.publications

Abstract : Postural instability is a common complication in advanced Parkinson’s disease (PD) associated with recurrent falls and fall-related injuries. The test of retropulsion, consisting of a rapid balance perturbation by a pull in the backward direction, is regarded as the gold standard for evaluating postural instability in PD and is a key component of the neurological examination and clinical rating in PD (e.g., MDS-UPDRS). However, significant variability in test execution and interpretation contributes to a low intra- and inter-rater test reliability. Here, we explore the potential for objective, vision-based assessment of the pull test (vPull) using 3D pose tracking applied to single-sensor RGB-Depth recordings of clinical assessments. The initial results in a cohort of healthy individuals (n = 15) demonstrate overall excellent agreement of vPull-derived metrics with the gold standard marker-based motion capture. Subsequently, in a cohort of PD patients and controls (n = 15 each), we assessed the inter-rater reliability of vPull and analyzed PD-related impairments in postural response (including pull-to-step latency, number of steps, retropulsion angle). These quantitative metrics effectively distinguish healthy performance from and within varying degrees of postural impairment in PD. vPull shows promise for straightforward clinical implementation with the potential to enhance the sensitivity and specificity of postural instability assessment and fall risk prediction in PD. … read on

Abstract : Mobile health technologies enable continuous, quantitative assessment of mobility and gait in real-world environments, facilitating early diagnoses of gait disorders, disease progression monitoring, and prediction of adverse events like falls. Traditionally, mobile gait assessment predominantly relied on body-fixed sensors positioned at the feet or lower trunk. Here, we investigate the potential of an algorithm utilizing an ear-worn motion sensor for spatiotemporal segmentation of gait patterns. We collected 3D acceleration profiles from the ear-worn sensor during varied walking speeds in 53 healthy adults. Temporal convolutional networks were trained to detect stepping sequences and predict spatial relations between steps. The resulting algorithm, mEar, accurately detects initial and final ground contacts (F1 score of 99% and 91%, respectively). It enables the determination of temporal and spatial gait cycle … … read on

Abstract : Human activity recognition (HAR) technology enables continuous behavior monitoring, which is particularly valuable in healthcare. This study investigates the viability of using an ear-worn motion sensor for classifying daily activities, including lying, sitting/standing, walking, ascending stairs, descending stairs, and running. Fifty healthy participants (between 20 and 47 years old) engaged in these activities while under monitoring. Various machine learning algorithms, ranging from interpretable shallow models to state-of-the-art deep learning approaches designed for HAR (i.e., DeepConvLSTM and ConvTransformer), were employed for classification. The results demonstrate the ear sensor’s efficacy, with deep learning models achieving a 98% accuracy rate of classification. The obtained classification models are agnostic regarding which ear the sensor is worn and robust against moderate variations in sensor orientation (e.g., due to differences in auricle anatomy), meaning no initial calibration of the sensor orientation is required. The study underscores the ear’s efficacy as a suitable site for monitoring human daily activity and suggests its potential for combining HAR with in-ear vital sign monitoring. This approach offers a practical method for comprehensive health monitoring by integrating sensors in a single anatomical location. This integration facilitates individualized health assessments, with potential applications in tele-monitoring, personalized health insights, and optimizing athletic training regimes. … read on

Abstract : Low-intensity noisy galvanic vestibular stimulation (nGVS) is a promising non-invasive treatment for enhancing vestibular perceptual performance and postural control in patients with chronic vestibular hypofunction. However, this approach has so far been studied mainly under laboratory conditions. Evidence indicates that continuous application of nGVS in daily life is necessary for it to be effective. To address this need, we have developed a mobile nGVS stimulator and conducted a series of pilot studies to evaluate its safety, tolerability, functionality, and therapeutic effects. The device is a lightweight, compact, and portable AC stimulator featuring a user-friendly interface for the individualized adjustment of nGVS parameters. It includes an integrated motion sensor that automatically activates stimulation during body movement and deactivates it during inactivity, optimizing its practical use in real-world settings. The stimulator adheres to strict safety standards and, in initial long-term use, has exhibited only mild side effects (e.g., skin irritation and headaches), likely attributable to the current electrode placement, which requires further optimization. As expected, the device consistently elicits known vestibular sensorimotor reflex responses in healthy individuals. Importantly, further pilot studies in healthy participants demonstrate that the device can reliably replicate known facilitating effects on vestibular perception and postural control. Together, these findings suggest that this mobile stimulation device can facilitate the translation of nGVS into therapeutic everyday use. … read on

Abstract : This cohort study aims to evaluate the predictive validity of multimodal clinical assessment and quantitative measures of in- and off-laboratory mobility for fall-risk estimation in patients with cerebellar ataxia (CA).Occurrence, severity, and consequences of falling were prospectively assessed for 6 months in 93 patients with hereditary (N = 36) and sporadic or secondary (N = 57) forms of CA and 63 healthy controls. Participants completed a multimodal clinical and functional fall risk assessment, in-laboratory gait examination, and a 2-week inertial sensor-based daily mobility monitoring. Multivariate logistic regression analyses were performed to evaluate the predictive capacity of all clinical and in- and off-laboratory mobility measures with respect to fall (1) status (non-faller vs. faller), (2) frequency (occasional vs. frequent falls), and (3) severity (benign vs. injurious fall) of patients. 64% of patients experienced one … … read on

Abstract : Die vorliegende Arbeit befasst sich mit dem dynamischen System der Kopf-Rumpf Koordination verschiedener Altersgruppen sowie Patienten mit einer bilateralen Vestibulopathie bei unterschiedlichen Ganggeschwindigkeiten und kognitivem Dual Task Paradigma. Ziel der Arbeit ist es zu untersuchen, in welcher Weise sich die Koordination in den Altersgruppen bei Gesunden sowie in der Gruppe der Patienten mit bilateraler Vestibulopathie (BVP) unterscheidet. Da sowohl das vestibuläre als auch das visuelle System direkt hiervon abhängig sind, kommt dieser Koordinationsleistung beim Gehen und der posturalen Kontrolle eine wichtige Funktion zu. Von besonderem Interesse ist es einerseits zu messen, ob bei allen Gruppen die Kopfbewegung bzw. die einwirkenden Kräfte sich ähneln und andererseits zu untersuchen, ob Hinweise auf kompensatorische Mechanismen zu finden sind. Hierzu wurde zunächst eine geeignete Messmethode mittels marker-basiertem 3-D Motion Tracking und kombinierten Inertialsensoren etabliert sowie ein reliables Versuchsprotokoll definiert. Anschließend wurden für die unterschiedlichen gesunden Altersgruppen (20-40 Jahre, 40-60 Jahre, 60-80 Jahre) sowie für die Gruppe mit BVP, Probanden rekrutiert. Erfasst wurden hierbei die Rumpf-Kopf-Position, die Beschleunigung und die Drehgeschwindigkeit der Rumpf-/Kopfpartie. Die vorliegende Arbeit konnte zeigen, dass Patienten mit einer BVP in Zusammenschau aller gemessenen Parameter sowie im Vergleich mit vorangegangenen Studien Kompensationsmechanismen entwickeln, um ihr sensorisches Defizit auszugleichen. Lediglich in wenigen … … read on

Abstract : There is increasing evidence for close interrelations between vestibular and emotional brain networks. A study in patients with bilateral peripheral vestibulopathy (BVP) showed relatively low vertigo-related anxiety (VRA), despite high physical impairment. The current working hypothesis proposes the integrity of the peripheral vestibular system as a prerequisite for development of VRA. Here we contribute by evaluating VRA and vestibular-related handicap in central vestibular disorders.Of 6396 patients presenting in a tertiary vertigo centre, 306 were identified with four clear central vestibular disorders: pure cerebellar ocular motor disorder (COD; 61), cerebellar ataxia (CA; 63), atypical parkinsonian syndromes (APS; 28), vestibular migraine (VM; 154). Their results of the Vertigo Handicap Questionnaire (VHQ), with its subscales for anxiety and handicapped activity, were compared to those of 65 … … read on

Abstract : The aim of the study was to distinguish the hypokinetic gait disorder in idiopathic normal pressure hydrocephalus (NPH) patients from the gait decline in the elderly population by quantifying pathological gait parameter thresholds utilizing a multiple condition gait assessment. 55 NPH patients and 55 age-matched healthy subjects underwent a standardized gait assessment with eight gait conditions. Spatiotemporal gait parameters were assessed through a pressure-sensitive carpet. Statistical analysis consisted of a binary logistic regression (BLR) model, logistic curve-fit evaluated by a Chi-square goodness-of-fit-test, receiver operating characteristic models with area under the curves (AUC), and inverse BLR. Most discriminative gait parameter thresholds were observed in pace, gait cycle, and support gait domains. The most distinct gait conditions were preferred walking speed and semantic dual task. During … … read on

Abstract : To study the behavioral relevance of postural and ocular-motor deficits on daily activity and risk of falling in patients with bilateral vestibular hypofunction (BVH).Thirty patients with BVH and 30 age- and gender-matched healthy controls participated in a continuous 2-week assessment of daily activities and mobility using a body-worn inertial sensor and a 6-month prospective fall risk assessment. At inclusion, patients and controls further underwent a multi-modal clinical, score- and instrument-based assessment of general health and balance status. We analyzed the relationship between clinical, lab-, and sensor-based measures and their validity to identify those patients at a risk of general, frequent, and severe falling.Patients exhibited impairments in daily activity in particular in terms of reduced ambulatory activity (p = 0.009). 43% of patients experienced falls (13% in controls, p = 0.008 … … read on

Abstract : To evaluate the predictive validity of multimodal clinical assessment outcomes and quantitative measures of in- and off-laboratory mobility for fall-risk estimation in patients with different forms of neurological gait disorders.The occurrence, severity, and consequences of falls were prospectively assessed for 6 months in 333 patients with early stage gait disorders due to vestibular, cerebellar, hypokinetic, vascular, functional, or other neurological diseases and 63 healthy controls. At inclusion, participants completed a comprehensive multimodal clinical and functional fall-risk assessment, an in-laboratory gait examination, and an inertial-sensor-based daily mobility monitoring for 14 days. Multivariate logistic regression analyses were performed to identify explanatory characteristics for predicting the (1) the fall status (non-faller vs. faller), (2 … … read on

Abstract : Results: In the preliminary analysis, patients showed a characteristic cerebellar gait disorder with broadened base of support and increased gait variability. 51 out of 80 patients reported fall events in the follow-up assessment with 23% occasional and 41% frequent fallers. There were 23% severe falls, which made medical attention necessary. In the final regression model, most distinct variables were the fall status within the last 12 month during initial assessment (OR 4.49, p= 0.02), the score of the Falls Efficacy Scale-International (FES-I)(OR 1.14, p= 0.048) as well as the coefficient of variation of stride time (OR 4.67, p< 0.01).Conclusion: Our results confirm the association between fall events and increased gait variability as a marker of dynamic stability in cerebellar patients. Interestingly, no ambulatory mobility markers showed significant results in the final regression model. Furthermore, previous fall events as … … read on

Abstract : Methods: For the Prospective Assessment of Falls and Mobility–study (PAss FaMous-study, DRKS-ID: DRKS00007762) 396 subjects and patients were recruited and examined by a standardized fall risk assessment, an in-laboratory-based gait analysis on a pressure sensitive carpet, and an off-laboratory tracking of physical activity via a wearable inertial sensor. A follow-up of 6 months with prospective recordings of falls via fall calendar and telephone interview was established. After testing for possible differences via ANOVA models, binary logistic regression procedures for model I “fall status”, model II “fall frequency” and model III “fall severity” were performed.Results: The regression model I showed a correct prediction in 82% of the cases, model II and model III in 88%. As retrieved in Table 1, the significant factors were retrospective fall status, MOCA, FGA, ABC-D, SF-12, gait velocity, stride time, CV of stride time … … read on

Abstract : The aim of this study was to establish a comprehensive and yet parsimonious model of daily mobility activity in patients with neurological gait disorders. Patients (N = 240) with early-stage neurological (peripheral vestibular, cerebellar, hypokinetic, vascular or functional) gait disorders and healthy controls (N = 35) were clinically assessed with standardized scores related to functional mobility, balance confidence, quality of life, cognitive function, and fall history. Subsequently, daily mobility was recorded for 14 days by means of a body-worn inertial sensor (ActivPAL®). Fourteen mobility measures derived from ActivPAL recordings were submitted to principle component analysis (PCA). Group differences within each factor obtained from PCA were analyzed and hierarchical regression analysis was performed to identify predictive characteristics from clinical assessment for each factor. PCA yielded five … … read on

Abstract : It was an incidental observation in our tertiary outpatient dizziness center that patients with acquired bilateral vestibulopathy (BVP) rarely complain about being anxious about falling. This is surprising, since a bilateral vestibular deficit impairs postural stability and thus causes frequent falls [1], in particular during locomotion on uneven ground and in darkness when vision cannot substitute. In a controlled cross-sectional study, the rate of recurrent fallers was increased in BVP patients despite a low-to-normal fear of falling as determined by the Falls Efficiency Score International [2]. Two epidemiological studies had shown that patients with vestibular disorders with episodic vertigo, such as vestibular migraine and Menière’s disease, suffer from increased psychiatric comorbidity with anxiety and affective disorders, which was not the case in patients withBVP [3–5]. Furthermore, a recent study on the susceptibility to fear … … read on

Abstract : Recent epidemiological studies indicate that about one-third of the general population suffers from a more or less disabling height intolerance, with a relevant impact on quality of life in many of them. Acrophobia, the most severe form of visual height intolerance, has a life-time prevalence of around 5%. Although it is commonly believed that fear of heights should continuously aggravate with increasing elevation, this issue has not been systematically investigated yet. Here, we examined this topic using immersive virtual reality, an established tool in therapy for fear of heights, that allows to flexibly manipulate height stimuli. In a comprehensive cohort (including insusceptible subjects as well as subjects with height intolerance up to acrophobia) height intolerance severity was graded by an established metric scale (vHISS). Participants were randomly exposed to different virtual elevations using a head-mounted display … … read on

Abstract : There is strong evidence that the presence of noise can enhance information processing in sensory systems via stochastic resonance (SR).To examine the presence of SR in human vestibulospinal reflex function.Healthy subjects were stimulated with 1 Hz sinusoidal GVS of varying amplitudes (0–1.9 mA). Coherence between GVS input and stimulation-induced motion responses was determined and psychometric function fits were subsequently used to determine individual vestibulospinal reflex thresholds. This procedure was repeated with additional application of imperceptible white noise GVS (nGVS).nGVS significantly facilitated the detectability of weak subthreshold vestibular inputs (p < 0.001) and thereby effectively lowered the vestibulospinal threshold in 90% of participants (p < 0.001, mean reduction: 17.5 ± 14.6%).This finding provides evidence for the … … read on

Abstract : To identify thresholds for pathognomonic gait parameters in functional gait disorders.Characteristics of functional gait disorders are e.g. transient fluctuations in stance and gait, excessive slowness or hesitation that is not compatible with neurological disease, uneconomic postures with wastage of muscular energy, the ‘walking on ice’ gait pattern with typical small cautious steps with fixed ankle joints and sudden buckling of the knees that generally do not lead to falls (Lempert et al., 1991). Early diagnosis is important: Over half of the patients with psychogenic disorder of stance and gait remain unchanged after five and a half years. If the disorder is present no longer than four months complete remission can often be achieved (Brandt et al., 1994).We used a pressure-sensitive GAITRite© carpet to assess gait analysis during eight gait conditions (three different walking speeds, two … … read on

Abstract : To examine the mechanism underlying previously reported ameliorating effects of noisy galvanic vestibular stimulation (GVS) on balance performance in patients with bilateral vestibulopathy (BVP) and determine those patients (incomplete versus complete vestibular loss) that might benefit from this intervention.Vestibulospinal reflex thresholds were determined in 12 patients with BVP [2 with complete loss (cBVP) and 10 with residual function (rBVP)]. Patients were stimulated with 1 Hz sinusoidal GVS of increasing amplitudes (0–1.9 mA). Coherence between GVS input and stimulation-induced body motion was determined and psychometric function fits were subsequently used to determine individual vestibulospinal reflex thresholds. The procedure was repeated with an additional application of imperceptible white noise GVS (nGVS).All patients with rBVP but none with cBVP … … read on

Abstract : Patients with bilateral vestibulopathy (BVP) suffer from persistent imbalance during standing and walking as well as an impaired gaze stabilization during head movements. Disabilities associated with BVP severely compromise patients’ daily activities and are often linked to an increased risk of falls. Currently, the only established treatment option in BVP is physical therapy. However, treatment effects of physical therapy in BVP are most often limited and many patients do not adequately recover performance. Therefore, a number of technical therapeutic approaches are being explored that either try to substitute lost vestibular sensation with a congruent stimulation of other sense modalities or to artificially mimic vestibular function by means of an implantable vestibular prosthesis. Besides, attempts have recently been made to augment and optimize residual vestibular function in patients with BVP using an … … read on

Abstract : To examine the effects of imperceptible levels of white noise galvanic vestibular stimulation (nGVS) on dynamic walking stability in patients with bilateral vestibulopathy (BVP).Walking performance of 13 patients with confirmed BVP (mean age 50.1 ± 5.5 years) at slow, preferred, and fast speeds was examined during walking with zero-amplitude nGVS (sham trial) and nonzero-amplitude nGVS set to 80% of the individual cutaneous threshold for GVS (nGVS trial). Eight standard gait measures were analyzed: stride time, stride length, base of support, double support time percentage as well as the bilateral phase coordination index, and the coefficient of variation (CV) of stride time, stride length, and base of support.Compared to the sham trial, nGVS improved stride time CV by 26.0% ± 8.4% (p < 0.041), stride length CV by 26.0% ± 7.7% (p < 0.029), base of support CV by 27.8% ± 2.9% (p < 0 … … read on

Abstract : Background The vestibular system is essential for orientation, eye coordination and balance. Disorders of the vestibular system are more common in older people and present with symptoms such as imbalance which is usually compensated with an increase in sensory loading to the visual and proprioceptive systems. This compensation is often insufficient in cases of increasing demands during turning, different gait speeds and cognitive loading. In this study, we investigated the relationship of the position and forces acting on the semicircular canal (Reid’s plane) during such gait tasks and its effects on gait trajectory and stability. Furthermore, we attempted to quantify the effects of these forces and positions on the gait cycle. Methods 10 young healthy subjects (20–40 years), 10 older healthy subjects (40–60 years), and 10 bilateral vestibulopathy patients (BVP) were recruited for the study. Motion capturing was … … read on

Abstract : Stochastic resonance (SR) is a phenomenon, wherein the response of a nonlinear system to weak input signals can be optimized by addition of a particular non-zero level of noise. Here we tested for the presence of SR in the vestibular system by evaluating if a white noise galvanic vestibular stimulation (GVS) lowers the vestibular detection threshold.Sixteen healthy subjects (mean age 28.9 ± 2.0 years) participated in the study. Vestibular threshold detection was done by identifying the amplitude of a 1 Hz sinusoidal GVS (Digitimer, Hertfordshire, UK) at which subjects exhibit motion induced by the stimulation. Threshold detection was performed without and with an additional white noise GVS within a frequency range of 0–30 Hz and an amplitude set to 80% of the individual cutaneous threshold for GVS. Each threshold detection task consisted in ten bipolar sinusoidal GVS trials with amplitudes … … read on

Abstract : Chronic loss of vestibular sensation (bilateral vestibulopathy) results in sustained postural instability during standing and walking, especially in situations where other sensory sources are not available, eg, while walking in darkness or on uneven ground [9]. Consequently, patients with limited vestibular feedback suffer from reduced mobility and live with an increased risk of falling [11]. Disturbed vestibular function is not limited to peripheral bilateral vestibulopathy (BVP) but can also be caused by central dysfunction in neurodegenerative disorders such as Parkinson’s disease [8]. Current therapeutic options in vestibular hypofunction are mainly based on vestibular rehabilitation therapy with training of balance and eye-head coordination by physical therapists (Fig. 1A). However, in most cases the training only results in partial relief of symptoms [10]. Two new therapeutic alternatives are currently under development that directly target vestibular dysfunctions. The first approach consists of a vestibular implant (Fig. 1B), which has shown promising effects in alleviating postural symptoms and other signs of vestibular hypofunction in selected patients [1]. Nevertheless, the advantages of such an invasive vestibular implant must be carefully balanced against the surgical risks and potential side effects. The second new therapeutic approach aims to amplify residual vestibular function in patients through non-invasive noise stimulation of the vestibular periphery (Fig. 1C)[12]. Non-invasive noisy galvanic vestibular stimulation (nGVS) is a technique using the application of weak sensory noise through subthreshold electrical stimulation to enhance vestibular … … read on