2BALANCE: Test-retest reliability of a cognitive-motor dual-task protocol

PURPOSE: Aside from typical symptoms such as dizziness and vertigo, persons with vestibular disorders often have cognitive and motor problems. These symptoms have been assessed in single-task condition. However, dual-tasks assessing cognitive-motor interference might be an added value as they reflect daily life situations better. Therefore, the 2BALANCE protocol was developed. In the current study, the test-retest reliability of this protocol was assessed. METHODS: The 2BALANCE protocol was performed twice in 20 healthy young adults with an in-between test interval of two weeks. Two motor tasks and five different cognitive tasks were performed in single and dual-task condition. Intraclass correlation coefficients (ICC), the standard error of measurement, and the minimal detectable difference were calculated. RESULTS: All cognitive tasks, with the exception of the mental rotation task, had favorable reliability results (0.26≤ICC≤0.91). The dynamic motor task indicated overall substantial reliability values in all conditions (0.67≤ICC≤0.98). Similar results were found for the static motor task during dual-tasking (0.50≤ICC≤0.92), but were slightly lower in single-task condition (–0.26≤ICC≤0.75). CONCLUSIONS: The 2BALANCE protocol was overall consistent across trials. However, the mental rotation task showed lowest reliability values.

Comparison of verticality perception and postural sway induced by double temple-mastoidal and bipolar binaural 20 Hz sinusoidal galvanic vestibular stimulation

BACKGROUND: Galvanic vestibular stimulation (GVS) is believed to be one of the most valuable tools for studying the vestibular system. In our opinion, its combined effect on posture and perception needs to be examined more. OBJECTIVE: The present study was conducted to investigate the effect of a 20 Hz sinusoidal Galvanic Vestibular Stimulation (sGVS) on the body sway and subjective visual vertical (SVV) deviation through two sets of electrode montages (bipolar binaural and double temple-mastoidal stimulation) during a three-stage experiment (baseline, threshold, and supra-threshold levels). METHODS: While the individuals (32 normal individuals, 10 males, the mean age of 25.37±3.00 years) were standing on a posturography device and SVV goggles were put on, the parameters of the body sway and SVV deviation were measured simultaneously. Following the baseline stage (measuring without stimulation), the parameters were investigated during the threshold and supra-threshold stages (1 mA above the threshold) for 20 seconds. This was done separately for each electrode montage. Then, the results were compared between the three experimental stages and the two electrode montages. RESULTS: In both electrode montages, “the maximum amplitude” of the mediolateral (ML) and anteroposterior (AP) body sway decreased and increased in the threshold and supra-threshold stages, respectively, compared to the baseline stage. Comparison of the amount of “amplitude change” caused by each electrode montages showed that the double temple-mastoidal stimulation induced a significantly greater amplitude change in body sway during both threshold and supra-threshold stages (relative to the baseline stage). The absolute mean values of the SVV deviation were significantly different between the baseline and supra-threshold levels in both electrode montages. The SVV deviation in double temple-mastoidal stimulation was a bit greater than that in the bipolar binaural stimulation. CONCLUSION: Double temple-mastoidal stimulation has induced greater amount of change in the body sway and SVV deviation. This may be due to the more effective stimulation of the otoliths than semicircular canals.

The perception threshold of the vestibular Coriolis illusion

BACKGROUND: The vestibular Coriolis illusion is a disorienting sensation that results from a transient head rotation about one axis during sustained body rotation about another axis. Although often used in spatial disorientation training for pilots and laboratory studies on motion sickness, little is known about the minimum required rotation rate to produce the illusion. OBJECTIVE: This study determined the perception threshold associated with the Coriolis illusion. METHODS: Nineteen participants performed a standardized pitching head movement during continuous whole-body yaw rotation at rates varying between 5 to 50 deg/s. The participants reported their motion sensation in relation to three hypothesized perception thresholds: 1) any sense of motion, 2) a sense of rotation, and 3) a sense of rotation and its direction (i.e., the factual Coriolis illusion). The corresponding thresholds were estimated from curves fitted by a generalized linear model. RESULTS: On average threshold 1 was significantly lower (8 deg/s) than thresholds 2 and 3. The latter thresholds did not differ from each other and their pooled value was 10 deg/s. CONCLUSIONS: The Coriolis illusion is perceived at yaw rates exceeding 10 deg/s using a pitching head movement with 40 deg amplitude and 55 deg/s peak velocity. Model analysis shows that this corresponds to an internal rotation vector of 6 deg/s. With this vector the Coriolis perception threshold can be predicted for any other head movement.

The impact of disease duration in persistent postural-perceptual dizziness (PPPD) on the quality of life, dizziness handicap and mental health

BACKGROUND: Persistent Postural-Perceptual Dizziness (PPPD) is a chronic functional disorder which interferes with the way individuals experience their personal, social and work life. OBJECTIVE: To study the impact of disease duration in PPPD on the quality of life (QOL), dizziness handicap and mental health on the patients. METHODS: A prospective study comparing the EQ-5D for QOL, Dizziness Handicap Inventory (DHI) and DASS-21 between 27 patients with PPPD and 27 of those who have recovered from an acute vestibular event. Similar parameters between PPPD patients with symptoms less than one year and more than a year were compared. RESULTS: The PPPD patients were predominantly females and middle-aged with significantly higher DHI scores (mean 48.3 + 25.7, p = 0.00002), higher total mean scores in the DASS-21 (mean 21.6 + 13.7, p = 0.009) and poorer QOL with mean EQ-5D VAS of 67.9 + 17.3 (p < 0.00001). PPPD patients with symptoms for more than a year had significant increase in physical handicap (p = 0.041) as well as anxiety levels (p = 0.008). CONCLUSIONS: PPPD is predominantly seen in females and middle-aged which significantly reduces the QOL, increases dizziness handicap and increases depression, anxiety and stress levels. The increase in duration of illness further increases the anxiety levels and physical handicap.

Report of oscillopsia in ataxia patients correlates with activity, not vestibular ocular reflex gain

BACKGROUND: Patients with cerebellar ataxia report oscillopsia, “bouncy vision” during activity, yet little is known how this impacts daily function. The purpose of this study was to quantify the magnitude of oscillopsia and investigate its relation to vestibulo-ocular reflex (VOR) function and daily activity in cerebellar ataxia. METHODS: 19 patients diagnosed with cerebellar ataxia and reports of oscillopsia with activity were examined using the video head impulse test (vHIT), Oscillopsia Functional Index (OFI), and clinical gait measures. Video head impulse data was compared against 40 healthy controls. RESULTS: OFI scores in ataxia patients were severe and inversely correlated with gait velocity (r = –0.55, p < 0.05), but did not correlate with VOR gains. The mean VOR gain in the ataxic patients was significantly reduced and more varied compared with healthy controls. All patients had abnormal VOR gains and eye/head movement patterns in at least one semicircular canal during VHIT with passive head rotation. CONCLUSIONS: Patients with cerebellar ataxia and oscillopsia have impaired VOR gains, yet severity of oscillopsia and VOR gains are not correlated. Patients with cerebellar ataxia have abnormal oculomotor behavior during passive head rotation that is correlated with gait velocity, but not magnitude of oscillopsia.

Curriculum for vestibular medicine (vestmed) proposed by the barany society

This document presents the initiative of the Bárány Society to improve diagnosis and care of patients presenting with vestibular symptoms worldwide. The Vestibular Medicine (VestMed) concept embraces a wide approach to the potential causes of vestibular symptoms, acknowledging that vertigo, dizziness, and unsteadiness are non-specific symptoms that may arise from a broad spectrum of disorders, spanning from the inner ear to the brainstem, cerebellum and supratentorial cerebral networks, to many disorders beyond these structures. The Bárány Society Vestibular Medicine Curriculum (BS-VestMed-Cur) is based on the concept that VestMed is practiced by different physician specialties and non-physician allied health professionals. Each profession has its characteristic disciplinary role and profile, but all work in overlapping areas. Each discipline requires good awareness of the variety of disorders that can present with vestibular symptoms, their underlying mechanisms and etiologies, diagnostic criteria and treatment options. Similarly, all disciplines require an understanding of their own limitations, the contribution to patient care from other professionals and when to involve other members of the VestMed community. Therefore, the BS-VestMed-Cur is the same for all health professionals involved, the overlaps and differences of the various relevant professions being defined by different levels of detail and depth of knowledge and skills. The BS-VestMed-Cur defines a Basic and an Expert Level Curriculum. The Basic Level Curriculum covers the VestMed topics in less detail and depth, yet still conveys the concept of the wide net approach. It is designed for health professionals as an introduction to, and first step toward, VestMed expertise. The Expert Level Curriculum defines a Focused and Broad Expert. It covers the VestMed spectrum in high detail and requires a high level of understanding. In the Basic and Expert Level Curricula, the range of topics is the same and runs from anatomy, physiology and physics of the vestibular system, to vestibular symptoms, history taking, bedside examination, ancillary testing, the various vestibular disorders, their treatment and professional attitudes. Additionally, research topics relevant to clinical practice are included in the Expert Level Curriculum. For Focused Expert proficiency, the Basic Level Curriculum is required to ensure a broad overview and additionally requires an expansion of knowledge and skills in one or a few specific topics related to the focused expertise, e.g. inner ear surgery. Broad Expert proficiency targets professionals who deal with all sorts of patients presenting with vestibular symptoms (e.g. ORL, neurologists, audiovestibular physicians, physical therapists), requiring a high level of VestMed expertise across the whole spectrum. For the Broad Expert, the Expert Level Curriculum is required in which the minimum attainment targets for all the topics go beyond the Basic Level Curriculum. The minimum requirements regarding knowledge and skills vary between Broad Experts, since they are tuned to the activity profile and underlying specialty of the expert. The BS-VestMed-Cur aims to provide a basis for current and future teaching and training programs for physicians and non-physicians. The Basic Level Curriculum could also serve as a resource for inspiration for teaching VestMed to students, postgraduate generalists such as primary care physicians and undergraduate health professionals or anybody wishing to enter VestMed. VestMed is considered a set of competences related to an area of practice of established physician specialties and non-physician health professions rather than a separate clinical specialty. This curriculum does not aim to define a new single clinical specialty. The BS-VestMed-Cur should also integrate with, facilitate and encourage translational research in the vestibular field.

Predicting individual acclimation to the cross-coupled illusion for artificial gravity

BACKGROUND: The cross-coupled (CC) illusion and associated motion sickness limits the tolerability of fast-spin-rate centrifugation for artificial gravity implementation. Humans acclimate to the CC illusion through repeated exposure; however, substantial inter-individual differences in acclimation exist, which remain poorly understood. To address this, we investigated several potential predictors of individual acclimation to the CC illusion. METHODS: Eleven subjects were exposed to the CC illusion for up to 50 25-minute acclimation sessions. The metric of acclimation rate was calculated as the slope of each subject’s linear increase in spin rate across sessions. As potential predictors of acclimation rate, we gathered age, gender, demographics, and activity history, and measured subjects’ vestibular perceptual thresholds in the yaw, pitch, and roll rotation axes. RESULTS: We found a significant, negative correlation (p = 0.025) between subjects’ acclimation rate and roll threshold, suggesting lower thresholds yielded faster acclimation. Additionally, a leave-one-out cross-validation analysis indicated that roll thresholds are predictive of acclimation rates. Correlations between acclimation and other measures were not found but were difficult to assess within our sample. CONCLUSIONS: The ability to predict individual differences in CC illusion acclimation rate using roll thresholds is critical to optimizing acclimation training, improving the feasibility of fast-rotation, short-radius centrifugation for artificial gravity.

Vestibular activities and participation measure: Turkish validity and reliability

BACKGROUND: International Classification of Functioning, Disability and Health (ICF) has an important role in rehabilitation in terms of assessments. In the field of vestibular rehabilitation, Vestibular Activities of Participation (VAP) measure is the first assessment developed in a perspective of ICF. OBJECTIVE: It was aimed to adapt cross-culturally and analyze psychometric properties of VAP into Turkish Language. METHODS: The VAP was translated into Turkish language by the authors and back translated by a blind native English speaker. The final version was applied to 310 participants. Internal consistency was analyzed with Cronbach’s alpha and test-retest reliability analyzed with Intraclass Correlation coefficient (ICC). Validity of the scale investigated with Exploratory and Confirmatory Factor analysis (EFA and CFA). RESULTS: Cronbach’s alpha reliability coefficient was found 0.94, and the reliability of the subscales ranged from 0.75 to 0.95; ICC was found 0.94. VAP resulted 8-factor structure and explained 88%of the total variance. In CFA (χ2) / df ratio shows good agreement with 2.472 and the goodness of fit indices of TLI (0.814), CFI (0.893) and RMSEA (0.075) showed acceptable fit. CONCLUSIONS: This study showed that VAP-Turkish version is valid and reliable in Turkish speaking populations, and might be used to determine impact of vestibular disorders on activities and participation.

Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright

BACKGROUND: Humans demonstrate many physiological changes in microgravity for which long-duration head down bed rest (HDBR) is a reliable analog. However, information on how HDBR affects sensory processing is lacking. OBJECTIVE: We previously showed (25) that microgravity alters the weighting applied to visual cues in determining the perceptual upright (PU), an effect that lasts long after return. Does long-duration HDBR have comparable effects? METHODS: We assessed static spatial orientation using the luminous line test (subjective visual vertical, SVV) and the oriented character recognition test (PU) before, during and after 21 days of 6° HDBR in 10 participants. Methods were essentially identical as previously used in orbit (25). RESULTS: Overall, HDBR had no effect on the reliance on visual relative to body cues in determining the PU. However, when considering the three critical time points (pre-bed rest, end of bed rest, and 14 days post-bed rest) there was a significant decrease in reliance on visual relative to body cues, as found in microgravity. The ratio had an average time constant of 7.28 days and returned to pre-bed-rest levels within 14 days. The SVV was unaffected. CONCLUSIONS: We conclude that bed rest can be a useful analog for the study of the perception of static self-orientation during long-term exposure to microgravity. More detailed work on the precise time course of our effects is needed in both bed rest and microgravity conditions.