scores and emotional aspects related to functionality [55].
Additionally, a VR training environment can provide participants with task-specific training, accurate sensory andtactile feedback, and motivation [58]. Therefore, mediVR
KAGURA dual-task training may facilitate neurorehabilitation of cognitive and motor function.
Notably, the application of VR technology in the future
may benefit from a larger pool of automated data andadvancements in artificial intelligence. For example, eye
trackers may become a standard feature of VR headsets;
this will allow for the collection of data from both healthy
controls and individuals with disabilities. Given thepotential for this to ensure equity in therapeutic settings
despite differences in ability, further studies are required
to explore this issue.

Limitations
This study had several limitations. First, the mediVR
KAGURA-guided training session was short (100 tasks
for 10 min) because we could not use the machine fora longer duration due to funding limitations. Consequently, adjustments to the settings and treatment
protocol were not attempted, although research indicates that longer interventions are more effective[23]. Second, the long-term effects on PPPD were notinvestigated. Further randomized and long-term studies comparing mediVR KAGURA-guided training andother rehabilitation programs are required to validate
the effectiveness of this VR-guided method. Lastly, theYamaguchi et al. Journal of NeuroEngineering and Rehabilitation(2022) 19:92

sample size was insufficient for some analyses. Nonetheless, the study provides proof of concept, supporting
the need for additional studies with larger sample sizes.

Conclusion
Our findings indicated that a single session of VRguided, dual-task, trunk balance training using a
mediVR KAGURA system improved static and dynamicbalance ability, NPQ scores, and HADS-A scores inpatients with PPPD compared to conventional physiotherapy. VR-guided training using mediVR KAGURA
offers a safe and cost-effective solution for PPPD. As
such, further prospective studies need to explore theadequate conditions for this VR-guided method.
Abbreviations
PPPD: Persistent postural-perceptual dizziness; VR: Virtual reality; NPQ: Niigata
PPPD Questionnaire; PPV: Phobic postural vertigo; CSD: Chronic subjective diz‑ziness; DHI: Dizziness Handicap Inventory; HADS: Hospital Anxiety and Depres‑sion Scale; OD: Orthostatic dysregulation; PSQI: Pittsburgh Sleep Quality Index;
COP: Center of pressure; VCF: Velocity of COP in the eyes-closed/foam rubber
condition; VRF: Velocity of Romberg’s ratio with foam rubber; VFCF: Velocity
of foam ratio in the eyes-closed/foam rubber condition; FT: Foulage test; SD:Standard deviation.

Supplementary Information
The online version contains supplementary material available at https://​doi.​
org/​10.​1186/​s12984-​022-​01068-6.
Additional file 1. Overview of the assessment tools used in this study andtheir respective scoring systems. Scoring and criteria of questionnaire andequilibrium test.
Additional file 2. Movie during mediVR-guided training. Motion during
the VR-training.
Acknowledgements
Speech therapist Shoko Noda assisted with performing the experiment. We
would like to thank Editage (http://​www.​edita​ge.​com) for editing and review‑ing this manuscript for English language.
Author contributions
TY and TM: investigation, project administration, methodology, visualization,
writing—original draft, data curation, formal analysis, conceptualization,
writing—review and editing, validation. KT, FI, and NU: investigation, project
administration, and methodology. MH: project administration, methodology,
software, conceptualization, resources, and validation. TM and SK: supervision,
resources, validation. All authors have read and approved the final version ofthis manuscript.
Funding
This research received no specific grants from funding agencies in the public,commercial, or not-for-profit sectors.
Availability of data and materials
All data that support the findings of this study are available from the cor‑
responding author, Toru Miwa, upon reasonable request.

Page 8 of 10

Declarations
Ethics approval and consent to participate
This study was approved by the Kitano Hospital Clinical Research Ethics
Committee (Approval Number: 1911003), and all participants provided writ‑ten informed consent. The study adhered to the tenets of the Declaration of
Helsinki.
Consent for publication
All participants provided consent for this publication.
Competing interests
Masahiko Hara is a stockholder of mediVR, Inc., a company with unlisted stockand ongoing international Patent Cooperation Treaty applications for several
patents related to mediVR KAGURA-guided rehabilitation. All other authors
have no competing interest to declare.
Author details
1
Department of Otolaryngology‑Head and Neck Surgery, Tazuke Kofukai
Medical Research Institute, Kitano Hospital, Osaka, Japan. 2 Department
of Otolaryngology‑Head and Neck Surgery, Kyoto University, Kyoto, Japan.
3
Department of Otolaryngology, Osaka Metropolitan University Schoolof Medicine, 1‑4‑3 Asahi‑machi, Abeno‑ku, Osaka 545‑8585, Japan. 4 Depart‑
ment of Medical Device Development, mediVR, Inc., Toyonaka, Japan. 5 Centerfor Community‑Based Healthcare Research and Education, Shimane Univer‑sity, Izumo, Japan.
Received: 11 August 2021 Accepted: 12 August 2022

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