Analysis Of Sway Research Articles

Developing Programs for Converting MIDAS GEN to ANSYS Models Based on Python

The reasonableness and accuracy of engineering design are often assessed through the use of a variety of structural design analysis software, which are then compared and verified. However, it is challenging for a single analysis software to meet the diverse and complex design requirements. In order to meet the specific engineering requirements, it is necessary to convert the MIDAS result model into an ANSYS structural model and conduct a nonlinear analysis and simulation in ANSYS. Nevertheless, the existing interface is unable to facilitate direct conversion of the model. Accordingly, this paper presents a Python-based ANSYS APDL program that enables the complete conversion of MIDAS GEN structural models to ANSYS finite element models. The program is capable of converting a range of data, including material, section, element, connection, load, node mass, constraint, time history function, and so forth. The program is capable of converting specific connection units, including elastic and general connection units. Additionally, the beam-column section direction, beam end freedom release, rigid element, and special anti-rocking structure of the structure can be considered. Ultimately, the theatre model is transformed. Following a comparison of the analysis results, it was found that the mass and mode of the model before and after the transformation were essentially identical. The maximum error of the first six orders of the structure is 2.95%, with the structural displacement under gravity load remaining essentially unchanged. The research and analysis demonstrate the accuracy and reliability of the MIDAS GEN conversion ANSYS program. The conversion program significantly reduces the time required for direct modeling in ANSYS, enhancing work efficiency. The study has considerable practical significance for the seismic sway design and analysis of buildings based on vibration isolation design.

Impact of proprioceptive cervical dizziness in chronic neck pain syndromes on gait and stance during active head-turn challenges.

An earlier observational study described selected patients with acute neck pain syndrome, who experienced short bursts of cervical vertigo elicited by rapid head movements. The current study on a larger cohort of 20 patients with chronic or frequently recurring neck pain syndrome and age-matched controls focused on two major questions: (1) Can head movements in subjects with exacerbations of neck pain and restrictions of neck mobility also elicit bursts of vertigo? (2) What is the impact on postural balance measured by analysis of body sway and locomotion? A detailed questionnaire was applied, posture and gait were evaluated by use of instrumented posturography-and gait analysis with and without slow or rapid horizontal head rotations in the yaw plane with and without sight/visual input. All patients reported some or frequent episodes of dizziness in the range of seconds only elicited by rapid, not by slow head movements. Postural sway in patients was unremarkable in undisturbed conditions without head movements, but specifically increased by rapid but not slow head turns. The latter is best explained by the lack of continuous control of velocity and amplitude of saccadic head movements. Gait analysis revealed a slowed and cautious gait pattern already at undisturbed condition that was even exaggerated during rapid head turns. These observations demonstrate that chronic or recurrent neck pain is associated with episodic experiences of dizziness and above results in both chronic and episodic alterations of stance and gait that resemble those described for patients with phobic postural vertigo/persistent postural perceptual dizziness, a functional gait disorder.

Dynamical systems theory applied to short walking trials

Human walking is an extremely complex neuromuscular activity whose simplicity disappears when an attempt is made to provide a quantitative description of the process. The dynamical systems theory provides a framework for analyzing the stability and chaotic nature of dynamical systems, employing Floquet multipliers (FM) and long and short-term Lyapunov exponents (LE), respectively. This report compares FM and LE from three methods: method A (false nearest neighbors and numerical approximation), method B (false nearest neighbors and semi-analytical technique) and method C (singular value decomposition and semi-analytical technique). Data from 33 healthy older adults with no history of falls were used to explain the dynamic system. A surrogate center of mass trajectory was calculated for the analysis of sway in the transverse plane. Results revealed methodological differences in LE and FM calculations with semi-analytical solutions providing closer approximations to observed gait behavior. The long-term LE from Methods A and B were similar, but other LE pairings differed. Method A’s short-term LE indicated chaotic gaits for all subjects, while long-term LE from Methods A and B indicated chaos for half the subjects. Method C showed non-chaotic gait for most subjects. Method B’s FM indicated over 30% of subjects had unstable gait. Method C yielded values of LE and FM that most closely matched the subjects’ gait patterns. This study offers a methodological foundation for gait analysis using short time-series data, facilitating deeper insights into both stability and chaos within gait dynamics.

Impact of professional dance training on characteristics of postural sway.

The stability of human upright posture determines the range and dynamics of movements performed. Consequently, the repertoire and quality of the movements performed by a dancer are mainly determined by the efficiency of postural control. This is of particular importance in professional dance training that should focus on shaping optimal movement‑posture interaction. To get a deeper insight into this problem, the impact of the training on postural sway characteristics during quiet stance was analyzed in 16 female students in the seventh grade of a ballet school and compared with the size‑ and age‑matched group of secondary school students. Center of pressure trajectories were recorded for 25.6 s while standing quiet with eyes open (EO) and then with eyes closed (EC). The assessment of postural control was based on novel normalized sway parameters including sway vector (SV), sway anteroposterior (AP) and mediolateral (ML) directional indices (DIAP and DIML), and sway ratios (SRAP and SRML). The results document a significant contribution of vision to postural stability control in ballet students, which seems to compensate for training‑related changes in joint mobility and altered activity ranges of the legs' muscles. In the control group standing with EC, SV amplitude increased only by 18% whereas in the ballet students tested in the same conditions, the increase exceeded 72%. Under full control of standing posture (EO test), the training‑related increase of leg muscle forces allows dancers to maintain balance with lesser effort as documented here by 21% reduced SRAP. Additionally, the dancers while tested with their EC exhibited a 12% increase in the anteroposterior sway with a concomitant reduction of the mediolateral sway. The resulting changes in the postural control asymmetry were documented by both DIAP/DIML and SV azimuth. In conclusion, our novel analysis of postural sway seems a useful tool in monitoring the effects of training as well as the proper course of postural control development in children and adolescents.

Principal components analysis of postural sway in persons with unilateral lower limb amputation: A wearable sensor approach

Standing sway assessments can detect sensory imbalances which compromise postural control. Persons with lower limb amputation (LLA) often demonstrate impaired postural control, increasing fall risk. Here, principal features of postural sway were identified in persons with unilateral LLA using a single, commercially available wearable sensor. Sixty-one persons with LLA (n = 44 transtibial; n = 17 transfemoral) stood on a firm surface with eyes open/closed while wearing a single accelerometer mounted over the sacrum. Common parameters quantified spatiotemporal and spectral features of sway in anterior-posterior (AP) and mediolateral (ML) directions. Principal component (PC) dimensionality reduction was applied and loadings inspected to identify a reduced, non-redundant set among 14 original variables capturing 90 % variance. Six PCs described ≥ 90 % variance, with the first 3 explaining 75 %. With eyes open and closed, PC1 was loaded by variables characterizing trajectory planar size: area, jerk (i.e., sway smoothness), AP/ML RMS path distance, and AP/ML path range. With eyes open, PC2 was loaded by variables characterizing direction and spectral features: ellipse rotation, AP centroidal frequency, and ML jerk. With eyes closed, PC2 spectral loadings increased: ML centroidal frequency, ML frequency dispersion, and AP centroidal frequency. With eyes open, PC3 was loaded by ellipse rotation, jerk, ML velocity, ML centroidal frequency. With eyes closed, PC3 was loaded by ellipse rotation, ML centroidal frequency, ML frequency dispersion, and AP path velocity, characterizing off-axis error/corrections. RMS of path distance, ellipse rotation, centroidal frequency, frequency dispersion, path velocity, and jerk are a concise parameter set, derived from an accelerometer, to capture principal sway features in persons with LLA during standing balance with visual perturbations.

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

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. 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. 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. 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.

Comparison of sway meter and Kinovea software as a tool of measurement for the sway parameters during quiet standing: An observational study

BackgroundSeveral attempts have been made to quantify postural sway, from simple observational techniques to advanced computer technology. Measuring sway using commercial motion tracking devices and force plates are expensive and not feasible in evaluation on non-standardised surfaces. Video cameras can be used as an affordable alternative to perform human motion capturing, and this data can be analysed using motion tracking software like Kinovea; a free, reliable software that provides valid data, and an acceptable level of accuracy in angular and linear measurements. This study evaluated the reliability of Kinovea software to measure the sway amplitude in comparison with sway meter. MethodsThirty-six young women were recruited by convenience to this prospective observational study. Sway amplitude of the participants were measured using a sway meter on three different surfaces, with eyes opened and closed conditions, using modified Lords sway meter and videography. Videos were later analysed using Kinovea motion analysing software. The quantitative data of sway parameters were analysed for reliability using intraclass-correlation co-efficient and Bland Altman plot. ResultsThere was an excellent correlation (>0.90) between the sway measurement values obtained from both methods irrespective of the surfaces. But the reliability was greater for the medio-lateral sway on the pebbled surfaces (0.981), and least for the anterior posterior sway on the same surface. ConclusionThis study concludes that, there is an excellent reliability for the video based sway analysis using Kinovea software. Hence this method can be used as an affordable alternative to measure the sway parameters.

Differing postural control patterns in individuals with bilateral and unilateral hearing loss

ObjectivesHearing loss (HL) is associated with imbalance and increased fall risk. The mechanism underlying this relationship and differences across types of hearing loss remains unclear. Head mounted displays (HMD) can shed light on postural control mechanisms via an analysis of head sway. PurposeThe purpose of this study was to evaluate head sway in response to sensory perturbations in individuals with bilateral (BHL) or unilateral hearing loss (UHL) and compare them to controls. Materials and methodsWe recruited 36 controls, 23 individuals with UHL and 14 with BHL. An HMD (HTC Vive) measured head sway while participants stood on the floor, hips-width apart. Stimuli included two levels of visuals and sound. Root Mean Square Velocity (RMSV) and Power Spectral Density (PSD) were used to quantify head sway. ResultsAdjusting for age, individuals with BHL had significantly higher anterior-posterior and medio-lateral RMSV than controls and individuals with UHL. Individuals with UHL demonstrated significantly lower response to visual perturbations in RMSV AP and in all 3 frequency segments of PSD compared to controls. Individuals with UHL showed significantly lower movements at high frequencies compared to controls. Sounds or severity of HL did not impact head sway. ConclusionsIndividuals with BHL demonstrated increased sway with visual perturbations and should be clinically assessed for balance performance and fall risk. Individuals with UHL exhibited reduced responses to visual stimuli compared with controls, which may reflect conscious movement processing. Additional studies are needed to further understand the mechanistic relationship between hearing loss and imbalance.

The use of fractal dimension methods in clinical epidemiology: an application for postural assessment


 Background: this study considers the analysis of postural sway by comparing the use of a fractal dimension outcome (DBOX) with the usual sway ellipse area (SEA), calculated by the least squares method. Both the response variables come from centre of pressure (COP) dynamics detected by means of a force platform.
 Methods: recent literature regarding postural stability assessment in subjects with muscularskeletal disorders, or neuromuscular diseases affecting their motor skills, has suggested, both for practical and theoretical reasons, the use of some fractal dimension as a good outcome measurement for overall postural status. A sample group of 24 male subjects was recruited. The postural stabilogram was recorded both with eyes open (EO) and eyes closed (EC) while standing upright. A matched-pair comparison of the sway ellipse area with the COP dynamics box counting dimension was performed. A ROC analysis of the outcome variables was performed. Then, a ROC comparison of the tests, using the area under the curve (AUC) index, was conducted.
 Results: the comparison of paired groups showed a statistically significant difference between EO and EC status, according to the sway ellipse area and the fractal dimension (p<0.05). The ROC analysis, describing the test performance in terms of AUC difference, was statistically significant (p<0.05). The comparison of the AUCs showed an overall superior performance of the DBOX with respect to SEA (p<0.05).
 Conclusions: this study showed a statistically significant better overall performance of DBOX with respect to SEA, suggesting possible improvements of clinical practice, as well as theoretical insights into the response patterns.

What could posturography tell us about balance in essential tremor?

BackgroundEssential tremor (ET) is a neurological disorder characterized primarily by action tremor. Balance impairments in ET patients were formerly considered to be uncommon and simply age-related. However quantitative assessment with posturography has revealed impairments in control of both static and dynamic balance. Research questionThe aim of the present study is to assess postural stability with different posturographic techniques in ET patients. MethodsA prospective cross-sectional study conducted in two University Hospitals. Eleven patients diagnosed with essential tremor and twelve healthy controls were included. Balance assessment were performed with: sensory organization test (SOT) and limits of stability (LOS) of the computer dynamic posturography (CDP), results of free-field body sway analysis with mobile posturography (Vertiguard®), modified timed up and go test (TUG), Dizziness handicap inventory (DHI) and activities-specific balance confidence scale (ABC). ResultsPatients with ET showed poorer scores in the SOT than controls for composite balance and somatosensory input. They also performed worse in LOS tests and Vertiguard® device indicated a higher risk of falling. There were no differences in the modified TUG. The mean score of DHI was 15.64 and 85.16 for ABC. SignificancePosturography assessment (CDP and Vertiguard®) is more accurate in showing balance impairment in ET patients than clinical evaluation (modified TUG). Balance impairment involves deteriorated processing of somatosensory input which could be explained by cerebellar dysfunction. Balance deficits could be included into future diagnostic criteria.

Influence of Hearing Rehabilitation With Active Middle Ear and Bone Conduction Implants on Postural Control.

BackgroundAs audition also seems to contribute to balance control, additionally to visual, proprioceptive, and vestibular information, we hypothesize that hearing rehabilitation with active middle ear and bone conduction implants can influence postural control.MethodsIn a prospective explorative study, the impact of hearing rehabilitation with active middle ear [Vibrant Soundbrige (VSB), MED-EL, Innsbruck, Austria] and bone conduction implants [Bonebridge (BB), MED-EL, Innsbruck, Austria] on postural control in adults was examined in three experiments. Vestibulospinal control was measured by cranio-corpography (CCG), trunk sway velocity (°/s) by the Standard Balance Deficit Test (SBDT), and postural stability with a force plate system, each time in best aided (BA) and unaided (UA) condition with frontal-noise presentation (Fastl noise, 65 dB SPL), followed by subjective evaluation, respectively.ResultsIn 26 subjects [age 55.0 ± 12.8 years; unilateral VSB/BB: n = 15; bilateral VSB/BB: n = 3, bimodal (VSB/BB + hearing aid): n = 8], CCG-analysis showed no difference between BA and UA conditions for the means of distance, angle of displacement, and angle of rotation, respectively. Trunk sway measurements revealed a relevant increase of sway in standing on foam (p = 0.01, r = 0.51) and a relevant sway reduction in walking (p = 0.026, r = 0.44, roll plane) in BA condition. Selective postural subsystem analysis revealed a relevant increase of the vestibular component in BA condition (p = 0.017, r = 0.47). As measured with the Interactive Balance System (IBS), 42% of the subjects improved stability (ST) in BA condition, 31% showed no difference, and 27% deteriorated, while no difference was seen in comparison of means. Subjectively, 4–7% of participants felt that noise improved their balance, 73–85% felt no difference, and 7–23% reported deterioration by noise. Furthermore, 46–50% reported a better task performance in BA condition; 35–46% felt no difference and 4–15% found the UA situation more helpful.ConclusionsSubjectively, approximately half of the participants reported a benefit in task performance in BA condition. Objectively, this could only be shown in one mobile SBDT-task. Subsystem analysis of trunk sway provided insights in multisensory reweighting mechanisms.

Validation of Smartphone Sway Analysis for Fall Prevention

Analysis of the balance and sway of the elderly remains a field continuously studied for additional means of assessing the risks of falls. Almost 50% of falls among the elderly lead to serious injuries, and falls are the leading cause of death for the elderly. Thus, the development of a convenient method to assess the risks of falling would be beneficial in helping to diminish these risks. We recorded the sway data by using the widely acceptable force plate and simultaneously compared it to the angular orientation measured by a cell phone’s accelerometer attached to the subject. It was found that the correlation of the average path length and average velocity between the results from the force plate and the phone application were 0.83 and 0.86 respectively. Overall, the direction of the strongest correlation was in the anterior–posterior (AP) direction that is mostly associated with falls. The smart phone application was able to represent the results that were gathered by the force plate, thus opening the door to a simpler way to track sway variables in the elderly without the necessity to come to a doctor’s office.

Quantitative trunk sway analysis under challenging gait conditions in early and untreated Parkinson's disease.

Even experienced clinicians may encounter difficulties in making a definitive diagnosis in the early motor stages of Parkinson's disease (PD). We investigated whether quantitative biomechanical trunk sway analysis could support the diagnosis of PD early on. We quantified trunk sway performance using body-worn sensors during a test battery of six challenging gait conditions in a cohort of 17 early and untreated PD patients (with evidence of reduced tracer uptake in the basal ganglia on dopamine transporter scans) and 17 age- and sex-matched healthy controls (HCs). Compared to HC, the PD group (Hoehn & Yahr ≤ 2, Unified Parkinson's Disease Rating Scale motor score: mean 13.7 ± 3.5 points) showed significant trunk rigidity in five challenging gait tasks (decreased medio-lateral direction and sway angle area). Post hoc receiver operating characteristic analysis of the significant parameters revealed excellent discrimination with high sensitivity and specificity. In the early and untreated motor stages of PD, patients exhibit significant trunk rigidity during challenging gait tasks. Trunk sway motion recorded with body-worn sensors might be a useful tool to disclose a sometimes hard-to-trace cardinal motor sign of PD and support an early clinical diagnosis.

A Review of Dynamic Tree Behaviors: Measurement Methods on Tree Sway, Tree Tilt, and Root–Plate Movement

Urban forest ecosystems are being developed to provide various environmental services (e.g., the preservation of urban trees) to urban inhabitants. However, some trees are deteriorated asymptomatically without exhibiting an early sign of tree displacement, which results in a higher vulnerability under dynamic wind loads, especially during typhoon seasons, in the subtropical and tropical regions. As such, it is important to understand the tilt and sway behaviors of trees to cope up with the probability of tree failure and to improve the efficacy of tree management. Tree behaviors under wind loads have been broadly reviewed in the past literature, yet thorough discussions on the measurement methods for tree displacement and its analysis of broadleaf specimens are lacking. To understand the behavioral pattern of both broadleaf and conifer species, this paper presents a detailed review of sway behavior analysis from the perspectives of the aerial parts of the individual tree, including tree stem, canopy, and trunk, alongside a highlighted focus on the root–plate movement amid the soil-root system. The analytical approaches associated with the time-space domain and the time-frequency domain are being introduced. In addition to the review of dynamic tree behaviors, an integrated tree monitoring framework based on geographic information systems (GIS) to detect and visualize the extent of tree displacement using smart sensing technology (SST) is introduced. The monitoring system aims to establish an early warning indicator system for monitoring the displacement angles of trees over the territory of Hong Kong’s urban landscape. This pilot study highlights the importance of the monitoring system at an operational scale to be applicable in the urban areas showcasing the practical use of the Internet of Things (IoT) with an in-depth understanding of the wind-load effect toward the urban trees in the tropical and subtropical cities.

The Feasibility of Equine Field-Based Postural Sway Analysis Using a Single Inertial Sensor.

(1) Background: Postural sway is frequently used to quantify human postural control, balance, injury, and neurological deficits. However, there is considerably less research investigating the value of the metric in horses. Much of the existing equine postural sway research uses force or pressure plates to examine the centre of pressure, inferring change at the centre of mass (COM). This study looks at the inverse, using an inertial measurement unit (IMU) on the withers to investigate change at the COM, exploring the potential of postural sway evaluation in the applied domain. (2) Methods: The lipopolysaccharide model was used to induce transient bilateral lameness in seven equines. Horses were monitored intermittently by a withers fixed IMU over seven days. (3) Results: There was a significant effect of time on total protein, carpal circumference, and white blood cell count in the horses, indicating the presence of, and recovery from, inflammation. There was a greater amplitude of displacement in the craniocaudal (CC) versus the mediolateral (ML) direction. A significant difference was observed in the amplitude of displacement in the ML direction between 4–12 h and 168 h. (4) Conclusions: The significant reduction in ML displacement during the acute inflammation period alongside greater overall CC displacement may be a compensatory behaviour for bilateral lameness.

A Multidimensional Approach to Develop Sway Index Using Gaussian Mixture Model: A Way of Postural Sway Measurement and Analysis in Different Age Groups

Many classical postural sway measures are based on linear analysis of different temporal characteristics of the body’s center of pressure (CoP). In some of the classical sway analysis methods, the anterior–posterior and the mediolateral aspects are analyzed separately. While these classical measures are found to be affected by aging, they cover different aspects of stability. Moreover, linear postural sway analysis is not efficient due to complexity of the human physiological functions. This study developed a single sway index based on the nonlinear analysis of the multidimensional CoP data and compared it in different participant age groups in different standing tests. The sway index performance was compared with six classical sway measures and six universal sway parameters. In all, 17 younger active lifestyle participants (31 ± 5.7), 12 participants age between 50 and 60 years (56.2 ± 3.3), and 32 older participants age 60 years and above (69.6 ± 6.2) were recruited for this study. Participants were asked to undergo three standing tests of double stance, single stance, and tandem stance all with eyes closed for 20 s. Using a global machine-learnt Gaussian mixture model, the multidimensional CoP data were clustered, and consequently an index was derived based on the results. Most classical and universal sway measures in the single stance and tandem stance were found to be significantly different in younger participants compared with the older ones. Our proposed sway index was significantly different in younger participants compared with 50–60 years participants in addition to older participants. The sway index also outperformed all classical and universal sway measures in the single and tandem stance tests with the sensitivity of 90.9% and 87.5%, the specificity of 82.4% and 84.3%, and AUC of 0.90 (95% CI, 0.81–1) and 0.91 (95% CI, 0.82–0.99), respectively. The findings demonstrated a strong potential of the sway index to be used as a single yet effective sway measurement.

Simple Analysis of Elevator Rope Sway with Varying Length

Simple Analysis of Elevator Rope Sway with Varying Length

Which features of postural sway are effective in distinguishing Parkinson's disease from controls? A systematic review

BackgroundPostural sway may be useful as an objective measure of Parkinson's disease (PD). Existing studies have analyzed many different features of sway using different experimental paradigms. We aimed to determine what features have been used to measure sway and then to assess which feature(s) best differentiate PD patients from controls. We also aimed to determine whether any refinements might improve discriminative power and so assist in standardizing experimental conditions and analysis of data.MethodsIn this systematic review of the literature, effect size (ES) was calculated for every feature reported by each article and then collapsed across articles where appropriate. The influence of clinical medication status, visual state, and sampling rate on ES was also assessed.ResultsFour hundred and forty‐three papers were retrieved. 25 contained enough information for further analysis. The most commonly used features were not the most effective (e.g., PathLength, used 14 times, had ES of 0.47, while TotalEnergy, used only once, had ES of 1.78). Increased sampling rate was associated with increased ES (PathLength ES increased to 1.12 at 100 Hz from 0.40 at 10 Hz). Measurement during “OFF” clinical status was associated with increased ES (PathLength ES was 0.83 OFF compared to 0.21 ON).ConclusionsThis review identified promising features for analysis of postural sway in PD, recommending a sampling rate of 100 Hz and studying patients when OFF to maximize ES. ES complements statistical significance as it is clinically relevant and is easily compared across experiments. We suggest that machine learning is a promising tool for the future analysis of postural sway in PD.

Prodromal Spinocerebellar Ataxia Type 2 Subjects Have Quantifiable Gait and Postural Sway Deficits.

The search for valid preclinical biomarkers of cerebellar dysfunction is a key research goal for the upcoming era of early interventional approaches in spinocerebellar ataxias. This study aims to describe novel preclinical biomarkers of subtle gait and postural sway abnormalities in prodromal spinocerebellar ataxia type 2 (pre-SCA2). Thirty pre-SCA2 patients and their matched healthy controls underwent quantitative assessments of gait and postural sway using a wearable sensor-based system and semiquantitative evaluation of cerebellar features by SARA (Scale for the Assessment and Rating of Ataxia) score. Quantitative analysis of natural gait showed a significantly larger variability of the swing period, toe-off angle and toe-out angle in pre-SCA2, and larger mean coronal and transverse ranges of motion of the trunk at the lumbar location and of the sagittal range of motion of the trunk at the sternum location compared to controls. During tandem gait, pre-SCA2 subjects showed larger lumbar, trunk, and arm ranges of motion than controls. Postural sway analysis showed excessive body oscillation that was increased in tandem stance. Overall, these abnormalities were detected in pre-SCA2 patients without clinical evidence of abnormalities in SARA. The toe-off angle and swing time variability were significantly correlated with the time to ataxia onset, whereas the toe-off angle and transverse range of motion at trunk position during tandem gait were significantly associated with the SARA score. This study demonstrates early alteration of gait and postural sway control in prodromal SCA2 using a wearable sensor-based system. This offers new pathophysiological hints into this early disease stage and provides novel potential biomarkers for future clinical trials. © 2020 International Parkinson and Movement Disorder Society.

Mini-Logger- A Wearable Inertial Measurement Unit (IMU) for Postural Sway Analysis.

Postural instability assessment is an important tool in fall risk analysis and for timely intervention of falls to reduce or prevent fall injuries. Traditionally fall risk is measured though postural sway assessment and is collected through forceplates by mapping Center of Pressure (COP) excursions or using motion analysis camera system for marker sway trajectories. However, both of these systems are expensive and lack portability to their usage in clinical environments. In this study, we developed a novel wearable low-cost MEMS inertial sensor and validated its usage for human postural sway assessment in standing posture with eyes open/closed, vibration/no vibration, and proprioception /low proprioception conditions. The two objectives of this study were: 1) To develop and validate an Inertial Measurement Unit (IMU) for sway analysis 2) To determine the feasibility of the system in detecting human postural imbalances such as reduced proprioception or presence of stochastic resonance induced through subthreshold vibrations on the feet. The novel IMU was tested for sway against infra-red marker on a specialized platform with 4-degrees of freedom. Many parameters of postural sway such as sway velocity, Root Mean Square (RMS), and sway path length could successfully detect subtle postural changes due to varying proprioceptive and sub-threshold vibration conditions. We found agreement in sway signal determinism from the two methods.Clinical Relevance- This wearable sensor technology has potential to determine balance in reliable, easy and accurate way in clinical environments.